Support ALTER THING .. DEPENDS ON EXTENSION

This introduces a new dependency type which marks an object as depending
on an extension, such that if the extension is dropped, the object
automatically goes away; and also, if the database is dumped, the object
is included in the dump output.  Currently the grammar supports this for
indexes, triggers, materialized views and functions only, although the
utility code is generic so adding support for more object types is a
matter of touching the parser rules only.

Author: Abhijit Menon-Sen
Reviewed-by: Alexander Korotkov, Álvaro Herrera
Discussion: http://www.postgresql.org/message-id/20160115062649.GA5068@toroid.org

Author: alvherre

doc/src/sgml/catalogs.sgml

@@ -2876,6 +2876,19 @@
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><symbol>DEPENDENCY_AUTO_EXTENSION</> (<literal>x</>)</term>
+     <listitem>
+      <para>
+       The dependent object is not a member of the extension that is the
+       referenced object (and so should not be ignored by pg_dump), but
+       cannot function without it and should be dropped when the
+       extension itself is. The dependent object may be dropped on its
+       own as well.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><symbol>DEPENDENCY_PIN</> (<literal>p</>)</term>
      <listitem>

doc/src/sgml/ref/alter_function.sgml

@@ -29,6 +29,8 @@ ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="paramet
     OWNER TO { <replaceable>new_owner</replaceable> | CURRENT_USER | SESSION_USER }
 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>
 
 <phrase>where <replaceable class="PARAMETER">action</replaceable> is one of:</phrase>
 
@@ -148,6 +150,15 @@ ALTER FUNCTION <replaceable>name</replaceable> ( [ [ <replaceable class="paramet
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><replaceable class="parameter">extension_name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the extension that the function is to depend on.
+     </para>
+    </listitem>
+   </varlistentry>
+
     <varlistentry>
      <term><literal>CALLED ON NULL INPUT</literal></term>
      <term><literal>RETURNS NULL ON NULL INPUT</literal></term>
@@ -299,6 +310,15 @@ ALTER FUNCTION sqrt(integer) SET SCHEMA maths;
 </programlisting>
   </para>
 
+  <para>
+   To mark the function <literal>sqrt</literal> for type
+   <type>integer</type> as being dependent on the extension
+   <literal>mathlib</literal>:
+<programlisting>
+ALTER FUNCTION sqrt(integer) DEPENDS ON EXTENSION mathlib;
+</programlisting>
+  </para>
+
   <para>
    To adjust the search path that is automatically set for a function:
 <programlisting>

doc/src/sgml/ref/alter_index.sgml

@@ -23,6 +23,7 @@ PostgreSQL documentation
 <synopsis>
 ALTER INDEX [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> RENAME TO <replaceable class="PARAMETER">new_name</replaceable>
 ALTER INDEX [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> SET TABLESPACE <replaceable class="PARAMETER">tablespace_name</replaceable>
+ALTER INDEX <replaceable class="PARAMETER">name</replaceable> DEPENDS ON EXTENSION <replaceable class="PARAMETER">extension_name</replaceable>
 ALTER INDEX [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> SET ( <replaceable class="PARAMETER">storage_parameter</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )
 ALTER INDEX [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> RESET ( <replaceable class="PARAMETER">storage_parameter</replaceable> [, ... ] )
 ALTER INDEX ALL IN TABLESPACE <replaceable class="PARAMETER">name</replaceable> [ OWNED BY <replaceable class="PARAMETER">role_name</replaceable> [, ... ] ]
@@ -82,6 +83,16 @@ ALTER INDEX ALL IN TABLESPACE <replaceable class="PARAMETER">name</replaceable>
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>DEPENDS ON EXTENSION</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.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>SET ( <replaceable class="PARAMETER">storage_parameter</replaceable> = <replaceable class="PARAMETER">value</replaceable> [, ... ] )</literal></term>
     <listitem>
@@ -147,6 +158,15 @@ ALTER INDEX ALL IN TABLESPACE <replaceable class="PARAMETER">name</replaceable>
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><replaceable class="PARAMETER">extension_name</replaceable></term>
+      <listitem>
+       <para>
+        The name of the extension that the index is to depend on.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><replaceable class="PARAMETER">storage_parameter</replaceable></term>
       <listitem>

