Starting a new thread for a patch I posted earlier [1] to handle ON
CONFLICT DO NOTHING when inserting into a partitioned table. It's
intended for PG 11 and so registered in the upcoming CF.
Summary of the previous discussion and the patch for anyone interested:
Currently, if an INSERT statement for a partitioned table mentions the ON
CONFLICT clause, we error out immediately. It was implemented that way,
because it was thought that it could not be handled with zero support for
defining indexes on partitioned tables. Peter Geoghegan pointed out [2]
that it's too restrictive a view.
He pointed out that planner doesn't *always* expect indexes to be present
on the table when ON CONFLICT is specified. They must be present though
if DO UPDATE action is requested, because one would need to also specify
the exact columns on which conflict will be checked and those must covered
by the appropriate indexes. So, if the table is partitioned and DO UPDATE
is specified, lack of indexes will result in an error saying that a
suitable index is absent. DO UPDATE action cannot be supported until we
implement the feature to define indexes on partitioned tables.
OTOH, the DO NOTHING case should go through the planner without error,
because neither any columns need to be specified nor any indexes need to
be present covering them. So, DO NOTHING on partitioned tables might work
after all. Conflict can only be determined using indexes, which
partitioned tables don't allow, so how? Leaf partitions into which tuples
are ultimately stored can have indexes defined on them, which can be used
to check for the conflict.
The patch's job is simple:
- Remove the check in the parser that causes an error the moment the
ON CONFLICT clause is found.
- Fix leaf partition ResultRelInfo initialization code so that the call
ExecOpenIndices() specifies 'true' for speculative, so that the
information necessary for conflict checking will be initialized in the
leaf partition's ResultRelInfo
Thanks,
Amit
[1]
https://www.postgresql.org/message-id/62be3d7a-08f6-5dcb-f5c8-a5b764ca96df%40lab.ntt.co.jp
[2]
https://www.postgresql.org/message-id/CAH2-Wzm10T%2B_PWVM4XO5zaknVbAXkOH9-JW3gRVPm1njLHck_w%40mail.gmail.com
From 5029a9c6cbb9549024e701d56025c0de1f2b393f Mon Sep 17 00:00:00 2001
From: amit <amitlangot...@gmail.com>
Date: Mon, 3 Apr 2017 19:13:38 +0900
Subject: [PATCH] Allow ON CONFLICT DO NOTHING on partitioned tables
ON CONFLICT .. DO UPDATE still doesn't work, because it requires
specifying the conflict target. DO NOTHING doesn't require it,
but the executor will check for conflicts within only a given
leaf partitions, if relevant constraints exist.
Specifying the conflict target makes the planner look for the
required indexes on the parent table, which are not allowed, so an
error will always be reported in that case.
---
doc/src/sgml/ddl.sgml | 12 ++++++++----
src/backend/executor/execMain.c | 10 ++++++----
src/backend/parser/analyze.c | 8 --------
src/test/regress/expected/insert_conflict.out | 10 ++++++++++
src/test/regress/sql/insert_conflict.sql | 10 ++++++++++
5 files changed, 34 insertions(+), 16 deletions(-)
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index b05a9c2150..2c8a58aa09 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -3276,10 +3276,14 @@ ALTER TABLE measurement ATTACH PARTITION
measurement_y2008m02
<listitem>
<para>
Using the <literal>ON CONFLICT</literal> clause with partitioned tables
- will cause an error, because unique or exclusion constraints can only be
- created on individual partitions. There is no support for enforcing
- uniqueness (or an exclusion constraint) across an entire partitioning
- hierarchy.
+ will cause an error if the conflict target is specified (see
+ <xref linkend="sql-insert"> for more details). That means it's not
+ possible to specify <literal>DO UPDATE</literal> as the alternative
+ action, because it requires the conflict target to be specified.
+ On the other hand, specifying <literal>DO NOTHING</literal> as the
+ alternative action works fine. Note that in the latter case, a unique
+ constraint (or an exclusion constraint) of the individual leaf
+ partitions is considered, not across the whole partitioning hierarchy.
</para>
</listitem>
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index c11aa4fe21..b313ad1efa 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -3300,13 +3300,15 @@ ExecSetupPartitionTupleRouting(Relation rel,
0);
/*
- * Open partition indices (remember we do not support ON
CONFLICT in
- * case of partitioned tables, so we do not need support
information
- * for speculative insertion)
+ * Open partition indices. The user may have asked to check for
+ * conflicts within this leaf partition and do "nothing"
instead of
+ * throwing an error. Be prepared in that case by initializing
the
+ * index information needed by ExecInsert() to perform
speculative
+ * insertions.
*/
if (leaf_part_rri->ri_RelationDesc->rd_rel->relhasindex &&
leaf_part_rri->ri_IndexRelationDescs == NULL)
- ExecOpenIndices(leaf_part_rri, false);
+ ExecOpenIndices(leaf_part_rri, true);
leaf_part_rri++;
i++;
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 4fb793cfbf..73b99c2585 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -847,16 +847,8 @@ transformInsertStmt(ParseState *pstate, InsertStmt *stmt)
/* Process ON CONFLICT, if any. */
if (stmt->onConflictClause)
- {
- /* Bail out if target relation is partitioned table */
- if (pstate->p_target_rangetblentry->relkind ==
RELKIND_PARTITIONED_TABLE)
- ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("ON CONFLICT clause is not
supported with partitioned tables")));
-
qry->onConflict = transformOnConflictClause(pstate,
stmt->onConflictClause);
- }
/*
* If we have a RETURNING clause, we need to add the target relation to
diff --git a/src/test/regress/expected/insert_conflict.out
b/src/test/regress/expected/insert_conflict.out
index 8d005fddd4..617b0c0ed2 100644
--- a/src/test/regress/expected/insert_conflict.out
+++ b/src/test/regress/expected/insert_conflict.out
@@ -786,3 +786,13 @@ select * from selfconflict;
(3 rows)
drop table selfconflict;
+-- check that the following works:
+-- insert into partitioned_table on conflict do nothing
+create table parted_conflict_test (a int, b char) partition by list (a);
+create table parted_conflict_test_1 partition of parted_conflict_test (b
unique) for values in (1);
+insert into parted_conflict_test values (1, 'a') on conflict do nothing;
+insert into parted_conflict_test values (1, 'a') on conflict do nothing;
+-- however, on conflict do update is not supported yet
+insert into parted_conflict_test values (1) on conflict (b) do update set a =
excluded.a;
+ERROR: there is no unique or exclusion constraint matching the ON CONFLICT
specification
+drop table parted_conflict_test;
diff --git a/src/test/regress/sql/insert_conflict.sql
b/src/test/regress/sql/insert_conflict.sql
index df3a9b59b5..6a4495865f 100644
--- a/src/test/regress/sql/insert_conflict.sql
+++ b/src/test/regress/sql/insert_conflict.sql
@@ -471,3 +471,13 @@ commit;
select * from selfconflict;
drop table selfconflict;
+
+-- check that the following works:
+-- insert into partitioned_table on conflict do nothing
+create table parted_conflict_test (a int, b char) partition by list (a);
+create table parted_conflict_test_1 partition of parted_conflict_test (b
unique) for values in (1);
+insert into parted_conflict_test values (1, 'a') on conflict do nothing;
+insert into parted_conflict_test values (1, 'a') on conflict do nothing;
+-- however, on conflict do update is not supported yet
+insert into parted_conflict_test values (1) on conflict (b) do update set a =
excluded.a;
+drop table parted_conflict_test;
--
2.11.0
--
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