DROP DATABASE IF EXISTS variant

8 files changed, 43 insertions, 6 deletions

diff --git a/doc/src/sgml/ref/drop_database.sgml b/doc/src/sgml/ref/drop_database.sgml
index cd1297c2f4..7635bc17ee 100644
--- a/doc/src/sgml/ref/drop_database.sgml
+++ b/doc/src/sgml/ref/drop_database.sgml
@@ -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>
  
@@ -46,6 +46,16 @@ DROP DATABASE <replaceable class="PARAMETER">name</replaceable>
 
   <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>
      <para>
diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index 469b3f7281..ba30a8db2c 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -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,
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index a36491f4e7..460b516c1c 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2261,6 +2261,7 @@ _copyDropdbStmt(DropdbStmt *from)
 	DropdbStmt *newnode = makeNode(DropdbStmt);
 
 	COPY_STRING_FIELD(dbname);
+	COPY_SCALAR_FIELD(missing_ok);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index bdbd4e592a..561468b874 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1188,6 +1188,7 @@ static bool
 _equalDropdbStmt(DropdbStmt *a, DropdbStmt *b)
 {
 	COMPARE_STRING_FIELD(dbname);
+	COMPARE_SCALAR_FIELD(missing_ok);
 
 	return true;
 }
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 6ba9b244a5..e1a970b10f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -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;
 				}
 		;
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 1fdc1ee454..77523f5a31 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -840,7 +840,7 @@ ProcessUtility(Node *parsetree,
 			{
 				DropdbStmt *stmt = (DropdbStmt *) parsetree;
 
-				dropdb(stmt->dbname);
+				dropdb(stmt->dbname, stmt->missing_ok);
 			}
 			break;
 
diff --git a/src/include/commands/dbcommands.h b/src/include/commands/dbcommands.h
index 8b1d4acc05..eb73939f5d 100644
--- a/src/include/commands/dbcommands.h
+++ b/src/include/commands/dbcommands.h
@@ -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);
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index d023d872cb..93d7e6c9a8 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1672,6 +1672,7 @@ typedef struct DropdbStmt
 {
 	NodeTag		type;
 	char	   *dbname;			/* database to drop */
+	bool        missing_ok;     /* skip error if db is missing? */
 } DropdbStmt;
 
 /* ----------------------