-
Tom Lane authored
of shared or nailed system catalogs. This has two key benefits: * The new CLUSTER-based VACUUM FULL can be applied safely to all catalogs. * We no longer have to use an unsafe reindex-in-place approach for reindexing shared catalogs. CLUSTER on nailed catalogs now works too, although I left it disabled on shared catalogs because the resulting pg_index.indisclustered update would only be visible in one database. Since reindexing shared system catalogs is now fully transactional and crash-safe, the former special cases in REINDEX behavior have been removed; shared catalogs are treated the same as non-shared. This commit does not do anything about the recently-discussed problem of deadlocks between VACUUM FULL/CLUSTER on a system catalog and other concurrent queries; will address that in a separate patch. As a stopgap, parallel_schedule has been tweaked to run vacuum.sql by itself, to avoid such failures during the regression tests.
Tom Lane authoredof shared or nailed system catalogs. This has two key benefits: * The new CLUSTER-based VACUUM FULL can be applied safely to all catalogs. * We no longer have to use an unsafe reindex-in-place approach for reindexing shared catalogs. CLUSTER on nailed catalogs now works too, although I left it disabled on shared catalogs because the resulting pg_index.indisclustered update would only be visible in one database. Since reindexing shared system catalogs is now fully transactional and crash-safe, the former special cases in REINDEX behavior have been removed; shared catalogs are treated the same as non-shared. This commit does not do anything about the recently-discussed problem of deadlocks between VACUUM FULL/CLUSTER on a system catalog and other concurrent queries; will address that in a separate patch. As a stopgap, parallel_schedule has been tweaked to run vacuum.sql by itself, to avoid such failures during the regression tests.
cluster.c 47.30 KiB
/*-------------------------------------------------------------------------
*
* cluster.c
* CLUSTER a table on an index. This is now also used for VACUUM FULL.
*
* There is hardly anything left of Paul Brown's original implementation...
*
*
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994-5, Regents of the University of California
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.198 2010/02/07 20:48:10 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/heapam.h"
#include "access/relscan.h"
#include "access/rewriteheap.h"
#include "access/transam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/heap.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_namespace.h"
#include "catalog/toasting.h"
#include "commands/cluster.h"
#include "commands/tablecmds.h"
#include "commands/trigger.h"
#include "commands/vacuum.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/procarray.h"
#include "utils/acl.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/relcache.h"
#include "utils/relmapper.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
/*
* This struct is used to pass around the information on tables to be
* clustered. We need this so we can make a list of them when invoked without
* a specific table/index pair.
*/
typedef struct
{
Oid tableOid;
Oid indexOid;
} RelToCluster;
static void rebuild_relation(Relation OldHeap, Oid indexOid,
int freeze_min_age, int freeze_table_age);
static void copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex,
int freeze_min_age, int freeze_table_age,
bool *pSwapToastByContent, TransactionId *pFreezeXid);
static List *get_tables_to_cluster(MemoryContext cluster_context);
/*---------------------------------------------------------------------------
* This cluster code allows for clustering multiple tables at once. Because
* of this, we cannot just run everything on a single transaction, or we
* would be forced to acquire exclusive locks on all the tables being
* clustered, simultaneously --- very likely leading to deadlock.
*
* To solve this we follow a similar strategy to VACUUM code,
* clustering each relation in a separate transaction. For this to work,
* we need to:
* - provide a separate memory context so that we can pass information in
* a way that survives across transactions
* - start a new transaction every time a new relation is clustered
* - check for validity of the information on to-be-clustered relations,
* as someone might have deleted a relation behind our back, or
* clustered one on a different index
* - end the transaction
*
* The single-relation case does not have any such overhead.
*
* We also allow a relation to be specified without index. In that case,
* the indisclustered bit will be looked up, and an ERROR will be thrown
* if there is no index with the bit set.
*---------------------------------------------------------------------------
*/
void
cluster(ClusterStmt *stmt, bool isTopLevel)
{
if (stmt->relation != NULL)
{
/* This is the single-relation case. */
Oid tableOid,
indexOid = InvalidOid;
Relation rel;
/* Find and lock the table */
rel = heap_openrv(stmt->relation, AccessExclusiveLock);
tableOid = RelationGetRelid(rel);
/* Check permissions */
if (!pg_class_ownercheck(tableOid, GetUserId()))
aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
RelationGetRelationName(rel));
/*
* Reject clustering a remote temp table ... their local buffer
* manager is not going to cope.
*/
if (RELATION_IS_OTHER_TEMP(rel))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot cluster temporary tables of other sessions")));
if (stmt->indexname == NULL)
{
ListCell *index;
/* We need to find the index that has indisclustered set. */
foreach(index, RelationGetIndexList(rel))
{
HeapTuple idxtuple;
Form_pg_index indexForm;
indexOid = lfirst_oid(index);
idxtuple = SearchSysCache(INDEXRELID,
ObjectIdGetDatum(indexOid),
0, 0, 0); if (!HeapTupleIsValid(idxtuple))
elog(ERROR, "cache lookup failed for index %u", indexOid);
indexForm = (Form_pg_index) GETSTRUCT(idxtuple);
if (indexForm->indisclustered)
{
ReleaseSysCache(idxtuple);
break;
}
ReleaseSysCache(idxtuple);
indexOid = InvalidOid;
}
if (!OidIsValid(indexOid))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("there is no previously clustered index for table \"%s\"",
stmt->relation->relname)));
}
else
{
/*
* The index is expected to be in the same namespace as the
* relation.
*/
indexOid = get_relname_relid(stmt->indexname,
rel->rd_rel->relnamespace);
if (!OidIsValid(indexOid))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("index \"%s\" for table \"%s\" does not exist",
stmt->indexname, stmt->relation->relname)));
}
/* close relation, keep lock till commit */
heap_close(rel, NoLock);
/* Do the job */
cluster_rel(tableOid, indexOid, false, stmt->verbose, -1, -1);
}
else
{
/*
* This is the "multi relation" case. We need to cluster all tables
* that have some index with indisclustered set.
