CREATE TABLE IF NOT EXISTS.

Reviewed by Bernd Helmle.

doc/src/sgml/ref/create_table.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_table.sgml,v 1.128 2010/06/07 02:59:02 itagaki Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_table.sgml,v 1.129 2010/07/25 23:21:21 rhaas Exp $
 PostgreSQL documentation
 -->
 
@@ -21,7 +21,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE <replaceable class="PARAMETER">table_name</replaceable> ( [
+CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE [ IF NOT EXISTS ] <replaceable class="PARAMETER">table_name</replaceable> ( [
   { <replaceable class="PARAMETER">column_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [ DEFAULT <replaceable>default_expr</replaceable> ] [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
     | <replaceable>table_constraint</replaceable>
     | LIKE <replaceable>parent_table</replaceable> [ <replaceable>like_option</replaceable> ... ] }
@@ -32,7 +32,7 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE <replaceable class="PAR
 [ ON COMMIT { PRESERVE ROWS | DELETE ROWS | DROP } ]
 [ TABLESPACE <replaceable class="PARAMETER">tablespace</replaceable> ]
 
-CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE <replaceable class="PARAMETER">table_name</replaceable>
+CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE [ IF NOT EXISTS ] <replaceable class="PARAMETER">table_name</replaceable>
     OF <replaceable class="PARAMETER">type_name</replaceable> [ (
   { <replaceable class="PARAMETER">column_name</replaceable> WITH OPTIONS [ DEFAULT <replaceable>default_expr</replaceable> ] [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
     | <replaceable>table_constraint</replaceable> }
@@ -163,6 +163,18 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } ] TABLE <replaceable class="PAR
     </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.  Note that there is no guarantee that
+	  the existing relation is anything like the one that would have been
+	  created.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="PARAMETER">table_name</replaceable></term>
     <listitem>

src/backend/bootstrap/bootparse.y

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootparse.y,v 1.105 2010/02/07 20:48:09 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootparse.y,v 1.106 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -245,7 +245,8 @@ Boot_CreateStmt:
 													  ONCOMMIT_NOOP,
 													  (Datum) 0,
 													  false,
-													  true);
+													  true,
+													  false);
 						elog(DEBUG4, "relation created with oid %u", id);
 					}
 					do_end();

src/backend/catalog/heap.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.373 2010/04/05 01:09:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.374 2010/07/25 23:21:21 rhaas Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -903,11 +903,13 @@ heap_create_with_catalog(const char *relname,
 						 OnCommitAction oncommit,
 						 Datum reloptions,
 						 bool use_user_acl,
-						 bool allow_system_table_mods)
+						 bool allow_system_table_mods,
+						 bool if_not_exists)
 {
 	Relation	pg_class_desc;
 	Relation	new_rel_desc;
 	Acl		   *relacl;
+	Oid			existing_relid;
 	Oid			old_type_oid;
 	Oid			new_type_oid;
 	Oid			new_array_oid = InvalidOid;
@@ -921,10 +923,27 @@ heap_create_with_catalog(const char *relname,
 
 	CheckAttributeNamesTypes(tupdesc, relkind, allow_system_table_mods);
 
-	if (get_relname_relid(relname, relnamespace))
+	/*
+	 * If the relation already exists, it's an error, unless the user specifies
+	 * "IF NOT EXISTS".  In that case, we just print a notice and do nothing
+	 * further.
+	 */
+	existing_relid = get_relname_relid(relname, relnamespace);
+	if (existing_relid != InvalidOid)
+	{
+		if (if_not_exists)
+		{
+			ereport(NOTICE,
+					(errcode(ERRCODE_DUPLICATE_TABLE),
+					 errmsg("relation \"%s\" already exists, skipping",
+					 relname)));
+			heap_close(pg_class_desc, RowExclusiveLock);
+			return InvalidOid;
+		}
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_TABLE),
 				 errmsg("relation \"%s\" already exists", relname)));
+	}
 
