/*------------------------------------------------------------------------- * * cluster.c * CLUSTER a table on an index. * * There is hardly anything left of Paul Brown's original implementation... * * * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1994-5, Regents of the University of California * * * IDENTIFICATION * $Header: /cvsroot/pgsql/src/backend/commands/cluster.c,v 1.115 2003/08/08 21:41:28 momjian Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/genam.h" #include "access/heapam.h" #include "catalog/catalog.h" #include "catalog/catname.h" #include "catalog/dependency.h" #include "catalog/heap.h" #include "catalog/index.h" #include "catalog/indexing.h" #include "catalog/namespace.h" #include "commands/cluster.h" #include "commands/tablecmds.h" #include "miscadmin.h" #include "utils/acl.h" #include "utils/fmgroids.h" #include "utils/lsyscache.h" #include "utils/syscache.h" #include "utils/relcache.h" /* * We need one of these structs for each index in the relation to be * clustered. It's basically the data needed by index_create() so * we can rebuild the indexes on the new heap. */ typedef struct { Oid indexOID; char *indexName; IndexInfo *indexInfo; Oid accessMethodOID; Oid *classOID; bool isclustered; } IndexAttrs; /* * 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 cluster_rel(RelToCluster *rv, bool recheck); static Oid make_new_heap(Oid OIDOldHeap, const char *NewName); static void copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex); static List *get_indexattr_list(Relation OldHeap, Oid OldIndex); static void rebuild_indexes(Oid OIDOldHeap, List *indexes); static void swap_relfilenodes(Oid r1, Oid r2); 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 being 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) { if (stmt->relation != NULL) { /* This is the single-relation case. */ Oid tableOid, indexOid = InvalidOid; Relation rel; RelToCluster rvtc; /* 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)); if (stmt->indexname == NULL) { List *index; /* We need to find the index that has indisclustered set. */ foreach(index, RelationGetIndexList(rel)) { HeapTuple idxtuple; Form_pg_index indexForm; indexOid = lfirsto(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))); } /* All other checks are done in cluster_rel() */ rvtc.tableOid = tableOid; rvtc.indexOid = indexOid; /* close relation, keep lock till commit */ heap_close(rel, NoLock); /* Do the job */ cluster_rel(&rvtc, false); } else { /* * This is the "multi relation" case. We need to cluster all * tables that have some index with indisclustered set. */ MemoryContext cluster_context; List *rv, *rvs; /* * We cannot run this form of CLUSTER inside a user transaction * block; we'd be holding locks way too long. */ PreventTransactionChain((void *) stmt, "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 */ 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(); SetQuerySnapshot(); /* might be needed for functions in * indexes */ cluster_rel(rvtc, true); 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). * * Also create new indexes and swap the filenodes with the old indexes the * same way we do for the relation. 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. */ static void cluster_rel(RelToCluster *rvtc, bool recheck) { Relation OldHeap, OldIndex; /* Check for user-requested abort. */ CHECK_FOR_INTERRUPTS(); /* * 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 if the relation and index still exist before opening them */ if (!SearchSysCacheExists(RELOID, ObjectIdGetDatum(rvtc->tableOid), 0, 0, 0) || !SearchSysCacheExists(RELOID, ObjectIdGetDatum(rvtc->indexOid), 0, 0, 0)) return; /* Check that the user still owns the relation */ if (!pg_class_ownercheck(rvtc->tableOid, GetUserId())) return; /* * Check that the index is still the one with indisclustered set. */ tuple = SearchSysCache(INDEXRELID, ObjectIdGetDatum(rvtc->indexOid), 0, 0, 0); if (!HeapTupleIsValid(tuple)) return; /* could have gone away... */ indexForm = (Form_pg_index) GETSTRUCT(tuple); if (!indexForm->indisclustered) { ReleaseSysCache(tuple); return; } ReleaseSysCache(tuple); } /* * 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.) */ OldHeap = heap_open(rvtc->tableOid, AccessExclusiveLock); OldIndex = index_open(rvtc->indexOid); LockRelation(OldIndex, AccessExclusiveLock); /* * Check that index is in fact an index on the given relation */ if (OldIndex->rd_index == NULL || OldIndex->rd_index->indrelid != rvtc->tableOid) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is not an index for table \"%s\"", RelationGetRelationName(OldIndex), RelationGetRelationName(OldHeap)))); /* * 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"))); 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[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 when index access method does not handle nulls"), errhint("You may 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 when index access method does not handle nulls"))); } } /* * Disallow clustering system relations. This will definitely NOT * work for shared relations (we have no way to update pg_class rows * in other databases), nor for nailed-in-cache relations (the * relfilenode values for those are hardwired, see relcache.c). It * might work for other system relations, but I ain't gonna risk it. */ if (IsSystemRelation(OldHeap)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("\"%s\" is a system catalog", RelationGetRelationName(OldHeap)))); /* * Don't allow cluster on temp tables of other backends ... their * local buffer manager is not going to cope. */ if (isOtherTempNamespace(RelationGetNamespace(OldHeap))) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot cluster temp tables of other processes"))); /* Drop relcache refcnt on OldIndex, but keep lock */ index_close(OldIndex); /* rebuild_relation does all the dirty work */ rebuild_relation(OldHeap, rvtc->indexOid); /* NB: rebuild_relation does heap_close() on OldHeap */ } /* * rebuild_relation: rebuild an existing relation * * This is shared code between CLUSTER and TRUNCATE. In the TRUNCATE * case, the new relation is built and left empty. In the CLUSTER case, * it is filled with data read from the old relation in the order specified * by the index. * * OldHeap: table to rebuild --- must be opened and exclusive-locked! * indexOid: index to cluster by, or InvalidOid in TRUNCATE case * * NB: this routine closes OldHeap at the right time; caller should not. */ void rebuild_relation(Relation OldHeap, Oid indexOid) { Oid tableOid = RelationGetRelid(OldHeap); List *indexes; Oid OIDNewHeap; char NewHeapName[NAMEDATALEN]; ObjectAddress object; /* Save the information about all indexes on the relation. */ indexes = get_indexattr_list(OldHeap, indexOid); /* Close relcache entry, but keep lock until transaction commit */ heap_close(OldHeap, NoLock); /* * 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. */ snprintf(NewHeapName, sizeof(NewHeapName), "pg_temp_%u", tableOid); OIDNewHeap = make_new_heap(tableOid, NewHeapName); /* * We don't need CommandCounterIncrement() because make_new_heap did * it. */ /* * Copy the heap data into the new table in the desired order. */ if (OidIsValid(indexOid)) copy_heap_data(OIDNewHeap, tableOid, indexOid); /* To make the new heap's data visible (probably not needed?). */ CommandCounterIncrement(); /* Swap the relfilenodes of the old and new heaps. */ swap_relfilenodes(tableOid, OIDNewHeap); CommandCounterIncrement(); /* Destroy new heap with old filenode */ object.classId = RelOid_pg_class; 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 */ /* * Recreate each index on the relation. We do not need * CommandCounterIncrement() because rebuild_indexes does it. */ rebuild_indexes(tableOid, indexes); } /* * Create the new table that we will fill with correctly-ordered data. */ static Oid make_new_heap(Oid OIDOldHeap, const char *NewName) { TupleDesc OldHeapDesc, tupdesc; Oid OIDNewHeap; Relation OldHeap; OldHeap = heap_open(OIDOldHeap, AccessExclusiveLock); OldHeapDesc = RelationGetDescr(OldHeap); /* * Need to make a copy of the tuple descriptor, since * heap_create_with_catalog modifies it. */ tupdesc = CreateTupleDescCopyConstr(OldHeapDesc); OIDNewHeap = heap_create_with_catalog(NewName, RelationGetNamespace(OldHeap), tupdesc, OldHeap->rd_rel->relkind, OldHeap->rd_rel->relisshared, ONCOMMIT_NOOP, allowSystemTableMods); /* * 