Make ExecGetInsertedCols() and friends more robust and improve comments.

hlinnaka · hlinnaka · commit 2b81444a88cc · 2021-02-15T09:29:45.000+02:00
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 6214e2b, ri_RangeTableIndex is zero for ResultRelInfos created for partition tuple routing. Noted by Coverity. Backpatch down to v11, like commit 6214e2b. Reviewed-by: Tom Lane, Amit Langote
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
@@ -1182,18 +1182,18 @@ 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)
 	{
 		RangeTblEntry *rte = exec_rt_fetch(relinfo->ri_RangeTableIndex, estate);
 
 		return rte->insertedCols;
 	}
-	else
+	else if (relinfo->ri_RootResultRelInfo)
 	{
 		ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;
 		RangeTblEntry *rte = exec_rt_fetch(rootRelInfo->ri_RangeTableIndex, estate);
@@ -1205,6 +1205,16 @@ 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 */
@@ -1218,7 +1228,7 @@ ExecGetUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 
 		return rte->updatedCols;
 	}
-	else
+	else if (relinfo->ri_RootResultRelInfo)
 	{
 		ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;
 		RangeTblEntry *rte = exec_rt_fetch(rootRelInfo->ri_RangeTableIndex, estate);
@@ -1230,6 +1240,8 @@ ExecGetUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 		else
 			return rte->updatedCols;
 	}
+	else
+		return NULL;
 }
 
 /* Return a bitmap representing generated columns being updated */
@@ -1243,7 +1255,7 @@ ExecGetExtraUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 
 		return rte->extraUpdatedCols;
 	}
-	else
+	else if (relinfo->ri_RootResultRelInfo)
 	{
 		ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;
 		RangeTblEntry *rte = exec_rt_fetch(rootRelInfo->ri_RangeTableIndex, estate);
@@ -1255,6 +1267,8 @@ ExecGetExtraUpdatedCols(ResultRelInfo *relinfo, EState *estate)
 		else
 			return rte->extraUpdatedCols;
 	}
+	else
+		return NULL;
 }
 
 /* Return columns being updated, including generated columns */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
@@ -392,12 +392,15 @@ typedef struct OnConflictSetState
  * relation, and perhaps also fire triggers.  ResultRelInfo holds all the
  * information needed about a result relation, including indexes.
  *
- * Normally, a ResultRelInfo refers to a table that is in the query's
- * range table; then ri_RangeTableIndex is the RT index and ri_RelationDesc
- * is just a copy of the relevant es_relations[] entry.  But sometimes,
- * in ResultRelInfos used only for triggers, ri_RangeTableIndex is zero
- * and ri_RelationDesc is a separately-opened relcache pointer that needs
- * to be separately closed.  See ExecGetTriggerResultRel.
+ * Normally, a ResultRelInfo refers to a table that is in the query's range
+ * table; then ri_RangeTableIndex is the RT index and ri_RelationDesc is
+ * just a copy of the relevant es_relations[] entry.  However, in some
+ * situations we create ResultRelInfos for relations that are not in the
+ * range table, namely for targets of tuple routing in a partitioned table,
+ * and when firing triggers in tables other than the target tables (See
+ * ExecGetTriggerResultRel).  In these situations, ri_RangeTableIndex is 0
+ * and ri_RelationDesc is a separately-opened relcache pointer that needs to
+ * be separately closed.
  */
 typedef struct ResultRelInfo
 {

