From 6e437ce5a6b64c443cf7c907db0988bf571e6042 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Mon, 15 Feb 2021 09:28:08 +0200
Subject: [PATCH] Make ExecGetInsertedCols() and friends more robust and
 improve comments.

If ExecGetInsertedCols(), ExecGetUpdatedCols() or ExecGetExtraUpdatedCols()
were called with a ResultRelInfo that's not in the range table and isn't a
partition routing target, the functions would dereference a NULL pointer,
relinfo->ri_RootResultRelInfo. Such ResultRelInfos are created when firing
RI triggers in tables that are not modified directly. None of the current
callers of these functions pass such relations, so this isn't a live bug,
but let's make them more robust.

Also update comment in ResultRelInfo; after commit 6214e2b228,
ri_RangeTableIndex is zero for ResultRelInfos created for partition tuple
routing.

Noted by Coverity. Backpatch down to v11, like commit 6214e2b228.

Reviewed-by: Tom Lane, Amit Langote
---
 src/backend/executor/execUtils.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index e91a6ebddd..1c2c69673c 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -1075,10 +1075,10 @@ Bitmapset *
 ExecGetInsertedCols(ResultRelInfo *relinfo, EState *estate)
 {
 	/*
-	 * The columns are stored in the range table entry. If this ResultRelInfo
-	 * doesn't have an entry in the range table (i.e. if it represents a
-	 * partition routing target), fetch the parent's RTE and map the columns
-	 * to the order they are in the partition.
+	 * The columns are stored in the range table entry.  If this ResultRelInfo
+	 * represents a partition routing target, and doesn't have an entry of its
+	 * own in the range table, fetch the parent's RTE and map the columns to
+	 * the order they are in the partition.
 	 */
 	if (relinfo->ri_RangeTableIndex != 0)
 	{
@@ -1087,7 +1087,7 @@ ExecGetInsertedCols(ResultRelInfo *relinfo, EState *estate)
 
 		return rte->insertedCols;
 	}
-	else
+	else if (relinfo->ri_RootResultRelInfo)
 	{
 		ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;
 		RangeTblEntry *rte = rt_fetch(rootRelInfo->ri_RangeTableIndex,
@@ -1102,6 +1102,16 @@ ExecGetInsertedCols(ResultRelInfo *relinfo, EState *estate)
 		else
 			return rte->insertedCols;
 	}
+	else
+	{
+		/*
+		 * The relation isn't in the range table and it isn't a partition
+		 * routing target.  This ResultRelInfo must've been created only for
+		 * firing triggers and the relation is not being inserted into.  (See
+		 * ExecGetTriggerResultRel.)
+		 */
+		return NULL;
+	}
 }
 
 /* Return a bitmap representing columns being updated */
@@ -1116,7 +1126,7 @@ ExecGetUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 
 		return rte->updatedCols;
 	}
-	else
+	else if (relinfo->ri_RootResultRelInfo)
 	{
 		ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;
 		RangeTblEntry *rte = rt_fetch(rootRelInfo->ri_RangeTableIndex,
@@ -1131,4 +1141,6 @@ ExecGetUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 		else
 			return rte->updatedCols;
 	}
+	else
+		return NULL;
 }