pg_inherits.c File Reference

#include "postgres.h"
#include "access/genam.h"
#include "access/htup_details.h"
#include "access/table.h"
#include "catalog/indexing.h"
#include "catalog/pg_inherits.h"
#include "parser/parse_type.h"
#include "storage/lmgr.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"

Include dependency graph for pg_inherits.c:

Go to the source code of this file.

Data Structures
struct	SeenRelsEntry

Typedefs
typedef struct SeenRelsEntry	SeenRelsEntry

Functions
List *	find_inheritance_children (Oid parentrelId, LOCKMODE lockmode)
List *	find_inheritance_children_extended (Oid parentrelId, bool omit_detached, LOCKMODE lockmode, bool *detached_exist, TransactionId *detached_xmin)
List *	find_all_inheritors (Oid parentrelId, LOCKMODE lockmode, List **numparents)
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, bool expect_detach_pending, const char *childname)
bool	PartitionHasPendingDetach (Oid partoid)

Typedef Documentation

SeenRelsEntry

typedef struct SeenRelsEntry SeenRelsEntry

Function Documentation

DeleteInheritsTuple()

bool DeleteInheritsTuple	(	Oid	inhrelid,
		Oid	inhparent,
		bool	expect_detach_pending,
		const char *	childname
	)

Definition at line 552 of file pg_inherits.c.

{
    bool        found = false;
    Relation    catalogRelation;
    ScanKeyData key;
    SysScanDesc scan;
    HeapTuple   inheritsTuple;
 
    /*
     * Find pg_inherits entries by inhrelid.
     */
    catalogRelation = table_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)
        {
            bool        detach_pending;
 
            detach_pending =
                ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhdetachpending;
 
            /*
             * Raise error depending on state.  This should only happen for
             * partitions, but we have no way to cross-check.
             */
            if (detach_pending && !expect_detach_pending)
                ereport(ERROR,
                        (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                         errmsg("cannot detach partition \"%s\"",
                                childname ? childname : "unknown relation"),
                         errdetail("The partition is being detached concurrently or has an unfinished detach."),
                         errhint("Use ALTER TABLE ... DETACH PARTITION ... FINALIZE to complete the pending detach operation.")));
            if (!detach_pending && expect_detach_pending)
                ereport(ERROR,
                        (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                         errmsg("cannot complete detaching partition \"%s\"",
                                childname ? childname : "unknown relation"),
                         errdetail("There's no pending concurrent detach.")));
 
            CatalogTupleDelete(catalogRelation, &inheritsTuple->t_self);
            found = true;
        }
    }
 
    /* Done */
    systable_endscan(scan);
    table_close(catalogRelation, RowExclusiveLock);
 
    return found;
}

References BTEqualStrategyNumber, CatalogTupleDelete(), ereport, errcode(), errdetail(), errhint(), errmsg(), ERROR, fb(), GETSTRUCT(), HeapTupleIsValid, ObjectIdGetDatum(), OidIsValid, RowExclusiveLock, ScanKeyInit(), systable_beginscan(), systable_endscan(), systable_getnext(), table_close(), and table_open().

Referenced by index_concurrently_swap(), index_drop(), and RemoveInheritance().

find_all_inheritors()

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

Definition at line 255 of file pg_inherits.c.

{
    /* hash table for O(1) rel_oid -> rel_numparents cell lookup */
    HTAB       *seen_rels;
    HASHCTL     ctl;
    List       *rels_list,
               *rel_numparents;
    ListCell   *l;
 
    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.  Note
     * that we can't keep pointers into the output lists; but an index is
     * sufficient.
     */
    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 */
                ListCell   *numparents_cell;
 
                numparents_cell = list_nth_cell(rel_numparents,
                                                hash_entry->list_index);
                lfirst_int(numparents_cell)++;
            }
            else
            {
                /* if it's not there, add it. expect 1 parent, initially. */
                hash_entry->list_index = list_length(rels_list);
                rels_list = lappend_oid(rels_list, child_oid);
                rel_numparents = lappend_int(rel_numparents, 1);
            }
        }
    }
 
    if (numparents)
        *numparents = rel_numparents;
    else
        list_free(rel_numparents);
 
    hash_destroy(seen_rels);
 
    return rels_list;
}

References ctl, CurrentMemoryContext, fb(), find_inheritance_children(), HASH_BLOBS, HASH_CONTEXT, hash_create(), hash_destroy(), HASH_ELEM, HASH_ENTER, hash_search(), lappend_int(), lappend_oid(), lfirst_int, lfirst_oid, list_free(), list_length(), list_make1_int, list_make1_oid, and list_nth_cell().

