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Commit3acf422

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Revise mechanism for getting rid of temp tables at backend shutdown.
Instead of grovelling through pg_class to find them, make use of thehandy dandy dependency mechanism: just delete everything that dependson our temp schema. Unlike the pg_class scan, the dependency mechanismis smart enough to delete things in an order that doesn't fall foul ofany dependency restrictions. Fixes problem reported by David Heggie:a temp table with a serial column may cause a backend FATAL exit atshutdown time, if it chances to try to delete the temp sequence first.
1 parent00f1a41 commit3acf422

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3 files changed

+157
-88
lines changed

3 files changed

+157
-88
lines changed

‎src/backend/catalog/dependency.c‎

Lines changed: 144 additions & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.19 2003/01/10 21:08:07 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.20 2003/02/07 01:33:06 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -100,6 +100,11 @@ static bool recursiveDeletion(const ObjectAddress *object,
100100
constObjectAddress*callingObject,
101101
ObjectAddresses*oktodelete,
102102
RelationdepRel);
103+
staticbooldeleteDependentObjects(constObjectAddress*object,
104+
constchar*objDescription,
105+
DropBehaviorbehavior,
106+
ObjectAddresses*oktodelete,
107+
RelationdepRel);
103108
staticvoiddoDeletion(constObjectAddress*object);
104109
staticboolfind_expr_references_walker(Node*node,
105110
find_expr_references_context*context);
@@ -172,6 +177,64 @@ performDeletion(const ObjectAddress *object,
172177
}
173178

174179

180+
/*
181+
* deleteWhatDependsOn: attempt to drop everything that depends on the
182+
* specified object, though not the object itself. Behavior is always
183+
* CASCADE.
184+
*
185+
* This is currently used only to clean out the contents of a schema
186+
* (namespace): the passed object is a namespace.
187+
*/
188+
void
189+
deleteWhatDependsOn(constObjectAddress*object)
190+
{
191+
char*objDescription;
192+
RelationdepRel;
193+
ObjectAddressesoktodelete;
194+
195+
/*
196+
* Get object description for possible use in failure messages
197+
*/
198+
objDescription=getObjectDescription(object);
199+
200+
/*
201+
* We save some cycles by opening pg_depend just once and passing the
202+
* Relation pointer down to all the recursive deletion steps.
203+
*/
204+
depRel=heap_openr(DependRelationName,RowExclusiveLock);
205+
206+
/*
207+
* Construct a list of objects that are reachable by AUTO or INTERNAL
208+
* dependencies from the target object. These should be deleted silently,
209+
* even if the actual deletion pass first reaches one of them via a
210+
* non-auto dependency.
211+
*/
212+
init_object_addresses(&oktodelete);
213+
214+
findAutoDeletableObjects(object,&oktodelete,depRel);
215+
216+
/*
217+
* Now invoke only step 2 of recursiveDeletion: just recurse to the
218+
* stuff dependent on the given object.
219+
*/
220+
if (!deleteDependentObjects(object,objDescription,
221+
DROP_CASCADE,&oktodelete,depRel))
222+
elog(ERROR,"Failed to drop all objects depending on %s",
223+
objDescription);
224+
225+
/*
226+
* We do not need CommandCounterIncrement here, since if step 2 did
227+
* anything then each recursive call will have ended with one.
228+
*/
229+
230+
term_object_addresses(&oktodelete);
231+
232+
heap_close(depRel,RowExclusiveLock);
233+
234+
pfree(objDescription);
235+
}
236+
237+
175238
/*
176239
* findAutoDeletableObjects: find all objects that are reachable by AUTO or
177240
* INTERNAL dependency paths from the given object. Add them all to the
@@ -476,22 +539,90 @@ recursiveDeletion(const ObjectAddress *object,
476539

