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Commit04011cc

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Allow backends to start up without use of the flat-file copy of pg_database.
To make this work in the base case, pg_database now has a nailed-in-cacherelation descriptor that is initialized using hardwired knowledge inrelcache.c. This means pg_database is added to the set of relations thatneed to have a Schema_pg_xxx macro maintained in pg_attribute.h. When thispath is taken, we'll have to do a seqscan of pg_database to find the rowwe need.In the normal case, we are able to do an indexscan to find the database's rowby name. This is made possible by storing a global relcache init file thatdescribes only the shared catalogs and their indexes (and therefore is usableby all backends in any database). A new backend loads this cache file,finds its database OID after an indexscan on pg_database, and then loadsthe local relcache init file for that database.This change should effectively eliminate number of databases as a factorin backend startup time, even with large numbers of databases. However,the real reason for doing it is as a first step towards getting rid ofthe flat files altogether. There are still several other sub-projectsto be tackled before that can happen.
1 parenta1f0c9b commit04011cc

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13 files changed

+606
-354
lines changed

13 files changed

+606
-354
lines changed

‎src/backend/access/transam/xlog.c‎

Lines changed: 11 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
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*
10-
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.347 2009/08/08 16:39:17 tgl Exp $
10+
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.348 2009/08/12 20:53:30 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -5249,6 +5249,16 @@ StartupXLOG(void)
52495249
*/
52505250
ValidateXLOGDirectoryStructure();
52515251

5252+
/*
5253+
* Clear out any old relcache cache files. This is *necessary* if we
5254+
* do any WAL replay, since that would probably result in the cache files
5255+
* being out of sync with database reality. In theory we could leave
5256+
* them in place if the database had been cleanly shut down, but it
5257+
* seems safest to just remove them always and let them be rebuilt
5258+
* during the first backend startup.
5259+
*/
5260+
RelationCacheInitFileRemove();
5261+
52525262
/*
52535263
* Initialize on the assumption we want to recover to the same timeline
52545264
* that's active according to pg_control.

‎src/backend/postmaster/autovacuum.c‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -55,7 +55,7 @@
5555
*
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*
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* IDENTIFICATION
58-
* $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.100 2009/07/31 20:26:22 tgl Exp $
58+
* $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.101 2009/08/12 20:53:30 tgl Exp $
5959
*
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*-------------------------------------------------------------------------
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*/
@@ -1602,7 +1602,7 @@ AutoVacWorkerMain(int argc, char *argv[])
16021602

16031603
if (OidIsValid(dbid))
16041604
{
1605-
char*dbname;
1605+
chardbname[NAMEDATALEN];
16061606

16071607
/*
16081608
* Report autovac startup to the stats collector. We deliberately do
@@ -1620,7 +1620,7 @@ AutoVacWorkerMain(int argc, char *argv[])
16201620
* Note: if we have selected a just-deleted database (due to using
16211621
* stale stats info), we'll fail and exit here.
16221622
*/
1623-
InitPostgres(NULL,dbid,NULL,&dbname);
1623+
InitPostgres(NULL,dbid,NULL,dbname);
16241624
SetProcessingMode(NormalProcessing);
16251625
set_ps_display(dbname, false);
16261626
ereport(DEBUG1,

‎src/backend/postmaster/pgstat.c‎

Lines changed: 10 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
*
1414
*Copyright (c) 2001-2009, PostgreSQL Global Development Group
1515
*
16-
*$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.189 2009/06/11 14:49:01 momjian Exp $
16+
*$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.190 2009/08/12 20:53:30 tgl Exp $
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* ----------
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*/
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#include"postgres.h"
@@ -2138,6 +2138,7 @@ CreateSharedBackendStatus(void)
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*Called from InitPostgres. MyBackendId must be set,
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*but we must not have started any transaction yet (since the
21402140
*exit hook must run after the last transaction exit).
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*NOTE: MyDatabaseId isn't set yet; so the shutdown hook has to be careful.
21412142
* ----------
21422143
*/
21432144
void
@@ -2232,7 +2233,14 @@ pgstat_beshutdown_hook(int code, Datum arg)
22322233
{
22332234
volatilePgBackendStatus*beentry=MyBEEntry;
22342235

2235-
pgstat_report_stat(true);
2236+
/*
2237+
* If we got as far as discovering our own database ID, we can report
2238+
* what we did to the collector. Otherwise, we'd be sending an invalid
2239+
* database ID, so forget it. (This means that accesses to pg_database
2240+
* during failed backend starts might never get counted.)
2241+
*/
2242+
if (OidIsValid(MyDatabaseId))
2243+
pgstat_report_stat(true);
22362244

22372245
/*
22382246
* Clear my status entry, following the protocol of bumping st_changecount

‎src/backend/storage/lmgr/proc.c‎

Lines changed: 3 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.207 2009/06/11 14:49:02 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.208 2009/08/12 20:53:30 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -332,22 +332,14 @@ InitProcess(void)
332332
* InitProcessPhase2 -- make MyProc visible in the shared ProcArray.
333333
*
334334
* This is separate from InitProcess because we can't acquire LWLocks until
335-
* we've created a PGPROC, but in the EXEC_BACKEND casethere is a good deal
336-
*of stuff to be donebefore this step that will require LWLock access.
335+
* we've created a PGPROC, but in the EXEC_BACKEND caseProcArrayAdd won't
336+
*work until after we've doneCreateSharedMemoryAndSemaphores.
337337
*/
338338
void
339339
InitProcessPhase2(void)
340340
{
341341
Assert(MyProc!=NULL);
342342

343-
/*
344-
* We should now know what database we're in, so advertise that. (We need
345-
* not do any locking here, since no other backend can yet see our
346-
* PGPROC.)
347-
*/
348-
Assert(OidIsValid(MyDatabaseId));
349-
MyProc->databaseId=MyDatabaseId;
350-
351343
/*
352344
* Add our PGPROC to the PGPROC array in shared memory.
353345
*/

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