 	/*
 	 * Since we are going to create a rowtype as well, also check for

src/backend/catalog/toasting.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/toasting.c,v 1.32 2010/02/26 02:00:37 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/toasting.c,v 1.33 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -223,7 +223,9 @@ create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid, Datum reloptio
 										   ONCOMMIT_NOOP,
 										   reloptions,
 										   false,
-										   true);
+										   true,
+										   false);
+	Assert(toast_relid != InvalidOid);
 
 	/* make the toast relation visible, else index creation will fail */
 	CommandCounterIncrement();

src/backend/commands/cluster.c

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.203 2010/04/28 16:10:41 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.204 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -687,7 +687,9 @@ make_new_heap(Oid OIDOldHeap, Oid NewTableSpace)
 										  ONCOMMIT_NOOP,
 										  reloptions,
 										  false,
-										  true);
+										  true,
+										  false);
+	Assert(OIDNewHeap != InvalidOid);
 
 	ReleaseSysCache(tuple);
 

src/backend/commands/sequence.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/sequence.c,v 1.168 2010/02/20 21:24:02 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/sequence.c,v 1.169 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -203,8 +203,10 @@ DefineSequence(CreateSeqStmt *seq)
 	stmt->options = list_make1(defWithOids(false));
 	stmt->oncommit = ONCOMMIT_NOOP;
 	stmt->tablespacename = NULL;
+	stmt->if_not_exists = false;
 
 	seqoid = DefineRelation(stmt, RELKIND_SEQUENCE);
+	Assert(seqoid != InvalidOid);
 
 	rel = heap_open(seqoid, AccessExclusiveLock);
 	tupDesc = RelationGetDescr(rel);

src/backend/commands/tablecmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.333 2010/07/23 20:04:18 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.334 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -548,8 +548,18 @@ DefineRelation(CreateStmt *stmt, char relkind)
 										  stmt->oncommit,
 										  reloptions,
 										  true,
-										  allowSystemTableMods);
+										  allowSystemTableMods,
+										  stmt->if_not_exists);
 
+	/*
+	 * If heap_create_with_catalog returns InvalidOid, it means that the user
+	 * specified "IF NOT EXISTS" and the relation already exists.  In that
+	 * case we do nothing further.
+	 */
+	if (relationId == InvalidOid)
+		return InvalidOid;
+
+	/* Store inheritance information for new rel. */
 	StoreCatalogInheritance(relationId, inheritOids);
 
 	/*

src/backend/commands/typecmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/typecmds.c,v 1.148 2010/02/26 02:00:40 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/typecmds.c,v 1.149 2010/07/25 23:21:21 rhaas Exp $
  *
  * DESCRIPTION
  *	  The "DefineFoo" routines take the parse tree and pick out the
@@ -1506,6 +1506,7 @@ DefineCompositeType(const RangeVar *typevar, List *coldeflist)
 	CreateStmt *createStmt = makeNode(CreateStmt);
 	Oid			old_type_oid;
 	Oid			typeNamespace;
+	Oid			relid;
 
 	if (coldeflist == NIL)
 		ereport(ERROR,
@@ -1523,6 +1524,7 @@ DefineCompositeType(const RangeVar *typevar, List *coldeflist)
 	createStmt->options = list_make1(defWithOids(false));
 	createStmt->oncommit = ONCOMMIT_NOOP;
 	createStmt->tablespacename = NULL;
+	createStmt->if_not_exists = false;
 
 	/*
 	 * Check for collision with an existing type name. If there is one and
@@ -1546,7 +1548,9 @@ DefineCompositeType(const RangeVar *typevar, List *coldeflist)
 	/*
 	 * Finally create the relation.  This also creates the type.
 	 */
-	return DefineRelation(createStmt, RELKIND_COMPOSITE_TYPE);
+	relid = DefineRelation(createStmt, RELKIND_COMPOSITE_TYPE);
+	Assert(relid != InvalidOid);
+	return relid;
 }
 