477540
/*
478541
* Step 2: scan pg_depend records that link to this object, showing
479-
* the things that depend on it. Recursively delete those things. (We
480-
* don't delete the pg_depend records here, as the recursive call will
481-
* do that.) Note it's important to delete the dependent objects
542+
* the things that depend on it. Recursively delete those things.
543+
* Note it's important to delete the dependent objects
482544
* before the referenced one, since the deletion routines might do
483545
* things like try to update the pg_class record when deleting a check
484546
* constraint.
485-
*
486-
* Again, when dropping a whole object (subId = 0), find pg_depend
487-
* records for its sub-objects too.
488-
*
489-
* NOTE: because we are using SnapshotNow, if a recursive call deletes
490-
* any pg_depend tuples that our scan hasn't yet visited, we will not
491-
* see them as good when we do visit them.This is essential for
492-
* correct behavior if there are multiple dependency paths between two
493-
* objects --- else we might try to delete an already-deleted object.
494547
*/
548+
if (!deleteDependentObjects(object,objDescription,
549+
behavior,oktodelete,depRel))
550+
ok= false;
551+
552+
/*
553+
* We do not need CommandCounterIncrement here, since if step 2 did
554+
* anything then each recursive call will have ended with one.
555+
*/
556+
557+
/*
558+
* Step 3: delete the object itself.
559+
*/
560+
doDeletion(object);
561+
562+
/*
563+
* Delete any comments associated with this object. (This is a
564+
* convenient place to do it instead of having every object type know
565+
* to do it.)
566+
*/
567+
DeleteComments(object->objectId,object->classId,object->objectSubId);
568+
569+
/*
570+
* CommandCounterIncrement here to ensure that preceding changes are
571+
* all visible.
572+
*/
573+
CommandCounterIncrement();
574+
575+
/*
576+
* And we're done!
577+
*/
578+
pfree(objDescription);
579+
580+
returnok;
581+
}
582+
583+
584+
/*
585+
* deleteDependentObjects - find and delete objects that depend on 'object'
586+
*
587+
* Scan pg_depend records that link to the given object, showing
588+
* the things that depend on it. Recursively delete those things. (We
589+
* don't delete the pg_depend records here, as the recursive call will
590+
* do that.) Note it's important to delete the dependent objects
591+
* before the referenced one, since the deletion routines might do
592+
* things like try to update the pg_class record when deleting a check
593+
* constraint.
594+
*
595+
* When dropping a whole object (subId = 0), find pg_depend records for
596+
* its sub-objects too.
597+
*
598+
*object: the object to find dependencies on
599+
*objDescription: description of object (only used for error messages)
600+
*behavior: desired drop behavior
601+
*oktodelete: stuff that's AUTO-deletable
602+
*depRel: already opened pg_depend relation
603+
*
604+
* Returns TRUE if all is well, false if any problem found.
605+
*
606+
* NOTE: because we are using SnapshotNow, if a recursive call deletes
607+
* any pg_depend tuples that our scan hasn't yet visited, we will not
608+
* see them as good when we do visit them.This is essential for
609+
* correct behavior if there are multiple dependency paths between two
610+
* objects --- else we might try to delete an already-deleted object.
611+
*/
612+
staticbool
613+
deleteDependentObjects(constObjectAddress*object,
614+
constchar*objDescription,
615+
DropBehaviorbehavior,
616+
ObjectAddresses*oktodelete,
617+
RelationdepRel)
618+
{
619+
boolok= true;
620+
ScanKeyDatakey[3];
621+
intnkeys;
622+
SysScanDescscan;
623+
HeapTupletup;
624+
ObjectAddressotherObject;
625+
495626
ScanKeyEntryInitialize(&key[0],0x0,
496627
Anum_pg_depend_refclassid,F_OIDEQ,
497628
ObjectIdGetDatum(object->classId));
@@ -581,34 +712,6 @@ recursiveDeletion(const ObjectAddress *object,
581712

582713
systable_endscan(scan);
583714

584-
/*
585-
* We do not need CommandCounterIncrement here, since if step 2 did
586-
* anything then each recursive call will have ended with one.
587-
*/
588-
589-
/*
590-
* Step 3: delete the object itself.
591-
*/
592-
doDeletion(object);
593-
594-
/*
595-
* Delete any comments associated with this object. (This is a
596-
* convenient place to do it instead of having every object type know
597-
* to do it.)
598-
*/
599-
DeleteComments(object->objectId,object->classId,object->objectSubId);
600-
601-
/*
602-
* CommandCounterIncrement here to ensure that preceding changes are
603-
* all visible.
604-
*/
605-
CommandCounterIncrement();
606-
607-
/*
608-
* And we're done!
609-
*/
610-
pfree(objDescription);
611-
612715
returnok;
613716
}
614717

‎src/backend/catalog/namespace.c‎

Lines changed: 10 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -13,21 +13,17 @@
1313
* Portions Copyright (c) 1994, Regents of the University of California
1414
*
1515
* IDENTIFICATION
16-
* $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.45 2003/01/12 18:19:37 petere Exp $
16+
* $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.46 2003/02/07 01:33:06 tgl Exp $
1717
*
1818
*-------------------------------------------------------------------------
1919
*/
2020
#include"postgres.h"
2121

