plancat.c

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/*-------------------------------------------------------------------------
 *
 * plancat.c
 *     routines for accessing the system catalogs
 *
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/util/plancat.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include <math.h>
 
#include "access/genam.h"
#include "access/htup_details.h"
#include "access/nbtree.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "access/tableam.h"
#include "access/transam.h"
#include "access/xlog.h"
#include "catalog/catalog.h"
#include "catalog/heap.h"
#include "catalog/pg_am.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_statistic_ext_data.h"
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/supportnodes.h"
#include "optimizer/cost.h"
#include "optimizer/optimizer.h"
#include "optimizer/plancat.h"
#include "parser/parse_relation.h"
#include "parser/parsetree.h"
#include "partitioning/partdesc.h"
#include "rewrite/rewriteManip.h"
#include "statistics/statistics.h"
#include "storage/bufmgr.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/partcache.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
 
/* GUC parameter */
int         constraint_exclusion = CONSTRAINT_EXCLUSION_PARTITION;
 
/* Hook for plugins to get control in get_relation_info() */
get_relation_info_hook_type get_relation_info_hook = NULL;
 
 
static void get_relation_foreign_keys(PlannerInfo *root, RelOptInfo *rel,
                                      Relation relation, bool inhparent);
static bool infer_collation_opclass_match(InferenceElem *elem, Relation idxRel,
                                          List *idxExprs);
static List *get_relation_constraints(PlannerInfo *root,
                                      Oid relationObjectId, RelOptInfo *rel,
                                      bool include_noinherit,
                                      bool include_notnull,
                                      bool include_partition);
static List *build_index_tlist(PlannerInfo *root, IndexOptInfo *index,
                               Relation heapRelation);
static List *get_relation_statistics(RelOptInfo *rel, Relation relation);
static void set_relation_partition_info(PlannerInfo *root, RelOptInfo *rel,
                                        Relation relation);
static PartitionScheme find_partition_scheme(PlannerInfo *root,
                                             Relation relation);
static void set_baserel_partition_key_exprs(Relation relation,
                                            RelOptInfo *rel);
static void set_baserel_partition_constraint(Relation relation,
                                             RelOptInfo *rel);
 
 
/*
 * get_relation_info -
 *    Retrieves catalog information for a given relation.
 *
 * Given the Oid of the relation, return the following info into fields
 * of the RelOptInfo struct:
 *
 *  min_attr    lowest valid AttrNumber
 *  max_attr    highest valid AttrNumber
 *  indexlist   list of IndexOptInfos for relation's indexes
 *  statlist    list of StatisticExtInfo for relation's statistic objects
 *  serverid    if it's a foreign table, the server OID
 *  fdwroutine  if it's a foreign table, the FDW function pointers
 *  pages       number of pages
 *  tuples      number of tuples
 *  rel_parallel_workers user-defined number of parallel workers
 *
 * Also, add information about the relation's foreign keys to root->fkey_list.
 *
 * Also, initialize the attr_needed[] and attr_widths[] arrays.  In most
 * cases these are left as zeroes, but sometimes we need to compute attr
 * widths here, and we may as well cache the results for costsize.c.
 *
 * If inhparent is true, all we need to do is set up the attr arrays:
 * the RelOptInfo actually represents the appendrel formed by an inheritance
 * tree, and so the parent rel's physical size and index information isn't
 * important for it, however, for partitioned tables, we do populate the
 * indexlist as the planner uses unique indexes as unique proofs for certain
 * optimizations.
 */
void
get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
                  RelOptInfo *rel)
{
    Index       varno = rel->relid;
    Relation    relation;
    bool        hasindex;
    List       *indexinfos = NIL;
 
    /*
     * We need not lock the relation since it was already locked, either by
     * the rewriter or when expand_inherited_rtentry() added it to the query's
     * rangetable.
     */
    relation = table_open(relationObjectId, NoLock);
 
    /*
     * Relations without a table AM can be used in a query only if they are of
     * special-cased relkinds.  This check prevents us from crashing later if,
     * for example, a view's ON SELECT rule has gone missing.  Note that
     * table_open() already rejected indexes and composite types; spell the
     * error the same way it does.
     */
    if (!relation->rd_tableam)
    {
        if (!(relation->rd_rel->relkind == RELKIND_FOREIGN_TABLE ||
              relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE))
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("cannot open relation \"%s\"",
                            RelationGetRelationName(relation)),
                     errdetail_relkind_not_supported(relation->rd_rel->relkind)));
    }
 
    /* Temporary and unlogged relations are inaccessible during recovery. */
    if (!RelationIsPermanent(relation) && RecoveryInProgress())
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot access temporary or unlogged relations during recovery")));
 
    rel->min_attr = FirstLowInvalidHeapAttributeNumber + 1;
    rel->max_attr = RelationGetNumberOfAttributes(relation);
    rel->reltablespace = RelationGetForm(relation)->reltablespace;
 
    Assert(rel->max_attr >= rel->min_attr);
    rel->attr_needed = (Relids *)
        palloc0((rel->max_attr - rel->min_attr + 1) * sizeof(Relids));
    rel->attr_widths = (int32 *)
        palloc0((rel->max_attr - rel->min_attr + 1) * sizeof(int32));
 
    /*
     * Record which columns are defined as NOT NULL.  We leave this
     * unpopulated for non-partitioned inheritance parent relations as it's
     * ambiguous as to what it means.  Some child tables may have a NOT NULL
     * constraint for a column while others may not.  We could work harder and
     * build a unioned set of all child relations notnullattnums, but there's
     * currently no need.  The RelOptInfo corresponding to the !inh
     * RangeTblEntry does get populated.
     */
    if (!inhparent || relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
    {
        for (int i = 0; i < relation->rd_att->natts; i++)
        {
            FormData_pg_attribute *attr = &relation->rd_att->attrs[i];
 
            if (attr->attnotnull)
            {
                rel->notnullattnums = bms_add_member(rel->notnullattnums,
                                                     attr->attnum);
 
                /*
                 * Per RemoveAttributeById(), dropped columns will have their
                 * attnotnull unset, so we needn't check for dropped columns
                 * in the above condition.
                 */
                Assert(!attr->attisdropped);
            }
        }
    }
 
    /*
     * Estimate relation size --- unless it's an inheritance parent, in which
     * case the size we want is not the rel's own size but the size of its
     * inheritance tree.  That will be computed in set_append_rel_size().
     */
    if (!inhparent)
        estimate_rel_size(relation, rel->attr_widths - rel->min_attr,
                          &rel->pages, &rel->tuples, &rel->allvisfrac);
 
    /* Retrieve the parallel_workers reloption, or -1 if not set. */
    rel->rel_parallel_workers = RelationGetParallelWorkers(relation, -1);
 
    /*
     * Make list of indexes.  Ignore indexes on system catalogs if told to.
     * Don't bother with indexes from traditional inheritance parents.  For
     * partitioned tables, we need a list of at least unique indexes as these
     * serve as unique proofs for certain planner optimizations.  However,
     * let's not discriminate here and just record all partitioned indexes
     * whether they're unique indexes or not.
     */
    if ((inhparent && relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
        || (IgnoreSystemIndexes && IsSystemRelation(relation)))
        hasindex = false;
    else
        hasindex = relation->rd_rel->relhasindex;
 
    if (hasindex)
    {
        List       *indexoidlist;
        LOCKMODE    lmode;
        ListCell   *l;
 
        indexoidlist = RelationGetIndexList(relation);
 
        /*
         * For each index, we get the same type of lock that the executor will
         * need, and do not release it.  This saves a couple of trips to the
         * shared lock manager while not creating any real loss of
         * concurrency, because no schema changes could be happening on the
         * index while we hold lock on the parent rel, and no lock type used
         * for queries blocks any other kind of index operation.
         */
        lmode = root->simple_rte_array[varno]->rellockmode;
 
        foreach(l, indexoidlist)
        {
            Oid         indexoid = lfirst_oid(l);
            Relation    indexRelation;
            Form_pg_index index;
            IndexAmRoutine *amroutine;
            IndexOptInfo *info;
            int         ncolumns,
                        nkeycolumns;
            int         i;
 
            /*
             * Extract info from the relation descriptor for the index.
             */
            indexRelation = index_open(indexoid, lmode);
            index = indexRelation->rd_index;
 
            /*
             * Ignore invalid indexes, since they can't safely be used for
             * queries.  Note that this is OK because the data structure we
             * are constructing is only used by the planner --- the executor
             * still needs to insert into "invalid" indexes, if they're marked
             * indisready.
             */
            if (!index->indisvalid)
            {
                index_close(indexRelation, NoLock);
                continue;
            }
 
            /*
             * If the index is valid, but cannot yet be used, ignore it; but
             * mark the plan we are generating as transient. See
             * src/backend/access/heap/README.HOT for discussion.
             */
            if (index->indcheckxmin &&
                !TransactionIdPrecedes(HeapTupleHeaderGetXmin(indexRelation->rd_indextuple->t_data),
                                       TransactionXmin))
            {
                root->glob->transientPlan = true;
                index_close(indexRelation, NoLock);
                continue;
            }
 
            info = makeNode(IndexOptInfo);
 
            info->indexoid = index->indexrelid;
            info->reltablespace =
                RelationGetForm(indexRelation)->reltablespace;
            info->rel = rel;
            info->ncolumns = ncolumns = index->indnatts;
            info->nkeycolumns = nkeycolumns = index->indnkeyatts;
 
            info->indexkeys = (int *) palloc(sizeof(int) * ncolumns);
            info->indexcollations = (Oid *) palloc(sizeof(Oid) * nkeycolumns);
            info->opfamily = (Oid *) palloc(sizeof(Oid) * nkeycolumns);
            info->opcintype = (Oid *) palloc(sizeof(Oid) * nkeycolumns);
            info->canreturn = (bool *) palloc(sizeof(bool) * ncolumns);
 
            for (i = 0; i < ncolumns; i++)
            {
                info->indexkeys[i] = index->indkey.values[i];
                info->canreturn[i] = index_can_return(indexRelation, i + 1);
            }
 
            for (i = 0; i < nkeycolumns; i++)
            {
                info->opfamily[i] = indexRelation->rd_opfamily[i];
                info->opcintype[i] = indexRelation->rd_opcintype[i];
                info->indexcollations[i] = indexRelation->rd_indcollation[i];
            }
 
            info->relam = indexRelation->rd_rel->relam;
 
