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 978e011fe5e25a5d0496b4b1003e5c6d807122d6..63741b31c427608b3be1eff5c126e8e059d1e3fa 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 acb580df8804053528a7d8e86ba7b61979f51f73..6c197171dc3acfb47828832b15bc26ad079a41bb 100644 (file)
--- a/src/backend/commands/alter.c
+++ b/src/backend/commands/alter.c
@@ -425,6 +425,7 @@ 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,
@@ -454,7 +455,11 @@ 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 b7502722a275131ca9c3c282a1ea701c618b64c3..f9b5d29674d18769f5f5a6a25587852710d9f3bf 100644 (file)
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -237,6 +237,7 @@ 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