From 7c0ca2900f7cae490fd551096cb7dc581cfe45c8 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Thu, 17 Aug 2017 15:39:17 -0400
Subject: [PATCH] Don't lock tables in RelationGetPartitionDispatchInfo.
Instead, lock them in the caller using find_all_inheritors so that
they get locked in the standard order, minimizing deadlock risks.
Also in RelationGetPartitionDispatchInfo, avoid opening tables which
are not partitioned; there's no need.
Amit Langote, reviewed by Ashutosh Bapat and Amit Khandekar
Discussion: http://postgr.es/m/91b36fa1-c197-b72f-ca6e-56c593bae68c@lab.ntt.co.jp
---
src/backend/catalog/partition.c | 55 +++++++++++++++++----------------
src/backend/executor/execMain.c | 10 ++++--
src/include/catalog/partition.h | 3 +-
3 files changed, 37 insertions(+), 31 deletions(-)
diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
index 71bc4b3d105..21901380cb2 100644
--- a/src/backend/catalog/partition.c
+++ b/src/backend/catalog/partition.c
@@ -1000,12 +1000,16 @@ get_partition_qual_relid(Oid relid)
* RelationGetPartitionDispatchInfo
* Returns information necessary to route tuples down a partition tree
*
- * All the partitions will be locked with lockmode, unless it is NoLock.
- * A list of the OIDs of all the leaf partitions of rel is returned in
- * *leaf_part_oids.
+ * The number of elements in the returned array (that is, the number of
+ * PartitionDispatch objects for the partitioned tables in the partition tree)
+ * is returned in *num_parted and a list of the OIDs of all the leaf
+ * partitions of rel is returned in *leaf_part_oids.
+ *
+ * All the relations in the partition tree (including 'rel') must have been
+ * locked (using at least the AccessShareLock) by the caller.
*/
PartitionDispatch *
-RelationGetPartitionDispatchInfo(Relation rel, int lockmode,
+RelationGetPartitionDispatchInfo(Relation rel,
int *num_parted, List **leaf_part_oids)
{
PartitionDispatchData **pd;
@@ -1020,14 +1024,18 @@ RelationGetPartitionDispatchInfo(Relation rel, int lockmode,
offset;
/*
- * Lock partitions and make a list of the partitioned ones to prepare
- * their PartitionDispatch objects below.
+ * We rely on the relcache to traverse the partition tree to build both
+ * the leaf partition OIDs list and the array of PartitionDispatch objects
+ * for the partitioned tables in the tree. That means every partitioned
+ * table in the tree must be locked, which is fine since we require the
+ * caller to lock all the partitions anyway.
*
- * Cannot use find_all_inheritors() here, because then the order of OIDs
- * in parted_rels list would be unknown, which does not help, because we
- * assign indexes within individual PartitionDispatch in an order that is
- * predetermined (determined by the order of OIDs in individual partition
- * descriptors).
+ * For every partitioned table in the tree, starting with the root
+ * partitioned table, add its relcache entry to parted_rels, while also
+ * queuing its partitions (in the order in which they appear in the
+ * partition descriptor) to be looked at later in the same loop. This is
+ * a bit tricky but works because the foreach() macro doesn't fetch the
+ * next list element until the bottom of the loop.
*/
*num_parted = 1;
parted_rels = list_make1(rel);
@@ -1036,29 +1044,24 @@ RelationGetPartitionDispatchInfo(Relation rel, int lockmode,
APPEND_REL_PARTITION_OIDS(rel, all_parts, all_parents);
forboth(lc1, all_parts, lc2, all_parents)
{
- Relation partrel = heap_open(lfirst_oid(lc1), lockmode);
+ Oid partrelid = lfirst_oid(lc1);
Relation parent = lfirst(lc2);
- PartitionDesc partdesc = RelationGetPartitionDesc(partrel);
- /*
- * If this partition is a partitioned table, add its children to the
- * end of the list, so that they are processed as well.
- */
- if (partdesc)
+ if (get_rel_relkind(partrelid) == RELKIND_PARTITIONED_TABLE)
{
+ /*
+ * Already locked by the caller. Note that it is the
+ * responsibility of the caller to close the below relcache entry,
+ * once done using the information being collected here (for
+ * example, in ExecEndModifyTable).
+ */
+ Relation partrel = heap_open(partrelid, NoLock);
+
(*num_parted)++;
parted_rels = lappend(parted_rels, partrel);
parted_rel_parents = lappend(parted_rel_parents, parent);
APPEND_REL_PARTITION_OIDS(partrel, all_parts, all_parents);
}
- else
- heap_close(partrel, NoLock);
-
- /*
- * We keep the partitioned ones open until we're done using the
- * information being collected here (for example, see
- * ExecEndModifyTable).
- */
}
/*
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 6671a25ffb3..74071eede6e 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -43,6 +43,7 @@
#include "access/xact.h"
#include "catalog/namespace.h"
#include "catalog/partition.h"
+#include "catalog/pg_inherits_fn.h"
#include "catalog/pg_publication.h"
#include "commands/matview.h"
#include "commands/trigger.h"
@@ -3249,9 +3250,12 @@ ExecSetupPartitionTupleRouting(Relation rel,
int i;
ResultRelInfo *leaf_part_rri;
- /* Get the tuple-routing information and lock partitions */
- *pd = RelationGetPartitionDispatchInfo(rel, RowExclusiveLock, num_parted,
- &leaf_parts);
+ /*
+ * Get the information about the partition tree after locking all the
+ * partitions.
+ */
+ (void) find_all_inheritors(RelationGetRelid(rel), RowExclusiveLock, NULL);
+ *pd = RelationGetPartitionDispatchInfo(rel, num_parted, &leaf_parts);
*num_partitions = list_length(leaf_parts);
*partitions = (ResultRelInfo *) palloc(*num_partitions *
sizeof(ResultRelInfo));
diff --git a/src/include/catalog/partition.h b/src/include/catalog/partition.h
index 434ded37d74..7e415fe8727 100644
--- a/src/include/catalog/partition.h
+++ b/src/include/catalog/partition.h
@@ -87,8 +87,7 @@ extern Expr *get_partition_qual_relid(Oid relid);
/* For tuple routing */
extern PartitionDispatch *RelationGetPartitionDispatchInfo(Relation rel,
- int lockmode, int *num_parted,
- List **leaf_part_oids);
+ int *num_parted, List **leaf_part_oids);
extern void FormPartitionKeyDatum(PartitionDispatch pd,
TupleTableSlot *slot,
EState *estate,
--
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