            /*
             * We don't have an AM for partitioned indexes, so we'll just
             * NULLify the AM related fields for those.
             */
            if (indexRelation->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
            {
                /* We copy just the fields we need, not all of rd_indam */
                amroutine = indexRelation->rd_indam;
                info->amcanorderbyop = amroutine->amcanorderbyop;
                info->amoptionalkey = amroutine->amoptionalkey;
                info->amsearcharray = amroutine->amsearcharray;
                info->amsearchnulls = amroutine->amsearchnulls;
                info->amcanparallel = amroutine->amcanparallel;
                info->amhasgettuple = (amroutine->amgettuple != NULL);
                info->amhasgetbitmap = amroutine->amgetbitmap != NULL &&
                    relation->rd_tableam->scan_bitmap_next_block != NULL;
                info->amcanmarkpos = (amroutine->ammarkpos != NULL &&
                                      amroutine->amrestrpos != NULL);
                info->amcostestimate = amroutine->amcostestimate;
                Assert(info->amcostestimate != NULL);
 
                /* Fetch index opclass options */
                info->opclassoptions = RelationGetIndexAttOptions(indexRelation, true);
 
                /*
                 * Fetch the ordering information for the index, if any.
                 */
                if (info->relam == BTREE_AM_OID)
                {
                    /*
                     * If it's a btree index, we can use its opfamily OIDs
                     * directly as the sort ordering opfamily OIDs.
                     */
                    Assert(amroutine->amcanorder);
 
                    info->sortopfamily = info->opfamily;
                    info->reverse_sort = (bool *) palloc(sizeof(bool) * nkeycolumns);
                    info->nulls_first = (bool *) palloc(sizeof(bool) * nkeycolumns);
 
                    for (i = 0; i < nkeycolumns; i++)
                    {
                        int16       opt = indexRelation->rd_indoption[i];
 
                        info->reverse_sort[i] = (opt & INDOPTION_DESC) != 0;
                        info->nulls_first[i] = (opt & INDOPTION_NULLS_FIRST) != 0;
                    }
                }
                else if (amroutine->amcanorder)
                {
                    /*
                     * Otherwise, identify the corresponding btree opfamilies
                     * by trying to map this index's "<" operators into btree.
                     * Since "<" uniquely defines the behavior of a sort
                     * order, this is a sufficient test.
                     *
                     * XXX This method is rather slow and also requires the
                     * undesirable assumption that the other index AM numbers
                     * its strategies the same as btree.  It'd be better to
                     * have a way to explicitly declare the corresponding
                     * btree opfamily for each opfamily of the other index
                     * type.  But given the lack of current or foreseeable
                     * amcanorder index types, it's not worth expending more
                     * effort on now.
                     */
                    info->sortopfamily = (Oid *) palloc(sizeof(Oid) * nkeycolumns);
                    info->reverse_sort = (bool *) palloc(sizeof(bool) * nkeycolumns);
                    info->nulls_first = (bool *) palloc(sizeof(bool) * nkeycolumns);
 
                    for (i = 0; i < nkeycolumns; i++)
                    {
                        int16       opt = indexRelation->rd_indoption[i];
                        Oid         ltopr;
                        Oid         btopfamily;
                        Oid         btopcintype;
                        int16       btstrategy;
 
                        info->reverse_sort[i] = (opt & INDOPTION_DESC) != 0;
                        info->nulls_first[i] = (opt & INDOPTION_NULLS_FIRST) != 0;
 
                        ltopr = get_opfamily_member(info->opfamily[i],
                                                    info->opcintype[i],
                                                    info->opcintype[i],
                                                    BTLessStrategyNumber);
                        if (OidIsValid(ltopr) &&
                            get_ordering_op_properties(ltopr,
                                                       &btopfamily,
                                                       &btopcintype,
                                                       &btstrategy) &&
                            btopcintype == info->opcintype[i] &&
                            btstrategy == BTLessStrategyNumber)
                        {
                            /* Successful mapping */
                            info->sortopfamily[i] = btopfamily;
                        }
                        else
                        {
                            /* Fail ... quietly treat index as unordered */
                            info->sortopfamily = NULL;
                            info->reverse_sort = NULL;
                            info->nulls_first = NULL;
                            break;
                        }
                    }
                }
                else
                {
                    info->sortopfamily = NULL;
                    info->reverse_sort = NULL;
                    info->nulls_first = NULL;
                }
            }
            else
            {
                info->amcanorderbyop = false;
                info->amoptionalkey = false;
                info->amsearcharray = false;
                info->amsearchnulls = false;
                info->amcanparallel = false;
                info->amhasgettuple = false;
                info->amhasgetbitmap = false;
                info->amcanmarkpos = false;
                info->amcostestimate = NULL;
 
                info->sortopfamily = NULL;
                info->reverse_sort = NULL;
                info->nulls_first = NULL;
            }
 
            /*
             * Fetch the index expressions and predicate, if any.  We must
             * modify the copies we obtain from the relcache to have the
             * correct varno for the parent relation, so that they match up
             * correctly against qual clauses.
             */
            info->indexprs = RelationGetIndexExpressions(indexRelation);
            info->indpred = RelationGetIndexPredicate(indexRelation);
            if (info->indexprs && varno != 1)
                ChangeVarNodes((Node *) info->indexprs, 1, varno, 0);
            if (info->indpred && varno != 1)
                ChangeVarNodes((Node *) info->indpred, 1, varno, 0);
 
            /* Build targetlist using the completed indexprs data */
            info->indextlist = build_index_tlist(root, info, relation);
 
            info->indrestrictinfo = NIL;    /* set later, in indxpath.c */
            info->predOK = false;   /* set later, in indxpath.c */
            info->unique = index->indisunique;
            info->immediate = index->indimmediate;
            info->hypothetical = false;
 
            /*
             * Estimate the index size.  If it's not a partial index, we lock
             * the number-of-tuples estimate to equal the parent table; if it
             * is partial then we have to use the same methods as we would for
             * a table, except we can be sure that the index is not larger
             * than the table.  We must ignore partitioned indexes here as
             * there are not physical indexes.
             */
            if (indexRelation->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
            {
                if (info->indpred == NIL)
                {
                    info->pages = RelationGetNumberOfBlocks(indexRelation);
                    info->tuples = rel->tuples;
                }
                else
                {
                    double      allvisfrac; /* dummy */
 
                    estimate_rel_size(indexRelation, NULL,
                                      &info->pages, &info->tuples, &allvisfrac);
                    if (info->tuples > rel->tuples)
                        info->tuples = rel->tuples;
                }
 
                if (info->relam == BTREE_AM_OID)
                {
                    /*
                     * For btrees, get tree height while we have the index
                     * open
                     */
                    info->tree_height = _bt_getrootheight(indexRelation);
                }
                else
                {
                    /* For other index types, just set it to "unknown" for now */
                    info->tree_height = -1;
                }
            }
            else
            {
                /* Zero these out for partitioned indexes */
                info->pages = 0;
                info->tuples = 0.0;
                info->tree_height = -1;
            }
 
            index_close(indexRelation, NoLock);
 
            /*
             * We've historically used lcons() here.  It'd make more sense to
             * use lappend(), but that causes the planner to change behavior
             * in cases where two indexes seem equally attractive.  For now,
             * stick with lcons() --- few tables should have so many indexes
             * that the O(N^2) behavior of lcons() is really a problem.
             */
            indexinfos = lcons(info, indexinfos);
        }
 
        list_free(indexoidlist);
    }
 
    rel->indexlist = indexinfos;
 
    rel->statlist = get_relation_statistics(rel, relation);
 
    /* Grab foreign-table info using the relcache, while we have it */
    if (relation->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
    {
        rel->serverid = GetForeignServerIdByRelId(RelationGetRelid(relation));
        rel->fdwroutine = GetFdwRoutineForRelation(relation, true);
    }
    else
    {
        rel->serverid = InvalidOid;
        rel->fdwroutine = NULL;
    }
 
    /* Collect info about relation's foreign keys, if relevant */
    get_relation_foreign_keys(root, rel, relation, inhparent);
 
    /* Collect info about functions implemented by the rel's table AM. */
    if (relation->rd_tableam &&
        relation->rd_tableam->scan_set_tidrange != NULL &&
        relation->rd_tableam->scan_getnextslot_tidrange != NULL)
        rel->amflags |= AMFLAG_HAS_TID_RANGE;
 
    /*
     * Collect info about relation's partitioning scheme, if any. Only
     * inheritance parents may be partitioned.
     */
    if (inhparent && relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
        set_relation_partition_info(root, rel, relation);
 
    table_close(relation, NoLock);
 
    /*
     * Allow a plugin to editorialize on the info we obtained from the
     * catalogs.  Actions might include altering the assumed relation size,
     * removing an index, or adding a hypothetical index to the indexlist.
     */
    if (get_relation_info_hook)
        (*get_relation_info_hook) (root, relationObjectId, inhparent, rel);
}
 
/*
 * get_relation_foreign_keys -
 *    Retrieves foreign key information for a given relation.
 *
 * ForeignKeyOptInfos for relevant foreign keys are created and added to
 * root->fkey_list.  We do this now while we have the relcache entry open.
 * We could sometimes avoid making useless ForeignKeyOptInfos if we waited
 * until all RelOptInfos have been built, but the cost of re-opening the
 * relcache entries would probably exceed any savings.
 */
static void
get_relation_foreign_keys(PlannerInfo *root, RelOptInfo *rel,
                          Relation relation, bool inhparent)
{
    List       *rtable = root->parse->rtable;
    List       *cachedfkeys;
    ListCell   *lc;
 
    /*
     * If it's not a baserel, we don't care about its FKs.  Also, if the query
     * references only a single relation, we can skip the lookup since no FKs
     * could satisfy the requirements below.
     */
    if (rel->reloptkind != RELOPT_BASEREL ||
        list_length(rtable) < 2)
        return;
 
    /*
     * If it's the parent of an inheritance tree, ignore its FKs.  We could
     * make useful FK-based deductions if we found that all members of the
     * inheritance tree have equivalent FK constraints, but detecting that
     * would require code that hasn't been written.
     */
    if (inhparent)
        return;
 