doc/src/sgml/ref/alter_materialized_view.sgml

@@ -23,6 +23,8 @@ PostgreSQL documentation
 <synopsis>
 ALTER MATERIALIZED VIEW [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
     <replaceable class="PARAMETER">action</replaceable> [, ... ]
+ALTER MATERIALIZED VIEW <replaceable class="PARAMETER">name</replaceable>
+    DEPENDS ON EXTENSION <replaceable class="PARAMETER">extension_name</replaceable>
 ALTER MATERIALIZED VIEW [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
     RENAME [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> TO <replaceable class="PARAMETER">new_column_name</replaceable>
 ALTER MATERIALIZED VIEW [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
@@ -67,6 +69,12 @@ 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
@@ -99,6 +107,15 @@ ALTER MATERIALIZED VIEW ALL IN TABLESPACE <replaceable class="parameter">name</r
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><replaceable class="PARAMETER">extension_name</replaceable></term>
+     <listitem>
+      <para>
+       The name of the extension that the materialized view is to depend on.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><replaceable class="PARAMETER">new_column_name</replaceable></term>
      <listitem>

doc/src/sgml/ref/alter_trigger.sgml

@@ -22,6 +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>
 </synopsis>
  </refsynopsisdiv>
 
@@ -32,7 +33,9 @@ ALTER TRIGGER <replaceable class="PARAMETER">name</replaceable> ON <replaceable
    <command>ALTER TRIGGER</command> changes properties of an existing
    trigger.  The <literal>RENAME</literal> clause changes the name of
    the given trigger without otherwise changing the trigger
-   definition.
+   definition.  The <literal>DEPENDS ON EXTENSION</literal> clause marks
+   the trigger as dependent on an extension, such that if the extension is
+   dropped, the trigger will automatically be dropped as well.
   </para>
 
   <para>
@@ -70,6 +73,15 @@ ALTER TRIGGER <replaceable class="PARAMETER">name</replaceable> ON <replaceable
      </para>
     </listitem>
    </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="PARAMETER">extension_name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the extension that the trigger is to depend on.
+     </para>
+    </listitem>
+   </varlistentry>
   </variablelist>
  </refsect1>
 
@@ -92,6 +104,12 @@ ALTER TRIGGER <replaceable class="PARAMETER">name</replaceable> ON <replaceable
    To rename an existing trigger:
 <programlisting>
 ALTER TRIGGER emp_stamp ON emp RENAME TO emp_track_chgs;
+</programlisting></para>
+
+  <para>
+   To mark a trigger as being dependent on an extension:
+<programlisting>
+ALTER TRIGGER emp_stamp ON emp DEPENDS ON EXTENSION emplib;
 </programlisting></para>
  </refsect1>
 

src/backend/catalog/dependency.c

@@ -589,6 +589,7 @@ findDependentObjects(const ObjectAddress *object,
 		{
 			case DEPENDENCY_NORMAL:
 			case DEPENDENCY_AUTO:
+			case DEPENDENCY_AUTO_EXTENSION:
 				/* no problem */
 				break;
 			case DEPENDENCY_INTERNAL:
@@ -788,6 +789,7 @@ findDependentObjects(const ObjectAddress *object,
 				subflags = DEPFLAG_NORMAL;
 				break;
 			case DEPENDENCY_AUTO:
+			case DEPENDENCY_AUTO_EXTENSION:
 				subflags = DEPFLAG_AUTO;
 				break;
 			case DEPENDENCY_INTERNAL:

src/backend/catalog/objectaddress.c

@@ -1015,6 +1015,31 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 	return address;
 }
 
+/*
+ * Return an ObjectAddress based on a RangeVar and an object name. The
+ * name of the relation identified by the RangeVar is prepended to the
+ * (possibly empty) list passed in as objname. This is useful to find
+ * the ObjectAddress of objects that depend on a relation. All other
+ * considerations are exactly as for get_object_address above.
+ */
+ObjectAddress
+get_object_address_rv(ObjectType objtype, RangeVar *rel, List *objname,
+					  List *objargs, Relation *relp, LOCKMODE lockmode,
+					  bool missing_ok)
+{
+	if (rel)
+	{
+		objname = lcons(makeString(rel->relname), objname);
+		if (rel->schemaname)
+			objname = lcons(makeString(rel->schemaname), objname);
+		if (rel->catalogname)
+			objname = lcons(makeString(rel->catalogname), objname);
+	}
+
+	return get_object_address(objtype, objname, objargs,
+							  relp, lockmode, missing_ok);
+}
+
 /*
  * Find an ObjectAddress for a type of object that is identified by an
  * unqualified name.