*/
MemoryContext cluster_context;
List *rvs;
ListCell *rv;
/*
* We cannot run this form of CLUSTER inside a user transaction block;
* we'd be holding locks way too long.
*/
PreventTransactionChain(isTopLevel, "CLUSTER");
/*
* Create special memory context for cross-transaction storage.
*
* Since it is a child of PortalContext, it will go away even in case
* of error.
*/
cluster_context = AllocSetContextCreate(PortalContext,
"Cluster",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
/*
* Build the list of relations to cluster. Note that this lives in
* cluster_context. */
rvs = get_tables_to_cluster(cluster_context);
/* Commit to get out of starting transaction */
PopActiveSnapshot();
CommitTransactionCommand();
/* Ok, now that we've got them all, cluster them one by one */
foreach(rv, rvs)
{
RelToCluster *rvtc = (RelToCluster *) lfirst(rv);
/* Start a new transaction for each relation. */
StartTransactionCommand();
/* functions in indexes may want a snapshot set */
PushActiveSnapshot(GetTransactionSnapshot());
cluster_rel(rvtc->tableOid, rvtc->indexOid, true, stmt->verbose,
-1, -1);
PopActiveSnapshot();
CommitTransactionCommand();
}
/* Start a new transaction for the cleanup work. */
StartTransactionCommand();
/* Clean up working storage */
MemoryContextDelete(cluster_context);
}
}
/*
* cluster_rel
*
* This clusters the table by creating a new, clustered table and
* swapping the relfilenodes of the new table and the old table, so
* the OID of the original table is preserved. Thus we do not lose
* GRANT, inheritance nor references to this table (this was a bug
* in releases thru 7.3).
*
* Indexes are rebuilt too, via REINDEX. Since we are effectively bulk-loading
* the new table, it's better to create the indexes afterwards than to fill
* them incrementally while we load the table.
*
* If indexOid is InvalidOid, the table will be rewritten in physical order
* instead of index order. This is the new implementation of VACUUM FULL,
* and error messages should refer to the operation as VACUUM not CLUSTER.
*/
void
cluster_rel(Oid tableOid, Oid indexOid, bool recheck, bool verbose,
int freeze_min_age, int freeze_table_age)
{
Relation OldHeap;
/* Check for user-requested abort. */
CHECK_FOR_INTERRUPTS();
/*
* We grab exclusive access to the target rel and index for the duration
* of the transaction. (This is redundant for the single-transaction
* case, since cluster() already did it.) The index lock is taken inside
* check_index_is_clusterable.
*/
OldHeap = try_relation_open(tableOid, AccessExclusiveLock);
/* If the table has gone away, we can skip processing it */
if (!OldHeap)
return;
/*
* Since we may open a new transaction for each relation, we have to check * that the relation still is what we think it is.
*
* If this is a single-transaction CLUSTER, we can skip these tests. We
* *must* skip the one on indisclustered since it would reject an attempt
* to cluster a not-previously-clustered index.
*/
if (recheck)
{
HeapTuple tuple;
Form_pg_index indexForm;
/* Check that the user still owns the relation */
if (!pg_class_ownercheck(tableOid, GetUserId()))
{
relation_close(OldHeap, AccessExclusiveLock);
return;
}
/*
* Silently skip a temp table for a remote session. Only doing this
* check in the "recheck" case is appropriate (which currently means
* somebody is executing a database-wide CLUSTER), because there is
* another check in cluster() which will stop any attempt to cluster
* remote temp tables by name. There is another check in
* cluster_rel which is redundant, but we leave it for extra safety.
*/
if (RELATION_IS_OTHER_TEMP(OldHeap))
{
relation_close(OldHeap, AccessExclusiveLock);
return;
}
if (OidIsValid(indexOid))
{
/*
* Check that the index still exists
*/
if (!SearchSysCacheExists(RELOID,
ObjectIdGetDatum(indexOid),
0, 0, 0))
{
relation_close(OldHeap, AccessExclusiveLock);
return;
}
/*
* Check that the index is still the one with indisclustered set.
*/
tuple = SearchSysCache(INDEXRELID,
ObjectIdGetDatum(indexOid),
0, 0, 0);
if (!HeapTupleIsValid(tuple)) /* probably can't happen */
{
relation_close(OldHeap, AccessExclusiveLock);
return;
}
indexForm = (Form_pg_index) GETSTRUCT(tuple);
if (!indexForm->indisclustered)
{
ReleaseSysCache(tuple);
relation_close(OldHeap, AccessExclusiveLock);
return;
}
ReleaseSysCache(tuple);
}
}
/*
* We allow VACUUM FULL, but not CLUSTER, on shared catalogs. CLUSTER
* would work in most respects, but the index would only get marked as * indisclustered in the current database, leading to unexpected behavior
* if CLUSTER were later invoked in another database.
*/
if (OidIsValid(indexOid) && OldHeap->rd_rel->relisshared)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot cluster a shared catalog")));
/*
* Don't process temp tables of other backends ... their local
* buffer manager is not going to cope.
*/
if (RELATION_IS_OTHER_TEMP(OldHeap))
{
if (OidIsValid(indexOid))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot cluster temporary tables of other sessions")));
else
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot vacuum temporary tables of other sessions")));
}
/*
* Also check for active uses of the relation in the current transaction,
* including open scans and pending AFTER trigger events.
*/
CheckTableNotInUse(OldHeap, OidIsValid(indexOid) ? "CLUSTER" : "VACUUM");
/* Check heap and index are valid to cluster on */
if (OidIsValid(indexOid))
check_index_is_clusterable(OldHeap, indexOid, recheck);
/* Log what we're doing (this could use more effort) */
if (OidIsValid(indexOid))
ereport(verbose ? INFO : DEBUG2,
(errmsg("clustering \"%s.%s\"",
get_namespace_name(RelationGetNamespace(OldHeap)),
RelationGetRelationName(OldHeap))));
else
ereport(verbose ? INFO : DEBUG2,
(errmsg("vacuuming \"%s.%s\"",
get_namespace_name(RelationGetNamespace(OldHeap)),
RelationGetRelationName(OldHeap))));
/* rebuild_relation does all the dirty work */
rebuild_relation(OldHeap, indexOid, freeze_min_age, freeze_table_age);
/* NB: rebuild_relation does heap_close() on OldHeap */
}
/*
* Verify that the specified heap and index are valid to cluster on
*
* Side effect: obtains exclusive lock on the index. The caller should
* already have exclusive lock on the table, so the index lock is likely
* redundant, but it seems best to grab it anyway to ensure the index
* definition can't change under us.