 /*

src/backend/commands/view.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/view.c,v 1.120 2010/01/02 16:57:40 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/view.c,v 1.121 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -222,6 +222,8 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace)
 	}
 	else
 	{
+		Oid		relid;
+
 		/*
 		 * now set the parameters for keys/inheritance etc. All of these are
 		 * uninteresting for views...
@@ -233,13 +235,16 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace)
 		createStmt->options = list_make1(defWithOids(false));
 		createStmt->oncommit = ONCOMMIT_NOOP;
 		createStmt->tablespacename = NULL;
+		createStmt->if_not_exists = false;
 
 		/*
 		 * finally create the relation (this will error out if there's an
 		 * existing view, so we don't need more code to complain if "replace"
 		 * is false).
 		 */
-		return DefineRelation(createStmt, RELKIND_VIEW);
+		relid = DefineRelation(createStmt, RELKIND_VIEW);
+		Assert(relid != InvalidOid);
+		return relid;
 	}
 }
 

src/backend/executor/execMain.c

@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.352 2010/07/22 00:47:52 rhaas Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.353 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2190,7 +2190,9 @@ OpenIntoRel(QueryDesc *queryDesc)
 											  into->onCommit,
 											  reloptions,
 											  true,
-											  allowSystemTableMods);
+											  allowSystemTableMods,
+											  false);
+	Assert(intoRelationId != InvalidOid);
 
 	FreeTupleDesc(tupdesc);
 

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.465 2010/07/12 17:01:05 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.466 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2537,6 +2537,7 @@ _copyCreateStmt(CreateStmt *from)
 	COPY_NODE_FIELD(options);
 	COPY_SCALAR_FIELD(oncommit);
 	COPY_STRING_FIELD(tablespacename);
+	COPY_SCALAR_FIELD(if_not_exists);
 
 	return newnode;
 }

src/backend/nodes/equalfuncs.c

@@ -22,7 +22,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.385 2010/02/26 02:00:43 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.386 2010/07/25 23:21:21 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1104,6 +1104,7 @@ _equalCreateStmt(CreateStmt *a, CreateStmt *b)
 	COMPARE_NODE_FIELD(options);
 	COMPARE_SCALAR_FIELD(oncommit);
 	COMPARE_STRING_FIELD(tablespacename);
+	COMPARE_SCALAR_FIELD(if_not_exists);
 
 	return true;
 }

src/backend/nodes/outfuncs.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.386 2010/07/12 17:01:05 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.387 2010/07/25 23:21:21 rhaas Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -1795,6 +1795,7 @@ _outCreateStmt(StringInfo str, CreateStmt *node)
 	WRITE_NODE_FIELD(options);
 	WRITE_ENUM_FIELD(oncommit, OnCommitAction);
 	WRITE_STRING_FIELD(tablespacename);
+	WRITE_BOOL_FIELD(if_not_exists);
 }
 
 static void

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.713 2010/06/13 17:43:12 rhaas Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.714 2010/07/25 23:21:21 rhaas Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -2212,6 +2212,23 @@ CreateStmt:	CREATE OptTemp TABLE qualified_name '(' OptTableElementList ')'
 					n->options = $9;
 					n->oncommit = $10;
 					n->tablespacename = $11;
+					n->if_not_exists = false;
+					$$ = (Node *)n;
+				}
+		| CREATE OptTemp TABLE IF_P NOT EXISTS qualified_name '('
+			OptTableElementList ')' OptInherit OptWith OnCommitOption
+			OptTableSpace
+				{
+					CreateStmt *n = makeNode(CreateStmt);
+					$7->istemp = $2;
+					n->relation = $7;
+					n->tableElts = $9;
+					n->inhRelations = $11;
+					n->constraints = NIL;
+					n->options = $12;
+					n->oncommit = $13;
+					n->tablespacename = $14;
+					n->if_not_exists = true;
 					$$ = (Node *)n;
 				}
 		| CREATE OptTemp TABLE qualified_name OF any_name
@@ -2227,6 +2244,22 @@ CreateStmt:	CREATE OptTemp TABLE qualified_name '(' OptTableElementList ')'
 					n->options = $8;
 					n->oncommit = $9;
 					n->tablespacename = $10;
+					n->if_not_exists = false;
+					$$ = (Node *)n;
+				}
+		| CREATE OptTemp TABLE IF_P NOT EXISTS qualified_name OF any_name
+			OptTypedTableElementList OptWith OnCommitOption OptTableSpace
+				{
+					CreateStmt *n = makeNode(CreateStmt);
+					n->relation = $7;
+					n->tableElts = $10;
+					n->ofTypename = makeTypeNameFromNameList($9);
+					n->ofTypename->location = @9;
+					n->constraints = NIL;
+					n->options = $11;
+					n->oncommit = $12;
+					n->tablespacename = $13;
+					n->if_not_exists = true;
 					$$ = (Node *)n;
 				}
 		;

