REINDEX CONCURRENTLY

This adds the CONCURRENTLY option to the REINDEX command.  A REINDEX
CONCURRENTLY on a specific index creates a new index (like CREATE
INDEX CONCURRENTLY), then renames the old index away and the new index
in place and adjusts the dependencies, and then drops the old
index (like DROP INDEX CONCURRENTLY).  The REINDEX command also has
the capability to run its other variants (TABLE, DATABASE) with the
CONCURRENTLY option (but not SYSTEM).

The reindexdb command gets the --concurrently option.

Author: Michael Paquier, Andreas Karlsson, Peter Eisentraut
Reviewed-by: Andres Freund, Fujii Masao, Jim Nasby, Sergei Kornilov
Discussion: https://www.postgresql.org/message-id/flat/60052986-956b-4478-45ed-8bd119e9b9cf%402ndquadrant.com#74948a1044c56c5e817a5050f554ddee

1 files changed, 779 insertions, 110 deletions

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index d6eb48cb4e6..c68d8d58167 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -58,6 +58,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/partcache.h"
+#include "utils/pg_rusage.h"
 #include "utils/regproc.h"
 #include "utils/snapmgr.h"
 #include "utils/syscache.h"
@@ -83,6 +84,7 @@ static char *ChooseIndexNameAddition(List *colnames);
 static List *ChooseIndexColumnNames(List *indexElems);
 static void RangeVarCallbackForReindexIndex(const RangeVar *relation,
 								Oid relId, Oid oldRelId, void *arg);
+static bool ReindexRelationConcurrently(Oid relationOid, int options);
 static void ReindexPartitionedIndex(Relation parentIdx);
 
 /*
@@ -297,6 +299,90 @@ CheckIndexCompatible(Oid oldId,
 	return ret;
 }
 
+
+/*
+ * WaitForOlderSnapshots
+ *
+ * Wait for transactions that might have an older snapshot than the given xmin
+ * limit, because it might not contain tuples deleted just before it has
+ * been taken. Obtain a list of VXIDs of such transactions, and wait for them
+ * individually. This is used when building an index concurrently.
+ *
+ * We can exclude any running transactions that have xmin > the xmin given;
+ * their oldest snapshot must be newer than our xmin limit.
+ * We can also exclude any transactions that have xmin = zero, since they
+ * evidently have no live snapshot at all (and any one they might be in
+ * process of taking is certainly newer than ours).  Transactions in other
+ * DBs can be ignored too, since they'll never even be able to see the
+ * index being worked on.
+ *
+ * We can also exclude autovacuum processes and processes running manual
+ * lazy VACUUMs, because they won't be fazed by missing index entries
+ * either.  (Manual ANALYZEs, however, can't be excluded because they
+ * might be within transactions that are going to do arbitrary operations
+ * later.)
+ *
+ * Also, GetCurrentVirtualXIDs never reports our own vxid, so we need not
+ * check for that.
+ *
+ * If a process goes idle-in-transaction with xmin zero, we do not need to
+ * wait for it anymore, per the above argument.  We do not have the
+ * infrastructure right now to stop waiting if that happens, but we can at
+ * least avoid the folly of waiting when it is idle at the time we would
+ * begin to wait.  We do this by repeatedly rechecking the output of
+ * GetCurrentVirtualXIDs.  If, during any iteration, a particular vxid
+ * doesn't show up in the output, we know we can forget about it.
+ */
+static void
+WaitForOlderSnapshots(TransactionId limitXmin)
+{
+	int			n_old_snapshots;
+	int			i;
+	VirtualTransactionId *old_snapshots;
+
+	old_snapshots = GetCurrentVirtualXIDs(limitXmin, true, false,
+										  PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
+										  &n_old_snapshots);
+
+	for (i = 0; i < n_old_snapshots; i++)
+	{
+		if (!VirtualTransactionIdIsValid(old_snapshots[i]))
+			continue;			/* found uninteresting in previous cycle */
+
+		if (i > 0)
+		{
+			/* see if anything's changed ... */
+			VirtualTransactionId *newer_snapshots;
+			int			n_newer_snapshots;
+			int			j;
+			int			k;
+
+			newer_snapshots = GetCurrentVirtualXIDs(limitXmin,
+													true, false,
+													PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
+													&n_newer_snapshots);
+			for (j = i; j < n_old_snapshots; j++)
+			{
+				if (!VirtualTransactionIdIsValid(old_snapshots[j]))
+					continue;	/* found uninteresting in previous cycle */
+				for (k = 0; k < n_newer_snapshots; k++)
+				{
+					if (VirtualTransactionIdEquals(old_snapshots[j],
+												   newer_snapshots[k]))
+						break;
+				}
+				if (k >= n_newer_snapshots) /* not there anymore */
+					SetInvalidVirtualTransactionId(old_snapshots[j]);
+			}
+			pfree(newer_snapshots);
+		}
+
+		if (VirtualTransactionIdIsValid(old_snapshots[i]))
+			VirtualXactLock(old_snapshots[i], true);
+	}
+}
+
+
 /*
  * DefineIndex
  *		Creates a new index.
@@ -345,7 +431,6 @@ DefineIndex(Oid relationId,
 	List	   *indexColNames;
 	List	   *allIndexParams;
 	Relation	rel;
-	Relation	indexRelation;
 	HeapTuple	tuple;
 	Form_pg_am	accessMethodForm;
 	IndexAmRoutine *amRoutine;
@@ -360,9 +445,7 @@ DefineIndex(Oid relationId,
 	int			numberOfAttributes;
 	int			numberOfKeyAttributes;
 	TransactionId limitXmin;
-	VirtualTransactionId *old_snapshots;
 	ObjectAddress address;
-	int			n_old_snapshots;
 	LockRelId	heaprelid;
 	LOCKTAG		heaplocktag;
 	LOCKMODE	lockmode;
@@ -1151,34 +1234,11 @@ DefineIndex(Oid relationId,
 	 * HOT-chain or the extension of the chain is HOT-safe for this index.
 	 */
 