src/backend/commands/alter.c

@@ -390,6 +390,43 @@ ExecRenameStmt(RenameStmt *stmt)
 	}
 }
 
+/*
+ * Executes an ALTER OBJECT / 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
+ * altered object now depends on.
+ */
+ObjectAddress
+ExecAlterObjectDependsStmt(AlterObjectDependsStmt *stmt, ObjectAddress *refAddress)
+{
+	ObjectAddress	address;
+	ObjectAddress	refAddr;
+	Relation		rel;
+
+	address =
+		get_object_address_rv(stmt->objectType, stmt->relation, stmt->objname,
+							  stmt->objargs, &rel, AccessExclusiveLock, false);
+
+	/*
+	 * If a relation was involved, it would have been opened and locked.
+	 * We don't need the relation here, but we'll retain the lock until
+	 * commit.
+	 */
+	if (rel)
+		heap_close(rel, NoLock);
+
+	refAddr = get_object_address(OBJECT_EXTENSION, list_make1(stmt->extname),
+								 NULL, &rel, AccessExclusiveLock, false);
+	Assert(rel == NULL);
+	if (refAddress)
+		*refAddress = refAddr;
+
+	recordDependencyOn(&address, refAddress, DEPENDENCY_AUTO_EXTENSION);
+
+	return address;
+}
+
 /*
  * Executes an ALTER OBJECT / SET SCHEMA statement.  Based on the object
  * type, the function appropriate to that type is executed.

src/backend/nodes/copyfuncs.c

@@ -3204,6 +3204,20 @@ _copyRenameStmt(const RenameStmt *from)
 	return newnode;
 }
 
+static AlterObjectDependsStmt *
+_copyAlterObjectDependsStmt(const AlterObjectDependsStmt *from)
+{
+	AlterObjectDependsStmt *newnode = makeNode(AlterObjectDependsStmt);
+
+	COPY_SCALAR_FIELD(objectType);
+	COPY_NODE_FIELD(relation);
+	COPY_NODE_FIELD(objname);
+	COPY_NODE_FIELD(objargs);
+	COPY_NODE_FIELD(extname);
+
+	return newnode;
+}
+
 static AlterObjectSchemaStmt *
 _copyAlterObjectSchemaStmt(const AlterObjectSchemaStmt *from)
 {
@@ -4682,6 +4696,9 @@ copyObject(const void *from)
 		case T_RenameStmt:
 			retval = _copyRenameStmt(from);
 			break;
+		case T_AlterObjectDependsStmt:
+			retval = _copyAlterObjectDependsStmt(from);
+			break;
 		case T_AlterObjectSchemaStmt:
 			retval = _copyAlterObjectSchemaStmt(from);
 			break;

src/backend/nodes/equalfuncs.c

@@ -1325,6 +1325,18 @@ _equalRenameStmt(const RenameStmt *a, const RenameStmt *b)
 	return true;
 }
 
+static bool
+_equalAlterObjectDependsStmt(const AlterObjectDependsStmt *a, const AlterObjectDependsStmt *b)
+{
+	COMPARE_SCALAR_FIELD(objectType);
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_NODE_FIELD(objname);
+	COMPARE_NODE_FIELD(objargs);
+	COMPARE_NODE_FIELD(extname);
+
+	return true;
+}
+
 static bool
 _equalAlterObjectSchemaStmt(const AlterObjectSchemaStmt *a, const AlterObjectSchemaStmt *b)
 {
@@ -3004,6 +3016,9 @@ equal(const void *a, const void *b)
 		case T_RenameStmt:
 			retval = _equalRenameStmt(a, b);
 			break;
+		case T_AlterObjectDependsStmt:
+			retval = _equalAlterObjectDependsStmt(a, b);
+			break;
 		case T_AlterObjectSchemaStmt:
 			retval = _equalAlterObjectSchemaStmt(a, b);
 			break;