    /*
     * Extract data about relation's FKs from the relcache.  Note that this
     * list belongs to the relcache and might disappear in a cache flush, so
     * we must not do any further catalog access within this function.
     */
    cachedfkeys = RelationGetFKeyList(relation);
 
    /*
     * Figure out which FKs are of interest for this query, and create
     * ForeignKeyOptInfos for them.  We want only FKs that reference some
     * other RTE of the current query.  In queries containing self-joins,
     * there might be more than one other RTE for a referenced table, and we
     * should make a ForeignKeyOptInfo for each occurrence.
     *
     * Ideally, we would ignore RTEs that correspond to non-baserels, but it's
     * too hard to identify those here, so we might end up making some useless
     * ForeignKeyOptInfos.  If so, match_foreign_keys_to_quals() will remove
     * them again.
     */
    foreach(lc, cachedfkeys)
    {
        ForeignKeyCacheInfo *cachedfk = (ForeignKeyCacheInfo *) lfirst(lc);
        Index       rti;
        ListCell   *lc2;
 
        /* conrelid should always be that of the table we're considering */
        Assert(cachedfk->conrelid == RelationGetRelid(relation));
 
        /* Scan to find other RTEs matching confrelid */
        rti = 0;
        foreach(lc2, rtable)
        {
            RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc2);
            ForeignKeyOptInfo *info;
 
            rti++;
            /* Ignore if not the correct table */
            if (rte->rtekind != RTE_RELATION ||
                rte->relid != cachedfk->confrelid)
                continue;
            /* Ignore if it's an inheritance parent; doesn't really match */
            if (rte->inh)
                continue;
            /* Ignore self-referential FKs; we only care about joins */
            if (rti == rel->relid)
                continue;
 
            /* OK, let's make an entry */
            info = makeNode(ForeignKeyOptInfo);
            info->con_relid = rel->relid;
            info->ref_relid = rti;
            info->nkeys = cachedfk->nkeys;
            memcpy(info->conkey, cachedfk->conkey, sizeof(info->conkey));
            memcpy(info->confkey, cachedfk->confkey, sizeof(info->confkey));
            memcpy(info->conpfeqop, cachedfk->conpfeqop, sizeof(info->conpfeqop));
            /* zero out fields to be filled by match_foreign_keys_to_quals */
            info->nmatched_ec = 0;
            info->nconst_ec = 0;
            info->nmatched_rcols = 0;
            info->nmatched_ri = 0;
            memset(info->eclass, 0, sizeof(info->eclass));
            memset(info->fk_eclass_member, 0, sizeof(info->fk_eclass_member));
            memset(info->rinfos, 0, sizeof(info->rinfos));
 
            root->fkey_list = lappend(root->fkey_list, info);
        }
    }
}
 
/*
 * infer_arbiter_indexes -
 *    Determine the unique indexes used to arbitrate speculative insertion.
 *
 * Uses user-supplied inference clause expressions and predicate to match a
 * unique index from those defined and ready on the heap relation (target).
 * An exact match is required on columns/expressions (although they can appear
 * in any order).  However, the predicate given by the user need only restrict
 * insertion to a subset of some part of the table covered by some particular
 * unique index (in particular, a partial unique index) in order to be
 * inferred.
 *
 * The implementation does not consider which B-Tree operator class any
 * particular available unique index attribute uses, unless one was specified
 * in the inference specification. The same is true of collations.  In
 * particular, there is no system dependency on the default operator class for
 * the purposes of inference.  If no opclass (or collation) is specified, then
 * all matching indexes (that may or may not match the default in terms of
 * each attribute opclass/collation) are used for inference.
 */
List *
infer_arbiter_indexes(PlannerInfo *root)
{
    OnConflictExpr *onconflict = root->parse->onConflict;
 
    /* Iteration state */
    RangeTblEntry *rte;
    Relation    relation;
    Oid         indexOidFromConstraint = InvalidOid;
    List       *indexList;
    ListCell   *l;
 
    /* Normalized inference attributes and inference expressions: */
    Bitmapset  *inferAttrs = NULL;
    List       *inferElems = NIL;
 
    /* Results */
    List       *results = NIL;
 
    /*
     * Quickly return NIL for ON CONFLICT DO NOTHING without an inference
     * specification or named constraint.  ON CONFLICT DO UPDATE statements
     * must always provide one or the other (but parser ought to have caught
     * that already).
     */
    if (onconflict->arbiterElems == NIL &&
        onconflict->constraint == InvalidOid)
        return NIL;
 
    /*
     * We need not lock the relation since it was already locked, either by
     * the rewriter or when expand_inherited_rtentry() added it to the query's
     * rangetable.
     */
    rte = rt_fetch(root->parse->resultRelation, root->parse->rtable);
 
    relation = table_open(rte->relid, NoLock);
 
    /*
     * Build normalized/BMS representation of plain indexed attributes, as
     * well as a separate list of expression items.  This simplifies matching
     * the cataloged definition of indexes.
     */
    foreach(l, onconflict->arbiterElems)
    {
        InferenceElem *elem = (InferenceElem *) lfirst(l);
        Var        *var;
        int         attno;
 
        if (!IsA(elem->expr, Var))
        {
            /* If not a plain Var, just shove it in inferElems for now */
            inferElems = lappend(inferElems, elem->expr);
            continue;
        }
 
        var = (Var *) elem->expr;
        attno = var->varattno;
 
        if (attno == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("whole row unique index inference specifications are not supported")));
 
        inferAttrs = bms_add_member(inferAttrs,
                                    attno - FirstLowInvalidHeapAttributeNumber);
    }
 
    /*
     * Lookup named constraint's index.  This is not immediately returned
     * because some additional sanity checks are required.
     */
    if (onconflict->constraint != InvalidOid)
    {
        indexOidFromConstraint = get_constraint_index(onconflict->constraint);
 
        if (indexOidFromConstraint == InvalidOid)
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("constraint in ON CONFLICT clause has no associated index")));
    }
 
    /*
     * Using that representation, iterate through the list of indexes on the
     * target relation to try and find a match
     */
    indexList = RelationGetIndexList(relation);
 
    foreach(l, indexList)
    {
        Oid         indexoid = lfirst_oid(l);
        Relation    idxRel;
        Form_pg_index idxForm;
        Bitmapset  *indexedAttrs;
        List       *idxExprs;
        List       *predExprs;
        AttrNumber  natt;
        ListCell   *el;
 
        /*
         * Extract info from the relation descriptor for the index.  Obtain
         * the same lock type that the executor will ultimately use.
         *
         * Let executor complain about !indimmediate case directly, because
         * enforcement needs to occur there anyway when an inference clause is
         * omitted.
         */
        idxRel = index_open(indexoid, rte->rellockmode);
        idxForm = idxRel->rd_index;
 
        if (!idxForm->indisvalid)
            goto next;
 
        /*
         * Note that we do not perform a check against indcheckxmin (like e.g.
         * get_relation_info()) here to eliminate candidates, because
         * uniqueness checking only cares about the most recently committed
         * tuple versions.
         */
 
        /*
         * Look for match on "ON constraint_name" variant, which may not be
         * unique constraint.  This can only be a constraint name.
         */
        if (indexOidFromConstraint == idxForm->indexrelid)
        {
            if (!idxForm->indisunique && onconflict->action == ONCONFLICT_UPDATE)
                ereport(ERROR,
                        (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                         errmsg("ON CONFLICT DO UPDATE not supported with exclusion constraints")));
 
            results = lappend_oid(results, idxForm->indexrelid);
            list_free(indexList);
            index_close(idxRel, NoLock);
            table_close(relation, NoLock);
            return results;
        }
        else if (indexOidFromConstraint != InvalidOid)
        {
            /* No point in further work for index in named constraint case */
            goto next;
        }
 
        /*
         * Only considering conventional inference at this point (not named
         * constraints), so index under consideration can be immediately
         * skipped if it's not unique
         */
        if (!idxForm->indisunique)
            goto next;
 
        /* Build BMS representation of plain (non expression) index attrs */
        indexedAttrs = NULL;
        for (natt = 0; natt < idxForm->indnkeyatts; natt++)
        {
            int         attno = idxRel->rd_index->indkey.values[natt];
 
            if (attno != 0)
                indexedAttrs = bms_add_member(indexedAttrs,
                                              attno - FirstLowInvalidHeapAttributeNumber);
        }
 
        /* Non-expression attributes (if any) must match */
        if (!bms_equal(indexedAttrs, inferAttrs))
            goto next;
 
        /* Expression attributes (if any) must match */
        idxExprs = RelationGetIndexExpressions(idxRel);
        foreach(el, onconflict->arbiterElems)
        {
            InferenceElem *elem = (InferenceElem *) lfirst(el);
 
            /*
             * Ensure that collation/opclass aspects of inference expression
             * element match.  Even though this loop is primarily concerned
             * with matching expressions, it is a convenient point to check
             * this for both expressions and ordinary (non-expression)
             * attributes appearing as inference elements.
             */
            if (!infer_collation_opclass_match(elem, idxRel, idxExprs))
                goto next;
 
            /*
             * Plain Vars don't factor into count of expression elements, and
             * the question of whether or not they satisfy the index
             * definition has already been considered (they must).
             */
            if (IsA(elem->expr, Var))
                continue;
 
            /*
             * Might as well avoid redundant check in the rare cases where
             * infer_collation_opclass_match() is required to do real work.
             * Otherwise, check that element expression appears in cataloged
             * index definition.
             */
            if (elem->infercollid != InvalidOid ||
                elem->inferopclass != InvalidOid ||
                list_member(idxExprs, elem->expr))
                continue;
 
            goto next;
        }
 
        /*
         * Now that all inference elements were matched, ensure that the
         * expression elements from inference clause are not missing any
         * cataloged expressions.  This does the right thing when unique
         * indexes redundantly repeat the same attribute, or if attributes
         * redundantly appear multiple times within an inference clause.
         */
        if (list_difference(idxExprs, inferElems) != NIL)
            goto next;
 