-	/* Open and lock the parent heap relation */
-	rel = table_open(relationId, ShareUpdateExclusiveLock);
-
-	/* And the target index relation */
-	indexRelation = index_open(indexRelationId, RowExclusiveLock);
-
 	/* Set ActiveSnapshot since functions in the indexes may need it */
 	PushActiveSnapshot(GetTransactionSnapshot());
 
-	/* We have to re-build the IndexInfo struct, since it was lost in commit */
-	indexInfo = BuildIndexInfo(indexRelation);
-	Assert(!indexInfo->ii_ReadyForInserts);
-	indexInfo->ii_Concurrent = true;
-	indexInfo->ii_BrokenHotChain = false;
-
-	/* Now build the index */
-	index_build(rel, indexRelation, indexInfo, false, true);
-
-	/* Close both the relations, but keep the locks */
-	table_close(rel, NoLock);
-	index_close(indexRelation, NoLock);
-
-	/*
-	 * Update the pg_index row to mark the index as ready for inserts. Once we
-	 * commit this transaction, any new transactions that open the table must
-	 * insert new entries into the index for insertions and non-HOT updates.
-	 */
-	index_set_state_flags(indexRelationId, INDEX_CREATE_SET_READY);
+	/* Perform concurrent build of index */
+	index_concurrently_build(relationId, indexRelationId);
 
 	/* we can do away with our snapshot */
 	PopActiveSnapshot();
@@ -1250,74 +1310,9 @@ DefineIndex(Oid relationId,
 	 * The index is now valid in the sense that it contains all currently
 	 * interesting tuples.  But since it might not contain tuples deleted just
 	 * before the reference snap was taken, we have to wait out any
-	 * transactions that might have older snapshots.  Obtain a list of VXIDs
-	 * of such transactions, and wait for them individually.
-	 *
-	 * We can exclude any running transactions that have xmin > the xmin of
-	 * our reference snapshot; their oldest snapshot must be newer than ours.
-	 * We can also exclude any transactions that have xmin = zero, since they
-	 * evidently have no live snapshot at all (and any one they might be in
-	 * process of taking is certainly newer than ours).  Transactions in other
-	 * DBs can be ignored too, since they'll never even be able to see this
-	 * index.
-	 *
-	 * We can also exclude autovacuum processes and processes running manual
-	 * lazy VACUUMs, because they won't be fazed by missing index entries
-	 * either.  (Manual ANALYZEs, however, can't be excluded because they
-	 * might be within transactions that are going to do arbitrary operations
-	 * later.)
-	 *
-	 * Also, GetCurrentVirtualXIDs never reports our own vxid, so we need not
-	 * check for that.
-	 *
-	 * If a process goes idle-in-transaction with xmin zero, we do not need to
-	 * wait for it anymore, per the above argument.  We do not have the
-	 * infrastructure right now to stop waiting if that happens, but we can at
-	 * least avoid the folly of waiting when it is idle at the time we would
-	 * begin to wait.  We do this by repeatedly rechecking the output of
-	 * GetCurrentVirtualXIDs.  If, during any iteration, a particular vxid
-	 * doesn't show up in the output, we know we can forget about it.
+	 * transactions that might have older snapshots.
 	 */
-	old_snapshots = GetCurrentVirtualXIDs(limitXmin, true, false,
-										  PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
-										  &n_old_snapshots);
-
-	for (i = 0; i < n_old_snapshots; i++)
-	{
-		if (!VirtualTransactionIdIsValid(old_snapshots[i]))
-			continue;			/* found uninteresting in previous cycle */
-
-		if (i > 0)
-		{
-			/* see if anything's changed ... */
-			VirtualTransactionId *newer_snapshots;
-			int			n_newer_snapshots;
-			int			j;
-			int			k;
-
-			newer_snapshots = GetCurrentVirtualXIDs(limitXmin,
-													true, false,
-													PROC_IS_AUTOVACUUM | PROC_IN_VACUUM,
-													&n_newer_snapshots);
-			for (j = i; j < n_old_snapshots; j++)
-			{
-				if (!VirtualTransactionIdIsValid(old_snapshots[j]))
-					continue;	/* found uninteresting in previous cycle */
-				for (k = 0; k < n_newer_snapshots; k++)
-				{
-					if (VirtualTransactionIdEquals(old_snapshots[j],
-												   newer_snapshots[k]))
-						break;
-				}
-				if (k >= n_newer_snapshots) /* not there anymore */
-					SetInvalidVirtualTransactionId(old_snapshots[j]);
-			}
-			pfree(newer_snapshots);
-		}
-
-		if (VirtualTransactionIdIsValid(old_snapshots[i]))
-			VirtualXactLock(old_snapshots[i], true);
-	}
+	WaitForOlderSnapshots(limitXmin);
 
