inherit.c

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/*-------------------------------------------------------------------------
 *
 * inherit.c
 *    Routines to process child relations in inheritance trees
 *
 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/path/inherit.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/partition.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "optimizer/appendinfo.h"
#include "optimizer/inherit.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/restrictinfo.h"
#include "parser/parsetree.h"
#include "partitioning/partdesc.h"
#include "partitioning/partprune.h"
#include "utils/rel.h"


static void expand_partitioned_rtentry(PlannerInfo *root, RelOptInfo *relinfo,
                                       RangeTblEntry *parentrte,
                                       Index parentRTindex, Relation parentrel,
                                       PlanRowMark *top_parentrc, LOCKMODE lockmode);
static void expand_single_inheritance_child(PlannerInfo *root,
                                            RangeTblEntry *parentrte,
                                            Index parentRTindex, Relation parentrel,
                                            PlanRowMark *top_parentrc, Relation childrel,
                                            RangeTblEntry **childrte_p,
                                            Index *childRTindex_p);
static Bitmapset *translate_col_privs(const Bitmapset *parent_privs,
                                      List *translated_vars);
static void expand_appendrel_subquery(PlannerInfo *root, RelOptInfo *rel,
                                      RangeTblEntry *rte, Index rti);


/*
 * expand_inherited_rtentry
 *      Expand a rangetable entry that has the "inh" bit set.
 *
 * "inh" is only allowed in two cases: RELATION and SUBQUERY RTEs.
 *
 * "inh" on a plain RELATION RTE means that it is a partitioned table or the
 * parent of a traditional-inheritance set.  In this case we must add entries
 * for all the interesting child tables to the query's rangetable, and build
 * additional planner data structures for them, including RelOptInfos,
 * AppendRelInfos, and possibly PlanRowMarks.
 *
 * Note that the original RTE is considered to represent the whole inheritance
 * set.  In the case of traditional inheritance, the first of the generated
 * RTEs is an RTE for the same table, but with inh = false, to represent the
 * parent table in its role as a simple member of the inheritance set.  For
 * partitioning, we don't need a second RTE because the partitioned table
 * itself has no data and need not be scanned.
 *
 * "inh" on a SUBQUERY RTE means that it's the parent of a UNION ALL group,
 * which is treated as an appendrel similarly to inheritance cases; however,
 * we already made RTEs and AppendRelInfos for the subqueries.  We only need
 * to build RelOptInfos for them, which is done by expand_appendrel_subquery.
 */
void
expand_inherited_rtentry(PlannerInfo *root, RelOptInfo *rel,
                         RangeTblEntry *rte, Index rti)
{
    Oid         parentOID;
    Relation    oldrelation;
    LOCKMODE    lockmode;
    PlanRowMark *oldrc;
    bool        old_isParent = false;
    int         old_allMarkTypes = 0;

    Assert(rte->inh);           /* else caller error */

    if (rte->rtekind == RTE_SUBQUERY)
    {
        expand_appendrel_subquery(root, rel, rte, rti);
        return;
    }

    Assert(rte->rtekind == RTE_RELATION);

    parentOID = rte->relid;

    /*
     * We used to check has_subclass() here, but there's no longer any need
     * to, because subquery_planner already did.
     */

    /*
     * The rewriter should already have obtained an appropriate lock on each
     * relation named in the query, so we can open the parent relation without
     * locking it.  However, for each child relation we add to the query, we
     * must obtain an appropriate lock, because this will be the first use of
     * those relations in the parse/rewrite/plan pipeline.  Child rels should
     * use the same lockmode as their parent.
     */
    oldrelation = table_open(parentOID, NoLock);
    lockmode = rte->rellockmode;

    /*
     * If parent relation is selected FOR UPDATE/SHARE, we need to mark its
     * PlanRowMark as isParent = true, and generate a new PlanRowMark for each
     * child.
     */
    oldrc = get_plan_rowmark(root->rowMarks, rti);
    if (oldrc)
    {
        old_isParent = oldrc->isParent;
        oldrc->isParent = true;
        /* Save initial value of allMarkTypes before children add to it */
        old_allMarkTypes = oldrc->allMarkTypes;
    }

    /* Scan the inheritance set and expand it */
    if (oldrelation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
    {
        /*
         * Partitioned table, so set up for partitioning.
         */
        Assert(rte->relkind == RELKIND_PARTITIONED_TABLE);