        /*
         * If it's a partial index, its predicate must be implied by the ON
         * CONFLICT's WHERE clause.
         */
        predExprs = RelationGetIndexPredicate(idxRel);
 
        if (!predicate_implied_by(predExprs, (List *) onconflict->arbiterWhere, false))
            goto next;
 
        results = lappend_oid(results, idxForm->indexrelid);
next:
        index_close(idxRel, NoLock);
    }
 
    list_free(indexList);
    table_close(relation, NoLock);
 
    if (results == NIL)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
                 errmsg("there is no unique or exclusion constraint matching the ON CONFLICT specification")));
 
    return results;
}
 
/*
 * infer_collation_opclass_match - ensure infer element opclass/collation match
 *
 * Given unique index inference element from inference specification, if
 * collation was specified, or if opclass was specified, verify that there is
 * at least one matching indexed attribute (occasionally, there may be more).
 * Skip this in the common case where inference specification does not include
 * collation or opclass (instead matching everything, regardless of cataloged
 * collation/opclass of indexed attribute).
 *
 * At least historically, Postgres has not offered collations or opclasses
 * with alternative-to-default notions of equality, so these additional
 * criteria should only be required infrequently.
 *
 * Don't give up immediately when an inference element matches some attribute
 * cataloged as indexed but not matching additional opclass/collation
 * criteria.  This is done so that the implementation is as forgiving as
 * possible of redundancy within cataloged index attributes (or, less
 * usefully, within inference specification elements).  If collations actually
 * differ between apparently redundantly indexed attributes (redundant within
 * or across indexes), then there really is no redundancy as such.
 *
 * Note that if an inference element specifies an opclass and a collation at
 * once, both must match in at least one particular attribute within index
 * catalog definition in order for that inference element to be considered
 * inferred/satisfied.
 */
static bool
infer_collation_opclass_match(InferenceElem *elem, Relation idxRel,
                              List *idxExprs)
{
    AttrNumber  natt;
    Oid         inferopfamily = InvalidOid; /* OID of opclass opfamily */
    Oid         inferopcinputtype = InvalidOid; /* OID of opclass input type */
    int         nplain = 0;     /* # plain attrs observed */
 
    /*
     * If inference specification element lacks collation/opclass, then no
     * need to check for exact match.
     */
    if (elem->infercollid == InvalidOid && elem->inferopclass == InvalidOid)
        return true;
 
    /*
     * Lookup opfamily and input type, for matching indexes
     */
    if (elem->inferopclass)
    {
        inferopfamily = get_opclass_family(elem->inferopclass);
        inferopcinputtype = get_opclass_input_type(elem->inferopclass);
    }
 
    for (natt = 1; natt <= idxRel->rd_att->natts; natt++)
    {
        Oid         opfamily = idxRel->rd_opfamily[natt - 1];
        Oid         opcinputtype = idxRel->rd_opcintype[natt - 1];
        Oid         collation = idxRel->rd_indcollation[natt - 1];
        int         attno = idxRel->rd_index->indkey.values[natt - 1];
 
        if (attno != 0)
            nplain++;
 
        if (elem->inferopclass != InvalidOid &&
            (inferopfamily != opfamily || inferopcinputtype != opcinputtype))
        {
            /* Attribute needed to match opclass, but didn't */
            continue;
        }
 
        if (elem->infercollid != InvalidOid &&
            elem->infercollid != collation)
        {
            /* Attribute needed to match collation, but didn't */
            continue;
        }
 
        /* If one matching index att found, good enough -- return true */
        if (IsA(elem->expr, Var))
        {
            if (((Var *) elem->expr)->varattno == attno)
                return true;
        }
        else if (attno == 0)
        {
            Node       *nattExpr = list_nth(idxExprs, (natt - 1) - nplain);
 
            /*
             * Note that unlike routines like match_index_to_operand() we
             * don't need to care about RelabelType.  Neither the index
             * definition nor the inference clause should contain them.
             */
            if (equal(elem->expr, nattExpr))
                return true;
        }
    }
 
    return false;
}
 
/*
 * estimate_rel_size - estimate # pages and # tuples in a table or index
 *
 * We also estimate the fraction of the pages that are marked all-visible in
 * the visibility map, for use in estimation of index-only scans.
 *
 * If attr_widths isn't NULL, it points to the zero-index entry of the
 * relation's attr_widths[] cache; we fill this in if we have need to compute
 * the attribute widths for estimation purposes.
 */
void
estimate_rel_size(Relation rel, int32 *attr_widths,
                  BlockNumber *pages, double *tuples, double *allvisfrac)
{
    BlockNumber curpages;
    BlockNumber relpages;
    double      reltuples;
    BlockNumber relallvisible;
    double      density;
 
    if (RELKIND_HAS_TABLE_AM(rel->rd_rel->relkind))
    {
        table_relation_estimate_size(rel, attr_widths, pages, tuples,
                                     allvisfrac);
    }
    else if (rel->rd_rel->relkind == RELKIND_INDEX)
    {
        /*
         * XXX: It'd probably be good to move this into a callback, individual
         * index types e.g. know if they have a metapage.
         */
 
        /* it has storage, ok to call the smgr */
        curpages = RelationGetNumberOfBlocks(rel);
 
        /* report estimated # pages */
        *pages = curpages;
        /* quick exit if rel is clearly empty */
        if (curpages == 0)
        {
            *tuples = 0;
            *allvisfrac = 0;
            return;
        }
 
        /* coerce values in pg_class to more desirable types */
        relpages = (BlockNumber) rel->rd_rel->relpages;
        reltuples = (double) rel->rd_rel->reltuples;
        relallvisible = (BlockNumber) rel->rd_rel->relallvisible;
 
        /*
         * Discount the metapage while estimating the number of tuples. This
         * is a kluge because it assumes more than it ought to about index
         * structure.  Currently it's OK for btree, hash, and GIN indexes but
         * suspect for GiST indexes.
         */
        if (relpages > 0)
        {
            curpages--;
            relpages--;
        }
 
        /* estimate number of tuples from previous tuple density */
        if (reltuples >= 0 && relpages > 0)
            density = reltuples / (double) relpages;
        else
        {
            /*
             * If we have no data because the relation was never vacuumed,
             * estimate tuple width from attribute datatypes.  We assume here
             * that the pages are completely full, which is OK for tables
             * (since they've presumably not been VACUUMed yet) but is
             * probably an overestimate for indexes.  Fortunately
             * get_relation_info() can clamp the overestimate to the parent
             * table's size.
             *
             * Note: this code intentionally disregards alignment
             * considerations, because (a) that would be gilding the lily
             * considering how crude the estimate is, and (b) it creates
             * platform dependencies in the default plans which are kind of a
             * headache for regression testing.
             *
             * XXX: Should this logic be more index specific?
             */
            int32       tuple_width;
 
            tuple_width = get_rel_data_width(rel, attr_widths);
            tuple_width += MAXALIGN(SizeofHeapTupleHeader);
            tuple_width += sizeof(ItemIdData);
            /* note: integer division is intentional here */
            density = (BLCKSZ - SizeOfPageHeaderData) / tuple_width;
        }
        *tuples = rint(density * (double) curpages);
 
        /*
         * We use relallvisible as-is, rather than scaling it up like we do
         * for the pages and tuples counts, on the theory that any pages added
         * since the last VACUUM are most likely not marked all-visible.  But
         * costsize.c wants it converted to a fraction.
         */
        if (relallvisible == 0 || curpages <= 0)
            *allvisfrac = 0;
        else if ((double) relallvisible >= curpages)
            *allvisfrac = 1;
        else
            *allvisfrac = (double) relallvisible / curpages;
    }
    else
    {
        /*
         * Just use whatever's in pg_class.  This covers foreign tables,
         * sequences, and also relkinds without storage (shouldn't get here?);
         * see initializations in AddNewRelationTuple().  Note that FDW must
         * cope if reltuples is -1!
         */
        *pages = rel->rd_rel->relpages;
        *tuples = rel->rd_rel->reltuples;
        *allvisfrac = 0;
    }
}
 
 
/*
 * get_rel_data_width
 *
 * Estimate the average width of (the data part of) the relation's tuples.
 *
 * If attr_widths isn't NULL, it points to the zero-index entry of the
 * relation's attr_widths[] cache; use and update that cache as appropriate.
 *
 * Currently we ignore dropped columns.  Ideally those should be included
 * in the result, but we haven't got any way to get info about them; and
 * since they might be mostly NULLs, treating them as zero-width is not
 * necessarily the wrong thing anyway.
 */
int32
get_rel_data_width(Relation rel, int32 *attr_widths)
{
    int64       tuple_width = 0;
    int         i;
 
    for (i = 1; i <= RelationGetNumberOfAttributes(rel); i++)
    {
        Form_pg_attribute att = TupleDescAttr(rel->rd_att, i - 1);
        int32       item_width;
 
        if (att->attisdropped)
            continue;
 
        /* use previously cached data, if any */
        if (attr_widths != NULL && attr_widths[i] > 0)
        {
            tuple_width += attr_widths[i];
            continue;
        }
 
        /* This should match set_rel_width() in costsize.c */
        item_width = get_attavgwidth(RelationGetRelid(rel), i);
        if (item_width <= 0)
        {
            item_width = get_typavgwidth(att->atttypid, att->atttypmod);
            Assert(item_width > 0);
        }
        if (attr_widths != NULL)
            attr_widths[i] = item_width;
        tuple_width += item_width;
    }
 
    return clamp_width_est(tuple_width);
}
 
/*
 * get_relation_data_width
 *
 * External API for get_rel_data_width: same behavior except we have to
 * open the relcache entry.
 */
int32
get_relation_data_width(Oid relid, int32 *attr_widths)
{
    int32       result;
    Relation    relation;
 
    /* As above, assume relation is already locked */
    relation = table_open(relid, NoLock);
 
    result = get_rel_data_width(relation, attr_widths);
 
    table_close(relation, NoLock);
 
    return result;
}
 
 
/*
 * get_relation_constraints
 *
 * Retrieve the applicable constraint expressions of the given relation.
 *
 * Returns a List (possibly empty) of constraint expressions.  Each one
 * has been canonicalized, and its Vars are changed to have the varno
 * indicated by rel->relid.  This allows the expressions to be easily
 * compared to expressions taken from WHERE.
 *
 * If include_noinherit is true, it's okay to include constraints that
 * are marked NO INHERIT.
 *
 * If include_notnull is true, "col IS NOT NULL" expressions are generated
 * and added to the result for each column that's marked attnotnull.
 *
 * If include_partition is true, and the relation is a partition,
 * also include the partitioning constraints.
 *
 * Note: at present this is invoked at most once per relation per planner
 * run, and in many cases it won't be invoked at all, so there seems no
 * point in caching the data in RelOptInfo.
 */
static List *
get_relation_constraints(PlannerInfo *root,
                         Oid relationObjectId, RelOptInfo *rel,
                         bool include_noinherit,
                         bool include_notnull,
                         bool include_partition)
{
    List       *result = NIL;
    Index       varno = rel->relid;
    Relation    relation;
    TupleConstr *constr;
 
