partition.c

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/*-------------------------------------------------------------------------
 *
 * partition.c
 *        Partitioning related data structures and functions.
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        src/backend/catalog/partition.c
 *
 *-------------------------------------------------------------------------
*/
#include "postgres.h"

#include "access/attmap.h"
#include "access/genam.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/indexing.h"
#include "catalog/partition.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_partitioned_table.h"
#include "nodes/makefuncs.h"
#include "optimizer/optimizer.h"
#include "partitioning/partbounds.h"
#include "rewrite/rewriteManip.h"
#include "utils/fmgroids.h"
#include "utils/partcache.h"
#include "utils/rel.h"
#include "utils/syscache.h"

static Oid  get_partition_parent_worker(Relation inhRel, Oid relid,
                                        bool *detach_pending);
static void get_partition_ancestors_worker(Relation inhRel, Oid relid,
                                           List **ancestors);

/*
 * get_partition_parent
 *      Obtain direct parent of given relation
 *
 * Returns inheritance parent of a partition by scanning pg_inherits
 *
 * If the partition is in the process of being detached, an error is thrown,
 * unless even_if_detached is passed as true.
 *
 * Note: Because this function assumes that the relation whose OID is passed
 * as an argument will have precisely one parent, it should only be called
 * when it is known that the relation is a partition.
 */
Oid
get_partition_parent(Oid relid, bool even_if_detached)
{
    Relation    catalogRelation;
    Oid         result;
    bool        detach_pending;

    catalogRelation = table_open(InheritsRelationId, AccessShareLock);

    result = get_partition_parent_worker(catalogRelation, relid,
                                         &detach_pending);

    if (!OidIsValid(result))
        elog(ERROR, "could not find tuple for parent of relation %u", relid);

    if (detach_pending && !even_if_detached)
        elog(ERROR, "relation %u has no parent because it's being detached",
             relid);

    table_close(catalogRelation, AccessShareLock);

    return result;
}

/*
 * get_partition_parent_worker
 *      Scan the pg_inherits relation to return the OID of the parent of the
 *      given relation
 *
 * If the partition is being detached, *detach_pending is set true (but the
 * original parent is still returned.)
 */
static Oid
get_partition_parent_worker(Relation inhRel, Oid relid, bool *detach_pending)
{
    SysScanDesc scan;
    ScanKeyData key[2];
    Oid         result = InvalidOid;
    HeapTuple   tuple;

    *detach_pending = false;

    ScanKeyInit(&key[0],
                Anum_pg_inherits_inhrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
    ScanKeyInit(&key[1],
                Anum_pg_inherits_inhseqno,
                BTEqualStrategyNumber, F_INT4EQ,
                Int32GetDatum(1));

    scan = systable_beginscan(inhRel, InheritsRelidSeqnoIndexId, true,
                              NULL, 2, key);
    tuple = systable_getnext(scan);
    if (HeapTupleIsValid(tuple))
    {
        Form_pg_inherits form = (Form_pg_inherits) GETSTRUCT(tuple);

        /* Let caller know of partition being detached */
        if (form->inhdetachpending)
            *detach_pending = true;
        result = form->inhparent;
    }

    systable_endscan(scan);

    return result;
}

/*
 * get_partition_ancestors
 *      Obtain ancestors of given relation
 *
 * Returns a list of ancestors of the given relation.
 *
 * Note: Because this function assumes that the relation whose OID is passed
 * as an argument and each ancestor will have precisely one parent, it should
 * only be called when it is known that the relation is a partition.
 */
List *
get_partition_ancestors(Oid relid)
{
    List       *result = NIL;
    Relation    inhRel;

    inhRel = table_open(InheritsRelationId, AccessShareLock);

    get_partition_ancestors_worker(inhRel, relid, &result);

    table_close(inhRel, AccessShareLock);

    return result;
}

/*
 * get_partition_ancestors_worker
 *      recursive worker for get_partition_ancestors
 */
static void
get_partition_ancestors_worker(Relation inhRel, Oid relid, List **ancestors)
{
    Oid         parentOid;
    bool        detach_pending;

    /*
     * Recursion ends at the topmost level, ie., when there's no parent; also
     * when the partition is being detached.
     */
    parentOid = get_partition_parent_worker(inhRel, relid, &detach_pending);
    if (parentOid == InvalidOid || detach_pending)
        return;

    *ancestors = lappend_oid(*ancestors, parentOid);
    get_partition_ancestors_worker(inhRel, parentOid, ancestors);
}

/*
 * index_get_partition
 *      Return the OID of index of the given partition that is a child
 *      of the given index, or InvalidOid if there isn't one.
 */
Oid
index_get_partition(Relation partition, Oid indexId)
{
    List       *idxlist = RelationGetIndexList(partition);
    ListCell   *l;

    foreach(l, idxlist)
    {
        Oid         partIdx = lfirst_oid(l);
        HeapTuple   tup;
        Form_pg_class classForm;
        bool        ispartition;

        tup = SearchSysCache1(RELOID, ObjectIdGetDatum(partIdx));
        if (!HeapTupleIsValid(tup))
            elog(ERROR, "cache lookup failed for relation %u", partIdx);
        classForm = (Form_pg_class) GETSTRUCT(tup);
        ispartition = classForm->relispartition;
        ReleaseSysCache(tup);
        if (!ispartition)
            continue;
        if (get_partition_parent(partIdx, false) == indexId)
        {
            list_free(idxlist);
            return partIdx;
        }
    }

