pg_inherits.h File Reference

#include "catalog/genbki.h"
#include "catalog/pg_inherits_d.h"
#include "nodes/pg_list.h"
#include "storage/lock.h"

Include dependency graph for pg_inherits.h:

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Go to the source code of this file.

Typedefs
typedef FormData_pg_inherits *	Form_pg_inherits

Functions
	CATALOG (pg_inherits, 2611, InheritsRelationId) BKI_WITHOUT_OIDS
List *	find_inheritance_children (Oid parentrelId, LOCKMODE lockmode)
List *	find_all_inheritors (Oid parentrelId, LOCKMODE lockmode, List **parents)
bool	has_subclass (Oid relationId)
bool	has_superclass (Oid relationId)
bool	typeInheritsFrom (Oid subclassTypeId, Oid superclassTypeId)
void	StoreSingleInheritance (Oid relationId, Oid parentOid, int32 seqNumber)
bool	DeleteInheritsTuple (Oid inhrelid, Oid inhparent)

Variables
	FormData_pg_inherits

Typedef Documentation

Form_pg_inherits

typedef FormData_pg_inherits* Form_pg_inherits

Definition at line 44 of file pg_inherits.h.

Function Documentation

CATALOG()

CATALOG	(	pg_inherits	,
		2611	,
		InheritsRelationId
	)

Definition at line 32 of file pg_inherits.h.

{
    Oid         inhrelid;
    Oid         inhparent;
    int32       inhseqno;
} FormData_pg_inherits;

DeleteInheritsTuple()

bool DeleteInheritsTuple	(	Oid	inhrelid,
		Oid	inhparent
	)

Definition at line 449 of file pg_inherits.c.

References BTEqualStrategyNumber, CatalogTupleDelete(), GETSTRUCT, heap_close, heap_open(), HeapTupleIsValid, InheritsRelidSeqnoIndexId, ObjectIdGetDatum, OidIsValid, RowExclusiveLock, ScanKeyInit(), systable_beginscan(), systable_endscan(), systable_getnext(), and HeapTupleData::t_self.

Referenced by index_drop(), and RemoveInheritance().

{
    bool        found = false;
    Relation    catalogRelation;
    ScanKeyData key;
    SysScanDesc scan;
    HeapTuple   inheritsTuple;

    /*
     * Find pg_inherits entries by inhrelid.
     */
    catalogRelation = heap_open(InheritsRelationId, RowExclusiveLock);
    ScanKeyInit(&key,
                Anum_pg_inherits_inhrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(inhrelid));
    scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
                              true, NULL, 1, &key);

    while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
    {
        Oid         parent;

        /* Compare inhparent if it was given, and do the actual deletion. */
        parent = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhparent;
        if (!OidIsValid(inhparent) || parent == inhparent)
        {
            CatalogTupleDelete(catalogRelation, &inheritsTuple->t_self);
            found = true;
        }
    }

    /* Done */
    systable_endscan(scan);
    heap_close(catalogRelation, RowExclusiveLock);

    return found;
}

find_all_inheritors()

List* find_all_inheritors	(	Oid	parentrelId,
		LOCKMODE	lockmode,
		List **	parents
	)

Definition at line 166 of file pg_inherits.c.

References CurrentMemoryContext, HASHCTL::entrysize, find_inheritance_children(), HASH_BLOBS, HASH_CONTEXT, hash_create(), hash_destroy(), HASH_ELEM, HASH_ENTER, hash_search(), HASHCTL::hcxt, HASHCTL::keysize, lappend_int(), lappend_oid(), lfirst_int, lfirst_oid, list_free(), list_make1_int, list_make1_oid, SeenRelsEntry::numparents_cell, and List::tail.

Referenced by acquire_inherited_sample_rows(), ATExecAddInherit(), ATExecAttachPartition(), ATExecValidateConstraint(), ATPrepAlterColumnType(), ATSimpleRecursion(), check_default_allows_bound(), CreateTrigger(), ExecSetupPartitionTupleRouting(), ExecuteTruncate(), expand_inherited_rtentry(), expand_vacuum_rel(), OpenTableList(), ProcessUtilitySlow(), rename_constraint_internal(), renameatt_internal(), and sepgsql_dml_privileges().