        /*
         * Recursively expand and lock the partitions.  While at it, also
         * extract the partition key columns of all the partitioned tables.
         */
        expand_partitioned_rtentry(root, rel, rte, rti,
                                   oldrelation, oldrc, lockmode);
    }
    else
    {
        /*
         * Ordinary table, so process traditional-inheritance children.  (Note
         * that partitioned tables are not allowed to have inheritance
         * children, so it's not possible for both cases to apply.)
         */
        List       *inhOIDs;
        ListCell   *l;

        /* Scan for all members of inheritance set, acquire needed locks */
        inhOIDs = find_all_inheritors(parentOID, lockmode, NULL);

        /*
         * We used to special-case the situation where the table no longer has
         * any children, by clearing rte->inh and exiting.  That no longer
         * works, because this function doesn't get run until after decisions
         * have been made that depend on rte->inh.  We have to treat such
         * situations as normal inheritance.  The table itself should always
         * have been found, though.
         */
        Assert(inhOIDs != NIL);
        Assert(linitial_oid(inhOIDs) == parentOID);

        /* Expand simple_rel_array and friends to hold child objects. */
        expand_planner_arrays(root, list_length(inhOIDs));

        /*
         * Expand inheritance children in the order the OIDs were returned by
         * find_all_inheritors.
         */
        foreach(l, inhOIDs)
        {
            Oid         childOID = lfirst_oid(l);
            Relation    newrelation;
            RangeTblEntry *childrte;
            Index       childRTindex;

            /* Open rel if needed; we already have required locks */
            if (childOID != parentOID)
                newrelation = table_open(childOID, NoLock);
            else
                newrelation = oldrelation;

            /*
             * It is possible that the parent table has children that are temp
             * tables of other backends.  We cannot safely access such tables
             * (because of buffering issues), and the best thing to do seems
             * to be to silently ignore them.
             */
            if (childOID != parentOID && RELATION_IS_OTHER_TEMP(newrelation))
            {
                table_close(newrelation, lockmode);
                continue;
            }

            /* Create RTE and AppendRelInfo, plus PlanRowMark if needed. */
            expand_single_inheritance_child(root, rte, rti, oldrelation,
                                            oldrc, newrelation,
                                            &childrte, &childRTindex);

            /* Create the otherrel RelOptInfo too. */
            (void) build_simple_rel(root, childRTindex, rel);

            /* Close child relations, but keep locks */
            if (childOID != parentOID)
                table_close(newrelation, NoLock);
        }
    }

    /*
     * Some children might require different mark types, which would've been
     * reported into oldrc.  If so, add relevant entries to the top-level
     * targetlist and update parent rel's reltarget.  This should match what
     * preprocess_targetlist() would have added if the mark types had been
     * requested originally.
     */
    if (oldrc)
    {
        int         new_allMarkTypes = oldrc->allMarkTypes;
        Var        *var;
        TargetEntry *tle;
        char        resname[32];
        List       *newvars = NIL;

        /* The old PlanRowMark should already have necessitated adding TID */
        Assert(old_allMarkTypes & ~(1 << ROW_MARK_COPY));

        /* Add whole-row junk Var if needed, unless we had it already */
        if ((new_allMarkTypes & (1 << ROW_MARK_COPY)) &&
            !(old_allMarkTypes & (1 << ROW_MARK_COPY)))
        {
            var = makeWholeRowVar(planner_rt_fetch(oldrc->rti, root),
                                  oldrc->rti,
                                  0,
                                  false);
            snprintf(resname, sizeof(resname), "wholerow%u", oldrc->rowmarkId);
            tle = makeTargetEntry((Expr *) var,
                                  list_length(root->processed_tlist) + 1,
                                  pstrdup(resname),
                                  true);
            root->processed_tlist = lappend(root->processed_tlist, tle);
            newvars = lappend(newvars, var);
        }

        /* Add tableoid junk Var, unless we had it already */
        if (!old_isParent)
        {
            var = makeVar(oldrc->rti,
                          TableOidAttributeNumber,
                          OIDOID,
                          -1,
                          InvalidOid,
                          0);
            snprintf(resname, sizeof(resname), "tableoid%u", oldrc->rowmarkId);
            tle = makeTargetEntry((Expr *) var,
                                  list_length(root->processed_tlist) + 1,
                                  pstrdup(resname),
                                  true);
            root->processed_tlist = lappend(root->processed_tlist, tle);
            newvars = lappend(newvars, var);
        }