    /*
     * We assume the relation has already been safely locked.
     */
    relation = table_open(relationObjectId, NoLock);
 
    constr = relation->rd_att->constr;
    if (constr != NULL)
    {
        int         num_check = constr->num_check;
        int         i;
 
        for (i = 0; i < num_check; i++)
        {
            Node       *cexpr;
 
            /*
             * If this constraint hasn't been fully validated yet, we must
             * ignore it here.  Also ignore if NO INHERIT and we weren't told
             * that that's safe.
             */
            if (!constr->check[i].ccvalid)
                continue;
            if (constr->check[i].ccnoinherit && !include_noinherit)
                continue;
 
            cexpr = stringToNode(constr->check[i].ccbin);
 
            /*
             * Run each expression through const-simplification and
             * canonicalization.  This is not just an optimization, but is
             * necessary, because we will be comparing it to
             * similarly-processed qual clauses, and may fail to detect valid
             * matches without this.  This must match the processing done to
             * qual clauses in preprocess_expression()!  (We can skip the
             * stuff involving subqueries, however, since we don't allow any
             * in check constraints.)
             */
            cexpr = eval_const_expressions(root, cexpr);
 
            cexpr = (Node *) canonicalize_qual((Expr *) cexpr, true);
 
            /* Fix Vars to have the desired varno */
            if (varno != 1)
                ChangeVarNodes(cexpr, 1, varno, 0);
 
            /*
             * Finally, convert to implicit-AND format (that is, a List) and
             * append the resulting item(s) to our output list.
             */
            result = list_concat(result,
                                 make_ands_implicit((Expr *) cexpr));
        }
 
        /* Add NOT NULL constraints in expression form, if requested */
        if (include_notnull && constr->has_not_null)
        {
            int         natts = relation->rd_att->natts;
 
            for (i = 1; i <= natts; i++)
            {
                Form_pg_attribute att = TupleDescAttr(relation->rd_att, i - 1);
 
                if (att->attnotnull && !att->attisdropped)
                {
                    NullTest   *ntest = makeNode(NullTest);
 
                    ntest->arg = (Expr *) makeVar(varno,
                                                  i,
                                                  att->atttypid,
                                                  att->atttypmod,
                                                  att->attcollation,
                                                  0);
                    ntest->nulltesttype = IS_NOT_NULL;
 
                    /*
                     * argisrow=false is correct even for a composite column,
                     * because attnotnull does not represent a SQL-spec IS NOT
                     * NULL test in such a case, just IS DISTINCT FROM NULL.
                     */
                    ntest->argisrow = false;
                    ntest->location = -1;
                    result = lappend(result, ntest);
                }
            }
        }
    }
 
    /*
     * Add partitioning constraints, if requested.
     */
    if (include_partition && relation->rd_rel->relispartition)
    {
        /* make sure rel->partition_qual is set */
        set_baserel_partition_constraint(relation, rel);
        result = list_concat(result, rel->partition_qual);
    }
 
    table_close(relation, NoLock);
 
    return result;
}
 
/*
 * Try loading data for the statistics object.
 *
 * We don't know if the data (specified by statOid and inh value) exist.
 * The result is stored in stainfos list.
 */
static void
get_relation_statistics_worker(List **stainfos, RelOptInfo *rel,
                               Oid statOid, bool inh,
                               Bitmapset *keys, List *exprs)
{
    Form_pg_statistic_ext_data dataForm;
    HeapTuple   dtup;
 
    dtup = SearchSysCache2(STATEXTDATASTXOID,
                           ObjectIdGetDatum(statOid), BoolGetDatum(inh));
    if (!HeapTupleIsValid(dtup))
        return;
 
    dataForm = (Form_pg_statistic_ext_data) GETSTRUCT(dtup);
 
    /* add one StatisticExtInfo for each kind built */
    if (statext_is_kind_built(dtup, STATS_EXT_NDISTINCT))
    {
        StatisticExtInfo *info = makeNode(StatisticExtInfo);
 
        info->statOid = statOid;
        info->inherit = dataForm->stxdinherit;
        info->rel = rel;
        info->kind = STATS_EXT_NDISTINCT;
        info->keys = bms_copy(keys);
        info->exprs = exprs;
 
        *stainfos = lappend(*stainfos, info);
    }
 
    if (statext_is_kind_built(dtup, STATS_EXT_DEPENDENCIES))
    {
        StatisticExtInfo *info = makeNode(StatisticExtInfo);
 
        info->statOid = statOid;
        info->inherit = dataForm->stxdinherit;
        info->rel = rel;
        info->kind = STATS_EXT_DEPENDENCIES;
        info->keys = bms_copy(keys);
        info->exprs = exprs;
 
        *stainfos = lappend(*stainfos, info);
    }
 
    if (statext_is_kind_built(dtup, STATS_EXT_MCV))
    {
        StatisticExtInfo *info = makeNode(StatisticExtInfo);
 
        info->statOid = statOid;
        info->inherit = dataForm->stxdinherit;
        info->rel = rel;
        info->kind = STATS_EXT_MCV;
        info->keys = bms_copy(keys);
        info->exprs = exprs;
 
        *stainfos = lappend(*stainfos, info);
    }
 
    if (statext_is_kind_built(dtup, STATS_EXT_EXPRESSIONS))
    {
        StatisticExtInfo *info = makeNode(StatisticExtInfo);
 
        info->statOid = statOid;
        info->inherit = dataForm->stxdinherit;
        info->rel = rel;
        info->kind = STATS_EXT_EXPRESSIONS;
        info->keys = bms_copy(keys);
        info->exprs = exprs;
 
        *stainfos = lappend(*stainfos, info);
    }
 
    ReleaseSysCache(dtup);
}
 
/*
 * get_relation_statistics
 *      Retrieve extended statistics defined on the table.
 *
 * Returns a List (possibly empty) of StatisticExtInfo objects describing
 * the statistics.  Note that this doesn't load the actual statistics data,
 * just the identifying metadata.  Only stats actually built are considered.
 */
static List *
get_relation_statistics(RelOptInfo *rel, Relation relation)
{
    Index       varno = rel->relid;
    List       *statoidlist;
    List       *stainfos = NIL;
    ListCell   *l;
 
    statoidlist = RelationGetStatExtList(relation);
 
    foreach(l, statoidlist)
    {
        Oid         statOid = lfirst_oid(l);
        Form_pg_statistic_ext staForm;
        HeapTuple   htup;
        Bitmapset  *keys = NULL;
        List       *exprs = NIL;
        int         i;
 
        htup = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(statOid));
        if (!HeapTupleIsValid(htup))
            elog(ERROR, "cache lookup failed for statistics object %u", statOid);
        staForm = (Form_pg_statistic_ext) GETSTRUCT(htup);
 
        /*
         * First, build the array of columns covered.  This is ultimately
         * wasted if no stats within the object have actually been built, but
         * it doesn't seem worth troubling over that case.
         */
        for (i = 0; i < staForm->stxkeys.dim1; i++)
            keys = bms_add_member(keys, staForm->stxkeys.values[i]);
 
        /*
         * Preprocess expressions (if any). We read the expressions, run them
         * through eval_const_expressions, and fix the varnos.
         *
         * XXX We don't know yet if there are any data for this stats object,
         * with either stxdinherit value. But it's reasonable to assume there
         * is at least one of those, possibly both. So it's better to process
         * keys and expressions here.
         */
        {
            bool        isnull;
            Datum       datum;
 
            /* decode expression (if any) */
            datum = SysCacheGetAttr(STATEXTOID, htup,
                                    Anum_pg_statistic_ext_stxexprs, &isnull);
 
            if (!isnull)
            {
                char       *exprsString;
 
                exprsString = TextDatumGetCString(datum);
                exprs = (List *) stringToNode(exprsString);
                pfree(exprsString);
 
                /*
                 * Run the expressions through eval_const_expressions. This is
                 * not just an optimization, but is necessary, because the
                 * planner will be comparing them to similarly-processed qual
                 * clauses, and may fail to detect valid matches without this.
                 * We must not use canonicalize_qual, however, since these
                 * aren't qual expressions.
                 */
                exprs = (List *) eval_const_expressions(NULL, (Node *) exprs);
 
                /* May as well fix opfuncids too */
                fix_opfuncids((Node *) exprs);
 
                /*
                 * Modify the copies we obtain from the relcache to have the
                 * correct varno for the parent relation, so that they match
                 * up correctly against qual clauses.
                 */
                if (varno != 1)
                    ChangeVarNodes((Node *) exprs, 1, varno, 0);
            }
        }
 
        /* extract statistics for possible values of stxdinherit flag */
 
        get_relation_statistics_worker(&stainfos, rel, statOid, true, keys, exprs);
 
        get_relation_statistics_worker(&stainfos, rel, statOid, false, keys, exprs);
 
        ReleaseSysCache(htup);
        bms_free(keys);
    }
 
    list_free(statoidlist);
 
    return stainfos;
}
 
/*
 * relation_excluded_by_constraints
 *
 * Detect whether the relation need not be scanned because it has either
 * self-inconsistent restrictions, or restrictions inconsistent with the
 * relation's applicable constraints.
 *
 * Note: this examines only rel->relid, rel->reloptkind, and
 * rel->baserestrictinfo; therefore it can be called before filling in
 * other fields of the RelOptInfo.
 */
bool
relation_excluded_by_constraints(PlannerInfo *root,
                                 RelOptInfo *rel, RangeTblEntry *rte)
{
    bool        include_noinherit;
    bool        include_notnull;
    bool        include_partition = false;
    List       *safe_restrictions;
    List       *constraint_pred;
    List       *safe_constraints;
    ListCell   *lc;
 
    /* As of now, constraint exclusion works only with simple relations. */
    Assert(IS_SIMPLE_REL(rel));
 
    /*
     * If there are no base restriction clauses, we have no hope of proving
     * anything below, so fall out quickly.
     */
    if (rel->baserestrictinfo == NIL)
        return false;
 