*/
void
check_index_is_clusterable(Relation OldHeap, Oid indexOid, bool recheck)
{
Relation OldIndex;
OldIndex = index_open(indexOid, AccessExclusiveLock);
/*
* Check that index is in fact an index on the given relation
*/ if (OldIndex->rd_index == NULL ||
OldIndex->rd_index->indrelid != RelationGetRelid(OldHeap))
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is not an index for table \"%s\"",
RelationGetRelationName(OldIndex),
RelationGetRelationName(OldHeap))));
/* Index AM must allow clustering */
if (!OldIndex->rd_am->amclusterable)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot cluster on index \"%s\" because access method does not support clustering",
RelationGetRelationName(OldIndex))));
/*
* Disallow clustering on incomplete indexes (those that might not index
* every row of the relation). We could relax this by making a separate
* seqscan pass over the table to copy the missing rows, but that seems
* expensive and tedious.
*/
if (!heap_attisnull(OldIndex->rd_indextuple, Anum_pg_index_indpred))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot cluster on partial index \"%s\"",
RelationGetRelationName(OldIndex))));
if (!OldIndex->rd_am->amindexnulls)
{
AttrNumber colno;
/*
* If the AM doesn't index nulls, then it's a partial index unless we
* can prove all the rows are non-null. Note we only need look at the
* first column; multicolumn-capable AMs are *required* to index nulls
* in columns after the first.
*/
colno = OldIndex->rd_index->indkey.values[0];
if (colno > 0)
{
/* ordinary user attribute */
if (!OldHeap->rd_att->attrs[colno - 1]->attnotnull)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot cluster on index \"%s\" because access method does not handle null values",
RelationGetRelationName(OldIndex)),
recheck
? errhint("You might be able to work around this by marking column \"%s\" NOT NULL, or use ALTER TABLE ... SET WITHOUT CLUSTER to remove the cluster specification from the table.",
NameStr(OldHeap->rd_att->attrs[colno - 1]->attname))
: errhint("You might be able to work around this by marking column \"%s\" NOT NULL.",
NameStr(OldHeap->rd_att->attrs[colno - 1]->attname))));
}
else if (colno < 0)
{
/* system column --- okay, always non-null */
}
else
/* index expression, lose... */
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot cluster on expressional index \"%s\" because its index access method does not handle null values",
RelationGetRelationName(OldIndex))));
}
/*
* Disallow if index is left over from a failed CREATE INDEX CONCURRENTLY;
* it might well not contain entries for every heap row, or might not even
* be internally consistent. (But note that we don't check indcheckxmin;
* the worst consequence of following broken HOT chains would be that we
* might put recently-dead tuples out-of-order in the new table, and there * is little harm in that.)
*/
if (!OldIndex->rd_index->indisvalid)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot cluster on invalid index \"%s\"",
RelationGetRelationName(OldIndex))));
/* Drop relcache refcnt on OldIndex, but keep lock */
index_close(OldIndex, NoLock);
}
/*
* mark_index_clustered: mark the specified index as the one clustered on
*
* With indexOid == InvalidOid, will mark all indexes of rel not-clustered.
*/
void
mark_index_clustered(Relation rel, Oid indexOid)
{
HeapTuple indexTuple;
Form_pg_index indexForm;
Relation pg_index;
ListCell *index;
/*
* If the index is already marked clustered, no need to do anything.
*/
if (OidIsValid(indexOid))
{
indexTuple = SearchSysCache(INDEXRELID,
ObjectIdGetDatum(indexOid),
0, 0, 0);
if (!HeapTupleIsValid(indexTuple))
elog(ERROR, "cache lookup failed for index %u", indexOid);
indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
if (indexForm->indisclustered)
{
ReleaseSysCache(indexTuple);
return;
}
ReleaseSysCache(indexTuple);
}
/*
* Check each index of the relation and set/clear the bit as needed.
*/
pg_index = heap_open(IndexRelationId, RowExclusiveLock);
foreach(index, RelationGetIndexList(rel))
{
Oid thisIndexOid = lfirst_oid(index);
indexTuple = SearchSysCacheCopy(INDEXRELID,
ObjectIdGetDatum(thisIndexOid),
0, 0, 0);
if (!HeapTupleIsValid(indexTuple))
elog(ERROR, "cache lookup failed for index %u", thisIndexOid);
indexForm = (Form_pg_index) GETSTRUCT(indexTuple);
/*
* Unset the bit if set. We know it's wrong because we checked this
* earlier.
*/
if (indexForm->indisclustered)
{
indexForm->indisclustered = false;
simple_heap_update(pg_index, &indexTuple->t_self, indexTuple); CatalogUpdateIndexes(pg_index, indexTuple);
/* Ensure we see the update in the index's relcache entry */
CacheInvalidateRelcacheByRelid(thisIndexOid);
}
else if (thisIndexOid == indexOid)
{
indexForm->indisclustered = true;
simple_heap_update(pg_index, &indexTuple->t_self, indexTuple);
CatalogUpdateIndexes(pg_index, indexTuple);
/* Ensure we see the update in the index's relcache entry */
CacheInvalidateRelcacheByRelid(thisIndexOid);
}
heap_freetuple(indexTuple);
}
heap_close(pg_index, RowExclusiveLock);
}
/*
* rebuild_relation: rebuild an existing relation in index or physical order
*
* OldHeap: table to rebuild --- must be opened and exclusive-locked!
* indexOid: index to cluster by, or InvalidOid to rewrite in physical order.
