From d08fae3773ea3b9930d3efc0429a38614c2dd706 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 15 Feb 2019 17:12:46 +0900
Subject: [PATCH] Fix support for CREATE TABLE IF NOT EXISTS AS EXECUTE

The grammar IF NOT EXISTS for CTAS is supported since 9.5 and documented
as such, however the case of using EXECUTE as query has never been
covered as EXECUTE CTAS statements and normal CTAS statements are parsed
separately.

Author: Andreas Karlsson
Discussion: https://postgr.es/m/2ddcc188-e37c-a0be-32bf-a56b07c3559e@proxel.se
Backpatch-through: 9.5
---
 src/backend/parser/gram.y                  | 18 ++++++++++++++++++
 src/test/regress/expected/create_table.out | 14 ++++++++++++++
 src/test/regress/sql/create_table.sql      |  8 ++++++++
 3 files changed, 40 insertions(+)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index a0ef488003f..ced7f814f77 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -9583,11 +9583,29 @@ ExecuteStmt: EXECUTE name execute_param_clause
 					ctas->into = $4;
 					ctas->relkind = OBJECT_TABLE;
 					ctas->is_select_into = false;
+					ctas->if_not_exists = false;
 					/* cram additional flags into the IntoClause */
 					$4->rel->relpersistence = $2;
 					$4->skipData = !($9);
 					$$ = (Node *) ctas;
 				}
+			| CREATE OptTemp TABLE IF_P NOT EXISTS create_as_target AS
+				EXECUTE name execute_param_clause opt_with_data
+				{
+					CreateTableAsStmt *ctas = makeNode(CreateTableAsStmt);
+					ExecuteStmt *n = makeNode(ExecuteStmt);
+					n->name = $10;
+					n->params = $11;
+					ctas->query = (Node *) n;
+					ctas->into = $7;
+					ctas->relkind = OBJECT_TABLE;
+					ctas->is_select_into = false;
+					ctas->if_not_exists = true;
+					/* cram additional flags into the IntoClause */
+					$7->rel->relpersistence = $2;
+					$7->skipData = !($12);
+					$$ = (Node *) ctas;
+				}
 		;
 
 execute_param_clause: '(' expr_list ')'				{ $$ = $2; }
diff --git a/src/test/regress/expected/create_table.out b/src/test/regress/expected/create_table.out
index 41ceb874e8f..145bac1b2f2 100644
--- a/src/test/regress/expected/create_table.out
+++ b/src/test/regress/expected/create_table.out
@@ -250,6 +250,20 @@ ERROR:  relation "as_select1" already exists
 CREATE TABLE IF NOT EXISTS as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
 NOTICE:  relation "as_select1" already exists, skipping
 DROP TABLE as_select1;
+PREPARE select1 AS SELECT 1 as a;
+CREATE TABLE as_select1 AS EXECUTE select1;
+CREATE TABLE as_select1 AS EXECUTE select1;
+ERROR:  relation "as_select1" already exists
+SELECT * FROM as_select1;
+ a 
+---
+ 1
+(1 row)
+
+CREATE TABLE IF NOT EXISTS as_select1 AS EXECUTE select1;
+NOTICE:  relation "as_select1" already exists, skipping
+DROP TABLE as_select1;
+DEALLOCATE select1;
 -- check that the oid column is added before the primary key is checked
 CREATE TABLE oid_pk (f1 INT, PRIMARY KEY(oid)) WITH OIDS;
 DROP TABLE oid_pk;
diff --git a/src/test/regress/sql/create_table.sql b/src/test/regress/sql/create_table.sql
index 78bdc8bf5e7..ec19f9a34f8 100644
--- a/src/test/regress/sql/create_table.sql
+++ b/src/test/regress/sql/create_table.sql
@@ -266,6 +266,14 @@ CREATE TABLE as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
 CREATE TABLE IF NOT EXISTS as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
 DROP TABLE as_select1;
 
+PREPARE select1 AS SELECT 1 as a;
+CREATE TABLE as_select1 AS EXECUTE select1;
+CREATE TABLE as_select1 AS EXECUTE select1;
+SELECT * FROM as_select1;
+CREATE TABLE IF NOT EXISTS as_select1 AS EXECUTE select1;
+DROP TABLE as_select1;
+DEALLOCATE select1;
+
 -- check that the oid column is added before the primary key is checked
 CREATE TABLE oid_pk (f1 INT, PRIMARY KEY(oid)) WITH OIDS;
 DROP TABLE oid_pk;