{
    /* hash table for O(1) rel_oid -> rel_numparents cell lookup */
    HTAB       *seen_rels;
    HASHCTL     ctl;
    List       *rels_list,
               *rel_numparents;
    ListCell   *l;

    memset(&ctl, 0, sizeof(ctl));
    ctl.keysize = sizeof(Oid);
    ctl.entrysize = sizeof(SeenRelsEntry);
    ctl.hcxt = CurrentMemoryContext;

    seen_rels = hash_create("find_all_inheritors temporary table",
                            32, /* start small and extend */
                            &ctl,
                            HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);

    /*
     * We build a list starting with the given rel and adding all direct and
     * indirect children.  We can use a single list as both the record of
     * already-found rels and the agenda of rels yet to be scanned for more
     * children.  This is a bit tricky but works because the foreach() macro
     * doesn't fetch the next list element until the bottom of the loop.
     */
    rels_list = list_make1_oid(parentrelId);
    rel_numparents = list_make1_int(0);

    foreach(l, rels_list)
    {
        Oid         currentrel = lfirst_oid(l);
        List       *currentchildren;
        ListCell   *lc;

        /* Get the direct children of this rel */
        currentchildren = find_inheritance_children(currentrel, lockmode);

        /*
         * Add to the queue only those children not already seen. This avoids
         * making duplicate entries in case of multiple inheritance paths from
         * the same parent.  (It'll also keep us from getting into an infinite
         * loop, though theoretically there can't be any cycles in the
         * inheritance graph anyway.)
         */
        foreach(lc, currentchildren)
        {
            Oid         child_oid = lfirst_oid(lc);
            bool        found;
            SeenRelsEntry *hash_entry;

            hash_entry = hash_search(seen_rels, &child_oid, HASH_ENTER, &found);
            if (found)
            {
                /* if the rel is already there, bump number-of-parents counter */
                lfirst_int(hash_entry->numparents_cell)++;
            }
            else
            {
                /* if it's not there, add it. expect 1 parent, initially. */
                rels_list = lappend_oid(rels_list, child_oid);
                rel_numparents = lappend_int(rel_numparents, 1);
                hash_entry->numparents_cell = rel_numparents->tail;
            }
        }
    }

    if (numparents)
        *numparents = rel_numparents;
    else
        list_free(rel_numparents);

    hash_destroy(seen_rels);

    return rels_list;
}

find_inheritance_children()

List* find_inheritance_children	(	Oid	parentrelId,
		LOCKMODE	lockmode
	)

Definition at line 56 of file pg_inherits.c.

References AccessShareLock, BTEqualStrategyNumber, GETSTRUCT, has_subclass(), heap_close, heap_open(), i, InheritsParentIndexId, lappend_oid(), sort-test::list, LockRelationOid(), NIL, NoLock, ObjectIdGetDatum, oid_cmp(), palloc(), pfree(), qsort, RELOID, repalloc(), ScanKeyInit(), SearchSysCacheExists1, systable_beginscan(), systable_endscan(), systable_getnext(), and UnlockRelationOid().

Referenced by ATAddCheckConstraint(), ATExecAddColumn(), ATExecDropColumn(), ATExecDropConstraint(), ATPrepAlterColumnType(), CreateTrigger(), find_all_inheritors(), LockTableRecurse(), RelationBuildPartitionDesc(), rename_constraint_internal(), and renameatt_internal().

{
    List       *list = NIL;
    Relation    relation;
    SysScanDesc scan;
    ScanKeyData key[1];
    HeapTuple   inheritsTuple;
    Oid         inhrelid;
    Oid        *oidarr;
    int         maxoids,
                numoids,
                i;

    /*
     * Can skip the scan if pg_class shows the relation has never had a
     * subclass.
     */
    if (!has_subclass(parentrelId))
        return NIL;

    /*
     * Scan pg_inherits and build a working array of subclass OIDs.
     */
    maxoids = 32;
    oidarr = (Oid *) palloc(maxoids * sizeof(Oid));
    numoids = 0;

    relation = heap_open(InheritsRelationId, AccessShareLock);