*
* NB: this routine closes OldHeap at the right time; caller should not.
*/
static void
rebuild_relation(Relation OldHeap, Oid indexOid,
int freeze_min_age, int freeze_table_age)
{
Oid tableOid = RelationGetRelid(OldHeap);
Oid tableSpace = OldHeap->rd_rel->reltablespace;
Oid OIDNewHeap;
bool is_system_catalog;
bool swap_toast_by_content;
TransactionId frozenXid;
/* Mark the correct index as clustered */
if (OidIsValid(indexOid))
mark_index_clustered(OldHeap, indexOid);
/* Remember if it's a system catalog */
is_system_catalog = IsSystemRelation(OldHeap);
/* Close relcache entry, but keep lock until transaction commit */
heap_close(OldHeap, NoLock);
/* Create the transient table that will receive the re-ordered data */
OIDNewHeap = make_new_heap(tableOid, tableSpace);
/* Copy the heap data into the new table in the desired order */
copy_heap_data(OIDNewHeap, tableOid, indexOid,
freeze_min_age, freeze_table_age,
&swap_toast_by_content, &frozenXid);
/*
* Swap the physical files of the target and transient tables, then
* rebuild the target's indexes and throw away the transient table.
*/
finish_heap_swap(tableOid, OIDNewHeap, is_system_catalog,
swap_toast_by_content, frozenXid);
}
/*
* Create the transient table that will be filled with new data during
* CLUSTER, ALTER TABLE, and similar operations. The transient table
* duplicates the logical structure of the OldHeap, but is placed in
* NewTableSpace which might be different from OldHeap's.
* * After this, the caller should load the new heap with transferred/modified
* data, then call finish_heap_swap to complete the operation.
*/
Oid
make_new_heap(Oid OIDOldHeap, Oid NewTableSpace)
{
TupleDesc OldHeapDesc,
tupdesc;
char NewHeapName[NAMEDATALEN];
Oid OIDNewHeap;
Oid toastid;
Relation OldHeap;
HeapTuple tuple;
Datum reloptions;
bool isNull;
OldHeap = heap_open(OIDOldHeap, AccessExclusiveLock);
OldHeapDesc = RelationGetDescr(OldHeap);
/*
* Need to make a copy of the tuple descriptor, since
* heap_create_with_catalog modifies it. Note that the NewHeap will not
* receive any of the defaults or constraints associated with the OldHeap;
* we don't need 'em, and there's no reason to spend cycles inserting them
* into the catalogs only to delete them.
*/
tupdesc = CreateTupleDescCopy(OldHeapDesc);
/*
* But we do want to use reloptions of the old heap for new heap.
*/
tuple = SearchSysCache(RELOID,
ObjectIdGetDatum(OIDOldHeap),
0, 0, 0);
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for relation %u", OIDOldHeap);
reloptions = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
&isNull);
if (isNull)
reloptions = (Datum) 0;
/*
* Create the new heap, using a temporary name in the same namespace as
* the existing table. NOTE: there is some risk of collision with user
* relnames. Working around this seems more trouble than it's worth; in
* particular, we can't create the new heap in a different namespace from
* the old, or we will have problems with the TEMP status of temp tables.
*
* Note: the new heap is not a shared relation, even if we are rebuilding
* a shared rel. However, we do make the new heap mapped if the source
* is mapped. This simplifies swap_relation_files, and is absolutely
* necessary for rebuilding pg_class, for reasons explained there.
*/
snprintf(NewHeapName, sizeof(NewHeapName), "pg_temp_%u", OIDOldHeap);
OIDNewHeap = heap_create_with_catalog(NewHeapName,
RelationGetNamespace(OldHeap),
NewTableSpace,
InvalidOid,
InvalidOid,
InvalidOid,
OldHeap->rd_rel->relowner,
tupdesc,
NIL,
OldHeap->rd_rel->relkind,
false,
RelationIsMapped(OldHeap),
true,
0,
ONCOMMIT_NOOP, reloptions,
false,
true);
ReleaseSysCache(tuple);
/*
* Advance command counter so that the newly-created relation's catalog
* tuples will be visible to heap_open.
*/
CommandCounterIncrement();
/*
* If necessary, create a TOAST table for the new relation.
*
* If the relation doesn't have a TOAST table already, we can't need one
* for the new relation. The other way around is possible though: if
* some wide columns have been dropped, AlterTableCreateToastTable
* can decide that no TOAST table is needed for the new table.
*
* Note that AlterTableCreateToastTable ends with CommandCounterIncrement,
* so that the TOAST table will be visible for insertion.
*/
toastid = OldHeap->rd_rel->reltoastrelid;
if (OidIsValid(toastid))
{
/* keep the existing toast table's reloptions, if any */
tuple = SearchSysCache(RELOID,
ObjectIdGetDatum(toastid),
0, 0, 0);
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for relation %u", toastid);
reloptions = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
&isNull);
if (isNull)
reloptions = (Datum) 0;
AlterTableCreateToastTable(OIDNewHeap, reloptions);
ReleaseSysCache(tuple);
}
heap_close(OldHeap, NoLock);
return OIDNewHeap;
}
/*
* Do the physical copying of heap data.
*
* There are two output parameters:
* *pSwapToastByContent is set true if toast tables must be swapped by content.
* *pFreezeXid receives the TransactionId used as freeze cutoff point.
*/
static void
copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex,
int freeze_min_age, int freeze_table_age,
bool *pSwapToastByContent, TransactionId *pFreezeXid)
{
Relation NewHeap,
OldHeap,
OldIndex;
TupleDesc oldTupDesc;
TupleDesc newTupDesc;
int natts;
Datum *values;
bool *isnull;
IndexScanDesc indexScan;
HeapScanDesc heapScan;
bool use_wal; bool is_system_catalog;
TransactionId OldestXmin;
TransactionId FreezeXid;
RewriteState rwstate;
/*
* Open the relations we need.
