Avoid duplicates in ALTER ... DEPENDS ON EXTENSION

If the command is attempted for an extension that the object already
depends on, silently do nothing.

In particular, this means that if a database containing multiple such
entries is dumped, the restore will silently do the right thing and
record just the first one.  (At least, in a world where pg_dump does
dump such entries -- which it doesn't currently, but it will.)

Backpatch to 9.6, where this kind of dependency was introduced.

Reviewed-by: Ibrar Ahmed, Tom Lane (offlist)
Discussion: https://postgr.es/m/20200217225333.GA30974@alvherre.pgsql

diff --git a/src/backend/catalog/pg_depend.c b/src/backend/catalog/pg_depend.c
index c6f75c5aa8f2c23d91aa3f6024dcdfc4ab20e3d8..a9da621f5a6c97e1a70329236753438ae8f9840a 100644 (file)
--- a/src/backend/catalog/pg_depend.c
+++ b/src/backend/catalog/pg_depend.c
@@ -485,6 +485,49 @@ getExtensionOfObject(Oid classId, Oid objectId)
    return result;
 }
 
+/*
+ * Return (possibly NIL) list of extensions that the given object depends on
+ * in DEPENDENCY_AUTO_EXTENSION mode.
+ */
+List *
+getAutoExtensionsOfObject(Oid classId, Oid objectId)
+{
+   List       *result = NIL;
+   Relation    depRel;
+   ScanKeyData key[2];
+   SysScanDesc scan;
+   HeapTuple   tup;
+
+   depRel = heap_open(DependRelationId, AccessShareLock);
+
+   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 == ExtensionRelationId &&
+           depform->deptype == DEPENDENCY_AUTO_EXTENSION)
+           result = lappend_oid(result, depform->refobjid);
+   }
+
+   systable_endscan(scan);
+
+   heap_close(depRel, AccessShareLock);
+
+   return result;
+}
+
 /*
  * Detect whether a sequence is marked as "owned" by a column
  *

diff --git a/src/backend/commands/alter.c b/src/backend/commands/alter.c
index 302f496b7d97a856bbe6ef608a7ee811af7994ee..4505ab013044a9551e08b040bc410fe245f3027e 100644 (file)
--- a/src/backend/commands/alter.c
+++ b/src/backend/commands/alter.c
@@ -427,6 +427,7 @@ 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,
@@ -456,7 +457,11 @@ ExecAlterObjectDependsStmt(AlterObjectDependsStmt *stmt, ObjectAddress *refAddre
    if (refAddress)
        *refAddress = refAddr;
 
-   recordDependencyOn(&address, &refAddr, DEPENDENCY_AUTO_EXTENSION);
+   /* Avoid duplicates */
+   currexts = getAutoExtensionsOfObject(address.classId,
+                                        address.objectId);
+   if (!list_member_oid(currexts, refAddr.objectId))
+       recordDependencyOn(&address, &refAddr, DEPENDENCY_AUTO_EXTENSION);
 
    return address;
 }

diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 184215a367d95a0066b5664325a9aef5455d9c0c..ff06c9aa77788ef05a38e4d53adfa7b333541f6b 100644 (file)
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -252,6 +252,7 @@ extern long changeDependencyFor(Oid classId, Oid objectId,
                    Oid newRefObjectId);
 
 extern Oid getExtensionOfObject(Oid classId, Oid objectId);
+extern List *getAutoExtensionsOfObject(Oid classId, Oid objectId);
 
 extern bool sequenceIsOwned(Oid seqId, char deptype, Oid *tableId, int32 *colId);
 extern List *getOwnedSequences(Oid relid, AttrNumber attnum);

diff --git a/src/test/modules/test_extensions/expected/test_extdepend.out b/src/test/modules/test_extensions/expected/test_extdepend.out
index 11e441ddd37794acfa07cb6c35c9b929a2bcb938..40533e90de30e0ece611f297319b3f345fff98c7 100644 (file)
--- a/src/test/modules/test_extensions/expected/test_extdepend.out
+++ b/src/test/modules/test_extensions/expected/test_extdepend.out
@@ -47,6 +47,8 @@ SELECT * FROM test_extdep_commands \gexec
  CREATE INDEX e ON a (a1)
  ALTER INDEX e DEPENDS ON EXTENSION test_ext5
  RESET search_path
+-- A dependent object made dependent again has no effect
+ALTER FUNCTION test_ext.b() DEPENDS ON EXTENSION test_ext5;
 -- make sure we have the right dependencies on the extension
 SELECT deptype, p.*
   FROM pg_depend, pg_identify_object(classid, objid, objsubid) AS p

diff --git a/src/test/modules/test_extensions/sql/test_extdepend.sql b/src/test/modules/test_extensions/sql/test_extdepend.sql
index cf44145dcb343b35515d7accde3e98134f9c0d8e..cc170ab70975c5b68ce0f8ef0f56417cfe7d730c 100644 (file)
--- a/src/test/modules/test_extensions/sql/test_extdepend.sql
+++ b/src/test/modules/test_extensions/sql/test_extdepend.sql
@@ -27,6 +27,8 @@ COPY test_extdep_commands FROM stdin;
 SELECT * FROM test_extdep_commands;
 -- First, test that dependent objects go away when the extension is dropped.
 SELECT * FROM test_extdep_commands \gexec
+-- A dependent object made dependent again has no effect
+ALTER FUNCTION test_ext.b() DEPENDS ON EXTENSION test_ext5;
 -- make sure we have the right dependencies on the extension
 SELECT deptype, p.*
   FROM pg_depend, pg_identify_object(classid, objid, objsubid) AS p