From 107097ee289dc4156f12b165018834544268506f Mon Sep 17 00:00:00 2001
From: Ahmet Gedemenli <afgedemenli@gmail.com>
Date: Fri, 15 Jan 2021 18:42:15 +0300
Subject: [PATCH] Fix assert failure when creating statistics

---
 src/backend/distributed/commands/statistics.c |  7 ++++
 .../deparser/deparse_statistics_stmts.c       |  9 +++++-
 .../regress/expected/propagate_statistics.out | 32 ++++++++++++++++++-
 src/test/regress/sql/propagate_statistics.sql |  9 ++++++
 4 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/src/backend/distributed/commands/statistics.c b/src/backend/distributed/commands/statistics.c
index ac04aa550..c87677794 100644
--- a/src/backend/distributed/commands/statistics.c
+++ b/src/backend/distributed/commands/statistics.c
@@ -82,6 +82,13 @@ PreprocessCreateStatisticsStmt(Node *node, const char *queryString,
 
 	QualifyTreeNode((Node *) stmt);
 
+	Oid statsOid = get_statistics_object_oid(stmt->defnames, true);
+	if (statsOid != InvalidOid)
+	{
+		/* if stats object already exists, don't create DDLJobs */
+		return NIL;
+	}
+
 	char *ddlCommand = DeparseTreeNode((Node *) stmt);
 
 	DDLJob *ddlJob = palloc0(sizeof(DDLJob));
diff --git a/src/backend/distributed/deparser/deparse_statistics_stmts.c b/src/backend/distributed/deparser/deparse_statistics_stmts.c
index 125d4494f..4da69a041 100644
--- a/src/backend/distributed/deparser/deparse_statistics_stmts.c
+++ b/src/backend/distributed/deparser/deparse_statistics_stmts.c
@@ -236,9 +236,16 @@ static void
 AppendColumnNames(StringInfo buf, CreateStatsStmt *stmt)
 {
 	ColumnRef *column = NULL;
+
 	foreach_ptr(column, stmt->exprs)
 	{
-		Assert(IsA(column, ColumnRef));
+		if (!IsA(column, ColumnRef) || list_length(column->fields) != 1)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg(
+						 "only simple column references are allowed in CREATE STATISTICS")));
+		}
 
 		char *columnName = NameListToQuotedString(column->fields);
 
diff --git a/src/test/regress/expected/propagate_statistics.out b/src/test/regress/expected/propagate_statistics.out
index 80e501fff..1c798c526 100644
--- a/src/test/regress/expected/propagate_statistics.out
+++ b/src/test/regress/expected/propagate_statistics.out
@@ -91,6 +91,20 @@ SELECT create_distributed_table('ownertest','a');
 
 (1 row)
 
+-- test invalid column expressions
+CREATE TABLE test (x int, y int);
+SELECT create_distributed_table('test','x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CREATE STATISTICS stats_xy ON (x, y) FROM test;
+ERROR:  only simple column references are allowed in CREATE STATISTICS
+CREATE STATISTICS stats_xy ON x+y FROM test;
+ERROR:  only simple column references are allowed in CREATE STATISTICS
+CREATE STATISTICS stats_xy ON x,y FROM test;
+CREATE STATISTICS IF NOT EXISTS stats_xy ON x+y FROM test;
 \c - - - :worker_1_port
 SELECT stxname
 FROM pg_statistic_ext
@@ -182,7 +196,23 @@ ORDER BY stxname ASC;
  st1_new_980090
  st1_new_980092
  st1_new_980094
-(80 rows)
+ stats_xy_980161
+ stats_xy_980163
+ stats_xy_980165
+ stats_xy_980167
+ stats_xy_980169
+ stats_xy_980171
+ stats_xy_980173
+ stats_xy_980175
+ stats_xy_980177
+ stats_xy_980179
+ stats_xy_980181
+ stats_xy_980183
+ stats_xy_980185
+ stats_xy_980187
+ stats_xy_980189
+ stats_xy_980191
+(96 rows)
 
 SELECT count(DISTINCT stxnamespace)
 FROM pg_statistic_ext
diff --git a/src/test/regress/sql/propagate_statistics.sql b/src/test/regress/sql/propagate_statistics.sql
index 8a0372cf7..51d3076f2 100644
--- a/src/test/regress/sql/propagate_statistics.sql
+++ b/src/test/regress/sql/propagate_statistics.sql
@@ -75,6 +75,15 @@ CREATE STATISTICS sc1.s9 ON a,b FROM ownertest;
 ALTER STATISTICS sc1.s9 OWNER TO pg_signal_backend;
 SELECT create_distributed_table('ownertest','a');
 
+-- test invalid column expressions
+CREATE TABLE test (x int, y int);
+SELECT create_distributed_table('test','x');
+
+CREATE STATISTICS stats_xy ON (x, y) FROM test;
+CREATE STATISTICS stats_xy ON x+y FROM test;
+CREATE STATISTICS stats_xy ON x,y FROM test;
+CREATE STATISTICS IF NOT EXISTS stats_xy ON x+y FROM test;
+
 \c - - - :worker_1_port
 SELECT stxname
 FROM pg_statistic_ext