*/
NewHeap = heap_open(OIDNewHeap, AccessExclusiveLock);
OldHeap = heap_open(OIDOldHeap, AccessExclusiveLock);
if (OidIsValid(OIDOldIndex))
OldIndex = index_open(OIDOldIndex, AccessExclusiveLock);
else
OldIndex = NULL;
/*
* Their tuple descriptors should be exactly alike, but here we only need
* assume that they have the same number of columns.
*/
oldTupDesc = RelationGetDescr(OldHeap);
newTupDesc = RelationGetDescr(NewHeap);
Assert(newTupDesc->natts == oldTupDesc->natts);
/* Preallocate values/isnull arrays */
natts = newTupDesc->natts;
values = (Datum *) palloc(natts * sizeof(Datum));
isnull = (bool *) palloc(natts * sizeof(bool));
/*
* We need to log the copied data in WAL iff WAL archiving/streaming
* is enabled AND it's not a temp rel.
*/
use_wal = XLogIsNeeded() && !NewHeap->rd_istemp;
/*
* Write an XLOG UNLOGGED record if WAL-logging was skipped because
* WAL archiving is not enabled.
*/
if (!use_wal && !NewHeap->rd_istemp)
{
char reason[NAMEDATALEN + 32];
if (OldIndex != NULL)
snprintf(reason, sizeof(reason), "CLUSTER on \"%s\"",
RelationGetRelationName(NewHeap));
else
snprintf(reason, sizeof(reason), "VACUUM FULL on \"%s\"",
RelationGetRelationName(NewHeap));
XLogReportUnloggedStatement(reason);
}
/* use_wal off requires rd_targblock be initially invalid */
Assert(NewHeap->rd_targblock == InvalidBlockNumber);
/*
* If both tables have TOAST tables, perform toast swap by content. It is
* possible that the old table has a toast table but the new one doesn't,
* if toastable columns have been dropped. In that case we have to do
* swap by links. This is okay because swap by content is only essential
* for system catalogs, and we don't support schema changes for them.
*/
if (OldHeap->rd_rel->reltoastrelid && NewHeap->rd_rel->reltoastrelid)
{
*pSwapToastByContent = true;
/*
* When doing swap by content, any toast pointers written into NewHeap
* must use the old toast table's OID, because that's where the toast
* data will eventually be found. Set this up by setting rd_toastoid.
* Note that we must hold NewHeap open until we are done writing data, * since the relcache will not guarantee to remember this setting once
* the relation is closed. Also, this technique depends on the fact
* that no one will try to read from the NewHeap until after we've
* finished writing it and swapping the rels --- otherwise they could
* follow the toast pointers to the wrong place.
*/
NewHeap->rd_toastoid = OldHeap->rd_rel->reltoastrelid;
}
else
*pSwapToastByContent = false;
/*
* compute xids used to freeze and weed out dead tuples. We use -1
* freeze_min_age to avoid having CLUSTER freeze tuples earlier than a
* plain VACUUM would.
*/
vacuum_set_xid_limits(freeze_min_age, freeze_table_age,
OldHeap->rd_rel->relisshared,
&OldestXmin, &FreezeXid, NULL);
/*
* FreezeXid will become the table's new relfrozenxid, and that mustn't go
* backwards, so take the max.
*/
if (TransactionIdPrecedes(FreezeXid, OldHeap->rd_rel->relfrozenxid))
FreezeXid = OldHeap->rd_rel->relfrozenxid;
/* return selected value to caller */
*pFreezeXid = FreezeXid;
/* Remember if it's a system catalog */
is_system_catalog = IsSystemRelation(OldHeap);
/* Initialize the rewrite operation */
rwstate = begin_heap_rewrite(NewHeap, OldestXmin, FreezeXid, use_wal);
/*
* Scan through the OldHeap, either in OldIndex order or sequentially,
* and copy each tuple into the NewHeap. To ensure we see recently-dead
* tuples that still need to be copied, we scan with SnapshotAny and use
* HeapTupleSatisfiesVacuum for the visibility test.
*/
if (OldIndex != NULL)
{
heapScan = NULL;
indexScan = index_beginscan(OldHeap, OldIndex,
SnapshotAny, 0, (ScanKey) NULL);
}
else
{
heapScan = heap_beginscan(OldHeap, SnapshotAny, 0, (ScanKey) NULL);
indexScan = NULL;
}
for (;;)
{
HeapTuple tuple;
HeapTuple copiedTuple;
Buffer buf;
bool isdead;
int i;
CHECK_FOR_INTERRUPTS();
if (OldIndex != NULL)
{
tuple = index_getnext(indexScan, ForwardScanDirection);
if (tuple == NULL)
break;
/* Since we used no scan keys, should never need to recheck */
if (indexScan->xs_recheck)
elog(ERROR, "CLUSTER does not support lossy index conditions");
buf = indexScan->xs_cbuf;
}
else
{
tuple = heap_getnext(heapScan, ForwardScanDirection);
if (tuple == NULL)
break;
buf = heapScan->rs_cbuf;
}
LockBuffer(buf, BUFFER_LOCK_SHARE);
switch (HeapTupleSatisfiesVacuum(tuple->t_data, OldestXmin, buf))
{
case HEAPTUPLE_DEAD:
/* Definitely dead */
isdead = true;
break;
case HEAPTUPLE_LIVE:
case HEAPTUPLE_RECENTLY_DEAD:
/* Live or recently dead, must copy it */
isdead = false;
break;
case HEAPTUPLE_INSERT_IN_PROGRESS:
/*
* Since we hold exclusive lock on the relation, normally
* the only way to see this is if it was inserted earlier
* in our own transaction. However, it can happen in system
* catalogs, since we tend to release write lock before commit
* there. Give a warning if neither case applies; but in
* any case we had better copy it.
*/
if (!is_system_catalog &&
!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetXmin(tuple->t_data)))
elog(WARNING, "concurrent insert in progress within table \"%s\"",
RelationGetRelationName(OldHeap));
/* treat as live */
isdead = false;
break;
case HEAPTUPLE_DELETE_IN_PROGRESS:
/*
* Similar situation to INSERT_IN_PROGRESS case.
