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Commitc5d6d5b

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Improve parallel restore's ability to cope with selective restore (-L option).
The original coding tended to break down in the face of modified restoreorders, as shown in bug #5626 from Albert Ullrich, because it would flip overinto parallel-restore operation too soon. That causes problems because wedon't have sufficient dependency information in dump archives to allow safeparallel processing of SECTION_PRE_DATA items. Even if we did, it's probablyundesirable to allow that to override the commanded restore order.To fix the problem of omitted items causing unexpected changes in restoreorder, tweak SortTocFromFile so that omitted items end up at the head ofthe list not the tail. This ensures that they'll be examined and theirdependencies will be marked satisfied before we get to any interestingitems.In HEAD and 9.0, we can easily change restore_toc_entries_parallel so thatall SECTION_PRE_DATA items are guaranteed to be processed in the initialserial-restore loop, and hence in commanded order. Only DATA and POST_DATAitems are candidates for parallel processing. For them there might bevariations from the commanded order because of parallelism, but we shoulddo it in a safe order thanks to dependencies.In 8.4 it's much harder to make such a guarantee. I settled for notletting the initial loop break out into parallel processing mode ifit sees a DATA/POST_DATA item that's not to be restored; this at leastprevents a non-restorable item from causing premature exit from the loop.This means that 8.4 will be more likely to fail given a badly-ordered -Llist than 9.x, but we don't really promise any such thing will work anyway.
1 parent5abd2d7 commitc5d6d5b

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1 file changed

+38
-19
lines changed

1 file changed

+38
-19
lines changed

‎src/bin/pg_dump/pg_backup_archiver.c

Lines changed: 38 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@
1515
*
1616
*
1717
* IDENTIFICATION
18-
*$PostgreSQL: pgsql/src/bin/pg_dump/pg_backup_archiver.c,v 1.187 2010/07/06 19:18:59 momjian Exp $
18+
*$PostgreSQL: pgsql/src/bin/pg_dump/pg_backup_archiver.c,v 1.188 2010/08/21 13:59:44 tgl Exp $
1919
*
2020
*-------------------------------------------------------------------------
2121
*/
@@ -102,7 +102,7 @@ static bool _tocEntryIsACL(TocEntry *te);
102102
staticvoid_disableTriggersIfNecessary(ArchiveHandle*AH,TocEntry*te,RestoreOptions*ropt);
103103
staticvoid_enableTriggersIfNecessary(ArchiveHandle*AH,TocEntry*te,RestoreOptions*ropt);
104104
staticTocEntry*getTocEntryByDumpId(ArchiveHandle*AH,DumpIdid);
105-
staticvoid_moveAfter(ArchiveHandle*AH,TocEntry*pos,TocEntry*te);
105+
staticvoid_moveBefore(ArchiveHandle*AH,TocEntry*pos,TocEntry*te);
106106
staticint_discoverArchiveFormat(ArchiveHandle*AH);
107107

108108
staticvoiddump_lo_buf(ArchiveHandle*AH);
@@ -995,15 +995,11 @@ SortTocFromFile(Archive *AHX, RestoreOptions *ropt)
995995
char*endptr;
996996
DumpIdid;
997997
TocEntry*te;
998-
TocEntry*tePrev;
999998

1000999
/* Allocate space for the 'wanted' array, and init it */
10011000
ropt->idWanted= (bool*)malloc(sizeof(bool)*AH->maxDumpId);
10021001
memset(ropt->idWanted,0,sizeof(bool)*AH->maxDumpId);
10031002

1004-
/* Set prev entry as head of list */
1005-
tePrev=AH->toc;
1006-
10071003
/* Setup the file */
10081004
fh=fopen(ropt->tocFile,PG_BINARY_R);
10091005
if (!fh)
@@ -1018,7 +1014,7 @@ SortTocFromFile(Archive *AHX, RestoreOptions *ropt)
10181014
cmnt[0]='\0';
10191015

10201016
/* Ignore if all blank */
1021-
if (strspn(buf," \t\r")==strlen(buf))
1017+
if (strspn(buf," \t\r\n")==strlen(buf))
10221018
continue;
10231019

10241020
/* Get an ID, check it's valid and not already seen */
@@ -1036,10 +1032,21 @@ SortTocFromFile(Archive *AHX, RestoreOptions *ropt)
10361032
die_horribly(AH,modulename,"could not find entry for ID %d\n",
10371033
id);
10381034