        /*
         * Add the newly added Vars to parent's reltarget.  We needn't worry
         * about the children's reltargets, they'll be made later.
         */
        add_vars_to_targetlist(root, newvars, bms_make_singleton(0), false);
    }

    table_close(oldrelation, NoLock);
}

/*
 * expand_partitioned_rtentry
 *      Recursively expand an RTE for a partitioned table.
 */
static void
expand_partitioned_rtentry(PlannerInfo *root, RelOptInfo *relinfo,
                           RangeTblEntry *parentrte,
                           Index parentRTindex, Relation parentrel,
                           PlanRowMark *top_parentrc, LOCKMODE lockmode)
{
    PartitionDesc partdesc;
    Bitmapset  *live_parts;
    int         num_live_parts;
    int         i;

    check_stack_depth();

    Assert(parentrte->inh);

    partdesc = PartitionDirectoryLookup(root->glob->partition_directory,
                                        parentrel);

    /* A partitioned table should always have a partition descriptor. */
    Assert(partdesc);

    /*
     * Note down whether any partition key cols are being updated. Though it's
     * the root partitioned table's updatedCols we are interested in, we
     * instead use parentrte to get the updatedCols. This is convenient
     * because parentrte already has the root partrel's updatedCols translated
     * to match the attribute ordering of parentrel.
     */
    if (!root->partColsUpdated)
        root->partColsUpdated =
            has_partition_attrs(parentrel, parentrte->updatedCols, NULL);

    /*
     * There shouldn't be any generated columns in the partition key.
     */
    Assert(!has_partition_attrs(parentrel, parentrte->extraUpdatedCols, NULL));

    /* Nothing further to do here if there are no partitions. */
    if (partdesc->nparts == 0)
        return;

    /*
     * Perform partition pruning using restriction clauses assigned to parent
     * relation.  live_parts will contain PartitionDesc indexes of partitions
     * that survive pruning.  Below, we will initialize child objects for the
     * surviving partitions.
     */
    live_parts = prune_append_rel_partitions(relinfo);

    /* Expand simple_rel_array and friends to hold child objects. */
    num_live_parts = bms_num_members(live_parts);
    if (num_live_parts > 0)
        expand_planner_arrays(root, num_live_parts);

    /*
     * We also store partition RelOptInfo pointers in the parent relation.
     * Since we're palloc0'ing, slots corresponding to pruned partitions will
     * contain NULL.
     */
    Assert(relinfo->part_rels == NULL);
    relinfo->part_rels = (RelOptInfo **)
        palloc0(relinfo->nparts * sizeof(RelOptInfo *));

    /*
     * Create a child RTE for each live partition.  Note that unlike
     * traditional inheritance, we don't need a child RTE for the partitioned
     * table itself, because it's not going to be scanned.
     */
    i = -1;
    while ((i = bms_next_member(live_parts, i)) >= 0)
    {
        Oid         childOID = partdesc->oids[i];
        Relation    childrel;
        RangeTblEntry *childrte;
        Index       childRTindex;
        RelOptInfo *childrelinfo;

        /* Open rel, acquiring required locks */
        childrel = table_open(childOID, lockmode);

        /*
         * Temporary partitions belonging to other sessions should have been
         * disallowed at definition, but for paranoia's sake, let's double
         * check.
         */
        if (RELATION_IS_OTHER_TEMP(childrel))
            elog(ERROR, "temporary relation from another session found as partition");

        /* Create RTE and AppendRelInfo, plus PlanRowMark if needed. */
        expand_single_inheritance_child(root, parentrte, parentRTindex,
                                        parentrel, top_parentrc, childrel,
                                        &childrte, &childRTindex);

        /* Create the otherrel RelOptInfo too. */
        childrelinfo = build_simple_rel(root, childRTindex, relinfo);
        relinfo->part_rels[i] = childrelinfo;

        /* If this child is itself partitioned, recurse */
        if (childrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
            expand_partitioned_rtentry(root, childrelinfo,
                                       childrte, childRTindex,
                                       childrel, top_parentrc, lockmode);

        /* Close child relation, but keep locks */
        table_close(childrel, NoLock);
    }
}