 	/*
 	 * Index can now be marked valid -- update its pg_index entry
@@ -2204,7 +2199,7 @@ ChooseIndexColumnNames(List *indexElems)
  *		Recreate a specific index.
  */
 void
-ReindexIndex(RangeVar *indexRelation, int options)
+ReindexIndex(RangeVar *indexRelation, int options, bool concurrent)
 {
 	Oid			indOid;
 	Oid			heapOid = InvalidOid;
@@ -2216,7 +2211,8 @@ ReindexIndex(RangeVar *indexRelation, int options)
 	 * obtain lock on table first, to avoid deadlock hazard.  The lock level
 	 * used here must match the index lock obtained in reindex_index().
 	 */
-	indOid = RangeVarGetRelidExtended(indexRelation, AccessExclusiveLock,
+	indOid = RangeVarGetRelidExtended(indexRelation,
+									  concurrent ? ShareUpdateExclusiveLock : AccessExclusiveLock,
 									  0,
 									  RangeVarCallbackForReindexIndex,
 									  (void *) &heapOid);
@@ -2236,7 +2232,10 @@ ReindexIndex(RangeVar *indexRelation, int options)
 	persistence = irel->rd_rel->relpersistence;
 	index_close(irel, NoLock);
 
-	reindex_index(indOid, false, persistence, options);
+	if (concurrent)
+		ReindexRelationConcurrently(indOid, options);
+	else
+		reindex_index(indOid, false, persistence, options);
 }
 
 /*
@@ -2304,18 +2303,26 @@ RangeVarCallbackForReindexIndex(const RangeVar *relation,
  *		Recreate all indexes of a table (and of its toast table, if any)
  */
 Oid
-ReindexTable(RangeVar *relation, int options)
+ReindexTable(RangeVar *relation, int options, bool concurrent)
 {
 	Oid			heapOid;
+	bool		result;
 
 	/* The lock level used here should match reindex_relation(). */
-	heapOid = RangeVarGetRelidExtended(relation, ShareLock, 0,
+	heapOid = RangeVarGetRelidExtended(relation,
+									   concurrent ? ShareUpdateExclusiveLock : ShareLock,
+									   0,
 									   RangeVarCallbackOwnsTable, NULL);
 
-	if (!reindex_relation(heapOid,
-						  REINDEX_REL_PROCESS_TOAST |
-						  REINDEX_REL_CHECK_CONSTRAINTS,
-						  options))
+	if (concurrent)
+		result = ReindexRelationConcurrently(heapOid, options);
+	else
+		result = reindex_relation(heapOid,
+								  REINDEX_REL_PROCESS_TOAST |
+								  REINDEX_REL_CHECK_CONSTRAINTS,
+								  options);
+
+	if (!result)
 		ereport(NOTICE,
 				(errmsg("table \"%s\" has no indexes",
 						relation->relname)));
@@ -2333,7 +2340,7 @@ ReindexTable(RangeVar *relation, int options)
  */
 void
 ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
-					  int options)
+					  int options, bool concurrent)
 {
 	Oid			objectOid;
 	Relation	relationRelation;
@@ -2345,12 +2352,18 @@ ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
 	List	   *relids = NIL;
 	ListCell   *l;
 	int			num_keys;
+	bool		concurrent_warning = false;
 
 	AssertArg(objectName);
 	Assert(objectKind == REINDEX_OBJECT_SCHEMA ||
 		   objectKind == REINDEX_OBJECT_SYSTEM ||
 		   objectKind == REINDEX_OBJECT_DATABASE);
 
