Add ALTER .. NO DEPENDS ON

Commit f2fcad2 (9.6 era) added the ability to mark objects as
dependent an extension, but forgot to add a way for such dependencies to
be removed.  This commit fixes that oversight.

Strictly speaking this should be backpatched to 9.6, but due to lack of
demand we're not doing so at this time.

Discussion: https://postgr.es/m/20200217225333.GA30974@alvherre.pgsql
Reviewed-by: ahsan hadi <ahsan.hadi@gmail.com>
Reviewed-by: Ibrar Ahmed <ibrar.ahmad@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>

Author: alvherre

doc/src/sgml/ref/alter_function.sgml

@@ -30,7 +30,7 @@ ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="param
 ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ]
     SET SCHEMA <replaceable>new_schema</replaceable>
 ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ]
-    DEPENDS ON EXTENSION <replaceable>extension_name</replaceable>
+    [ NO ] DEPENDS ON EXTENSION <replaceable>extension_name</replaceable>
 
 <phrase>where <replaceable class="parameter">action</replaceable> is one of:</phrase>
 
@@ -153,10 +153,14 @@ ALTER FUNCTION <replaceable>name</replaceable> [ ( [ [ <replaceable class="param
    </varlistentry>
 
    <varlistentry>
-    <term><replaceable class="parameter">extension_name</replaceable></term>
+    <term><literal>DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable></literal></term>
+    <term><literal>NO DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable></literal></term>
     <listitem>
      <para>
-      The name of the extension that the function is to depend on.
+      This form marks the function as dependent on the extension, or no longer
+      dependent on that extension if <literal>NO</literal> is specified.
+      A function that's marked as dependent on an extension is automatically
+      dropped when the extension is dropped.
      </para>
     </listitem>
    </varlistentry>

doc/src/sgml/ref/alter_index.sgml

@@ -100,11 +100,14 @@ ALTER INDEX ALL IN TABLESPACE <replaceable class="parameter">name</replaceable>
    </varlistentry>
 
    <varlistentry>
-    <term><literal>DEPENDS ON EXTENSION</literal></term>
+    <term><literal>DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable></literal></term>
+    <term><literal>NO DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable></literal></term>
     <listitem>
      <para>
-      This form marks the index as dependent on the extension, such that if the
-      extension is dropped, the index will automatically be dropped as well.
+      This form marks the index as dependent on the extension, or no longer
+      dependent on that extension if <literal>NO</literal> is specified.
+      An index that's marked as dependent on an extension is automatically
+      dropped when the extension is dropped.
      </para>
     </listitem>
    </varlistentry>

doc/src/sgml/ref/alter_materialized_view.sgml

@@ -68,12 +68,6 @@ ALTER MATERIALIZED VIEW ALL IN TABLESPACE <replaceable class="parameter">name</r
    anyway.)
   </para>
 
-  <para>
-   The <literal>DEPENDS ON EXTENSION</literal> form marks the materialized view
-   as dependent on an extension, such that the materialized view will
-   automatically be dropped if the extension is dropped.
-  </para>
-
   <para>
    The statement subforms and actions available for
    <command>ALTER MATERIALIZED VIEW</command> are a subset of those available
@@ -110,7 +104,10 @@ ALTER MATERIALIZED VIEW ALL IN TABLESPACE <replaceable class="parameter">name</r
      <term><replaceable class="parameter">extension_name</replaceable></term>
      <listitem>
       <para>
-       The name of the extension that the materialized view is to depend on.
+       The name of the extension that the materialized view is to depend on (or no longer
+       dependent on, if <literal>NO</literal> is specified).  A materialized view
+       that's marked as dependent on an extension is automatically dropped when
+       the extension is dropped.
       </para>
      </listitem>
     </varlistentry>

doc/src/sgml/ref/alter_trigger.sgml

@@ -22,7 +22,7 @@ PostgreSQL documentation
  <refsynopsisdiv>
 <synopsis>
 ALTER TRIGGER <replaceable class="parameter">name</replaceable> ON <replaceable class="parameter">table_name</replaceable> RENAME TO <replaceable class="parameter">new_name</replaceable>
-ALTER TRIGGER <replaceable class="parameter">name</replaceable> ON <replaceable class="parameter">table_name</replaceable> DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable>
+ALTER TRIGGER <replaceable class="parameter">name</replaceable> ON <replaceable class="parameter">table_name</replaceable> [ NO ] DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable>
 </synopsis>
  </refsynopsisdiv>
 