*/
Assert(!(tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI));
if (!is_system_catalog &&
!TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetXmax(tuple->t_data)))
elog(WARNING, "concurrent delete in progress within table \"%s\"",
RelationGetRelationName(OldHeap));
/* treat as recently dead */
isdead = false;
break;
default:
elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result");
isdead = false; /* keep compiler quiet */
break;
}
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
if (isdead)
{
/* heap rewrite module still needs to see it... */ rewrite_heap_dead_tuple(rwstate, tuple);
continue;
}
/*
* We cannot simply copy the tuple as-is, for several reasons:
*
* 1. We'd like to squeeze out the values of any dropped columns, both
* to save space and to ensure we have no corner-case failures. (It's
* possible for example that the new table hasn't got a TOAST table
* and so is unable to store any large values of dropped cols.)
*
* 2. The tuple might not even be legal for the new table; this is
* currently only known to happen as an after-effect of ALTER TABLE
* SET WITHOUT OIDS.
*
* So, we must reconstruct the tuple from component Datums.
*/
heap_deform_tuple(tuple, oldTupDesc, values, isnull);
/* Be sure to null out any dropped columns */
for (i = 0; i < natts; i++)
{
if (newTupDesc->attrs[i]->attisdropped)
isnull[i] = true;
}
copiedTuple = heap_form_tuple(newTupDesc, values, isnull);
/* Preserve OID, if any */
if (NewHeap->rd_rel->relhasoids)
HeapTupleSetOid(copiedTuple, HeapTupleGetOid(tuple));
/* The heap rewrite module does the rest */
rewrite_heap_tuple(rwstate, tuple, copiedTuple);
heap_freetuple(copiedTuple);
}
if (OldIndex != NULL)
index_endscan(indexScan);
else
heap_endscan(heapScan);
/* Write out any remaining tuples, and fsync if needed */
end_heap_rewrite(rwstate);
/* Reset rd_toastoid just to be tidy --- it shouldn't be looked at again */
NewHeap->rd_toastoid = InvalidOid;
/* Clean up */
pfree(values);
pfree(isnull);
if (OldIndex != NULL)
index_close(OldIndex, NoLock);
heap_close(OldHeap, NoLock);
heap_close(NewHeap, NoLock);
}
/*
* Swap the physical files of two given relations.
*
* We swap the physical identity (reltablespace and relfilenode) while
* keeping the same logical identities of the two relations.
*
* We can swap associated TOAST data in either of two ways: recursively swap
* the physical content of the toast tables (and their indexes), or swap the
* TOAST links in the given relations' pg_class entries. The former is needed
* to manage rewrites of shared catalogs (where we cannot change the pg_class * links) while the latter is the only way to handle cases in which a toast
* table is added or removed altogether.
*
* Additionally, the first relation is marked with relfrozenxid set to
* frozenXid. It seems a bit ugly to have this here, but the caller would
* have to do it anyway, so having it here saves a heap_update. Note: in
* the swap-toast-links case, we assume we don't need to change the toast
* table's relfrozenxid: the new version of the toast table should already
* have relfrozenxid set to RecentXmin, which is good enough.
*
* Lastly, if r2 and its toast table and toast index (if any) are mapped,
* their OIDs are emitted into mapped_tables[]. This is hacky but beats
* having to look the information up again later in finish_heap_swap.
*/
static void
swap_relation_files(Oid r1, Oid r2, bool target_is_pg_class,
bool swap_toast_by_content,
TransactionId frozenXid,
Oid *mapped_tables)
{
Relation relRelation;
HeapTuple reltup1,
reltup2;
Form_pg_class relform1,
relform2;
Oid relfilenode1,
relfilenode2;
Oid swaptemp;
CatalogIndexState indstate;
/* We need writable copies of both pg_class tuples. */
relRelation = heap_open(RelationRelationId, RowExclusiveLock);
reltup1 = SearchSysCacheCopy(RELOID,
ObjectIdGetDatum(r1),
0, 0, 0);
if (!HeapTupleIsValid(reltup1))
elog(ERROR, "cache lookup failed for relation %u", r1);
relform1 = (Form_pg_class) GETSTRUCT(reltup1);
reltup2 = SearchSysCacheCopy(RELOID,
ObjectIdGetDatum(r2),
0, 0, 0);
if (!HeapTupleIsValid(reltup2))
elog(ERROR, "cache lookup failed for relation %u", r2);
relform2 = (Form_pg_class) GETSTRUCT(reltup2);
relfilenode1 = relform1->relfilenode;
relfilenode2 = relform2->relfilenode;
if (OidIsValid(relfilenode1) && OidIsValid(relfilenode2))
{
/* Normal non-mapped relations: swap relfilenodes and reltablespaces */
Assert(!target_is_pg_class);
swaptemp = relform1->relfilenode;
relform1->relfilenode = relform2->relfilenode;
relform2->relfilenode = swaptemp;
swaptemp = relform1->reltablespace;
relform1->reltablespace = relform2->reltablespace;
relform2->reltablespace = swaptemp;
/* Also swap toast links, if we're swapping by links */
if (!swap_toast_by_content)
{
swaptemp = relform1->reltoastrelid;
relform1->reltoastrelid = relform2->reltoastrelid;
relform2->reltoastrelid = swaptemp;
/* we should NOT swap reltoastidxid */
}
}
else
{
/*
* Mapped-relation case. Here we have to swap the relation mappings
* instead of modifying the pg_class columns. Both must be mapped.
*/
if (OidIsValid(relfilenode1) || OidIsValid(relfilenode2))
elog(ERROR, "cannot swap mapped relation \"%s\" with non-mapped relation",
NameStr(relform1->relname));
/*
* We can't change the tablespace of a mapped rel, and we can't handle
* toast link swapping for one either, because we must not apply any
* critical changes to its pg_class row. These cases should be
* prevented by upstream permissions tests, so this check is a
* non-user-facing emergency backstop.