+	if (objectKind == REINDEX_OBJECT_SYSTEM && concurrent)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("concurrent reindex of system catalogs is not supported")));
+
 	/*
 	 * Get OID of object to reindex, being the database currently being used
 	 * by session for a database or for system catalogs, or the schema defined
@@ -2453,6 +2466,25 @@ ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
 			!pg_class_ownercheck(relid, GetUserId()))
 			continue;
 
+		/*
+		 * Skip system tables that index_create() would reject to index
+		 * concurrently.  XXX We need the additional check for
+		 * FirstNormalObjectId to skip information_schema tables, because
+		 * IsCatalogClass() here does not cover information_schema, but the
+		 * check in index_create() will error on the TOAST tables of
+		 * information_schema tables.
+		 */
+		if (concurrent &&
+			(IsCatalogClass(relid, classtuple) || relid < FirstNormalObjectId))
+		{
+			if (!concurrent_warning)
+				ereport(WARNING,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("concurrent reindex is not supported for catalog relations, skipping all")));
+			concurrent_warning = true;
+			continue;
+		}
+
 		/* Save the list of relation OIDs in private context */
 		old = MemoryContextSwitchTo(private_context);
 
@@ -2479,26 +2511,663 @@ ReindexMultipleTables(const char *objectName, ReindexObjectType objectKind,
 	foreach(l, relids)
 	{
 		Oid			relid = lfirst_oid(l);
+		bool		result;
 
 		StartTransactionCommand();
 		/* functions in indexes may want a snapshot set */
 		PushActiveSnapshot(GetTransactionSnapshot());
-		if (reindex_relation(relid,
-							 REINDEX_REL_PROCESS_TOAST |
-							 REINDEX_REL_CHECK_CONSTRAINTS,
-							 options))
 