    ScanKeyInit(&key[0],
                Anum_pg_inherits_inhparent,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(parentrelId));

    scan = systable_beginscan(relation, InheritsParentIndexId, true,
                              NULL, 1, key);

    while ((inheritsTuple = systable_getnext(scan)) != NULL)
    {
        inhrelid = ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhrelid;
        if (numoids >= maxoids)
        {
            maxoids *= 2;
            oidarr = (Oid *) repalloc(oidarr, maxoids * sizeof(Oid));
        }
        oidarr[numoids++] = inhrelid;
    }

    systable_endscan(scan);

    heap_close(relation, AccessShareLock);

    /*
     * If we found more than one child, sort them by OID.  This ensures
     * reasonably consistent behavior regardless of the vagaries of an
     * indexscan.  This is important since we need to be sure all backends
     * lock children in the same order to avoid needless deadlocks.
     */
    if (numoids > 1)
        qsort(oidarr, numoids, sizeof(Oid), oid_cmp);

    /*
     * Acquire locks and build the result list.
     */
    for (i = 0; i < numoids; i++)
    {
        inhrelid = oidarr[i];

        if (lockmode != NoLock)
        {
            /* Get the lock to synchronize against concurrent drop */
            LockRelationOid(inhrelid, lockmode);

            /*
             * Now that we have the lock, double-check to see if the relation
             * really exists or not.  If not, assume it was dropped while we
             * waited to acquire lock, and ignore it.
             */
            if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(inhrelid)))
            {
                /* Release useless lock */
                UnlockRelationOid(inhrelid, lockmode);
                /* And ignore this relation */
                continue;
            }
        }

        list = lappend_oid(list, inhrelid);
    }

    pfree(oidarr);

    return list;
}

has_subclass()

bool has_subclass

(

Oid

relationId

)

Definition at line 261 of file pg_inherits.c.

References elog, ERROR, GETSTRUCT, HeapTupleIsValid, ObjectIdGetDatum, ReleaseSysCache(), relhassubclass, RELOID, and SearchSysCache1().

Referenced by expand_inherited_rtentry(), find_inheritance_children(), and typeInheritsFrom().

{
    HeapTuple   tuple;
    bool        result;

    tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relationId));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for relation %u", relationId);

    result = ((Form_pg_class) GETSTRUCT(tuple))->relhassubclass;
    ReleaseSysCache(tuple);
    return result;
}

has_superclass()

bool has_superclass

(

Oid

relationId

)

Definition at line 281 of file pg_inherits.c.

References AccessShareLock, BTEqualStrategyNumber, heap_close, heap_open(), HeapTupleIsValid, InheritsRelidSeqnoIndexId, ObjectIdGetDatum, ScanKeyInit(), systable_beginscan(), systable_endscan(), and systable_getnext().

Referenced by ATExecDetachPartition(), CreateTrigger(), and DefineIndex().

{
    Relation    catalog;
    SysScanDesc scan;
    ScanKeyData skey;
    bool        result;

    catalog = heap_open(InheritsRelationId, AccessShareLock);
    ScanKeyInit(&skey, Anum_pg_inherits_inhrelid, BTEqualStrategyNumber,
                F_OIDEQ, ObjectIdGetDatum(relationId));
    scan = systable_beginscan(catalog, InheritsRelidSeqnoIndexId, true,
                              NULL, 1, &skey);
    result = HeapTupleIsValid(systable_getnext(scan));
    systable_endscan(scan);
    heap_close(catalog, AccessShareLock);

    return result;
}

StoreSingleInheritance()

void StoreSingleInheritance	(	Oid	relationId,
		Oid	parentOid,
		int32	seqNumber
	)

Definition at line 412 of file pg_inherits.c.

References CatalogTupleInsert(), heap_close, heap_form_tuple(), heap_freetuple(), heap_open(), Int32GetDatum, ObjectIdGetDatum, RelationGetDescr, RowExclusiveLock, and values.

Referenced by index_create(), and StoreCatalogInheritance1().