/*
 * expand_single_inheritance_child
 *      Build a RangeTblEntry and an AppendRelInfo, plus maybe a PlanRowMark.
 *
 * We now expand the partition hierarchy level by level, creating a
 * corresponding hierarchy of AppendRelInfos and RelOptInfos, where each
 * partitioned descendant acts as a parent of its immediate partitions.
 * (This is a difference from what older versions of PostgreSQL did and what
 * is still done in the case of table inheritance for unpartitioned tables,
 * where the hierarchy is flattened during RTE expansion.)
 *
 * PlanRowMarks still carry the top-parent's RTI, and the top-parent's
 * allMarkTypes field still accumulates values from all descendents.
 *
 * "parentrte" and "parentRTindex" are immediate parent's RTE and
 * RTI. "top_parentrc" is top parent's PlanRowMark.
 *
 * The child RangeTblEntry and its RTI are returned in "childrte_p" and
 * "childRTindex_p" resp.
 */
static void
expand_single_inheritance_child(PlannerInfo *root, RangeTblEntry *parentrte,
                                Index parentRTindex, Relation parentrel,
                                PlanRowMark *top_parentrc, Relation childrel,
                                RangeTblEntry **childrte_p,
                                Index *childRTindex_p)
{
    Query      *parse = root->parse;
    Oid         parentOID = RelationGetRelid(parentrel);
    Oid         childOID = RelationGetRelid(childrel);
    RangeTblEntry *childrte;
    Index       childRTindex;
    AppendRelInfo *appinfo;

    /*
     * Build an RTE for the child, and attach to query's rangetable list. We
     * copy most fields of the parent's RTE, but replace relation OID,
     * relkind, and inh for the child.  Also, set requiredPerms to zero since
     * all required permissions checks are done on the original RTE. Likewise,
     * set the child's securityQuals to empty, because we only want to apply
     * the parent's RLS conditions regardless of what RLS properties
     * individual children may have.  (This is an intentional choice to make
     * inherited RLS work like regular permissions checks.) The parent
     * securityQuals will be propagated to children along with other base
     * restriction clauses, so we don't need to do it here.
     */
    childrte = copyObject(parentrte);
    *childrte_p = childrte;
    childrte->relid = childOID;
    childrte->relkind = childrel->rd_rel->relkind;
    /* A partitioned child will need to be expanded further. */
    if (childrte->relkind == RELKIND_PARTITIONED_TABLE)
    {
        Assert(childOID != parentOID);
        childrte->inh = true;
    }
    else
        childrte->inh = false;
    childrte->requiredPerms = 0;
    childrte->securityQuals = NIL;
    parse->rtable = lappend(parse->rtable, childrte);
    childRTindex = list_length(parse->rtable);
    *childRTindex_p = childRTindex;

    /*
     * Build an AppendRelInfo struct for each parent/child pair.
     */
    appinfo = make_append_rel_info(parentrel, childrel,
                                   parentRTindex, childRTindex);
    root->append_rel_list = lappend(root->append_rel_list, appinfo);

    /*
     * Translate the column permissions bitmaps to the child's attnums (we
     * have to build the translated_vars list before we can do this).  But if
     * this is the parent table, we can leave copyObject's result alone.
     *
     * Note: we need to do this even though the executor won't run any
     * permissions checks on the child RTE.  The insertedCols/updatedCols
     * bitmaps may be examined for trigger-firing purposes.
     */
    if (childOID != parentOID)
    {
        childrte->selectedCols = translate_col_privs(parentrte->selectedCols,
                                                     appinfo->translated_vars);
        childrte->insertedCols = translate_col_privs(parentrte->insertedCols,
                                                     appinfo->translated_vars);
        childrte->updatedCols = translate_col_privs(parentrte->updatedCols,
                                                    appinfo->translated_vars);
        childrte->extraUpdatedCols = translate_col_privs(parentrte->extraUpdatedCols,
                                                         appinfo->translated_vars);
    }

    /*
     * Store the RTE and appinfo in the respective PlannerInfo arrays, which
     * the caller must already have allocated space for.
     */
    Assert(childRTindex < root->simple_rel_array_size);
    Assert(root->simple_rte_array[childRTindex] == NULL);
    root->simple_rte_array[childRTindex] = childrte;
    Assert(root->append_rel_array[childRTindex] == NULL);
    root->append_rel_array[childRTindex] = appinfo;