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.335 2010/02/26 02:01:04 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.336 2010/07/25 23:21:22 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -512,6 +512,13 @@ standard_ProcessUtility(Node *parsetree,
 						relOid = DefineRelation((CreateStmt *) stmt,
 												RELKIND_RELATION);
 
+						/*
+						 * If "IF NOT EXISTS" was specified and the relation
+						 * already exists, do nothing further.
+						 */
+						if (relOid == InvalidOid)
+							continue;
+
 						/*
 						 * Let AlterTableCreateToastTable decide if this one
 						 * needs a secondary relation too.

src/include/catalog/heap.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/heap.h,v 1.98 2010/02/26 02:01:21 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/heap.h,v 1.99 2010/07/25 23:21:22 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -61,7 +61,8 @@ extern Oid heap_create_with_catalog(const char *relname,
 						 OnCommitAction oncommit,
 						 Datum reloptions,
 						 bool use_user_acl,
-						 bool allow_system_table_mods);
+						 bool allow_system_table_mods,
+						 bool if_not_exists);
 
 extern void heap_drop_with_catalog(Oid relid);
 

src/include/nodes/parsenodes.h

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.432 2010/02/26 02:01:25 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.433 2010/07/25 23:21:22 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1375,6 +1375,7 @@ typedef struct CreateStmt
 	List	   *options;		/* options from WITH clause */
 	OnCommitAction oncommit;	/* what do we do at COMMIT? */
 	char	   *tablespacename; /* table space to use, or NULL */
+	bool		if_not_exists;	/* just do nothing if it already exists? */
 } CreateStmt;
 
 /* ----------

src/test/regress/expected/create_table.out

@@ -196,7 +196,11 @@ CREATE TABLE array_index_op_test (
 	i			int4[],
 	t			text[]
 );
-CREATE TABLE test_tsvector( 
+CREATE TABLE IF NOT EXISTS test_tsvector( 
 	t text, 
 	a tsvector 
 );
+CREATE TABLE IF NOT EXISTS test_tsvector( 
+	t text
+);
+NOTICE:  relation "test_tsvector" already exists, skipping

src/test/regress/expected/typed_table.out

@@ -2,6 +2,8 @@ CREATE TABLE ttable1 OF nothing;
 ERROR:  type "nothing" does not exist
 CREATE TYPE person_type AS (id int, name text);
 CREATE TABLE persons OF person_type;
+CREATE TABLE IF NOT EXISTS persons OF person_type;
+NOTICE:  relation "persons" already exists, skipping
 SELECT * FROM persons;
  id | name 
 ----+------

src/test/regress/sql/create_table.sql

@@ -232,8 +232,11 @@ CREATE TABLE array_index_op_test (
 	t			text[]
 );
 
-CREATE TABLE test_tsvector( 
+CREATE TABLE IF NOT EXISTS test_tsvector( 
 	t text, 
 	a tsvector 
 );
 
+CREATE TABLE IF NOT EXISTS test_tsvector( 
+	t text
+);

src/test/regress/sql/typed_table.sql

@@ -2,6 +2,7 @@ CREATE TABLE ttable1 OF nothing;
 
 CREATE TYPE person_type AS (id int, name text);
 CREATE TABLE persons OF person_type;
+CREATE TABLE IF NOT EXISTS persons OF person_type;
 SELECT * FROM persons;
 \d persons