*/
if (relform1->reltablespace != relform2->reltablespace)
elog(ERROR, "cannot change tablespace of mapped relation \"%s\"",
NameStr(relform1->relname));
if (!swap_toast_by_content &&
(relform1->reltoastrelid || relform2->reltoastrelid))
elog(ERROR, "cannot swap toast by links for mapped relation \"%s\"",
NameStr(relform1->relname));
/*
* Fetch the mappings --- shouldn't fail, but be paranoid
*/
relfilenode1 = RelationMapOidToFilenode(r1, relform1->relisshared);
if (!OidIsValid(relfilenode1))
elog(ERROR, "could not find relation mapping for relation \"%s\", OID %u",
NameStr(relform1->relname), r1);
relfilenode2 = RelationMapOidToFilenode(r2, relform2->relisshared);
if (!OidIsValid(relfilenode2))
elog(ERROR, "could not find relation mapping for relation \"%s\", OID %u",
NameStr(relform2->relname), r2);
/*
* Send replacement mappings to relmapper. Note these won't actually
* take effect until CommandCounterIncrement.
*/
RelationMapUpdateMap(r1, relfilenode2, relform1->relisshared, false);
RelationMapUpdateMap(r2, relfilenode1, relform2->relisshared, false);
/* Pass OIDs of mapped r2 tables back to caller */
*mapped_tables++ = r2;
}
/*
* In the case of a shared catalog, these next few steps will only affect
* our own database's pg_class row; but that's okay, because they are
* all noncritical updates. That's also an important fact for the case
* of a mapped catalog, because it's possible that we'll commit the map
* change and then fail to commit the pg_class update.
*/
/* set rel1's frozen Xid */
if (relform1->relkind != RELKIND_INDEX)
{
Assert(TransactionIdIsNormal(frozenXid));
relform1->relfrozenxid = frozenXid;
}
/* swap size statistics too, since new rel has freshly-updated stats */
{
int4 swap_pages;
float4 swap_tuples;
swap_pages = relform1->relpages;
relform1->relpages = relform2->relpages;
relform2->relpages = swap_pages;
swap_tuples = relform1->reltuples;
relform1->reltuples = relform2->reltuples;
relform2->reltuples = swap_tuples;
}
/*
* Update the tuples in pg_class --- unless the target relation of the
* swap is pg_class itself. In that case, there is zero point in making
* changes because we'd be updating the old data that we're about to
* throw away. Because the real work being done here for a mapped relation
* is just to change the relation map settings, it's all right to not
* update the pg_class rows in this case.
*/
if (!target_is_pg_class)
{
simple_heap_update(relRelation, &reltup1->t_self, reltup1);
simple_heap_update(relRelation, &reltup2->t_self, reltup2);
/* Keep system catalogs current */
indstate = CatalogOpenIndexes(relRelation);
CatalogIndexInsert(indstate, reltup1);
CatalogIndexInsert(indstate, reltup2);
CatalogCloseIndexes(indstate);
}
else
{
/* no update ... but we do still need relcache inval */
CacheInvalidateRelcacheByTuple(reltup1);
CacheInvalidateRelcacheByTuple(reltup2);
}
/*
* If we have toast tables associated with the relations being swapped,
* deal with them too.
*/
if (relform1->reltoastrelid || relform2->reltoastrelid)
{
if (swap_toast_by_content)
{
if (relform1->reltoastrelid && relform2->reltoastrelid)
{
/* Recursively swap the contents of the toast tables */
swap_relation_files(relform1->reltoastrelid,
relform2->reltoastrelid,
target_is_pg_class,
swap_toast_by_content,
frozenXid,
mapped_tables);
}
else
{
/* caller messed up */
elog(ERROR, "cannot swap toast files by content when there's only one");
}
}
else
{
/*
* We swapped the ownership links, so we need to change dependency
* data to match.
*
* NOTE: it is possible that only one table has a toast table.
*
* NOTE: at present, a TOAST table's only dependency is the one on
* its owning table. If more are ever created, we'd need to use * something more selective than deleteDependencyRecordsFor() to
* get rid of just the link we want.
*/
ObjectAddress baseobject,
toastobject;
long count;
/*
* We disallow this case for system catalogs, to avoid the
* possibility that the catalog we're rebuilding is one of the
* ones the dependency changes would change. It's too late
* to be making any data changes to the target catalog.
*/
if (IsSystemClass(relform1))
elog(ERROR, "cannot swap toast files by links for system catalogs");
/* Delete old dependencies */
if (relform1->reltoastrelid)
{
count = deleteDependencyRecordsFor(RelationRelationId,
relform1->reltoastrelid);
if (count != 1)
elog(ERROR, "expected one dependency record for TOAST table, found %ld",
count);
}
if (relform2->reltoastrelid)
{
count = deleteDependencyRecordsFor(RelationRelationId,
relform2->reltoastrelid);
if (count != 1)
elog(ERROR, "expected one dependency record for TOAST table, found %ld",
count);
}
/* Register new dependencies */
baseobject.classId = RelationRelationId;
baseobject.objectSubId = 0;
toastobject.classId = RelationRelationId;
toastobject.objectSubId = 0;
if (relform1->reltoastrelid)
{
baseobject.objectId = r1;
toastobject.objectId = relform1->reltoastrelid;
recordDependencyOn(&toastobject, &baseobject,
DEPENDENCY_INTERNAL);
}
if (relform2->reltoastrelid)
{
baseobject.objectId = r2;
toastobject.objectId = relform2->reltoastrelid;
recordDependencyOn(&toastobject, &baseobject,
DEPENDENCY_INTERNAL);
}
}
}
/*
* If we're swapping two toast tables by content, do the same for their
* indexes.
*/
if (swap_toast_by_content &&
relform1->reltoastidxid && relform2->reltoastidxid)
swap_relation_files(relform1->reltoastidxid,
relform2->reltoastidxid,
target_is_pg_class,
swap_toast_by_content,
InvalidTransactionId,
mapped_tables);
/* Clean up. */
heap_freetuple(reltup1);
heap_freetuple(reltup2);
heap_close(relRelation, RowExclusiveLock);
/*
* Close both relcache entries' smgr links. We need this kluge because
* both links will be invalidated during upcoming CommandCounterIncrement.