1035+
/* Mark it wanted */
10391036
ropt->idWanted[id-1]= true;
10401037

1041-
_moveAfter(AH,tePrev,te);
1042-
tePrev=te;
1038+
/*
1039+
* Move each item to the end of the list as it is selected, so that
1040+
* they are placed in the desired order. Any unwanted items will end
1041+
* up at the front of the list, which may seem unintuitive but it's
1042+
* what we need. In an ordinary serial restore that makes no
1043+
* difference, but in a parallel restore we need to mark unrestored
1044+
* items' dependencies as satisfied before we start examining
1045+
* restorable items. Otherwise they could have surprising
1046+
* side-effects on the order in which restorable items actually get
1047+
* restored.
1048+
*/
1049+
_moveBefore(AH,AH->toc,te);
10431050
}
10441051

10451052
if (fclose(fh)!=0)
@@ -1471,33 +1478,37 @@ warn_or_die_horribly(ArchiveHandle *AH,
14711478
va_end(ap);
14721479
}
14731480

1481+
#ifdefNOT_USED
1482+
14741483
staticvoid
14751484
_moveAfter(ArchiveHandle*AH,TocEntry*pos,TocEntry*te)
14761485
{
1486+
/* Unlink te from list */
14771487
te->prev->next=te->next;
14781488
te->next->prev=te->prev;
14791489

1490+
/* and insert it after "pos" */
14801491
te->prev=pos;
14811492
te->next=pos->next;
1482-
14831493
pos->next->prev=te;
14841494
pos->next=te;
14851495
}
14861496

1487-
#ifdefNOT_USED
1497+
#endif
14881498

14891499
staticvoid
14901500
_moveBefore(ArchiveHandle*AH,TocEntry*pos,TocEntry*te)
14911501
{
1502+
/* Unlink te from list */
14921503
te->prev->next=te->next;
14931504
te->next->prev=te->prev;
14941505

1506+
/* and insert it before "pos" */
14951507
te->prev=pos->prev;
14961508
te->next=pos;
14971509
pos->prev->next=te;
14981510
pos->prev=te;
14991511
}
1500-
#endif
15011512

15021513
staticTocEntry*
15031514
getTocEntryByDumpId(ArchiveHandle*AH,DumpIdid)
@@ -3180,13 +3191,16 @@ restore_toc_entries_parallel(ArchiveHandle *AH)
31803191
* Do all the early stuff in a single connection in the parent. There's no
31813192
* great point in running it in parallel, in fact it will actually run
31823193
* faster in a single connection because we avoid all the connection and
3183-
* setup overhead.
3194+
* setup overhead. Also, pg_dump is not currently very good about
3195+
* showing all the dependencies of SECTION_PRE_DATA items, so we do not
3196+
* risk trying to process them out-of-order.
31843197
*/
31853198
for (next_work_item=AH->toc->next;next_work_item!=AH->toc;next_work_item=next_work_item->next)
31863199
{
3200+
/* Non-PRE_DATA items are just ignored for now */
31873201
if (next_work_item->section==SECTION_DATA||
31883202
next_work_item->section==SECTION_POST_DATA)
3189-
break;
3203+
continue;
31903204

31913205
ahlog(AH,1,"processing item %d %s %s\n",
31923206
next_work_item->dumpId,
@@ -3229,12 +3243,17 @@ restore_toc_entries_parallel(ArchiveHandle *AH)
32293243
*/
32303244
par_list_header_init(&pending_list);
32313245
par_list_header_init(&ready_list);
3232-
for (;next_work_item!=AH->toc;next_work_item=next_work_item->next)
3246+
for (next_work_item=AH->toc->next;next_work_item!=AH->toc;next_work_item=next_work_item->next)
32333247
{
3234-
if (next_work_item->depCount>0)
3235-
par_list_append(&pending_list,next_work_item);
3236-
else
3237-
par_list_append(&ready_list,next_work_item);
3248+
/* All PRE_DATA items were dealt with above */
3249+
if (next_work_item->section==SECTION_DATA||
3250+
next_work_item->section==SECTION_POST_DATA)
3251+
{
3252+
if (next_work_item->depCount>0)
3253+
par_list_append(&pending_list,next_work_item);
3254+
else
3255+
par_list_append(&ready_list,next_work_item);
3256+
}
32383257
}
32393258

32403259
/*

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