    /*
     * Regardless of the setting of constraint_exclusion, detect
     * constant-FALSE-or-NULL restriction clauses.  Although const-folding
     * will reduce "anything AND FALSE" to just "FALSE", the baserestrictinfo
     * list can still have other members besides the FALSE constant, due to
     * qual pushdown and other mechanisms; so check them all.  This doesn't
     * fire very often, but it seems cheap enough to be worth doing anyway.
     * (Without this, we'd miss some optimizations that 9.5 and earlier found
     * via much more roundabout methods.)
     */
    foreach(lc, rel->baserestrictinfo)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
        Expr       *clause = rinfo->clause;
 
        if (clause && IsA(clause, Const) &&
            (((Const *) clause)->constisnull ||
             !DatumGetBool(((Const *) clause)->constvalue)))
            return true;
    }
 
    /*
     * Skip further tests, depending on constraint_exclusion.
     */
    switch (constraint_exclusion)
    {
        case CONSTRAINT_EXCLUSION_OFF:
            /* In 'off' mode, never make any further tests */
            return false;
 
        case CONSTRAINT_EXCLUSION_PARTITION:
 
            /*
             * When constraint_exclusion is set to 'partition' we only handle
             * appendrel members.  Partition pruning has already been applied,
             * so there is no need to consider the rel's partition constraints
             * here.
             */
            if (rel->reloptkind == RELOPT_OTHER_MEMBER_REL)
                break;          /* appendrel member, so process it */
            return false;
 
        case CONSTRAINT_EXCLUSION_ON:
 
            /*
             * In 'on' mode, always apply constraint exclusion.  If we are
             * considering a baserel that is a partition (i.e., it was
             * directly named rather than expanded from a parent table), then
             * its partition constraints haven't been considered yet, so
             * include them in the processing here.
             */
            if (rel->reloptkind == RELOPT_BASEREL)
                include_partition = true;
            break;              /* always try to exclude */
    }
 
    /*
     * Check for self-contradictory restriction clauses.  We dare not make
     * deductions with non-immutable functions, but any immutable clauses that
     * are self-contradictory allow us to conclude the scan is unnecessary.
     *
     * Note: strip off RestrictInfo because predicate_refuted_by() isn't
     * expecting to see any in its predicate argument.
     */
    safe_restrictions = NIL;
    foreach(lc, rel->baserestrictinfo)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
        if (!contain_mutable_functions((Node *) rinfo->clause))
            safe_restrictions = lappend(safe_restrictions, rinfo->clause);
    }
 
    /*
     * We can use weak refutation here, since we're comparing restriction
     * clauses with restriction clauses.
     */
    if (predicate_refuted_by(safe_restrictions, safe_restrictions, true))
        return true;
 
    /*
     * Only plain relations have constraints, so stop here for other rtekinds.
     */
    if (rte->rtekind != RTE_RELATION)
        return false;
 
    /*
     * If we are scanning just this table, we can use NO INHERIT constraints,
     * but not if we're scanning its children too.  (Note that partitioned
     * tables should never have NO INHERIT constraints; but it's not necessary
     * for us to assume that here.)
     */
    include_noinherit = !rte->inh;
 
    /*
     * Currently, attnotnull constraints must be treated as NO INHERIT unless
     * this is a partitioned table.  In future we might track their
     * inheritance status more accurately, allowing this to be refined.
     *
     * XXX do we need/want to change this?
     */
    include_notnull = (!rte->inh || rte->relkind == RELKIND_PARTITIONED_TABLE);
 
    /*
     * Fetch the appropriate set of constraint expressions.
     */
    constraint_pred = get_relation_constraints(root, rte->relid, rel,
                                               include_noinherit,
                                               include_notnull,
                                               include_partition);
 
    /*
     * We do not currently enforce that CHECK constraints contain only
     * immutable functions, so it's necessary to check here. We daren't draw
     * conclusions from plan-time evaluation of non-immutable functions. Since
     * they're ANDed, we can just ignore any mutable constraints in the list,
     * and reason about the rest.
     */
    safe_constraints = NIL;
    foreach(lc, constraint_pred)
    {
        Node       *pred = (Node *) lfirst(lc);
 
        if (!contain_mutable_functions(pred))
            safe_constraints = lappend(safe_constraints, pred);
    }
 
    /*
     * The constraints are effectively ANDed together, so we can just try to
     * refute the entire collection at once.  This may allow us to make proofs
     * that would fail if we took them individually.
     *
     * Note: we use rel->baserestrictinfo, not safe_restrictions as might seem
     * an obvious optimization.  Some of the clauses might be OR clauses that
     * have volatile and nonvolatile subclauses, and it's OK to make
     * deductions with the nonvolatile parts.
     *
     * We need strong refutation because we have to prove that the constraints
     * would yield false, not just NULL.
     */
    if (predicate_refuted_by(safe_constraints, rel->baserestrictinfo, false))
        return true;
 
    return false;
}
 
 
/*
 * build_physical_tlist
 *
 * Build a targetlist consisting of exactly the relation's user attributes,
 * in order.  The executor can special-case such tlists to avoid a projection
 * step at runtime, so we use such tlists preferentially for scan nodes.
 *
 * Exception: if there are any dropped or missing columns, we punt and return
 * NIL.  Ideally we would like to handle these cases too.  However this
 * creates problems for ExecTypeFromTL, which may be asked to build a tupdesc
 * for a tlist that includes vars of no-longer-existent types.  In theory we
 * could dig out the required info from the pg_attribute entries of the
 * relation, but that data is not readily available to ExecTypeFromTL.
 * For now, we don't apply the physical-tlist optimization when there are
 * dropped cols.
 *
 * We also support building a "physical" tlist for subqueries, functions,
 * values lists, table expressions, and CTEs, since the same optimization can
 * occur in SubqueryScan, FunctionScan, ValuesScan, CteScan, TableFunc,
 * NamedTuplestoreScan, and WorkTableScan nodes.
 */
List *
build_physical_tlist(PlannerInfo *root, RelOptInfo *rel)
{
    List       *tlist = NIL;
    Index       varno = rel->relid;
    RangeTblEntry *rte = planner_rt_fetch(varno, root);
    Relation    relation;
    Query      *subquery;
    Var        *var;
    ListCell   *l;
    int         attrno,
                numattrs;
    List       *colvars;
 
    switch (rte->rtekind)
    {
        case RTE_RELATION:
            /* Assume we already have adequate lock */
            relation = table_open(rte->relid, NoLock);
 
            numattrs = RelationGetNumberOfAttributes(relation);
            for (attrno = 1; attrno <= numattrs; attrno++)
            {
                Form_pg_attribute att_tup = TupleDescAttr(relation->rd_att,
                                                          attrno - 1);
 
                if (att_tup->attisdropped || att_tup->atthasmissing)
                {
                    /* found a dropped or missing col, so punt */
                    tlist = NIL;
                    break;
                }
 
                var = makeVar(varno,
                              attrno,
                              att_tup->atttypid,
                              att_tup->atttypmod,
                              att_tup->attcollation,
                              0);
 
                tlist = lappend(tlist,
                                makeTargetEntry((Expr *) var,
                                                attrno,
                                                NULL,
                                                false));
            }
 
            table_close(relation, NoLock);
            break;
 
        case RTE_SUBQUERY:
            subquery = rte->subquery;
            foreach(l, subquery->targetList)
            {
                TargetEntry *tle = (TargetEntry *) lfirst(l);
 
                /*
                 * A resjunk column of the subquery can be reflected as
                 * resjunk in the physical tlist; we need not punt.
                 */
                var = makeVarFromTargetEntry(varno, tle);
 
                tlist = lappend(tlist,
                                makeTargetEntry((Expr *) var,
                                                tle->resno,
                                                NULL,
                                                tle->resjunk));
            }
            break;
 
        case RTE_FUNCTION:
        case RTE_TABLEFUNC:
        case RTE_VALUES:
        case RTE_CTE:
        case RTE_NAMEDTUPLESTORE:
        case RTE_RESULT:
            /* Not all of these can have dropped cols, but share code anyway */
            expandRTE(rte, varno, 0, -1, true /* include dropped */ ,
                      NULL, &colvars);
            foreach(l, colvars)
            {
                var = (Var *) lfirst(l);
 
                /*
                 * A non-Var in expandRTE's output means a dropped column;
                 * must punt.
                 */
                if (!IsA(var, Var))
                {
                    tlist = NIL;
                    break;
                }
 
                tlist = lappend(tlist,
                                makeTargetEntry((Expr *) var,
                                                var->varattno,
                                                NULL,
                                                false));
            }
            break;
 
        default:
            /* caller error */
            elog(ERROR, "unsupported RTE kind %d in build_physical_tlist",
                 (int) rte->rtekind);
            break;
    }
 
    return tlist;
}
 
/*
 * build_index_tlist
 *
 * Build a targetlist representing the columns of the specified index.
 * Each column is represented by a Var for the corresponding base-relation
 * column, or an expression in base-relation Vars, as appropriate.
 *
 * There are never any dropped columns in indexes, so unlike
 * build_physical_tlist, we need no failure case.
 */
static List *
build_index_tlist(PlannerInfo *root, IndexOptInfo *index,
                  Relation heapRelation)
{
    List       *tlist = NIL;
    Index       varno = index->rel->relid;
    ListCell   *indexpr_item;
    int         i;
 
    indexpr_item = list_head(index->indexprs);
    for (i = 0; i < index->ncolumns; i++)
    {
        int         indexkey = index->indexkeys[i];
        Expr       *indexvar;
 
        if (indexkey != 0)
        {
            /* simple column */
            const FormData_pg_attribute *att_tup;
 
            if (indexkey < 0)
                att_tup = SystemAttributeDefinition(indexkey);
            else
                att_tup = TupleDescAttr(heapRelation->rd_att, indexkey - 1);
 
            indexvar = (Expr *) makeVar(varno,
                                        indexkey,
                                        att_tup->atttypid,
                                        att_tup->atttypmod,
                                        att_tup->attcollation,
                                        0);
        }
        else
        {
            /* expression column */
            if (indexpr_item == NULL)
                elog(ERROR, "wrong number of index expressions");
            indexvar = (Expr *) lfirst(indexpr_item);
            indexpr_item = lnext(index->indexprs, indexpr_item);
        }
 
        tlist = lappend(tlist,
                        makeTargetEntry(indexvar,
                                        i + 1,
                                        NULL,
                                        false));
    }
    if (indexpr_item != NULL)
        elog(ERROR, "wrong number of index expressions");
 
    return tlist;
}
 
/*
 * restriction_selectivity
 *
 * Returns the selectivity of a specified restriction operator clause.
 * This code executes registered procedures stored in the
 * operator relation, by calling the function manager.
 *
 * See clause_selectivity() for the meaning of the additional parameters.
 */
Selectivity
restriction_selectivity(PlannerInfo *root,
                        Oid operatorid,
                        List *args,
                        Oid inputcollid,
                        int varRelid)
{
    RegProcedure oprrest = get_oprrest(operatorid);
    float8      result;
 
