From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 7 Apr 2019 16:54:26 +0000 (-0400)
Subject: Clean up side-effects of commits ab5fcf2b0 et al.
X-Git-Tag: REL_10_8~44
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=67999b3547f7ee8b8c099f41ddab3001e2792202;p=postgresql

Clean up side-effects of commits ab5fcf2b0 et al.

Before those commits, partitioning-related code in the executor could
assume that ModifyTableState.resultRelInfo[] contains only leaf partitions.
However, now a fully-pruned update results in a dummy ModifyTable that
references the root partitioned table, and that breaks some stuff.

In v11, this led to an assertion or core dump in the tuple routing code.
Fix by disabling tuple routing, since we don't need that anyway.
(I chose to do that in HEAD as well for safety, even though the problem
doesn't manifest in HEAD as it stands.)

In v10, this confused ExecInitModifyTable's decision about whether it
needed to close the root table.  But we can get rid of that altogether
by being smarter about where to find the root table.

Note that since the referenced commits haven't shipped yet, this
isn't fixing any bug the field has seen.

Amit Langote, per a report from me

Discussion: https://postgr.es/m/20710.1554582479@sss.pgh.pa.us
---

diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 7de4568b03..e86ed44a47 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1933,16 +1933,9 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 
 	estate->es_result_relation_info = saved_resultRelInfo;
 
-	/* The root table RT index is at the head of the partitioned_rels list */
-	if (node->partitioned_rels)
-	{
-		Index		root_rti;
-		Oid			root_oid;
-
-		root_rti = linitial_int(node->partitioned_rels);
-		root_oid = getrelid(root_rti, estate->es_range_table);
-		rel = heap_open(root_oid, NoLock);	/* locked by InitPlan */
-	}
+	/* Examine the root partition if we have one, else target table */
+	if (mtstate->rootResultRelInfo)
+		rel = mtstate->rootResultRelInfo->ri_RelationDesc;
 	else
 		rel = mtstate->resultRelInfo->ri_RelationDesc;
 
@@ -2134,10 +2127,6 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 		mtstate->ps.ps_ExprContext = NULL;
 	}
 
-	/* Close the root partitioned rel if we opened it above. */
-	if (rel != mtstate->resultRelInfo->ri_RelationDesc)
-		heap_close(rel, NoLock);
-
 	/*
 	 * If needed, Initialize target list, projection and qual for ON CONFLICT
 	 * DO UPDATE.
diff --git a/src/test/regress/expected/inherit.out b/src/test/regress/expected/inherit.out
index da7608734c..79ea0c5774 100644
--- a/src/test/regress/expected/inherit.out
+++ b/src/test/regress/expected/inherit.out
@@ -665,6 +665,15 @@ select tableoid::regclass::text as relname, parted_tab.* from parted_tab order b
  parted_tab_part3 | 3 | a
 (3 rows)
 
+-- modifies partition key, but no rows will actually be updated
+explain update parted_tab set a = 2 where false;
+                       QUERY PLAN                       
+--------------------------------------------------------
+ Update on parted_tab  (cost=0.00..0.00 rows=0 width=0)
+   ->  Result  (cost=0.00..0.00 rows=0 width=0)
+         One-Time Filter: false
+(3 rows)
+
 drop table parted_tab;
 drop table some_tab cascade;
 NOTICE:  drop cascades to table some_tab_child
diff --git a/src/test/regress/sql/inherit.sql b/src/test/regress/sql/inherit.sql
index bbe453cf26..101a0394f8 100644
--- a/src/test/regress/sql/inherit.sql
+++ b/src/test/regress/sql/inherit.sql
@@ -168,6 +168,9 @@ from
 where parted_tab.a = ss.a;
 select tableoid::regclass::text as relname, parted_tab.* from parted_tab order by 1,2;
 
+-- modifies partition key, but no rows will actually be updated
+explain update parted_tab set a = 2 where false;
+
 drop table parted_tab;
 drop table some_tab cascade;