-			if (options & REINDEXOPT_VERBOSE)
+		if (concurrent)
+		{
+			result = ReindexRelationConcurrently(relid, options);
+			/* ReindexRelationConcurrently() does the verbose output */
+		}
+		else
+		{
+			result = reindex_relation(relid,
+									  REINDEX_REL_PROCESS_TOAST |
+									  REINDEX_REL_CHECK_CONSTRAINTS,
+									  options);
+
+			if (result && (options & REINDEXOPT_VERBOSE))
 				ereport(INFO,
 						(errmsg("table \"%s.%s\" was reindexed",
 								get_namespace_name(get_rel_namespace(relid)),
 								get_rel_name(relid))));
+
+			PopActiveSnapshot();
+		}
+
+		CommitTransactionCommand();
+	}
+	StartTransactionCommand();
+
+	MemoryContextDelete(private_context);
+}
+
+
+/*
+ * ReindexRelationConcurrently - process REINDEX CONCURRENTLY for given
+ * relation OID
+ *
+ * The relation can be either an index or a table.  If it is a table, all its
+ * valid indexes will be rebuilt, including its associated toast table
+ * indexes.  If it is an index, this index itself will be rebuilt.
+ *
+ * The locks taken on parent tables and involved indexes are kept until the
+ * transaction is committed, at which point a session lock is taken on each
+ * relation.  Both of these protect against concurrent schema changes.
+ */
+static bool
+ReindexRelationConcurrently(Oid relationOid, int options)
+{
+	List	   *heapRelationIds = NIL;
+	List	   *indexIds = NIL;
+	List	   *newIndexIds = NIL;
+	List	   *relationLocks = NIL;
+	List	   *lockTags = NIL;
+	ListCell   *lc,
+			   *lc2;
+	MemoryContext private_context;
+	MemoryContext oldcontext;
+	char		relkind;
+	char	   *relationName = NULL;
+	char	   *relationNamespace = NULL;
+	PGRUsage	ru0;
+
+	/*
+	 * Create a memory context that will survive forced transaction commits we
+	 * do below.  Since it is a child of PortalContext, it will go away
+	 * eventually even if we suffer an error; there's no need for special
+	 * abort cleanup logic.
+	 */
+	private_context = AllocSetContextCreate(PortalContext,
+											"ReindexConcurrent",
+											ALLOCSET_SMALL_SIZES);
+
+	if (options & REINDEXOPT_VERBOSE)
+	{
+		/* Save data needed by REINDEX VERBOSE in private context */
+		oldcontext = MemoryContextSwitchTo(private_context);
+
+		relationName = get_rel_name(relationOid);
+		relationNamespace = get_namespace_name(get_rel_namespace(relationOid));
+
+		pg_rusage_init(&ru0);
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	relkind = get_rel_relkind(relationOid);
+
+	/*
+	 * Extract the list of indexes that are going to be rebuilt based on the
+	 * list of relation Oids given by caller.
+	 */
+	switch (relkind)
+	{
+		case RELKIND_RELATION:
+		case RELKIND_MATVIEW:
+		case RELKIND_TOASTVALUE:
+			{
+				/*
+				 * In the case of a relation, find all its indexes including
+				 * toast indexes.
+				 */
+				Relation	heapRelation;
+
+				/* Save the list of relation OIDs in private context */
+				oldcontext = MemoryContextSwitchTo(private_context);
+
+				/* Track this relation for session locks */
+				heapRelationIds = lappend_oid(heapRelationIds, relationOid);
+
+				MemoryContextSwitchTo(oldcontext);
+
+				/* Open relation to get its indexes */
+				heapRelation = table_open(relationOid, ShareUpdateExclusiveLock);
+
+				/* Add all the valid indexes of relation to list */
+				foreach(lc, RelationGetIndexList(heapRelation))
+				{
+					Oid			cellOid = lfirst_oid(lc);
+					Relation	indexRelation = index_open(cellOid,
+														   ShareUpdateExclusiveLock);
+
+					if (!indexRelation->rd_index->indisvalid)
+						ereport(WARNING,
+								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+								 errmsg("cannot reindex concurrently invalid index \"%s.%s\", skipping",
+										get_namespace_name(get_rel_namespace(cellOid)),
+										get_rel_name(cellOid))));
+					else if (indexRelation->rd_index->indisexclusion)
+						ereport(WARNING,
+								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+								 errmsg("cannot reindex concurrently exclusion constraint index \"%s.%s\", skipping",
+										get_namespace_name(get_rel_namespace(cellOid)),
+										get_rel_name(cellOid))));
+					else
+					{
+						/* Save the list of relation OIDs in private context */
+						oldcontext = MemoryContextSwitchTo(private_context);
+
+						indexIds = lappend_oid(indexIds, cellOid);
+
+						MemoryContextSwitchTo(oldcontext);
+					}
+
+					index_close(indexRelation, NoLock);
+				}
+
+				/* Also add the toast indexes */
+				if (OidIsValid(heapRelation->rd_rel->reltoastrelid))
+				{
+					Oid			toastOid = heapRelation->rd_rel->reltoastrelid;
+					Relation	toastRelation = table_open(toastOid,
+														   ShareUpdateExclusiveLock);
+
+					/* Save the list of relation OIDs in private context */
+					oldcontext = MemoryContextSwitchTo(private_context);
+
+					/* Track this relation for session locks */
+					heapRelationIds = lappend_oid(heapRelationIds, toastOid);
+
+					MemoryContextSwitchTo(oldcontext);
+
+					foreach(lc2, RelationGetIndexList(toastRelation))
+					{
+						Oid			cellOid = lfirst_oid(lc2);
+						Relation	indexRelation = index_open(cellOid,
