doc/src/sgml/ref/drop_database.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/drop_database.sgml,v 1.20 2005/06/21 04:02:31 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/drop_database.sgml,v 1.21 2005/11/22 15:24:17 adunstan Exp $
 PostgreSQL documentation
 -->
 
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-DROP DATABASE <replaceable class="PARAMETER">name</replaceable>
+DROP DATABASE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
 </synopsis>
  </refsynopsisdiv>
  
@@ -45,6 +45,16 @@ DROP DATABASE <replaceable class="PARAMETER">name</replaceable>
   <title>Parameters</title>
 
   <variablelist>
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the database does not exist. A notice is issued 
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><replaceable class="PARAMETER">name</replaceable></term>
     <listitem>

src/backend/commands/dbcommands.c

@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.173 2005/10/15 02:49:15 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.174 2005/11/22 15:24:17 adunstan Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -551,7 +551,7 @@ createdb(const CreatedbStmt *stmt)
  * DROP DATABASE
  */
 void
-dropdb(const char *dbname)
+dropdb(const char *dbname, bool missing_ok)
 {
 	Oid			db_id;
 	bool		db_istemplate;
@@ -585,9 +585,25 @@ dropdb(const char *dbname)
 
 	if (!get_db_info(dbname, &db_id, NULL, NULL,
 					 &db_istemplate, NULL, NULL, NULL, NULL, NULL))
-		ereport(ERROR,
+	{
+		if (! missing_ok)
+		{
+			ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_DATABASE),
 				 errmsg("database \"%s\" does not exist", dbname)));
+		}
+		else
+		{
+			
+			/* Close pg_database, release the lock, since we changed nothing */
+			heap_close(pgdbrel, ExclusiveLock);
+			ereport(NOTICE, 
+					(errmsg("database \"%s\" does not exist, skipping", 
+							dbname)));
+
+			return;
+		}
+	}
 
 	if (!pg_database_ownercheck(db_id, GetUserId()))
 		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_DATABASE,

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 1.319 2005/11/21 12:49:31 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.320 2005/11/22 15:24:17 adunstan Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2261,6 +2261,7 @@ _copyDropdbStmt(DropdbStmt *from)
 	DropdbStmt *newnode = makeNode(DropdbStmt);
 
 	COPY_STRING_FIELD(dbname);
+	COPY_SCALAR_FIELD(missing_ok);
 
 	return newnode;
 }

src/backend/nodes/equalfuncs.c

@@ -18,7 +18,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.256 2005/11/21 12:49:31 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.257 2005/11/22 15:24:17 adunstan Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1188,6 +1188,7 @@ static bool
 _equalDropdbStmt(DropdbStmt *a, DropdbStmt *b)
 {
 	COMPARE_STRING_FIELD(dbname);
+	COMPARE_SCALAR_FIELD(missing_ok);
 
 	return true;
 }

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.514 2005/11/21 12:49:31 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.515 2005/11/22 15:24:17 adunstan Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -4698,7 +4698,7 @@ alterdb_opt_item:
 
 /*****************************************************************************
  *
- *		DROP DATABASE
+ *		DROP DATABASE [ IF EXISTS ]
  *
  * This is implicitly CASCADE, no need for drop behavior
  *****************************************************************************/
@@ -4707,6 +4707,14 @@ DropdbStmt: DROP DATABASE database_name
 				{
 					DropdbStmt *n = makeNode(DropdbStmt);
 					n->dbname = $3;
+					n->missing_ok = FALSE;
+					$$ = (Node *)n;
+				}
+			| DROP DATABASE IF_P EXISTS database_name
+				{
+					DropdbStmt *n = makeNode(DropdbStmt);
+					n->dbname = $5;
+					n->missing_ok = TRUE;
 					$$ = (Node *)n;
 				}
 		;

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.247 2005/11/21 12:49:32 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.248 2005/11/22 15:24:18 adunstan Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -840,7 +840,7 @@ ProcessUtility(Node *parsetree,
 			{
 				DropdbStmt *stmt = (DropdbStmt *) parsetree;
 
-				dropdb(stmt->dbname);
+				dropdb(stmt->dbname, stmt->missing_ok);
 			}
 			break;
 

src/include/commands/dbcommands.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/dbcommands.h,v 1.42 2005/10/15 02:49:44 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/commands/dbcommands.h,v 1.43 2005/11/22 15:24:18 adunstan Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,7 +53,7 @@ typedef struct xl_dbase_drop_rec
 } xl_dbase_drop_rec;
 
 extern void createdb(const CreatedbStmt *stmt);
-extern void dropdb(const char *dbname);
+extern void dropdb(const char *dbname, bool missing_ok);
 extern void RenameDatabase(const char *oldname, const char *newname);
 extern void AlterDatabase(AlterDatabaseStmt *stmt);
 extern void AlterDatabaseSet(AlterDatabaseSetStmt *stmt);

src/include/nodes/parsenodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.294 2005/11/21 12:49:32 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.295 2005/11/22 15:24:18 adunstan Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1672,6 +1672,7 @@ typedef struct DropdbStmt
 {
 	NodeTag		type;
 	char	   *dbname;			/* database to drop */
+	bool        missing_ok;     /* skip error if db is missing? */
 } DropdbStmt;
 
 /* ----------------------