    /*
     * Build a PlanRowMark if parent is marked FOR UPDATE/SHARE.
     */
    if (top_parentrc)
    {
        PlanRowMark *childrc = makeNode(PlanRowMark);

        childrc->rti = childRTindex;
        childrc->prti = top_parentrc->rti;
        childrc->rowmarkId = top_parentrc->rowmarkId;
        /* Reselect rowmark type, because relkind might not match parent */
        childrc->markType = select_rowmark_type(childrte,
                                                top_parentrc->strength);
        childrc->allMarkTypes = (1 << childrc->markType);
        childrc->strength = top_parentrc->strength;
        childrc->waitPolicy = top_parentrc->waitPolicy;

        /*
         * We mark RowMarks for partitioned child tables as parent RowMarks so
         * that the executor ignores them (except their existence means that
         * the child tables will be locked using the appropriate mode).
         */
        childrc->isParent = (childrte->relkind == RELKIND_PARTITIONED_TABLE);

        /* Include child's rowmark type in top parent's allMarkTypes */
        top_parentrc->allMarkTypes |= childrc->allMarkTypes;

        root->rowMarks = lappend(root->rowMarks, childrc);
    }
}

/*
 * translate_col_privs
 *    Translate a bitmapset representing per-column privileges from the
 *    parent rel's attribute numbering to the child's.
 *
 * The only surprise here is that we don't translate a parent whole-row
 * reference into a child whole-row reference.  That would mean requiring
 * permissions on all child columns, which is overly strict, since the
 * query is really only going to reference the inherited columns.  Instead
 * we set the per-column bits for all inherited columns.
 */
static Bitmapset *
translate_col_privs(const Bitmapset *parent_privs,
                    List *translated_vars)
{
    Bitmapset  *child_privs = NULL;
    bool        whole_row;
    int         attno;
    ListCell   *lc;

    /* System attributes have the same numbers in all tables */
    for (attno = FirstLowInvalidHeapAttributeNumber + 1; attno < 0; attno++)
    {
        if (bms_is_member(attno - FirstLowInvalidHeapAttributeNumber,
                          parent_privs))
            child_privs = bms_add_member(child_privs,
                                         attno - FirstLowInvalidHeapAttributeNumber);
    }

    /* Check if parent has whole-row reference */
    whole_row = bms_is_member(InvalidAttrNumber - FirstLowInvalidHeapAttributeNumber,
                              parent_privs);

    /* And now translate the regular user attributes, using the vars list */
    attno = InvalidAttrNumber;
    foreach(lc, translated_vars)
    {
        Var        *var = lfirst_node(Var, lc);

        attno++;
        if (var == NULL)        /* ignore dropped columns */
            continue;
        if (whole_row ||
            bms_is_member(attno - FirstLowInvalidHeapAttributeNumber,
                          parent_privs))
            child_privs = bms_add_member(child_privs,
                                         var->varattno - FirstLowInvalidHeapAttributeNumber);
    }

    return child_privs;
}

/*
 * expand_appendrel_subquery
 *      Add "other rel" RelOptInfos for the children of an appendrel baserel
 *
 * "rel" is a subquery relation that has the rte->inh flag set, meaning it
 * is a UNION ALL subquery that's been flattened into an appendrel, with
 * child subqueries listed in root->append_rel_list.  We need to build
 * a RelOptInfo for each child relation so that we can plan scans on them.
 */
static void
expand_appendrel_subquery(PlannerInfo *root, RelOptInfo *rel,
                          RangeTblEntry *rte, Index rti)
{
    ListCell   *l;

    foreach(l, root->append_rel_list)
    {
        AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
        Index       childRTindex = appinfo->child_relid;
        RangeTblEntry *childrte;
        RelOptInfo *childrel;

        /* append_rel_list contains all append rels; ignore others */
        if (appinfo->parent_relid != rti)
            continue;

        /* find the child RTE, which should already exist */
        Assert(childRTindex < root->simple_rel_array_size);
        childrte = root->simple_rte_array[childRTindex];
        Assert(childrte != NULL);

        /* Build the child RelOptInfo. */
        childrel = build_simple_rel(root, childRTindex, rel);