+															   ShareUpdateExclusiveLock);
+
+						if (!indexRelation->rd_index->indisvalid)
+							ereport(WARNING,
+									(errcode(ERRCODE_INDEX_CORRUPTED),
+									 errmsg("cannot reindex concurrently invalid index \"%s.%s\", skipping",
+											get_namespace_name(get_rel_namespace(cellOid)),
+											get_rel_name(cellOid))));
+						else
+						{
+							/*
+							 * Save the list of relation OIDs in private
+							 * context
+							 */
+							oldcontext = MemoryContextSwitchTo(private_context);
+
+							indexIds = lappend_oid(indexIds, cellOid);
+
+							MemoryContextSwitchTo(oldcontext);
+						}
+
+						index_close(indexRelation, NoLock);
+					}
+
+					table_close(toastRelation, NoLock);
+				}
+
+				table_close(heapRelation, NoLock);
+				break;
+			}
+		case RELKIND_INDEX:
+			{
+				/*
+				 * For an index simply add its Oid to list. Invalid indexes
+				 * cannot be included in list.
+				 */
+				Relation	indexRelation = index_open(relationOid, ShareUpdateExclusiveLock);
+				Oid			heapId = IndexGetRelation(relationOid, false);
+
+				/* A shared relation cannot be reindexed concurrently */
+				if (IsSharedRelation(heapId))
+					ereport(ERROR,
+							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+							 errmsg("concurrent reindex is not supported for shared relations")));
+
+				/* A system catalog cannot be reindexed concurrently */
+				if (IsSystemNamespace(get_rel_namespace(heapId)))
+					ereport(ERROR,
+							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+							 errmsg("concurrent reindex is not supported for catalog relations")));
+
+				/* Save the list of relation OIDs in private context */
+				oldcontext = MemoryContextSwitchTo(private_context);
+
+				/* Track the heap relation of this index for session locks */
+				heapRelationIds = list_make1_oid(heapId);
+
+				MemoryContextSwitchTo(oldcontext);
+
+				if (!indexRelation->rd_index->indisvalid)
+					ereport(WARNING,
+							(errcode(ERRCODE_INDEX_CORRUPTED),
+							 errmsg("cannot reindex concurrently invalid index \"%s.%s\", skipping",
+									get_namespace_name(get_rel_namespace(relationOid)),
+									get_rel_name(relationOid))));
+				else
+				{
+					/* Save the list of relation OIDs in private context */
+					oldcontext = MemoryContextSwitchTo(private_context);
+
+					indexIds = lappend_oid(indexIds, relationOid);
+
+					MemoryContextSwitchTo(oldcontext);
+				}
+
+				index_close(indexRelation, NoLock);
+				break;
+			}
+		case RELKIND_PARTITIONED_TABLE:
+			/* see reindex_relation() */
+			ereport(WARNING,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("REINDEX of partitioned tables is not yet implemented, skipping \"%s\"",
+							get_rel_name(relationOid))));
+			return false;
+		default:
+			/* Return error if type of relation is not supported */
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("cannot reindex concurrently this type of relation")));
+			break;
+	}
+
+	/* Definitely no indexes, so leave */
+	if (indexIds == NIL)
+	{
+		PopActiveSnapshot();
+		return false;
+	}
+
+	Assert(heapRelationIds != NIL);
+
+	/*-----
+	 * Now we have all the indexes we want to process in indexIds.
+	 *
+	 * The phases now are:
+	 *
+	 * 1. create new indexes in the catalog
+	 * 2. build new indexes
+	 * 3. let new indexes catch up with tuples inserted in the meantime
+	 * 4. swap index names
+	 * 5. mark old indexes as dead
+	 * 6. drop old indexes
+	 *
+	 * We process each phase for all indexes before moving to the next phase,
+	 * for efficiency.
+	 */
+
+	/*
+	 * Phase 1 of REINDEX CONCURRENTLY
+	 *
+	 * Create a new index with the same properties as the old one, but it is
+	 * only registered in catalogs and will be built later.  Then get session
+	 * locks on all involved tables.  See analogous code in DefineIndex() for
+	 * more detailed comments.
+	 */
+
+	foreach(lc, indexIds)
+	{
+		char	   *concurrentName;
+		Oid			indexId = lfirst_oid(lc);
+		Oid			newIndexId;
+		Relation	indexRel;
+		Relation	heapRel;
+		Relation	newIndexRel;
+		LockRelId	lockrelid;
+
+		indexRel = index_open(indexId, ShareUpdateExclusiveLock);
+		heapRel = table_open(indexRel->rd_index->indrelid,
+							 ShareUpdateExclusiveLock);
+
+		/* Choose a temporary relation name for the new index */
+		concurrentName = ChooseRelationName(get_rel_name(indexId),
+											NULL,
+											"ccnew",
+											get_rel_namespace(indexRel->rd_index->indrelid),
+											false);
+
+		/* Create new index definition based on given index */
+		newIndexId = index_concurrently_create_copy(heapRel,
+													indexId,
+													concurrentName);
+
+		/* Now open the relation of the new index, a lock is also needed on it */
+		newIndexRel = index_open(indexId, ShareUpdateExclusiveLock);
+
+		/*
+		 * Save the list of OIDs and locks in private context
+		 */
+		oldcontext = MemoryContextSwitchTo(private_context);
+
+		newIndexIds = lappend_oid(newIndexIds, newIndexId);
+
+		/*
+		 * Save lockrelid to protect each relation from drop then close