@@ -78,7 +78,10 @@ ALTER TRIGGER <replaceable class="parameter">name</replaceable> ON <replaceable
     <term><replaceable class="parameter">extension_name</replaceable></term>
     <listitem>
      <para>
-      The name of the extension that the trigger is to depend on.
+      The name of the extension that the trigger is to depend on (or no longer
+      dependent on, if <literal>NO</literal> is specified).  A trigger
+      that's marked as dependent on an extension is automatically dropped when
+      the extension is dropped.
      </para>
     </listitem>
    </varlistentry>

src/backend/catalog/pg_depend.c

@@ -278,6 +278,55 @@ deleteDependencyRecordsForClass(Oid classId, Oid objectId,
 	return count;
 }
 
+/*
+ * deleteDependencyRecordsForSpecific -- delete all records with given depender
+ * classId/objectId, dependee classId/objectId, of the given deptype.
+ * Returns the number of records deleted.
+ */
+long
+deleteDependencyRecordsForSpecific(Oid classId, Oid objectId, char deptype,
+								   Oid refclassId, Oid refobjectId)
+{
+	long		count = 0;
+	Relation	depRel;
+	ScanKeyData key[2];
+	SysScanDesc scan;
+	HeapTuple	tup;
+
+	depRel = table_open(DependRelationId, RowExclusiveLock);
+
+	ScanKeyInit(&key[0],
+				Anum_pg_depend_classid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(classId));
+	ScanKeyInit(&key[1],
+				Anum_pg_depend_objid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(objectId));
+
+	scan = systable_beginscan(depRel, DependDependerIndexId, true,
+							  NULL, 2, key);
+
+	while (HeapTupleIsValid(tup = systable_getnext(scan)))
+	{
+		Form_pg_depend depform = (Form_pg_depend) GETSTRUCT(tup);
+
+		if (depform->refclassid == refclassId &&
+			depform->refobjid == refobjectId &&
+			depform->deptype == deptype)
+		{
+			CatalogTupleDelete(depRel, &tup->t_self);
+			count++;
+		}
+	}
+
+	systable_endscan(scan);
+
+	table_close(depRel, RowExclusiveLock);
+
+	return count;
+}
+
 /*
  * Adjust dependency record(s) to point to a different object of the same type
  *

src/backend/commands/alter.c

@@ -421,7 +421,7 @@ ExecRenameStmt(RenameStmt *stmt)
 }
 
 /*
- * Executes an ALTER OBJECT / DEPENDS ON [EXTENSION] statement.
+ * Executes an ALTER OBJECT / [NO] DEPENDS ON EXTENSION statement.
  *
  * Return value is the address of the altered object.  refAddress is an output
  * argument which, if not null, receives the address of the object that the
@@ -433,7 +433,6 @@ ExecAlterObjectDependsStmt(AlterObjectDependsStmt *stmt, ObjectAddress *refAddre
 	ObjectAddress address;
 	ObjectAddress refAddr;
 	Relation	rel;
-	List   *currexts;
 
 	address =
 		get_object_address_rv(stmt->objectType, stmt->relation, (List *) stmt->object,
@@ -463,11 +462,22 @@ ExecAlterObjectDependsStmt(AlterObjectDependsStmt *stmt, ObjectAddress *refAddre
 	if (refAddress)
 		*refAddress = refAddr;
 
-	/* Avoid duplicates */
-	currexts = getAutoExtensionsOfObject(address.classId,
-										 address.objectId);
-	if (!list_member_oid(currexts, refAddr.objectId))
-		recordDependencyOn(&address, &refAddr, DEPENDENCY_AUTO_EXTENSION);
+	if (stmt->remove)
+	{
+		deleteDependencyRecordsForSpecific(address.classId, address.objectId,
+										   DEPENDENCY_AUTO_EXTENSION,
+										   refAddr.classId, refAddr.objectId);
+	}
+	else
+	{
+		List   *currexts;
+
+		/* Avoid duplicates */
+		currexts = getAutoExtensionsOfObject(address.classId,
+											 address.objectId);
+		if (!list_member_oid(currexts, refAddr.objectId))
+			recordDependencyOn(&address, &refAddr, DEPENDENCY_AUTO_EXTENSION);
+	}
 
 	return address;
 }

src/backend/nodes/copyfuncs.c

@@ -3638,6 +3638,7 @@ _copyAlterObjectDependsStmt(const AlterObjectDependsStmt *from)
 	COPY_NODE_FIELD(relation);
 	COPY_NODE_FIELD(object);
 	COPY_NODE_FIELD(extname);
+	COPY_SCALAR_FIELD(remove);
 
