From 9eefba181f7782d27d85d7e94e6028371e7ab2d7 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Thu, 21 Feb 2019 11:24:40 -0500 Subject: [PATCH] Delay lock acquisition for partitions until we route a tuple to them. Instead of locking all partitions to which we might route a tuple at executor startup, just lock them as we use them. In some cases such a partition might get locked at executor startup anyway because it appears in the query's range table for some other reason, but in other cases this is a bit savings. This changes the order in which partitions are locked in some cases, which might conceivably create deadlock hazards that don't exist today, but per discussion, it seems like such cases should be rare enough that we can neglect them in favor of improving performance. David Rowley, reviewed and tested by Tomas Vondra, Sho Kato, John Naylor, Tom Lane, and me. Discussion: http://postgr.es/m/CAKJS1f-=FnMqmQP6qitkD+xEddxw22ySLP-0xFk3JAqUX2yfMw@mail.gmail.com --- src/backend/executor/execPartition.c | 35 +++++++++++++--------------- 1 file changed, 16 insertions(+), 19 deletions(-) diff --git a/src/backend/executor/execPartition.c b/src/backend/executor/execPartition.c index 2a7bc01563..ab69404daa 100644 --- a/src/backend/executor/execPartition.c +++ b/src/backend/executor/execPartition.c @@ -191,9 +191,6 @@ static void find_matching_subplans_recurse(PartitionPruningData *prunedata, * tuple routing for partitioned tables, encapsulates it in * PartitionTupleRouting, and returns it. * - * Note that all the relations in the partition tree are locked using the - * RowExclusiveLock mode upon return from this function. - * * Callers must use the returned PartitionTupleRouting during calls to * ExecFindPartition(). The actual ResultRelInfo for a partition is only * allocated when the partition is found for the first time. @@ -208,9 +205,6 @@ ExecSetupPartitionTupleRouting(ModifyTableState *mtstate, Relation rel) PartitionTupleRouting *proute; ModifyTable *node = mtstate ? (ModifyTable *) mtstate->ps.plan : NULL; - /* Lock all the partitions. */ - (void) find_all_inheritors(RelationGetRelid(rel), RowExclusiveLock, NULL); - /* * Here we attempt to expend as little effort as possible in setting up * the PartitionTupleRouting. Each partition's ResultRelInfo is built on @@ -487,8 +481,9 @@ ExecHashSubPlanResultRelsByOid(ModifyTableState *mtstate, /* * ExecInitPartitionInfo - * Initialize ResultRelInfo and other information for a partition - * and store it in the next empty slot in the proute->partitions array. + * Lock the partition and initialize ResultRelInfo. Also setup other + * information for the partition and store it in the next empty slot in + * the proute->partitions array. * * Returns the ResultRelInfo */ @@ -510,11 +505,7 @@ ExecInitPartitionInfo(ModifyTableState *mtstate, EState *estate, oldcxt = MemoryContextSwitchTo(proute->memcxt); - /* - * We locked all the partitions in ExecSetupPartitionTupleRouting - * including the leaf partitions. - */ - partrel = table_open(dispatch->partdesc->oids[partidx], NoLock); + partrel = table_open(dispatch->partdesc->oids[partidx], RowExclusiveLock); leaf_part_rri = makeNode(ResultRelInfo); InitResultRelInfo(leaf_part_rri, @@ -964,11 +955,12 @@ ExecInitRoutingInfo(ModifyTableState *mtstate, /* * ExecInitPartitionDispatchInfo - * Initialize PartitionDispatch for a partitioned table and store it in - * the next available slot in the proute->partition_dispatch_info array. - * Also, record the index into this array in the parent_pd->indexes[] - * array in the partidx element so that we can properly retrieve the - * newly created PartitionDispatch later. + * Lock the partitioned table (if not locked already) and initialize + * PartitionDispatch for a partitioned table and store it in the next + * available slot in the proute->partition_dispatch_info array. Also, + * record the index into this array in the parent_pd->indexes[] array in + * the partidx element so that we can properly retrieve the newly created + * PartitionDispatch later. */ static PartitionDispatch ExecInitPartitionDispatchInfo(PartitionTupleRouting *proute, Oid partoid, @@ -982,8 +974,13 @@ ExecInitPartitionDispatchInfo(PartitionTupleRouting *proute, Oid partoid, oldcxt = MemoryContextSwitchTo(proute->memcxt); + /* + * Only sub-partitioned tables need to be locked here. The root + * partitioned table will already have been locked as it's referenced in + * the query's rtable. + */ if (partoid != RelationGetRelid(proute->partition_root)) - rel = table_open(partoid, NoLock); + rel = table_open(partoid, RowExclusiveLock); else rel = proute->partition_root; partdesc = RelationGetPartitionDesc(rel);