+		 * relations. The lockrelid on parent relation is not taken here to
+		 * avoid multiple locks taken on the same relation, instead we rely on
+		 * parentRelationIds built earlier.
+		 */
+		lockrelid = indexRel->rd_lockInfo.lockRelId;
+		relationLocks = lappend(relationLocks, &lockrelid);
+		lockrelid = newIndexRel->rd_lockInfo.lockRelId;
+		relationLocks = lappend(relationLocks, &lockrelid);
+
+		MemoryContextSwitchTo(oldcontext);
+
+		index_close(indexRel, NoLock);
+		index_close(newIndexRel, NoLock);
+		table_close(heapRel, NoLock);
+	}
+
+	/*
+	 * Save the heap lock for following visibility checks with other backends
+	 * might conflict with this session.
+	 */
+	foreach(lc, heapRelationIds)
+	{
+		Relation	heapRelation = table_open(lfirst_oid(lc), ShareUpdateExclusiveLock);
+		LockRelId	lockrelid = heapRelation->rd_lockInfo.lockRelId;
+		LOCKTAG    *heaplocktag;
+
+		/* Save the list of locks in private context */
+		oldcontext = MemoryContextSwitchTo(private_context);
+
+		/* Add lockrelid of heap relation to the list of locked relations */
+		relationLocks = lappend(relationLocks, &lockrelid);
+
+		heaplocktag = (LOCKTAG *) palloc(sizeof(LOCKTAG));
+
+		/* Save the LOCKTAG for this parent relation for the wait phase */
+		SET_LOCKTAG_RELATION(*heaplocktag, lockrelid.dbId, lockrelid.relId);
+		lockTags = lappend(lockTags, heaplocktag);
+
+		MemoryContextSwitchTo(oldcontext);
+
+		/* Close heap relation */
+		table_close(heapRelation, NoLock);
+	}
+
+	/* Get a session-level lock on each table. */
+	foreach(lc, relationLocks)
+	{
+		LockRelId	lockRel = *((LockRelId *) lfirst(lc));
+
+		LockRelationIdForSession(&lockRel, ShareUpdateExclusiveLock);
+	}
+
+	PopActiveSnapshot();
+	CommitTransactionCommand();
+	StartTransactionCommand();
+
+	/*
+	 * Phase 2 of REINDEX CONCURRENTLY
+	 *
+	 * Build the new indexes in a separate transaction for each index to avoid
+	 * having open transactions for an unnecessary long time.  But before
+	 * doing that, wait until no running transactions could have the table of
+	 * the index open with the old list of indexes.  See "phase 2" in
+	 * DefineIndex() for more details.
+	 */
+
+	WaitForLockersMultiple(lockTags, ShareLock);
+	CommitTransactionCommand();
+
+	forboth(lc, indexIds, lc2, newIndexIds)
+	{
+		Relation	indexRel;
+		Oid			oldIndexId = lfirst_oid(lc);
+		Oid			newIndexId = lfirst_oid(lc2);
+		Oid			heapId;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Start new transaction for this index's concurrent build */
+		StartTransactionCommand();
+
+		/* Set ActiveSnapshot since functions in the indexes may need it */
+		PushActiveSnapshot(GetTransactionSnapshot());
+
+		/*
+		 * Index relation has been closed by previous commit, so reopen it to
+		 * get its information.
+		 */
+		indexRel = index_open(oldIndexId, ShareUpdateExclusiveLock);
+		heapId = indexRel->rd_index->indrelid;
+		index_close(indexRel, NoLock);
+
+		/* Perform concurrent build of new index */
+		index_concurrently_build(heapId, newIndexId);
+
+		PopActiveSnapshot();
+		CommitTransactionCommand();
+	}
+	StartTransactionCommand();
+
+	/*
+	 * Phase 3 of REINDEX CONCURRENTLY
+	 *
+	 * During this phase the old indexes catch up with any new tuples that
+	 * were created during the previous phase.  See "phase 3" in DefineIndex()
+	 * for more details.
+	 */
+
+	WaitForLockersMultiple(lockTags, ShareLock);
+	CommitTransactionCommand();
+
+	foreach(lc, newIndexIds)
+	{
+		Oid			newIndexId = lfirst_oid(lc);
+		Oid			heapId;
+		TransactionId limitXmin;
+		Snapshot	snapshot;
+
+		CHECK_FOR_INTERRUPTS();
+
+		StartTransactionCommand();
+
+		heapId = IndexGetRelation(newIndexId, false);
+
+		/*
+		 * Take the "reference snapshot" that will be used by validate_index()
+		 * to filter candidate tuples.
+		 */
+		snapshot = RegisterSnapshot(GetTransactionSnapshot());
+		PushActiveSnapshot(snapshot);
+
+		validate_index(heapId, newIndexId, snapshot);
+
+		/*
+		 * We can now do away with our active snapshot, we still need to save
+		 * the xmin limit to wait for older snapshots.
+		 */
+		limitXmin = snapshot->xmin;
+
 		PopActiveSnapshot();
+		UnregisterSnapshot(snapshot);
+
+		/*
+		 * To ensure no deadlocks, we must commit and start yet another
+		 * transaction, and do our wait before any snapshot has been taken in
+		 * it.
+		 */
+		CommitTransactionCommand();
+		StartTransactionCommand();
+
+		/*
+		 * The index is now valid in the sense that it contains all currently
+		 * interesting tuples.  But since it might not contain tuples deleted just
+		 * before the reference snap was taken, we have to wait out any
+		 * transactions that might have older snapshots.
+		 */
+		WaitForOlderSnapshots(limitXmin);
+
 		CommitTransactionCommand();
 	}
+
+	/*
+	 * Phase 4 of REINDEX CONCURRENTLY
+	 *
+	 * Now that the new indexes have been validated, swap each new index with
+	 * its corresponding old index.
+	 *
+	 * We mark the new indexes as valid and the old indexes as not valid at
+	 * the same time to make sure we only get constraint violations from the
+	 * indexes with the correct names.
+	 */
+
 	StartTransactionCommand();
 