 	return newnode;
 }

src/backend/nodes/equalfuncs.c

@@ -1449,6 +1449,7 @@ _equalAlterObjectDependsStmt(const AlterObjectDependsStmt *a, const AlterObjectD
 	COMPARE_NODE_FIELD(relation);
 	COMPARE_NODE_FIELD(object);
 	COMPARE_NODE_FIELD(extname);
+	COMPARE_SCALAR_FIELD(remove);
 
 	return true;
 }

src/backend/parser/gram.y

@@ -320,7 +320,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	vac_analyze_option_list
 %type <node>	vac_analyze_option_arg
 %type <defelt>	drop_option
-%type <boolean>	opt_or_replace
+%type <boolean>	opt_or_replace opt_no
 				opt_grant_grant_option opt_grant_admin_option
 				opt_nowait opt_if_exists opt_with_data
 				opt_transaction_chain
@@ -9053,57 +9053,67 @@ opt_set_data: SET DATA_P							{ $$ = 1; }
  *****************************************************************************/
 
 AlterObjectDependsStmt:
-			ALTER FUNCTION function_with_argtypes DEPENDS ON EXTENSION name
+			ALTER FUNCTION function_with_argtypes opt_no DEPENDS ON EXTENSION name
 				{
 					AlterObjectDependsStmt *n = makeNode(AlterObjectDependsStmt);
 					n->objectType = OBJECT_FUNCTION;
 					n->object = (Node *) $3;
-					n->extname = makeString($7);
+					n->extname = makeString($8);
+					n->remove = $4;
 					$$ = (Node *)n;
 				}
-			| ALTER PROCEDURE function_with_argtypes DEPENDS ON EXTENSION name
+			| ALTER PROCEDURE function_with_argtypes opt_no DEPENDS ON EXTENSION name
 				{
 					AlterObjectDependsStmt *n = makeNode(AlterObjectDependsStmt);
 					n->objectType = OBJECT_PROCEDURE;
 					n->object = (Node *) $3;
-					n->extname = makeString($7);
+					n->extname = makeString($8);
+					n->remove = $4;
 					$$ = (Node *)n;
 				}
-			| ALTER ROUTINE function_with_argtypes DEPENDS ON EXTENSION name
+			| ALTER ROUTINE function_with_argtypes opt_no DEPENDS ON EXTENSION name
 				{
 					AlterObjectDependsStmt *n = makeNode(AlterObjectDependsStmt);
 					n->objectType = OBJECT_ROUTINE;
 					n->object = (Node *) $3;
-					n->extname = makeString($7);
+					n->extname = makeString($8);
+					n->remove = $4;
 					$$ = (Node *)n;
 				}
-			| ALTER TRIGGER name ON qualified_name DEPENDS ON EXTENSION name
+			| ALTER TRIGGER name ON qualified_name opt_no DEPENDS ON EXTENSION name
 				{
 					AlterObjectDependsStmt *n = makeNode(AlterObjectDependsStmt);
 					n->objectType = OBJECT_TRIGGER;
 					n->relation = $5;
 					n->object = (Node *) list_make1(makeString($3));
-					n->extname = makeString($9);
+					n->extname = makeString($10);
+					n->remove = $6;
 					$$ = (Node *)n;
 				}
-			| ALTER MATERIALIZED VIEW qualified_name DEPENDS ON EXTENSION name
+			| ALTER MATERIALIZED VIEW qualified_name opt_no DEPENDS ON EXTENSION name
 				{
 					AlterObjectDependsStmt *n = makeNode(AlterObjectDependsStmt);
 					n->objectType = OBJECT_MATVIEW;
 					n->relation = $4;
-					n->extname = makeString($8);
+					n->extname = makeString($9);
+					n->remove = $5;
 					$$ = (Node *)n;
 				}
-			| ALTER INDEX qualified_name DEPENDS ON EXTENSION name
+			| ALTER INDEX qualified_name opt_no DEPENDS ON EXTENSION name
 				{
 					AlterObjectDependsStmt *n = makeNode(AlterObjectDependsStmt);
 					n->objectType = OBJECT_INDEX;
 					n->relation = $3;
-					n->extname = makeString($7);
+					n->extname = makeString($8);
+					n->remove = $4;
 					$$ = (Node *)n;
 				}
 		;
 