        /* Child may itself be an inherited rel, either table or subquery. */
        if (childrte->inh)
            expand_inherited_rtentry(root, childrel, childrte, childRTindex);
    }
}


/*
 * apply_child_basequals
 *      Populate childrel's base restriction quals from parent rel's quals,
 *      translating them using appinfo.
 *
 * If any of the resulting clauses evaluate to constant false or NULL, we
 * return false and don't apply any quals.  Caller should mark the relation as
 * a dummy rel in this case, since it doesn't need to be scanned.
 */
bool
apply_child_basequals(PlannerInfo *root, RelOptInfo *parentrel,
                      RelOptInfo *childrel, RangeTblEntry *childRTE,
                      AppendRelInfo *appinfo)
{
    List       *childquals;
    Index       cq_min_security;
    ListCell   *lc;

    /*
     * The child rel's targetlist might contain non-Var expressions, which
     * means that substitution into the quals could produce opportunities for
     * const-simplification, and perhaps even pseudoconstant quals. Therefore,
     * transform each RestrictInfo separately to see if it reduces to a
     * constant or pseudoconstant.  (We must process them separately to keep
     * track of the security level of each qual.)
     */
    childquals = NIL;
    cq_min_security = UINT_MAX;
    foreach(lc, parentrel->baserestrictinfo)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
        Node       *childqual;
        ListCell   *lc2;

        Assert(IsA(rinfo, RestrictInfo));
        childqual = adjust_appendrel_attrs(root,
                                           (Node *) rinfo->clause,
                                           1, &appinfo);
        childqual = eval_const_expressions(root, childqual);
        /* check for flat-out constant */
        if (childqual && IsA(childqual, Const))
        {
            if (((Const *) childqual)->constisnull ||
                !DatumGetBool(((Const *) childqual)->constvalue))
            {
                /* Restriction reduces to constant FALSE or NULL */
                return false;
            }
            /* Restriction reduces to constant TRUE, so drop it */
            continue;
        }
        /* might have gotten an AND clause, if so flatten it */
        foreach(lc2, make_ands_implicit((Expr *) childqual))
        {
            Node       *onecq = (Node *) lfirst(lc2);
            bool        pseudoconstant;

            /* check for pseudoconstant (no Vars or volatile functions) */
            pseudoconstant =
                !contain_vars_of_level(onecq, 0) &&
                !contain_volatile_functions(onecq);
            if (pseudoconstant)
            {
                /* tell createplan.c to check for gating quals */
                root->hasPseudoConstantQuals = true;
            }
            /* reconstitute RestrictInfo with appropriate properties */
            childquals = lappend(childquals,
                                 make_restrictinfo((Expr *) onecq,
                                                   rinfo->is_pushed_down,
                                                   rinfo->outerjoin_delayed,
                                                   pseudoconstant,
                                                   rinfo->security_level,
                                                   NULL, NULL, NULL));
            /* track minimum security level among child quals */
            cq_min_security = Min(cq_min_security, rinfo->security_level);
        }
    }

    /*
     * In addition to the quals inherited from the parent, we might have
     * securityQuals associated with this particular child node.  (Currently
     * this can only happen in appendrels originating from UNION ALL;
     * inheritance child tables don't have their own securityQuals, see
     * expand_single_inheritance_child().)  Pull any such securityQuals up
     * into the baserestrictinfo for the child.  This is similar to
     * process_security_barrier_quals() for the parent rel, except that we
     * can't make any general deductions from such quals, since they don't
     * hold for the whole appendrel.
     */
    if (childRTE->securityQuals)
    {
        Index       security_level = 0;

        foreach(lc, childRTE->securityQuals)
        {
            List       *qualset = (List *) lfirst(lc);
            ListCell   *lc2;

            foreach(lc2, qualset)
            {
                Expr       *qual = (Expr *) lfirst(lc2);

                /* not likely that we'd see constants here, so no check */
                childquals = lappend(childquals,
                                     make_restrictinfo(qual,
                                                       true, false, false,
                                                       security_level,
                                                       NULL, NULL, NULL));
                cq_min_security = Min(cq_min_security, security_level);
            }
            security_level++;
        }
        Assert(security_level <= root->qual_security_level);
    }

    /*
     * OK, we've got all the baserestrictinfo quals for this child.
     */
    childrel->baserestrictinfo = childquals;
    childrel->baserestrict_min_security = cq_min_security;

    return true;
}