Add CINE option for CREATE TABLE AS and CREATE MATERIALIZED VIEW

Fabrízio de Royes Mello reviewed by Rushabh Lathia.

doc/src/sgml/ref/create_materialized_view.sgml

@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-CREATE MATERIALIZED VIEW <replaceable>table_name</replaceable>
+CREATE MATERIALIZED VIEW [ IF NOT EXISTS ] <replaceable>table_name</replaceable>
     [ (<replaceable>column_name</replaceable> [, ...] ) ]
     [ WITH ( <replaceable class="PARAMETER">storage_parameter</replaceable> [= <replaceable class="PARAMETER">value</replaceable>] [, ... ] ) ]
     [ TABLESPACE <replaceable class="PARAMETER">tablespace_name</replaceable> ]
@@ -53,6 +53,18 @@ CREATE MATERIALIZED VIEW <replaceable>table_name</replaceable>
  <refsect1>
   <title>Parameters</title>
 
+   <varlistentry>
+    <term><literal>IF NOT EXISTS</></term>
+    <listitem>
+     <para>
+      Do not throw an error if a materialized view with the same name already
+      exists. A notice is issued in this case.  Note that there is no guarantee
+      that the existing materialized view is anything like the one that would
+      have been created.
+     </para>
+    </listitem>
+   </varlistentry>
+
   <variablelist>
    <varlistentry>
     <term><replaceable>table_name</replaceable></term>

doc/src/sgml/ref/create_table_as.sgml

@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE <replaceable>table_name</replaceable>
+CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] <replaceable>table_name</replaceable>
     [ (<replaceable>column_name</replaceable> [, ...] ) ]
     [ WITH ( <replaceable class="PARAMETER">storage_parameter</replaceable> [= <replaceable class="PARAMETER">value</replaceable>] [, ... ] ) | WITH OIDS | WITHOUT OIDS ]
     [ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
@@ -90,6 +90,17 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE <replaceable
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>IF NOT EXISTS</></term>
+    <listitem>
+     <para>
+      Do not throw an error if a relation with the same name already exists.
+      A notice is issued in this case. Refer to <xref linkend="sql-createtable">
+      for details.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable>table_name</replaceable></term>
     <listitem>

src/backend/commands/createas.c

@@ -28,6 +28,7 @@
 #include "access/sysattr.h"
 #include "access/xact.h"
 #include "access/xlog.h"
+#include "catalog/namespace.h"
 #include "catalog/toasting.h"
 #include "commands/createas.h"
 #include "commands/matview.h"
@@ -86,6 +87,22 @@ ExecCreateTableAs(CreateTableAsStmt *stmt, const char *queryString,
 	QueryDesc  *queryDesc;
 	ScanDirection dir;
 
+	if (stmt->if_not_exists)
+	{
+		Oid	nspid;
+
+		nspid = RangeVarGetCreationNamespace(stmt->into->rel);
+
+		if (get_relname_relid(stmt->into->rel->relname, nspid))
+		{
+			ereport(NOTICE,
+					(errcode(ERRCODE_DUPLICATE_TABLE),
+					 errmsg("relation \"%s\" already exists, skipping",
+							stmt->into->rel->relname)));
+			return InvalidOid;
+		}
+	}
+
 	/*
 	 * Create the tuple receiver object and insert info it will need
 	 */

src/backend/nodes/copyfuncs.c

@@ -3317,6 +3317,7 @@ _copyCreateTableAsStmt(const CreateTableAsStmt *from)
 	COPY_NODE_FIELD(into);
 	COPY_SCALAR_FIELD(relkind);
 	COPY_SCALAR_FIELD(is_select_into);
+	COPY_SCALAR_FIELD(if_not_exists);
 
 	return newnode;
 }

src/backend/nodes/equalfuncs.c

@@ -1530,6 +1530,7 @@ _equalCreateTableAsStmt(const CreateTableAsStmt *a, const CreateTableAsStmt *b)
 	COMPARE_NODE_FIELD(into);
 	COMPARE_SCALAR_FIELD(relkind);
 	COMPARE_SCALAR_FIELD(is_select_into);
+	COMPARE_SCALAR_FIELD(if_not_exists);
 