+	forboth(lc, indexIds, lc2, newIndexIds)
+	{
+		char	   *oldName;
+		Oid			oldIndexId = lfirst_oid(lc);
+		Oid			newIndexId = lfirst_oid(lc2);
+		Oid			heapId;
+
+		CHECK_FOR_INTERRUPTS();
+
+		heapId = IndexGetRelation(oldIndexId, false);
+
+		/* Choose a relation name for old index */
+		oldName = ChooseRelationName(get_rel_name(oldIndexId),
+									 NULL,
+									 "ccold",
+									 get_rel_namespace(heapId),
+									 false);
+
+		/*
+		 * Swap old index with the new one.  This also marks the new one as
+		 * valid and the old one as not valid.
+		 */
+		index_concurrently_swap(newIndexId, oldIndexId, oldName);
+
+		/*
+		 * Invalidate the relcache for the table, so that after this commit
+		 * all sessions will refresh any cached plans that might reference the
+		 * index.
+		 */
+		CacheInvalidateRelcacheByRelid(heapId);
+
+		/*
+		 * CCI here so that subsequent iterations see the oldName in the
+		 * catalog and can choose a nonconflicting name for their oldName.
+		 * Otherwise, this could lead to conflicts if a table has two indexes
+		 * whose names are equal for the first NAMEDATALEN-minus-a-few
+		 * characters.
+		 */
+		CommandCounterIncrement();
+	}
+
+	/* Commit this transaction and make index swaps visible */
+	CommitTransactionCommand();
+	StartTransactionCommand();
+
+	/*
+	 * Phase 5 of REINDEX CONCURRENTLY
+	 *
+	 * Mark the old indexes as dead.  First we must wait until no running
+	 * transaction could be using the index for a query.  See also
+	 * index_drop() for more details.
+	 */
+
+	WaitForLockersMultiple(lockTags, AccessExclusiveLock);
+
+	foreach(lc, indexIds)
+	{
+		Oid			oldIndexId = lfirst_oid(lc);
+		Oid			heapId;
+
+		CHECK_FOR_INTERRUPTS();
+		heapId = IndexGetRelation(oldIndexId, false);
+		index_concurrently_set_dead(heapId, oldIndexId);
+	}
+
+	/* Commit this transaction to make the updates visible. */
+	CommitTransactionCommand();
+	StartTransactionCommand();
+
+	/*
+	 * Phase 6 of REINDEX CONCURRENTLY
+	 *
+	 * Drop the old indexes.
+	 */
+
+	WaitForLockersMultiple(lockTags, AccessExclusiveLock);
+
+	PushActiveSnapshot(GetTransactionSnapshot());
+
+	{
+		ObjectAddresses *objects = new_object_addresses();
+
+		foreach(lc, indexIds)
+		{
+			Oid			oldIndexId = lfirst_oid(lc);
+			ObjectAddress *object = palloc(sizeof(ObjectAddress));
+
+			object->classId = RelationRelationId;
+			object->objectId = oldIndexId;
+			object->objectSubId = 0;
+
+			add_exact_object_address(object, objects);
+		}
+
+		/*
+		 * Use PERFORM_DELETION_CONCURRENT_LOCK so that index_drop() uses the
+		 * right lock level.
+		 */
+		performMultipleDeletions(objects, DROP_RESTRICT,
+								 PERFORM_DELETION_CONCURRENT_LOCK | PERFORM_DELETION_INTERNAL);
+	}
+
+	PopActiveSnapshot();
+	CommitTransactionCommand();
+
+	/*
+	 * Finally, release the session-level lock on the table.
+	 */
+	foreach(lc, relationLocks)
+	{
+		LockRelId	lockRel = *((LockRelId *) lfirst(lc));
+
+		UnlockRelationIdForSession(&lockRel, ShareUpdateExclusiveLock);
+	}
+
+	/* Start a new transaction to finish process properly */
+	StartTransactionCommand();
+
+	/* Log what we did */
+	if (options & REINDEXOPT_VERBOSE)
+	{
+		if (relkind == RELKIND_INDEX)
+			ereport(INFO,
+					(errmsg("index \"%s.%s\" was reindexed",
+							relationNamespace, relationName),
+					 errdetail("%s.",
+							   pg_rusage_show(&ru0))));
+		else
+		{
+			foreach(lc, newIndexIds)
+			{
+				Oid			indOid = lfirst_oid(lc);
+
+				ereport(INFO,
+						(errmsg("index \"%s.%s\" was reindexed",
+								get_namespace_name(get_rel_namespace(indOid)),
+								get_rel_name(indOid))));
+				/* Don't show rusage here, since it's not per index. */
+			}
+
+			ereport(INFO,
+					(errmsg("table \"%s.%s\" was reindexed",
+							relationNamespace, relationName),
+					 errdetail("%s.",
+							   pg_rusage_show(&ru0))));
+		}
+	}
+
 	MemoryContextDelete(private_context);
+
+	return true;
 }
 
 /*