Original file line number	Diff line number	Diff line change
`@@ -1182,18 +1182,18 @@ Bitmapset *`
`1182`	`1182`	`ExecGetInsertedCols(ResultRelInfo relinfo, EState estate)`
`1183`	`1183`	`{`
`1184`	`1184`	`/*`
`1185`		`- * The columns are stored in the range table entry. If this ResultRelInfo`
`1186`		`- * doesn't have an entry in the range table (i.e. if it represents a`
`1187`		`- * partition routing target), fetch the parent's RTE and map the columns`
`1188`		`- * to the order they are in the partition.`
	`1185`	`+ * The columns are stored in the range table entry. If this ResultRelInfo`
	`1186`	`+ * represents a partition routing target, and doesn't have an entry of its`
	`1187`	`+ * own in the range table, fetch the parent's RTE and map the columns to`
	`1188`	`+ * the order they are in the partition.`
`1189`	`1189`	`*/`
`1190`	`1190`	`if (relinfo->ri_RangeTableIndex != 0)`
`1191`	`1191`	`{`
`1192`	`1192`	`RangeTblEntry *rte = exec_rt_fetch(relinfo->ri_RangeTableIndex, estate);`
`1193`	`1193`
`1194`	`1194`	`return rte->insertedCols;`
`1195`	`1195`	`}`
`1196`		`- else`
	`1196`	`+ else if (relinfo->ri_RootResultRelInfo)`
`1197`	`1197`	`{`
`1198`	`1198`	`ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;`
`1199`	`1199`	`RangeTblEntry *rte = exec_rt_fetch(rootRelInfo->ri_RangeTableIndex, estate);`
`@@ -1205,6 +1205,16 @@ ExecGetInsertedCols(ResultRelInfo relinfo, EState estate)`
`1205`	`1205`	`else`
`1206`	`1206`	`return rte->insertedCols;`
`1207`	`1207`	`}`
	`1208`	`+ else`
	`1209`	`+ {`
	`1210`	`+ /*`
	`1211`	`+ * The relation isn't in the range table and it isn't a partition`
	`1212`	`+ * routing target. This ResultRelInfo must've been created only for`
	`1213`	`+ * firing triggers and the relation is not being inserted into. (See`
	`1214`	`+ * ExecGetTriggerResultRel.)`
	`1215`	`+ */`
	`1216`	`+ return NULL;`
	`1217`	`+ }`
`1208`	`1218`	`}`
`1209`	`1219`
`1210`	`1220`	`/* Return a bitmap representing columns being updated */`
`@@ -1218,7 +1228,7 @@ ExecGetUpdatedCols(ResultRelInfo relinfo, EState estate)`
`1218`	`1228`
`1219`	`1229`	`return rte->updatedCols;`
`1220`	`1230`	`}`
`1221`		`- else`
	`1231`	`+ else if (relinfo->ri_RootResultRelInfo)`
`1222`	`1232`	`{`
`1223`	`1233`	`ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;`
`1224`	`1234`	`RangeTblEntry *rte = exec_rt_fetch(rootRelInfo->ri_RangeTableIndex, estate);`
`@@ -1230,6 +1240,8 @@ ExecGetUpdatedCols(ResultRelInfo relinfo, EState estate)`
`1230`	`1240`	`else`
`1231`	`1241`	`return rte->updatedCols;`
`1232`	`1242`	`}`
	`1243`	`+ else`
	`1244`	`+ return NULL;`
`1233`	`1245`	`}`
`1234`	`1246`
`1235`	`1247`	`/* Return a bitmap representing generated columns being updated */`
`@@ -1243,7 +1255,7 @@ ExecGetExtraUpdatedCols(ResultRelInfo relinfo, EState estate)`
`1243`	`1255`
`1244`	`1256`	`return rte->extraUpdatedCols;`
`1245`	`1257`	`}`
`1246`		`- else`
	`1258`	`+ else if (relinfo->ri_RootResultRelInfo)`
`1247`	`1259`	`{`
`1248`	`1260`	`ResultRelInfo *rootRelInfo = relinfo->ri_RootResultRelInfo;`
`1249`	`1261`	`RangeTblEntry *rte = exec_rt_fetch(rootRelInfo->ri_RangeTableIndex, estate);`
`@@ -1255,6 +1267,8 @@ ExecGetExtraUpdatedCols(ResultRelInfo relinfo, EState estate)`
`1255`	`1267`	`else`
`1256`	`1268`	`return rte->extraUpdatedCols;`
`1257`	`1269`	`}`
	`1270`	`+ else`
	`1271`	`+ return NULL;`
`1258`	`1272`	`}`
`1259`	`1273`
`1260`	`1274`	`/* Return columns being updated, including generated columns */`