 	return true;
 }

src/backend/parser/gram.y

@@ -3401,11 +3401,25 @@ CreateAsStmt:
 					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 = !($7);
 					$$ = (Node *) ctas;
 				}
+		| CREATE OptTemp TABLE IF_P NOT EXISTS create_as_target AS SelectStmt opt_with_data
+				{
+					CreateTableAsStmt *ctas = makeNode(CreateTableAsStmt);
+					ctas->query = $9;
+					ctas->into = $7;
+					ctas->relkind = OBJECT_TABLE;
+					ctas->is_select_into = false;
+					ctas->if_not_exists = true;
+					/* cram additional flags into the IntoClause */
+					$7->rel->relpersistence = $2;
+					$7->skipData = !($10);
+					$$ = (Node *) ctas;
+				}
 		;
 
 create_as_target:
@@ -3444,11 +3458,25 @@ CreateMatViewStmt:
 					ctas->into = $5;
 					ctas->relkind = OBJECT_MATVIEW;
 					ctas->is_select_into = false;
+					ctas->if_not_exists = false;
 					/* cram additional flags into the IntoClause */
 					$5->rel->relpersistence = $2;
 					$5->skipData = !($8);
 					$$ = (Node *) ctas;
 				}
+		| CREATE OptNoLog MATERIALIZED VIEW IF_P NOT EXISTS create_mv_target AS SelectStmt opt_with_data
+				{
+					CreateTableAsStmt *ctas = makeNode(CreateTableAsStmt);
+					ctas->query = $10;
+					ctas->into = $8;
+					ctas->relkind = OBJECT_MATVIEW;
+					ctas->is_select_into = false;
+					ctas->if_not_exists = true;
+					/* cram additional flags into the IntoClause */
+					$8->rel->relpersistence = $2;
+					$8->skipData = !($11);
+					$$ = (Node *) ctas;
+				}
 		;
 
 create_mv_target:

src/include/nodes/parsenodes.h

@@ -2652,6 +2652,7 @@ typedef struct CreateTableAsStmt
 	IntoClause *into;			/* destination table */
 	ObjectType	relkind;		/* OBJECT_TABLE or OBJECT_MATVIEW */
 	bool		is_select_into; /* it was written as SELECT INTO */
+	bool		if_not_exists;	/* just do nothing if it already exists? */
 } CreateTableAsStmt;
 
 /* ----------------------

src/test/regress/expected/create_table.out

@@ -218,3 +218,9 @@ CREATE TEMP TABLE pg_temp.doubly_temp (a int primary key);		-- also OK
 CREATE TEMP TABLE public.temp_to_perm (a int primary key);		-- not OK
 ERROR:  cannot create temporary relation in non-temporary schema
 DROP TABLE unlogged1, public.unlogged2;
+CREATE TABLE as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
+CREATE TABLE as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
+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;

src/test/regress/expected/matview.out

@@ -508,6 +508,10 @@ SET ROLE user_dw;
 CREATE TABLE foo_data AS SELECT i, md5(random()::text)
   FROM generate_series(1, 10) i;
 CREATE MATERIALIZED VIEW mv_foo AS SELECT * FROM foo_data;
+CREATE MATERIALIZED VIEW mv_foo AS SELECT * FROM foo_data;
+ERROR:  relation "mv_foo" already exists
+CREATE MATERIALIZED VIEW IF NOT EXISTS mv_foo AS SELECT * FROM foo_data;
+NOTICE:  relation "mv_foo" already exists, skipping
 CREATE UNIQUE INDEX ON mv_foo (i);
 RESET ROLE;
 REFRESH MATERIALIZED VIEW mv_foo;

src/test/regress/sql/create_table.sql

@@ -254,3 +254,8 @@ CREATE TEMP TABLE explicitly_temp (a int primary key);			-- also OK
 CREATE TEMP TABLE pg_temp.doubly_temp (a int primary key);		-- also OK
 CREATE TEMP TABLE public.temp_to_perm (a int primary key);		-- not OK
 DROP TABLE unlogged1, public.unlogged2;
+
+CREATE TABLE as_select1 AS SELECT * FROM pg_class WHERE relkind = 'r';
+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;

src/test/regress/sql/matview.sql

@@ -201,6 +201,8 @@ SET ROLE user_dw;
 CREATE TABLE foo_data AS SELECT i, md5(random()::text)
   FROM generate_series(1, 10) i;
 CREATE MATERIALIZED VIEW mv_foo AS SELECT * FROM foo_data;
+CREATE MATERIALIZED VIEW mv_foo AS SELECT * FROM foo_data;
+CREATE MATERIALIZED VIEW IF NOT EXISTS mv_foo AS SELECT * FROM foo_data;
 CREATE UNIQUE INDEX ON mv_foo (i);
 RESET ROLE;
 REFRESH MATERIALIZED VIEW mv_foo;