    /*
     * if the oprrest procedure is missing for whatever reason, use a
     * selectivity of 0.5
     */
    if (!oprrest)
        return (Selectivity) 0.5;
 
    result = DatumGetFloat8(OidFunctionCall4Coll(oprrest,
                                                 inputcollid,
                                                 PointerGetDatum(root),
                                                 ObjectIdGetDatum(operatorid),
                                                 PointerGetDatum(args),
                                                 Int32GetDatum(varRelid)));
 
    if (result < 0.0 || result > 1.0)
        elog(ERROR, "invalid restriction selectivity: %f", result);
 
    return (Selectivity) result;
}
 
/*
 * join_selectivity
 *
 * Returns the selectivity of a specified join operator clause.
 * This code executes registered procedures stored in the
 * operator relation, by calling the function manager.
 *
 * See clause_selectivity() for the meaning of the additional parameters.
 */
Selectivity
join_selectivity(PlannerInfo *root,
                 Oid operatorid,
                 List *args,
                 Oid inputcollid,
                 JoinType jointype,
                 SpecialJoinInfo *sjinfo)
{
    RegProcedure oprjoin = get_oprjoin(operatorid);
    float8      result;
 
    /*
     * if the oprjoin procedure is missing for whatever reason, use a
     * selectivity of 0.5
     */
    if (!oprjoin)
        return (Selectivity) 0.5;
 
    result = DatumGetFloat8(OidFunctionCall5Coll(oprjoin,
                                                 inputcollid,
                                                 PointerGetDatum(root),
                                                 ObjectIdGetDatum(operatorid),
                                                 PointerGetDatum(args),
                                                 Int16GetDatum(jointype),
                                                 PointerGetDatum(sjinfo)));
 
    if (result < 0.0 || result > 1.0)
        elog(ERROR, "invalid join selectivity: %f", result);
 
    return (Selectivity) result;
}
 
/*
 * function_selectivity
 *
 * Returns the selectivity of a specified boolean function clause.
 * This code executes registered procedures stored in the
 * pg_proc relation, by calling the function manager.
 *
 * See clause_selectivity() for the meaning of the additional parameters.
 */
Selectivity
function_selectivity(PlannerInfo *root,
                     Oid funcid,
                     List *args,
                     Oid inputcollid,
                     bool is_join,
                     int varRelid,
                     JoinType jointype,
                     SpecialJoinInfo *sjinfo)
{
    RegProcedure prosupport = get_func_support(funcid);
    SupportRequestSelectivity req;
    SupportRequestSelectivity *sresult;
 
    /*
     * If no support function is provided, use our historical default
     * estimate, 0.3333333.  This seems a pretty unprincipled choice, but
     * Postgres has been using that estimate for function calls since 1992.
     * The hoariness of this behavior suggests that we should not be in too
     * much hurry to use another value.
     */
    if (!prosupport)
        return (Selectivity) 0.3333333;
 
    req.type = T_SupportRequestSelectivity;
    req.root = root;
    req.funcid = funcid;
    req.args = args;
    req.inputcollid = inputcollid;
    req.is_join = is_join;
    req.varRelid = varRelid;
    req.jointype = jointype;
    req.sjinfo = sjinfo;
    req.selectivity = -1;       /* to catch failure to set the value */
 
    sresult = (SupportRequestSelectivity *)
        DatumGetPointer(OidFunctionCall1(prosupport,
                                         PointerGetDatum(&req)));
 
    /* If support function fails, use default */
    if (sresult != &req)
        return (Selectivity) 0.3333333;
 
    if (req.selectivity < 0.0 || req.selectivity > 1.0)
        elog(ERROR, "invalid function selectivity: %f", req.selectivity);
 
    return (Selectivity) req.selectivity;
}
 
/*
 * add_function_cost
 *
 * Get an estimate of the execution cost of a function, and *add* it to
 * the contents of *cost.  The estimate may include both one-time and
 * per-tuple components, since QualCost does.
 *
 * The funcid must always be supplied.  If it is being called as the
 * implementation of a specific parsetree node (FuncExpr, OpExpr,
 * WindowFunc, etc), pass that as "node", else pass NULL.
 *
 * In some usages root might be NULL, too.
 */
void
add_function_cost(PlannerInfo *root, Oid funcid, Node *node,
                  QualCost *cost)
{
    HeapTuple   proctup;
    Form_pg_proc procform;
 
    proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(proctup))
        elog(ERROR, "cache lookup failed for function %u", funcid);
    procform = (Form_pg_proc) GETSTRUCT(proctup);
 
    if (OidIsValid(procform->prosupport))
    {
        SupportRequestCost req;
        SupportRequestCost *sresult;
 
        req.type = T_SupportRequestCost;
        req.root = root;
        req.funcid = funcid;
        req.node = node;
 
        /* Initialize cost fields so that support function doesn't have to */
        req.startup = 0;
        req.per_tuple = 0;
 
        sresult = (SupportRequestCost *)
            DatumGetPointer(OidFunctionCall1(procform->prosupport,
                                             PointerGetDatum(&req)));
 
        if (sresult == &req)
        {
            /* Success, so accumulate support function's estimate into *cost */
            cost->startup += req.startup;
            cost->per_tuple += req.per_tuple;
            ReleaseSysCache(proctup);
            return;
        }
    }
 
    /* No support function, or it failed, so rely on procost */
    cost->per_tuple += procform->procost * cpu_operator_cost;
 
    ReleaseSysCache(proctup);
}
 
/*
 * get_function_rows
 *
 * Get an estimate of the number of rows returned by a set-returning function.
 *
 * The funcid must always be supplied.  In current usage, the calling node
 * will always be supplied, and will be either a FuncExpr or OpExpr.
 * But it's a good idea to not fail if it's NULL.
 *
 * In some usages root might be NULL, too.
 *
 * Note: this returns the unfiltered result of the support function, if any.
 * It's usually a good idea to apply clamp_row_est() to the result, but we
 * leave it to the caller to do so.
 */
double
get_function_rows(PlannerInfo *root, Oid funcid, Node *node)
{
    HeapTuple   proctup;
    Form_pg_proc procform;
    double      result;
 
    proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
    if (!HeapTupleIsValid(proctup))
        elog(ERROR, "cache lookup failed for function %u", funcid);
    procform = (Form_pg_proc) GETSTRUCT(proctup);
 
    Assert(procform->proretset);    /* else caller error */
 
    if (OidIsValid(procform->prosupport))
    {
        SupportRequestRows req;
        SupportRequestRows *sresult;
 
        req.type = T_SupportRequestRows;
        req.root = root;
        req.funcid = funcid;
        req.node = node;
 
        req.rows = 0;           /* just for sanity */
 
        sresult = (SupportRequestRows *)
            DatumGetPointer(OidFunctionCall1(procform->prosupport,
                                             PointerGetDatum(&req)));
 
        if (sresult == &req)
        {
            /* Success */
            ReleaseSysCache(proctup);
            return req.rows;
        }
    }
 
    /* No support function, or it failed, so rely on prorows */
    result = procform->prorows;
 
    ReleaseSysCache(proctup);
 
    return result;
}
 
/*
 * has_unique_index
 *
 * Detect whether there is a unique index on the specified attribute
 * of the specified relation, thus allowing us to conclude that all
 * the (non-null) values of the attribute are distinct.
 *
 * This function does not check the index's indimmediate property, which
 * means that uniqueness may transiently fail to hold intra-transaction.
 * That's appropriate when we are making statistical estimates, but beware
 * of using this for any correctness proofs.
 */
bool
has_unique_index(RelOptInfo *rel, AttrNumber attno)
{
    ListCell   *ilist;
 
    foreach(ilist, rel->indexlist)
    {
        IndexOptInfo *index = (IndexOptInfo *) lfirst(ilist);
 
        /*
         * Note: ignore partial indexes, since they don't allow us to conclude
         * that all attr values are distinct, *unless* they are marked predOK
         * which means we know the index's predicate is satisfied by the
         * query. We don't take any interest in expressional indexes either.
         * Also, a multicolumn unique index doesn't allow us to conclude that
         * just the specified attr is unique.
         */
        if (index->unique &&
            index->nkeycolumns == 1 &&
            index->indexkeys[0] == attno &&
            (index->indpred == NIL || index->predOK))
            return true;
    }
    return false;
}
 
 
/*
 * has_row_triggers
 *
 * Detect whether the specified relation has any row-level triggers for event.
 */
bool
has_row_triggers(PlannerInfo *root, Index rti, CmdType event)
{
    RangeTblEntry *rte = planner_rt_fetch(rti, root);
    Relation    relation;
    TriggerDesc *trigDesc;
    bool        result = false;
 
    /* Assume we already have adequate lock */
    relation = table_open(rte->relid, NoLock);
 
    trigDesc = relation->trigdesc;
    switch (event)
    {
        case CMD_INSERT:
            if (trigDesc &&
                (trigDesc->trig_insert_after_row ||
                 trigDesc->trig_insert_before_row))
                result = true;
            break;
        case CMD_UPDATE:
            if (trigDesc &&
                (trigDesc->trig_update_after_row ||
                 trigDesc->trig_update_before_row))
                result = true;
            break;
        case CMD_DELETE:
            if (trigDesc &&
                (trigDesc->trig_delete_after_row ||
                 trigDesc->trig_delete_before_row))
                result = true;
            break;
            /* There is no separate event for MERGE, only INSERT/UPDATE/DELETE */
        case CMD_MERGE:
            result = false;
            break;
        default:
            elog(ERROR, "unrecognized CmdType: %d", (int) event);
            break;
    }
 
    table_close(relation, NoLock);
    return result;
}
 
/*
 * has_stored_generated_columns
 *
 * Does table identified by RTI have any STORED GENERATED columns?
 */
bool
has_stored_generated_columns(PlannerInfo *root, Index rti)
{
    RangeTblEntry *rte = planner_rt_fetch(rti, root);
    Relation    relation;
    TupleDesc   tupdesc;
    bool        result = false;
 
