Fix crash when COPY involves relation with no locator data

Patch and report from Nikhil Sontakke. I added a test case in xc_copy and
some comments.

3 files changed, 16 insertions, 3 deletions

diff --git a/src/backend/pgxc/copy/remotecopy.c b/src/backend/pgxc/copy/remotecopy.c
index 9c8c3b0d82..23db6ecdd7 100644
--- a/src/backend/pgxc/copy/remotecopy.c
+++ b/src/backend/pgxc/copy/remotecopy.c
@@ -29,14 +29,16 @@ static void RemoteCopy_QuoteIdentifier(StringInfo query_buf, char *value);
 
 /*
  * RemoteCopy_GetRelationLoc
- * Get relation node list based on COPY data involved
+ * Get relation node list based on COPY data involved. An empty list is
+ * returned to caller if relation involved has no locator information
+ * as it is the case of a system relation.
  */
 void
 RemoteCopy_GetRelationLoc(RemoteCopyData *state,
 						  Relation rel,
                           List *attnums)
 {
-	ExecNodes  *exec_nodes = makeNode(ExecNodes);
+	ExecNodes  *exec_nodes = NULL;
 
 	/*
 	 * If target table does not exists on nodes (e.g. system table)
@@ -52,6 +54,7 @@ RemoteCopy_GetRelationLoc(RemoteCopyData *state,
 		 * This case corresponds to a replicated table with COPY TO
 		 *
 		 */
+		exec_nodes = makeNode(ExecNodes);
 		if (!state->is_from &&
 			IsLocatorReplicated(state->rel_loc->locatorType))
 			exec_nodes->nodeList = GetPreferredReplicationNode(state->rel_loc->nodeList);
@@ -63,7 +66,7 @@ RemoteCopy_GetRelationLoc(RemoteCopyData *state,
 	}
 
 	state->idx_dist_by_col = -1;
-	if (state->rel_loc->partAttrNum != 0)
+	if (state->rel_loc && state->rel_loc->partAttrNum != 0)
 	{
 		/*
 		 * Find the column used as key for data distribution.
diff --git a/src/test/regress/input/xc_copy.source b/src/test/regress/input/xc_copy.source
index d0e395c7f5..cf08efe74d 100644
--- a/src/test/regress/input/xc_copy.source
+++ b/src/test/regress/input/xc_copy.source
@@ -109,3 +109,8 @@ COPY "Xc_copy_2" FROM STDIN DELIMITER ',';
 \.
 COPY "Xc_copy_2" TO STDOUT;
 DROP TABLE "Xc_copy_2";
+
+-- Table with no locator data
+CREATE TABLE xc_copy_3 (c1 int) DISTRIBUTE BY HASH(c1);
+COPY (SELECT pclocatortype,pcattnum,pchashalgorithm,pchashbuckets FROM pgxc_class WHERE pgxc_class.pcrelid = 'xc_copy_3'::regclass) TO stdout;
+DROP TABLE xc_copy_3;
diff --git a/src/test/regress/output/xc_copy.source b/src/test/regress/output/xc_copy.source
index ddc5221d35..1defee54d2 100644
--- a/src/test/regress/output/xc_copy.source
+++ b/src/test/regress/output/xc_copy.source
@@ -108,3 +108,8 @@ COPY "Xc_copy_2" TO STDOUT;
 1	2
 3	4
 DROP TABLE "Xc_copy_2";
+-- Table with no locator data
+CREATE TABLE xc_copy_3 (c1 int) DISTRIBUTE BY HASH(c1);
+COPY (SELECT pclocatortype,pcattnum,pchashalgorithm,pchashbuckets FROM pgxc_class WHERE pgxc_class.pcrelid = 'xc_copy_3'::regclass) TO stdout;
+H	1	1	4096
+DROP TABLE xc_copy_3;