22-
#include"access/heapam.h"
2322
#include"access/xact.h"
24-
#include"catalog/catalog.h"
2523
#include"catalog/catname.h"
2624
#include"catalog/dependency.h"
27-
#include"catalog/heap.h"
2825
#include"catalog/namespace.h"
2926
#include"catalog/pg_conversion.h"
30-
#include"catalog/pg_inherits.h"
3127
#include"catalog/pg_namespace.h"
3228
#include"catalog/pg_opclass.h"
3329
#include"catalog/pg_operator.h"
@@ -42,10 +38,9 @@
4238
#include"utils/acl.h"
4339
#include"utils/builtins.h"
4440
#include"utils/catcache.h"
45-
#include"utils/fmgroids.h"
46-
#include"utils/guc.h"
4741
#include"utils/inval.h"
4842
#include"utils/lsyscache.h"
43+
#include"utils/memutils.h"
4944
#include"utils/syscache.h"
5045

5146

@@ -1691,50 +1686,19 @@ AtEOXact_Namespace(bool isCommit)
16911686
staticvoid
16921687
RemoveTempRelations(OidtempNamespaceId)
16931688
{
1694-
Relationpgclass;
1695-
HeapScanDescscan;
1696-
HeapTupletuple;
1697-
ScanKeyDatakey;
16981689
ObjectAddressobject;
16991690

17001691
/*
1701-
* Scan pg_class to find all the relations in the target namespace.
1702-
* Ignore indexes, though, on the assumption that they'll go away when
1703-
* their tables are deleted.
1704-
*
1705-
* NOTE: if there are deletion constraints between temp relations, then
1706-
* our CASCADE delete call may cause as-yet-unvisited objects to go
1707-
* away. This is okay because we are using SnapshotNow; when the scan
1708-
* does reach those pg_class tuples, they'll be ignored as already
1709-
* deleted.
1692+
* We want to get rid of everything in the target namespace, but not
1693+
* the namespace itself (deleting it only to recreate it later would be
1694+
* a waste of cycles). We do this by finding everything that has a
1695+
* dependency on the namespace.
17101696
*/
1711-
ScanKeyEntryInitialize(&key,0x0,
1712-
Anum_pg_class_relnamespace,
1713-
F_OIDEQ,
1714-
ObjectIdGetDatum(tempNamespaceId));
1715-
1716-
pgclass=heap_openr(RelationRelationName,AccessShareLock);
1717-
scan=heap_beginscan(pgclass,SnapshotNow,1,&key);
1718-
1719-
while ((tuple=heap_getnext(scan,ForwardScanDirection))!=NULL)
1720-
{
1721-
switch (((Form_pg_class)GETSTRUCT(tuple))->relkind)
1722-
{
1723-
caseRELKIND_RELATION:
1724-
caseRELKIND_SEQUENCE:
1725-
caseRELKIND_VIEW:
1726-
object.classId=RelOid_pg_class;
1727-
object.objectId=HeapTupleGetOid(tuple);
1728-
object.objectSubId=0;
1729-
performDeletion(&object,DROP_CASCADE);
1730-
break;
1731-
default:
1732-
break;
1733-
}
1734-
}
1697+
object.classId=get_system_catalog_relid(NamespaceRelationName);
1698+
object.objectId=tempNamespaceId;
1699+
object.objectSubId=0;
17351700

1736-
heap_endscan(scan);
1737-
heap_close(pgclass,AccessShareLock);
1701+
deleteWhatDependsOn(&object);
17381702
}
17391703

17401704
/*

‎src/include/catalog/dependency.h‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $Id: dependency.h,v 1.5 2002/09/04 20:31:37 momjian Exp $
10+
* $Id: dependency.h,v 1.6 2003/02/07 01:33:06 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -84,6 +84,8 @@ typedef struct ObjectAddress
8484
externvoidperformDeletion(constObjectAddress*object,
8585
DropBehaviorbehavior);
8686

87+
externvoiddeleteWhatDependsOn(constObjectAddress*object);
88+
8789
externvoidrecordDependencyOnExpr(constObjectAddress*depender,
8890
Node*expr,List*rtable,
8991
DependencyTypebehavior);

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