    list_free(idxlist);
    return InvalidOid;
}

/*
 * map_partition_varattnos - maps varattnos of all Vars in 'expr' (that have
 * varno 'fromrel_varno') from the attnums of 'from_rel' to the attnums of
 * 'to_rel', each of which may be either a leaf partition or a partitioned
 * table, but both of which must be from the same partitioning hierarchy.
 *
 * We need this because even though all of the same column names must be
 * present in all relations in the hierarchy, and they must also have the
 * same types, the attnums may be different.
 *
 * Note: this will work on any node tree, so really the argument and result
 * should be declared "Node *".  But a substantial majority of the callers
 * are working on Lists, so it's less messy to do the casts internally.
 */
List *
map_partition_varattnos(List *expr, int fromrel_varno,
                        Relation to_rel, Relation from_rel)
{
    if (expr != NIL)
    {
        AttrMap    *part_attmap;
        bool        found_whole_row;

        part_attmap = build_attrmap_by_name(RelationGetDescr(to_rel),
                                            RelationGetDescr(from_rel));
        expr = (List *) map_variable_attnos((Node *) expr,
                                            fromrel_varno, 0,
                                            part_attmap,
                                            RelationGetForm(to_rel)->reltype,
                                            &found_whole_row);
        /* Since we provided a to_rowtype, we may ignore found_whole_row. */
    }

    return expr;
}

/*
 * Checks if any of the 'attnums' is a partition key attribute for rel
 *
 * Sets *used_in_expr if any of the 'attnums' is found to be referenced in some
 * partition key expression.  It's possible for a column to be both used
 * directly and as part of an expression; if that happens, *used_in_expr may
 * end up as either true or false.  That's OK for current uses of this
 * function, because *used_in_expr is only used to tailor the error message
 * text.
 */
bool
has_partition_attrs(Relation rel, Bitmapset *attnums, bool *used_in_expr)
{
    PartitionKey key;
    int         partnatts;
    List       *partexprs;
    ListCell   *partexprs_item;
    int         i;

    if (attnums == NULL || rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
        return false;

    key = RelationGetPartitionKey(rel);
    partnatts = get_partition_natts(key);
    partexprs = get_partition_exprs(key);

    partexprs_item = list_head(partexprs);
    for (i = 0; i < partnatts; i++)
    {
        AttrNumber  partattno = get_partition_col_attnum(key, i);

        if (partattno != 0)
        {
            if (bms_is_member(partattno - FirstLowInvalidHeapAttributeNumber,
                              attnums))
            {
                if (used_in_expr)
                    *used_in_expr = false;
                return true;
            }
        }
        else
        {
            /* Arbitrary expression */
            Node       *expr = (Node *) lfirst(partexprs_item);
            Bitmapset  *expr_attrs = NULL;

            /* Find all attributes referenced */
            pull_varattnos(expr, 1, &expr_attrs);
            partexprs_item = lnext(partexprs, partexprs_item);

            if (bms_overlap(attnums, expr_attrs))
            {
                if (used_in_expr)
                    *used_in_expr = true;
                return true;
            }
        }
    }

    return false;
}

/*
 * get_default_partition_oid
 *
 * Given a relation OID, return the OID of the default partition, if one
 * exists.  Use get_default_oid_from_partdesc where possible, for
 * efficiency.
 */
Oid
get_default_partition_oid(Oid parentId)
{
    HeapTuple   tuple;
    Oid         defaultPartId = InvalidOid;

    tuple = SearchSysCache1(PARTRELID, ObjectIdGetDatum(parentId));

    if (HeapTupleIsValid(tuple))
    {
        Form_pg_partitioned_table part_table_form;

        part_table_form = (Form_pg_partitioned_table) GETSTRUCT(tuple);
        defaultPartId = part_table_form->partdefid;
        ReleaseSysCache(tuple);
    }

    return defaultPartId;
}

/*
 * update_default_partition_oid
 *
 * Update pg_partitioned_table.partdefid with a new default partition OID.
 */
void
update_default_partition_oid(Oid parentId, Oid defaultPartId)
{
    HeapTuple   tuple;
    Relation    pg_partitioned_table;
    Form_pg_partitioned_table part_table_form;

    pg_partitioned_table = table_open(PartitionedRelationId, RowExclusiveLock);

    tuple = SearchSysCacheCopy1(PARTRELID, ObjectIdGetDatum(parentId));

    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for partition key of relation %u",
             parentId);

    part_table_form = (Form_pg_partitioned_table) GETSTRUCT(tuple);
    part_table_form->partdefid = defaultPartId;
    CatalogTupleUpdate(pg_partitioned_table, &tuple->t_self, tuple);

    heap_freetuple(tuple);
    table_close(pg_partitioned_table, RowExclusiveLock);
}

/*
 * get_proposed_default_constraint
 *
 * This function returns the negation of new_part_constraints, which
 * would be an integral part of the default partition constraints after
 * addition of the partition to which the new_part_constraints belongs.
 */
List *
get_proposed_default_constraint(List *new_part_constraints)
{
    Expr       *defPartConstraint;

    defPartConstraint = make_ands_explicit(new_part_constraints);

    /*
     * Derive the partition constraints of default partition by negating the
     * given partition constraints. The partition constraint never evaluates
     * to NULL, so negating it like this is safe.
     */
    defPartConstraint = makeBoolExpr(NOT_EXPR,
                                     list_make1(defPartConstraint),
                                     -1);

    /* Simplify, to put the negated expression into canonical form */
    defPartConstraint =
        (Expr *) eval_const_expressions(NULL,
                                        (Node *) defPartConstraint);
    defPartConstraint = canonicalize_qual(defPartConstraint, true);

    return make_ands_implicit(defPartConstraint);
}