{
    Datum       values[Natts_pg_inherits];
    bool        nulls[Natts_pg_inherits];
    HeapTuple   tuple;
    Relation    inhRelation;

    inhRelation = heap_open(InheritsRelationId, RowExclusiveLock);

    /*
     * Make the pg_inherits entry
     */
    values[Anum_pg_inherits_inhrelid - 1] = ObjectIdGetDatum(relationId);
    values[Anum_pg_inherits_inhparent - 1] = ObjectIdGetDatum(parentOid);
    values[Anum_pg_inherits_inhseqno - 1] = Int32GetDatum(seqNumber);

    memset(nulls, 0, sizeof(nulls));

    tuple = heap_form_tuple(RelationGetDescr(inhRelation), values, nulls);

    CatalogTupleInsert(inhRelation, tuple);

    heap_freetuple(tuple);

    heap_close(inhRelation, RowExclusiveLock);
}

typeInheritsFrom()

bool typeInheritsFrom	(	Oid	subclassTypeId,
		Oid	superclassTypeId
	)

Definition at line 310 of file pg_inherits.c.

References AccessShareLock, BTEqualStrategyNumber, GETSTRUCT, has_subclass(), heap_close, heap_open(), InheritsRelidSeqnoIndexId, InvalidOid, lappend_oid(), lfirst_oid, list_free(), list_make1_oid, list_member_oid(), NIL, ObjectIdGetDatum, ScanKeyInit(), systable_beginscan(), systable_endscan(), systable_getnext(), typeidTypeRelid(), and typeOrDomainTypeRelid().

Referenced by can_coerce_type(), and coerce_type().

{
    bool        result = false;
    Oid         subclassRelid;
    Oid         superclassRelid;
    Relation    inhrel;
    List       *visited,
               *queue;
    ListCell   *queue_item;

    /* We need to work with the associated relation OIDs */
    subclassRelid = typeOrDomainTypeRelid(subclassTypeId);
    if (subclassRelid == InvalidOid)
        return false;           /* not a complex type or domain over one */
    superclassRelid = typeidTypeRelid(superclassTypeId);
    if (superclassRelid == InvalidOid)
        return false;           /* not a complex type */

    /* No point in searching if the superclass has no subclasses */
    if (!has_subclass(superclassRelid))
        return false;

    /*
     * Begin the search at the relation itself, so add its relid to the queue.
     */
    queue = list_make1_oid(subclassRelid);
    visited = NIL;

    inhrel = heap_open(InheritsRelationId, AccessShareLock);

    /*
     * Use queue to do a breadth-first traversal of the inheritance graph from
     * the relid supplied up to the root.  Notice that we append to the queue
     * inside the loop --- this is okay because the foreach() macro doesn't
     * advance queue_item until the next loop iteration begins.
     */
    foreach(queue_item, queue)
    {
        Oid         this_relid = lfirst_oid(queue_item);
        ScanKeyData skey;
        SysScanDesc inhscan;
        HeapTuple   inhtup;

        /*
         * If we've seen this relid already, skip it.  This avoids extra work
         * in multiple-inheritance scenarios, and also protects us from an
         * infinite loop in case there is a cycle in pg_inherits (though
         * theoretically that shouldn't happen).
         */
        if (list_member_oid(visited, this_relid))
            continue;

        /*
         * Okay, this is a not-yet-seen relid. Add it to the list of
         * already-visited OIDs, then find all the types this relid inherits
         * from and add them to the queue.
         */
        visited = lappend_oid(visited, this_relid);

        ScanKeyInit(&skey,
                    Anum_pg_inherits_inhrelid,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(this_relid));

        inhscan = systable_beginscan(inhrel, InheritsRelidSeqnoIndexId, true,
                                     NULL, 1, &skey);

        while ((inhtup = systable_getnext(inhscan)) != NULL)
        {
            Form_pg_inherits inh = (Form_pg_inherits) GETSTRUCT(inhtup);
            Oid         inhparent = inh->inhparent;

            /* If this is the target superclass, we're done */
            if (inhparent == superclassRelid)
            {
                result = true;
                break;
            }

            /* Else add to queue */
            queue = lappend_oid(queue, inhparent);
        }

        systable_endscan(inhscan);

        if (result)
            break;
    }

    /* clean up ... */
    heap_close(inhrel, AccessShareLock);

    list_free(visited);
    list_free(queue);

    return result;
}

Variable Documentation

FormData_pg_inherits

FormData_pg_inherits

Definition at line 37 of file pg_inherits.h.