Referenced by acquire_inherited_sample_rows(), apply_handle_truncate(), ATCheckPartitionsNotInUse(), ATExecAddInherit(), ATExecAttachPartition(), ATPrepAlterColumnType(), ATPrepCmd(), ATSimpleRecursion(), BeginCopyTo(), check_default_partition_contents(), CloneFkReferencing(), CreateTriggerFiringOn(), DefineIndex(), DetachPartitionFinalize(), ExecuteTruncate(), expand_inherited_rtentry(), expand_vacuum_rel(), get_tables_to_cluster_partitioned(), GetPubPartitionOptionRelations(), LockTableRecurse(), OpenTableList(), pg_partition_tree(), ProcessUtilitySlow(), QueueCheckConstraintValidation(), QueueNNConstraintValidation(), ReindexPartitions(), RemoveRelations(), rename_constraint_internal(), renameatt_internal(), renametrig(), and sepgsql_dml_privileges().

find_inheritance_children()

List * find_inheritance_children	(	Oid	parentrelId,
		LOCKMODE	lockmode
	)

Definition at line 58 of file pg_inherits.c.

{
    return find_inheritance_children_extended(parentrelId, true, lockmode,
                                              NULL, NULL);
}

References fb(), and find_inheritance_children_extended().

Referenced by ATAddCheckNNConstraint(), ATExecAddColumn(), ATExecAddIdentity(), ATExecAlterConstrInheritability(), ATExecDropColumn(), ATExecDropIdentity(), ATExecSetIdentity(), ATExecSetNotNull(), ATPrepAddPrimaryKey(), ATPrepAlterColumnType(), ATPrepDropExpression(), dropconstraint_internal(), find_all_inheritors(), rename_constraint_internal(), and renameatt_internal().

find_inheritance_children_extended()

List * find_inheritance_children_extended	(	Oid	parentrelId,
		bool	omit_detached,
		LOCKMODE	lockmode,
		bool *	detached_exist,
		TransactionId *	detached_xmin
	)

Definition at line 82 of file pg_inherits.c.

{
    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 = table_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)
    {
        /*
         * Cope with partitions concurrently being detached.  When we see a
         * partition marked "detach pending", we omit it from the returned set
         * of visible partitions if caller requested that and the tuple's xmin
         * does not appear in progress to the active snapshot.  (If there's no
         * active snapshot set, that means we're not running a user query, so
         * it's OK to always include detached partitions in that case; if the
         * xmin is still running to the active snapshot, then the partition
         * has not been detached yet and so we include it.)
         *
         * The reason for this hack is that we want to avoid seeing the
         * partition as alive in RI queries during REPEATABLE READ or
         * SERIALIZABLE transactions: such queries use a different snapshot
         * than the one used by regular (user) queries.
         */
        if (((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhdetachpending)
        {
            if (detached_exist)
                *detached_exist = true;
 
            if (omit_detached && ActiveSnapshotSet())
            {
                TransactionId xmin;
                Snapshot    snap;
 
                xmin = HeapTupleHeaderGetXmin(inheritsTuple->t_data);
                snap = GetActiveSnapshot();
 
                if (!XidInMVCCSnapshot(xmin, snap))
                {
                    if (detached_xmin)
                    {
                        /*
                         * Two detached partitions should not occur (see
                         * checks in MarkInheritDetached), but if they do,
                         * track the newer of the two.  Make sure to warn the
                         * user, so that they can clean up.  Since this is
                         * just a cross-check against potentially corrupt
                         * catalogs, we don't make it a full-fledged error
                         * message.
                         */
                        if (*detached_xmin != InvalidTransactionId)
                        {
                            elog(WARNING, "more than one partition pending detach found for table with OID %u",
                                 parentrelId);
                            if (TransactionIdFollows(xmin, *detached_xmin))
                                *detached_xmin = xmin;
                        }
                        else
                            *detached_xmin = xmin;
                    }
 
                    /* Don't add the partition to the output list */
                    continue;
                }
            }
        }
 
        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);
 
    table_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;
}

References AccessShareLock, ActiveSnapshotSet(), BTEqualStrategyNumber, elog, fb(), GetActiveSnapshot(), GETSTRUCT(), has_subclass(), HeapTupleHeaderGetXmin(), i, InvalidTransactionId, lappend_oid(), LockRelationOid(), NIL, NoLock, ObjectIdGetDatum(), oid_cmp(), palloc(), pfree(), qsort, repalloc(), ScanKeyInit(), SearchSysCacheExists1, systable_beginscan(), systable_endscan(), systable_getnext(), table_close(), table_open(), TransactionIdFollows(), UnlockRelationOid(), WARNING, and XidInMVCCSnapshot().

