Re-allow INSERT .. ON CONFLICT DO NOTHING on partitioned tables.

Commit 8355a011a0124bdf7ccbada206a967d427039553 was reverted in
f05230752d53c4aa74cffa9b699983bbb6bcb118, but this attempt is
hopefully better-considered: we now pass the correct value to
ExecOpenIndices, which should avoid the crash that we hit before.

Amit Langote, reviewed by Simon Riggs and by me.  Some final
editing by me.

Discussion: http://postgr.es/m/7ff1e8ec-dc39-96b1-7f47-ff5965dceeac@lab.ntt.co.jp

doc/src/sgml/ddl.sgml

@@ -3288,10 +3288,15 @@ 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-on-conflict" /> for more details on how the clause
+       works).  Therefore, it is not possible to specify
+       <literal>DO UPDATE</literal> as the alternative action, because
+       specifying the conflict target is mandatory in that case.  On the other
+       hand, specifying <literal>DO NOTHING</literal> as the alternative action
+       works fine provided the conflict target is not specified.  In that case,
+       unique constraints (or exclusion constraints) of the individual leaf
+       partitions are considered.
       </para>
      </listitem>
 

src/backend/commands/copy.c

@@ -2478,7 +2478,8 @@ CopyFrom(CopyState cstate)
 		int			num_parted,
 					num_partitions;
 
-		ExecSetupPartitionTupleRouting(cstate->rel,
+		ExecSetupPartitionTupleRouting(NULL,
+									   cstate->rel,
 									   1,
 									   estate,
 									   &partition_dispatch_info,

src/backend/executor/execPartition.c

@@ -63,7 +63,8 @@ static char *ExecBuildSlotPartitionKeyDescription(Relation rel,
  * RowExclusiveLock mode upon return from this function.
  */
 void
-ExecSetupPartitionTupleRouting(Relation rel,
+ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
+							   Relation rel,
 							   Index resultRTindex,
 							   EState *estate,
 							   PartitionDispatch **pd,
@@ -133,13 +134,17 @@ ExecSetupPartitionTupleRouting(Relation rel,
 		CheckValidResultRel(leaf_part_rri, CMD_INSERT);
 
 		/*
-		 * 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,
+							mtstate != NULL &&
+							mtstate->mt_onconflict != ONCONFLICT_NONE);
 
 		estate->es_leaf_result_relations =
 			lappend(estate->es_leaf_result_relations, leaf_part_rri);

src/backend/executor/nodeModifyTable.c

@@ -1953,7 +1953,8 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 		int			num_parted,
 					num_partitions;
 
-		ExecSetupPartitionTupleRouting(rel,
+		ExecSetupPartitionTupleRouting(mtstate,
+									   rel,
 									   node->nominalRelation,
 									   estate,
 									   &partition_dispatch_info,

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

src/include/executor/execPartition.h

@@ -49,7 +49,8 @@ typedef struct PartitionDispatchData
 
 typedef struct PartitionDispatchData *PartitionDispatch;
 
-extern void ExecSetupPartitionTupleRouting(Relation rel,
+extern void ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
+							   Relation rel,
 							   Index resultRTindex,
 							   EState *estate,
 							   PartitionDispatch **pd,

src/test/regress/expected/insert_conflict.out

@@ -786,3 +786,16 @@ 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
+-- but it works OK if we target the partition directly
+insert into parted_conflict_test_1 values (1) on conflict (b) do
+update set a = excluded.a;
+drop table parted_conflict_test;

src/test/regress/sql/insert_conflict.sql

@@ -471,3 +471,16 @@ 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;
+-- but it works OK if we target the partition directly
+insert into parted_conflict_test_1 values (1) on conflict (b) do
+update set a = excluded.a;
+drop table parted_conflict_test;