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. Note that * AlterTableCreateToastTable ends with CommandCounterIncrement(), so * that the TOAST table will be visible for insertion. */ AlterTableCreateToastTable(OIDNewHeap, true); heap_close(OldHeap, NoLock); return OIDNewHeap; } /* * Do the physical copying of heap data. */ static void copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex) { Relation NewHeap, OldHeap, OldIndex; IndexScanDesc scan; HeapTuple tuple; /* * Open the relations I need. Scan through the OldHeap on the OldIndex * and insert each tuple into the NewHeap. */ NewHeap = heap_open(OIDNewHeap, AccessExclusiveLock); OldHeap = heap_open(OIDOldHeap, AccessExclusiveLock); OldIndex = index_open(OIDOldIndex); scan = index_beginscan(OldHeap, OldIndex, SnapshotNow, 0, (ScanKey) NULL); while ((tuple = index_getnext(scan, ForwardScanDirection)) != NULL) { /* * We must copy the tuple because heap_insert() will overwrite the * commit-status fields of the tuple it's handed, and the * retrieved tuple will actually be in a disk buffer! Thus, the * source relation would get trashed, which is bad news if we * abort later on. (This was a bug in releases thru 7.0) * * Note that the copied tuple will have the original OID, if any, so * this does preserve OIDs. */ HeapTuple copiedTuple = heap_copytuple(tuple); simple_heap_insert(NewHeap, copiedTuple); heap_freetuple(copiedTuple); CHECK_FOR_INTERRUPTS(); } index_endscan(scan); index_close(OldIndex); heap_close(OldHeap, NoLock); heap_close(NewHeap, NoLock); } /* * Get the necessary info about the indexes of the relation and * return a list of IndexAttrs structures. */ static List * get_indexattr_list(Relation OldHeap, Oid OldIndex) { List *indexes = NIL; List *indlist; /* Ask the relcache to produce a list of the indexes of the old rel */ foreach(indlist, RelationGetIndexList(OldHeap)) { Oid indexOID = lfirsto(indlist); Relation oldIndex; IndexAttrs *attrs; oldIndex = index_open(indexOID); attrs = (IndexAttrs *) palloc(sizeof(IndexAttrs)); attrs->indexOID = indexOID; attrs->indexName = pstrdup(NameStr(oldIndex->rd_rel->relname)); attrs->accessMethodOID = oldIndex->rd_rel->relam; attrs->indexInfo = BuildIndexInfo(oldIndex); attrs->classOID = (Oid *) palloc(sizeof(Oid) * attrs->indexInfo->ii_NumIndexAttrs); memcpy(attrs->classOID, oldIndex->rd_index->indclass, sizeof(Oid) * attrs->indexInfo->ii_NumIndexAttrs); /* We adjust the isclustered attribute to correct new state */ attrs->isclustered = (indexOID == OldIndex); index_close(oldIndex); /* * Cons the gathered data into the list. We do not care about * ordering, and this is more efficient than append. */ indexes = lcons(attrs, indexes); } return indexes; } /* * Create new indexes and swap the filenodes with old indexes. Then drop * the new index (carrying the old index filenode along). */ static void rebuild_indexes(Oid OIDOldHeap, List *indexes) { List *elem; foreach(elem, indexes) { IndexAttrs *attrs = (IndexAttrs *) lfirst(elem); Oid newIndexOID; char newIndexName[NAMEDATALEN]; ObjectAddress object; Form_pg_index index; HeapTuple tuple; Relation pg_index; /* Create the new index under a temporary name */ snprintf(newIndexName, sizeof(newIndexName), "pg_temp_%u", attrs->indexOID); /* * The new index will have primary and constraint status set to * false, but since we will only use its filenode it doesn't * matter: after the filenode swap the index will keep the * constraint status of the old index. */ newIndexOID = index_create(OIDOldHeap, newIndexName, attrs->indexInfo, attrs->accessMethodOID, attrs->classOID, false, false, allowSystemTableMods); CommandCounterIncrement(); /* Swap the filenodes. */ swap_relfilenodes(attrs->indexOID, newIndexOID); CommandCounterIncrement(); /* * Make sure that indisclustered is correct: it should be set only * for the index we just clustered on. */ pg_index = heap_openr(IndexRelationName, RowExclusiveLock); tuple = SearchSysCacheCopy(INDEXRELID, ObjectIdGetDatum(attrs->indexOID), 0, 0, 0); if (!HeapTupleIsValid(tuple)) elog(ERROR, "cache lookup failed for index %u", attrs->indexOID); index = (Form_pg_index) GETSTRUCT(tuple); if (index->indisclustered != attrs->isclustered) { index->indisclustered = attrs->isclustered; simple_heap_update(pg_index, &tuple->t_self, tuple); CatalogUpdateIndexes(pg_index, tuple); } heap_freetuple(tuple); heap_close(pg_index, RowExclusiveLock); /* Destroy new index with old filenode */ object.classId = RelOid_pg_class; object.objectId = newIndexOID; object.objectSubId = 0; /* * The 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 its end */ } } /* * Swap the relfilenodes for two given relations. * * Also swap any TOAST links, so that the toast data moves along with * the main-table data. */ static void swap_relfilenodes(Oid r1, Oid r2) { Relation relRelation, rel; HeapTuple reltup1, reltup2; Form_pg_class relform1, relform2; Oid swaptemp; int i; CatalogIndexState indstate; /* We need writable copies of both pg_class tuples. */ relRelation = heap_openr(RelationRelationName, 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); /* * The buffer manager gets confused if we swap relfilenodes for * relations that are not both local or non-local to this transaction. * Flush the buffers on both relations so the buffer manager can * forget about'em. (XXX this might not be necessary anymore?) */ rel = relation_open(r1, NoLock); i = FlushRelationBuffers(rel, 0); if (i < 0) elog(ERROR, "FlushRelationBuffers returned %d", i); relation_close(rel, NoLock); rel = relation_open(r2, NoLock); i = FlushRelationBuffers(rel, 0); if (i < 0) elog(ERROR, "FlushRelationBuffers returned %d", i); relation_close(rel, NoLock); /* * Actually swap the filenode and TOAST fields in the two tuples */ swaptemp = relform1->relfilenode; relform1->relfilenode = relform2->relfilenode; relform2->relfilenode = swaptemp; swaptemp = relform1->reltoastrelid; relform1->reltoastrelid = relform2->reltoastrelid; relform2->reltoastrelid = swaptemp; /* we should not swap reltoastidxid */ /* 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 */ 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); /* * If we have toast tables associated with the relations being * swapped, change their dependency links to re-associate them with * their new owning relations. Otherwise the wrong one will get * dropped ... * * NOTE: for now, we can assume the new table will have a TOAST table if * and only if the old one does. This logic might need work if we get * smarter about dropped columns. * * 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 only * the link we want. */ if (relform1->reltoastrelid || relform2->reltoastrelid) { ObjectAddress baseobject, toastobject; long count; if (!(relform1->reltoastrelid && relform2->reltoastrelid)) elog(ERROR, "expected both swapped tables to have TOAST tables"); /* Delete old dependencies */ count = deleteDependencyRecordsFor(RelOid_pg_class, relform1->reltoastrelid); if (count != 1) elog(ERROR, "expected one dependency record for TOAST table, found %ld", count); count = deleteDependencyRecordsFor(RelOid_pg_class, relform2->reltoastrelid); if (count != 1) elog(ERROR, "expected one dependency record for TOAST table, found %ld", count); /* Register new dependencies */ baseobject.classId = RelOid_pg_class; baseobject.objectId = r1; baseobject.objectSubId = 0; toastobject.classId = RelOid_pg_class; toastobject.objectId = relform1->reltoastrelid; toastobject.objectSubId = 0; recordDependencyOn(&toastobject, &baseobject, DEPENDENCY_INTERNAL); baseobject.objectId = r2; toastobject.objectId = relform2->reltoastrelid; recordDependencyOn(&toastobject, &baseobject, DEPENDENCY_INTERNAL); } /* * Blow away the old relcache entries now. We need this kluge because * relcache.c indexes relcache entries by rd_node as well as OID. It * will get confused if it is asked to (re)build an entry with a new * rd_node value when there is still another entry laying about with * that same rd_node value. (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-local relation.) */ RelationForgetRelation(r1); RelationForgetRelation(r2); /* Clean up. */ heap_freetuple(reltup1); heap_freetuple(reltup2); heap_close(relRelation, RowExclusiveLock); } /* * 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 = relation_openr(IndexRelationName, AccessShareLock); ScanKeyEntryInitialize(&entry, 0, Anum_pg_index_indisclustered, 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; }