* Whichever of the rels is the second to be cleared will have a dangling
* reference to the other's smgr entry. Rather than trying to avoid this
* by ordering operations just so, it's easiest to close the links first.
* (Fortunately, since one of the entries is local in our transaction,
* it's sufficient to clear out our own relcache this way; the problem
* cannot arise for other backends when they see our update on the
* non-transient relation.)
*
* Caution: the placement of this step interacts with the decision to
* handle toast rels by recursion. When we are trying to rebuild pg_class
* itself, the smgr close on pg_class must happen after all accesses in
* this function.
*/
RelationCloseSmgrByOid(r1);
RelationCloseSmgrByOid(r2);
}
/*
* Remove the transient table that was built by make_new_heap, and finish
* cleaning up (including rebuilding all indexes on the old heap).
*/
void
finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
bool is_system_catalog,
bool swap_toast_by_content,
TransactionId frozenXid)
{
ObjectAddress object;
Oid mapped_tables[4];
int i;
/* Zero out possible results from swapped_relation_files */
memset(mapped_tables, 0, sizeof(mapped_tables));
/*
* Swap the contents of the heap relations (including any toast tables).
* Also set old heap's relfrozenxid to frozenXid.
*/
swap_relation_files(OIDOldHeap, OIDNewHeap,
(OIDOldHeap == RelationRelationId),
swap_toast_by_content, frozenXid, mapped_tables);
/*
* If it's a system catalog, queue an sinval message to flush all
* catcaches on the catalog when we reach CommandCounterIncrement.
*/
if (is_system_catalog)
CacheInvalidateCatalog(OIDOldHeap);
/*
* Rebuild each index on the relation (but not the toast table, which is
* all-new at this point). It is important to do this before the DROP
* step because if we are processing a system catalog that will be used
* during DROP, we want to have its indexes available. There is no
* advantage to the other order anyway because this is all transactional,
* so no chance to reclaim disk space before commit. We do not need
* a final CommandCounterIncrement() because reindex_relation does it.
*/
reindex_relation(OIDOldHeap, false, true);
/* Destroy new heap with old filenode */
object.classId = RelationRelationId;
object.objectId = OIDNewHeap;
object.objectSubId = 0;
/*
* The new relation is local to our transaction and we know nothing
* depends on it, so DROP_RESTRICT should be OK.
*/
performDeletion(&object, DROP_RESTRICT);
/* performDeletion does CommandCounterIncrement at end */
/*
* Now we must remove any relation mapping entries that we set up for the
* transient table, as well as its toast table and toast index if any.
* If we fail to do this before commit, the relmapper will complain about
* new permanent map entries being added post-bootstrap.
*/
for (i = 0; OidIsValid(mapped_tables[i]); i++)
RelationMapRemoveMapping(mapped_tables[i]);
/*
* At this point, everything is kosher except that, if we did toast swap
* by links, the toast table's name corresponds to the transient table.
* The name is irrelevant to the backend because it's referenced by OID,
* but users looking at the catalogs could be confused. Rename it to
* prevent this problem.
*
* Note no lock required on the relation, because we already hold an
* exclusive lock on it.
*/
if (!swap_toast_by_content)
{
Relation newrel;
newrel = heap_open(OIDOldHeap, NoLock);
if (OidIsValid(newrel->rd_rel->reltoastrelid))
{
Relation toastrel;
Oid toastidx;
Oid toastnamespace;
char NewToastName[NAMEDATALEN];
toastrel = relation_open(newrel->rd_rel->reltoastrelid,
AccessShareLock);
toastidx = toastrel->rd_rel->reltoastidxid;
toastnamespace = toastrel->rd_rel->relnamespace;
relation_close(toastrel, AccessShareLock);
/* rename the toast table ... */
snprintf(NewToastName, NAMEDATALEN, "pg_toast_%u",
OIDOldHeap);
RenameRelationInternal(newrel->rd_rel->reltoastrelid,
NewToastName,
toastnamespace);
/* ... and its index too */
snprintf(NewToastName, NAMEDATALEN, "pg_toast_%u_index",
OIDOldHeap);
RenameRelationInternal(toastidx,
NewToastName,
toastnamespace);
}
relation_close(newrel, NoLock);
}
}
/* * Get a list of tables that the current user owns and
* have indisclustered set. Return the list in a List * of rvsToCluster
* with the tableOid and the indexOid on which the table is already
* clustered.
*/
static List *
get_tables_to_cluster(MemoryContext cluster_context)
{
Relation indRelation;
HeapScanDesc scan;
ScanKeyData entry;
HeapTuple indexTuple;
Form_pg_index index;
MemoryContext old_context;
RelToCluster *rvtc;
List *rvs = NIL;
/*
* Get all indexes that have indisclustered set and are owned by
* appropriate user. System relations or nailed-in relations cannot ever
* have indisclustered set, because CLUSTER will refuse to set it when
* called with one of them as argument.
*/
indRelation = heap_open(IndexRelationId, AccessShareLock);
ScanKeyInit(&entry,
Anum_pg_index_indisclustered,
BTEqualStrategyNumber, F_BOOLEQ,
BoolGetDatum(true));
scan = heap_beginscan(indRelation, SnapshotNow, 1, &entry);
while ((indexTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
{
index = (Form_pg_index) GETSTRUCT(indexTuple);
if (!pg_class_ownercheck(index->indrelid, GetUserId()))
continue;
/*
* We have to build the list in a different memory context so it will
* survive the cross-transaction processing
*/
old_context = MemoryContextSwitchTo(cluster_context);
rvtc = (RelToCluster *) palloc(sizeof(RelToCluster));
rvtc->tableOid = index->indrelid;
rvtc->indexOid = index->indexrelid;
rvs = lcons(rvtc, rvs);
MemoryContextSwitchTo(old_context);
}
heap_endscan(scan);
relation_close(indRelation, AccessShareLock);
return rvs;
}