Referenced by find_inheritance_children(), and RelationBuildPartitionDesc().

has_subclass()

bool has_subclass

(

Oid

relationId

)

Definition at line 355 of file pg_inherits.c.

{
    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;
}

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

Referenced by find_inheritance_children_extended(), and typeInheritsFrom().

has_superclass()

bool has_superclass

(

Oid

relationId

)

Definition at line 377 of file pg_inherits.c.

{
    Relation    catalog;
    SysScanDesc scan;
    ScanKeyData skey;
    bool        result;
 
    catalog = table_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);
    table_close(catalog, AccessShareLock);
 
    return result;
}

References AccessShareLock, BTEqualStrategyNumber, fb(), HeapTupleIsValid, ObjectIdGetDatum(), ScanKeyInit(), systable_beginscan(), systable_endscan(), systable_getnext(), table_close(), and table_open().

Referenced by CreateTriggerFiringOn(), DefineIndex(), and DetachPartitionFinalize().

PartitionHasPendingDetach()

bool PartitionHasPendingDetach

(

Oid

partoid

)

Definition at line 620 of file pg_inherits.c.

{
    Relation    catalogRelation;
    ScanKeyData key;
    SysScanDesc scan;
    HeapTuple   inheritsTuple;
 
    /* We don't have a good way to verify it is in fact a partition */
 
    /*
     * Find the pg_inherits entry by inhrelid.  (There should only be one.)
     */
    catalogRelation = table_open(InheritsRelationId, RowExclusiveLock);
    ScanKeyInit(&key,
                Anum_pg_inherits_inhrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(partoid));
    scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
                              true, NULL, 1, &key);
 
    while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
    {
        bool        detached;
 
        detached =
            ((Form_pg_inherits) GETSTRUCT(inheritsTuple))->inhdetachpending;
 
        /* Done */
        systable_endscan(scan);
        table_close(catalogRelation, RowExclusiveLock);
 
        return detached;
    }
 
    elog(ERROR, "relation %u is not a partition", partoid);
    return false;               /* keep compiler quiet */
}

References BTEqualStrategyNumber, elog, ERROR, fb(), GETSTRUCT(), HeapTupleIsValid, ObjectIdGetDatum(), RowExclusiveLock, ScanKeyInit(), systable_beginscan(), systable_endscan(), systable_getnext(), table_close(), and table_open().

Referenced by ATPrepCmd().

StoreSingleInheritance()

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

Definition at line 508 of file pg_inherits.c.

{
    Datum       values[Natts_pg_inherits];
    bool        nulls[Natts_pg_inherits];
    HeapTuple   tuple;
    Relation    inhRelation;
 
    inhRelation = table_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);
    values[Anum_pg_inherits_inhdetachpending - 1] = BoolGetDatum(false);
 
    memset(nulls, 0, sizeof(nulls));
 
    tuple = heap_form_tuple(RelationGetDescr(inhRelation), values, nulls);
 
    CatalogTupleInsert(inhRelation, tuple);
 
    heap_freetuple(tuple);
 
    table_close(inhRelation, RowExclusiveLock);
}

References BoolGetDatum(), CatalogTupleInsert(), fb(), heap_form_tuple(), heap_freetuple(), Int32GetDatum(), ObjectIdGetDatum(), RelationGetDescr, RowExclusiveLock, table_close(), table_open(), and values.

Referenced by index_concurrently_swap(), index_create(), IndexSetParentIndex(), and StoreCatalogInheritance1().

typeInheritsFrom()

bool typeInheritsFrom	(	Oid	subclassTypeId,
		Oid	superclassTypeId
	)

Definition at line 406 of file pg_inherits.c.

{
    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 = table_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 ... */
    table_close(inhrel, AccessShareLock);
 
    list_free(visited);
    list_free(queue);
 
    return result;
}

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

Referenced by can_coerce_type(), and coerce_type().