+opt_no:		NO				{ $$ = true; }
+			| /* EMPTY */	{ $$ = false;	}
+		;
+
 /*****************************************************************************
  *
  * ALTER THING name SET SCHEMA name

src/include/catalog/dependency.h

@@ -196,6 +196,10 @@ extern long deleteDependencyRecordsFor(Oid classId, Oid objectId,
 extern long deleteDependencyRecordsForClass(Oid classId, Oid objectId,
 											Oid refclassId, char deptype);
 
+extern long deleteDependencyRecordsForSpecific(Oid classId, Oid objectId,
+											   char deptype,
+											   Oid refclassId, Oid refobjectId);
+
 extern long changeDependencyFor(Oid classId, Oid objectId,
 								Oid refClassId, Oid oldRefObjectId,
 								Oid newRefObjectId);

src/include/nodes/parsenodes.h

@@ -2936,6 +2936,7 @@ typedef struct AlterObjectDependsStmt
 	RangeVar   *relation;		/* in case a table is involved */
 	Node	   *object;			/* name of the object */
 	Value	   *extname;		/* extension name */
+	bool		remove;			/* set true to remove dep rather than add */
 } AlterObjectDependsStmt;
 
 /* ----------------------

src/test/modules/test_extensions/expected/test_extdepend.out

@@ -150,5 +150,39 @@ SELECT deptype, i.*
 (0 rows)
 
 DROP TABLE a;
+RESET search_path;
 DROP SCHEMA test_ext CASCADE;
 NOTICE:  drop cascades to extension test_ext5
+-- Fourth test: we can mark the objects as dependent, then unmark; then the
+-- drop of the extension does nothing
+SELECT * FROM test_extdep_commands \gexec
+ CREATE SCHEMA test_ext
+ CREATE EXTENSION test_ext5 SCHEMA test_ext
+ SET search_path TO test_ext
+ CREATE TABLE a (a1 int)
+
+ CREATE FUNCTION b() RETURNS TRIGGER LANGUAGE plpgsql AS
+   $$ BEGIN NEW.a1 := NEW.a1 + 42; RETURN NEW; END; $$
+ ALTER FUNCTION b() DEPENDS ON EXTENSION test_ext5
+
+ CREATE TRIGGER c BEFORE INSERT ON a FOR EACH ROW EXECUTE PROCEDURE b()
+ ALTER TRIGGER c ON a DEPENDS ON EXTENSION test_ext5
+
+ CREATE MATERIALIZED VIEW d AS SELECT * FROM a
+ ALTER MATERIALIZED VIEW d DEPENDS ON EXTENSION test_ext5
+
+ CREATE INDEX e ON a (a1)
+ ALTER INDEX e DEPENDS ON EXTENSION test_ext5
+ RESET search_path
+SET search_path TO test_ext;
+ALTER FUNCTION b() NO DEPENDS ON EXTENSION test_ext5;
+ALTER TRIGGER c ON a NO DEPENDS ON EXTENSION test_ext5;
+ALTER MATERIALIZED VIEW d NO DEPENDS ON EXTENSION test_ext5;
+ALTER INDEX e NO DEPENDS ON EXTENSION test_ext5;
+DROP EXTENSION test_ext5;
+DROP TRIGGER c ON a;
+DROP FUNCTION b();
+DROP MATERIALIZED VIEW d;
+DROP INDEX e;
+DROP SCHEMA test_ext CASCADE;
+NOTICE:  drop cascades to table a

src/test/modules/test_extensions/sql/test_extdepend.sql

@@ -70,6 +70,21 @@ SELECT deptype, i.*
         refobjid=(SELECT oid FROM pg_extension WHERE extname='test_ext5'))
 	OR (refclassid='pg_class'::regclass AND refobjid='test_ext.a'::regclass)
    AND NOT deptype IN ('i', 'a');
-
 DROP TABLE a;
+RESET search_path;
+DROP SCHEMA test_ext CASCADE;
+
+-- Fourth test: we can mark the objects as dependent, then unmark; then the
+-- drop of the extension does nothing
+SELECT * FROM test_extdep_commands \gexec
+SET search_path TO test_ext;
+ALTER FUNCTION b() NO DEPENDS ON EXTENSION test_ext5;
+ALTER TRIGGER c ON a NO DEPENDS ON EXTENSION test_ext5;
+ALTER MATERIALIZED VIEW d NO DEPENDS ON EXTENSION test_ext5;
+ALTER INDEX e NO DEPENDS ON EXTENSION test_ext5;
+DROP EXTENSION test_ext5;
+DROP TRIGGER c ON a;
+DROP FUNCTION b();
+DROP MATERIALIZED VIEW d;
+DROP INDEX e;
 DROP SCHEMA test_ext CASCADE;