    /* Assume we already have adequate lock */
    relation = table_open(rte->relid, NoLock);
 
    tupdesc = RelationGetDescr(relation);
    result = tupdesc->constr && tupdesc->constr->has_generated_stored;
 
    table_close(relation, NoLock);
 
    return result;
}
 
/*
 * get_dependent_generated_columns
 *
 * Get the column numbers of any STORED GENERATED columns of the relation
 * that depend on any column listed in target_cols.  Both the input and
 * result bitmapsets contain column numbers offset by
 * FirstLowInvalidHeapAttributeNumber.
 */
Bitmapset *
get_dependent_generated_columns(PlannerInfo *root, Index rti,
                                Bitmapset *target_cols)
{
    Bitmapset  *dependentCols = NULL;
    RangeTblEntry *rte = planner_rt_fetch(rti, root);
    Relation    relation;
    TupleDesc   tupdesc;
    TupleConstr *constr;
 
    /* Assume we already have adequate lock */
    relation = table_open(rte->relid, NoLock);
 
    tupdesc = RelationGetDescr(relation);
    constr = tupdesc->constr;
 
    if (constr && constr->has_generated_stored)
    {
        for (int i = 0; i < constr->num_defval; i++)
        {
            AttrDefault *defval = &constr->defval[i];
            Node       *expr;
            Bitmapset  *attrs_used = NULL;
 
            /* skip if not generated column */
            if (!TupleDescAttr(tupdesc, defval->adnum - 1)->attgenerated)
                continue;
 
            /* identify columns this generated column depends on */
            expr = stringToNode(defval->adbin);
            pull_varattnos(expr, 1, &attrs_used);
 
            if (bms_overlap(target_cols, attrs_used))
                dependentCols = bms_add_member(dependentCols,
                                               defval->adnum - FirstLowInvalidHeapAttributeNumber);
        }
    }
 
    table_close(relation, NoLock);
 
    return dependentCols;
}
 
/*
 * set_relation_partition_info
 *
 * Set partitioning scheme and related information for a partitioned table.
 */
static void
set_relation_partition_info(PlannerInfo *root, RelOptInfo *rel,
                            Relation relation)
{
    PartitionDesc partdesc;
 
    /*
     * Create the PartitionDirectory infrastructure if we didn't already.
     */
    if (root->glob->partition_directory == NULL)
    {
        root->glob->partition_directory =
            CreatePartitionDirectory(CurrentMemoryContext, true);
    }
 
    partdesc = PartitionDirectoryLookup(root->glob->partition_directory,
                                        relation);
    rel->part_scheme = find_partition_scheme(root, relation);
    Assert(partdesc != NULL && rel->part_scheme != NULL);
    rel->boundinfo = partdesc->boundinfo;
    rel->nparts = partdesc->nparts;
    set_baserel_partition_key_exprs(relation, rel);
    set_baserel_partition_constraint(relation, rel);
}
 
/*
 * find_partition_scheme
 *
 * Find or create a PartitionScheme for this Relation.
 */
static PartitionScheme
find_partition_scheme(PlannerInfo *root, Relation relation)
{
    PartitionKey partkey = RelationGetPartitionKey(relation);
    ListCell   *lc;
    int         partnatts,
                i;
    PartitionScheme part_scheme;
 
    /* A partitioned table should have a partition key. */
    Assert(partkey != NULL);
 
    partnatts = partkey->partnatts;
 
    /* Search for a matching partition scheme and return if found one. */
    foreach(lc, root->part_schemes)
    {
        part_scheme = lfirst(lc);
 
        /* Match partitioning strategy and number of keys. */
        if (partkey->strategy != part_scheme->strategy ||
            partnatts != part_scheme->partnatts)
            continue;
 
        /* Match partition key type properties. */
        if (memcmp(partkey->partopfamily, part_scheme->partopfamily,
                   sizeof(Oid) * partnatts) != 0 ||
            memcmp(partkey->partopcintype, part_scheme->partopcintype,
                   sizeof(Oid) * partnatts) != 0 ||
            memcmp(partkey->partcollation, part_scheme->partcollation,
                   sizeof(Oid) * partnatts) != 0)
            continue;
 
        /*
         * Length and byval information should match when partopcintype
         * matches.
         */
        Assert(memcmp(partkey->parttyplen, part_scheme->parttyplen,
                      sizeof(int16) * partnatts) == 0);
        Assert(memcmp(partkey->parttypbyval, part_scheme->parttypbyval,
                      sizeof(bool) * partnatts) == 0);
 
        /*
         * If partopfamily and partopcintype matched, must have the same
         * partition comparison functions.  Note that we cannot reliably
         * Assert the equality of function structs themselves for they might
         * be different across PartitionKey's, so just Assert for the function
         * OIDs.
         */
#ifdef USE_ASSERT_CHECKING
        for (i = 0; i < partkey->partnatts; i++)
            Assert(partkey->partsupfunc[i].fn_oid ==
                   part_scheme->partsupfunc[i].fn_oid);
#endif
 
        /* Found matching partition scheme. */
        return part_scheme;
    }
 
    /*
     * Did not find matching partition scheme. Create one copying relevant
     * information from the relcache. We need to copy the contents of the
     * array since the relcache entry may not survive after we have closed the
     * relation.
     */
    part_scheme = (PartitionScheme) palloc0(sizeof(PartitionSchemeData));
    part_scheme->strategy = partkey->strategy;
    part_scheme->partnatts = partkey->partnatts;
 
    part_scheme->partopfamily = (Oid *) palloc(sizeof(Oid) * partnatts);
    memcpy(part_scheme->partopfamily, partkey->partopfamily,
           sizeof(Oid) * partnatts);
 
    part_scheme->partopcintype = (Oid *) palloc(sizeof(Oid) * partnatts);
    memcpy(part_scheme->partopcintype, partkey->partopcintype,
           sizeof(Oid) * partnatts);
 
    part_scheme->partcollation = (Oid *) palloc(sizeof(Oid) * partnatts);
    memcpy(part_scheme->partcollation, partkey->partcollation,
           sizeof(Oid) * partnatts);
 
    part_scheme->parttyplen = (int16 *) palloc(sizeof(int16) * partnatts);
    memcpy(part_scheme->parttyplen, partkey->parttyplen,
           sizeof(int16) * partnatts);
 
    part_scheme->parttypbyval = (bool *) palloc(sizeof(bool) * partnatts);
    memcpy(part_scheme->parttypbyval, partkey->parttypbyval,
           sizeof(bool) * partnatts);
 
    part_scheme->partsupfunc = (FmgrInfo *)
        palloc(sizeof(FmgrInfo) * partnatts);
    for (i = 0; i < partnatts; i++)
        fmgr_info_copy(&part_scheme->partsupfunc[i], &partkey->partsupfunc[i],
                       CurrentMemoryContext);
 
    /* Add the partitioning scheme to PlannerInfo. */
    root->part_schemes = lappend(root->part_schemes, part_scheme);
 
    return part_scheme;
}
 
/*
 * set_baserel_partition_key_exprs
 *
 * Builds partition key expressions for the given base relation and fills
 * rel->partexprs.
 */
static void
set_baserel_partition_key_exprs(Relation relation,
                                RelOptInfo *rel)
{
    PartitionKey partkey = RelationGetPartitionKey(relation);
    int         partnatts;
    int         cnt;
    List      **partexprs;
    ListCell   *lc;
    Index       varno = rel->relid;
 
    Assert(IS_SIMPLE_REL(rel) && rel->relid > 0);
 
    /* A partitioned table should have a partition key. */
    Assert(partkey != NULL);
 
    partnatts = partkey->partnatts;
    partexprs = (List **) palloc(sizeof(List *) * partnatts);
    lc = list_head(partkey->partexprs);
 
    for (cnt = 0; cnt < partnatts; cnt++)
    {
        Expr       *partexpr;
        AttrNumber  attno = partkey->partattrs[cnt];
 
        if (attno != InvalidAttrNumber)
        {
            /* Single column partition key is stored as a Var node. */
            Assert(attno > 0);
 
            partexpr = (Expr *) makeVar(varno, attno,
                                        partkey->parttypid[cnt],
                                        partkey->parttypmod[cnt],
                                        partkey->parttypcoll[cnt], 0);
        }
        else
        {
            if (lc == NULL)
                elog(ERROR, "wrong number of partition key expressions");
 
            /* Re-stamp the expression with given varno. */
            partexpr = (Expr *) copyObject(lfirst(lc));
            ChangeVarNodes((Node *) partexpr, 1, varno, 0);
            lc = lnext(partkey->partexprs, lc);
        }
 
        /* Base relations have a single expression per key. */
        partexprs[cnt] = list_make1(partexpr);
    }
 
    rel->partexprs = partexprs;
 
    /*
     * A base relation does not have nullable partition key expressions, since
     * no outer join is involved.  We still allocate an array of empty
     * expression lists to keep partition key expression handling code simple.
     * See build_joinrel_partition_info() and match_expr_to_partition_keys().
     */
    rel->nullable_partexprs = (List **) palloc0(sizeof(List *) * partnatts);
}
 
/*
 * set_baserel_partition_constraint
 *
 * Builds the partition constraint for the given base relation and sets it
 * in the given RelOptInfo.  All Var nodes are restamped with the relid of the
 * given relation.
 */
static void
set_baserel_partition_constraint(Relation relation, RelOptInfo *rel)
{
    List       *partconstr;
 
    if (rel->partition_qual)    /* already done */
        return;
 
    /*
     * Run the partition quals through const-simplification similar to check
     * constraints.  We skip canonicalize_qual, though, because partition
     * quals should be in canonical form already; also, since the qual is in
     * implicit-AND format, we'd have to explicitly convert it to explicit-AND
     * format and back again.
     */
    partconstr = RelationGetPartitionQual(relation);
    if (partconstr)
    {
        partconstr = (List *) expression_planner((Expr *) partconstr);
        if (rel->relid != 1)
            ChangeVarNodes((Node *) partconstr, 1, rel->relid, 0);
        rel->partition_qual = partconstr;
    }
}