Several changes here, not very related but touching some of the same files.

* Buffer refcount cleanup (per my "progress report" to pghackers, 9/22).
* Add links to backend PROC structs to sinval's array of per-backend info,
and use these links for routines that need to check the state of all
backends (rather than the slow, complicated search of the ShmemIndex
hashtable that was used before).  Add databaseOID to PROC structs.
* Use this to implement an interlock that prevents DESTROY DATABASE of
a database containing running backends.  (It's a little tricky to prevent
a concurrently-starting backend from getting in there, since the new
backend is not able to lock anything at the time it tries to look up
its database in pg_database.  My solution is to recheck that the DB is
OK at the end of InitPostgres.  It may not be a 100% solution, but it's
a lot better than no interlock at all...)
* In ALTER TABLE RENAME, flush buffers for the relation before doing the
rename of the physical files, to ensure we don't get failures later from
mdblindwrt().
* Update TRUNCATE patch so that it actually compiles against current
sources :-(.
You should do "make clean all" after pulling these changes.

1 files changed, 23 insertions, 48 deletions

diff --git a/src/backend/utils/misc/database.c b/src/backend/utils/misc/database.c
index 321ab943aea..f5ff732b8f2 100644
--- a/src/backend/utils/misc/database.c
+++ b/src/backend/utils/misc/database.c
@@ -1,13 +1,13 @@
 /*-------------------------------------------------------------------------
  *
  * database.c
- *	  miscellanious initialization support stuff
+ *	  miscellaneous initialization support stuff
  *
  * Copyright (c) 1994, Regents of the University of California
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/misc/Attic/database.c,v 1.29 1999/09/18 19:08:07 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/misc/Attic/database.c,v 1.30 1999/09/24 00:25:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,10 +21,6 @@
 #include "miscadmin.h"
 #include "utils/syscache.h"
 
-#ifdef MULTIBYTE
-#include "mb/pg_wchar.h"
-#endif
-
 #ifdef NOT_USED
 /* GetDatabaseInfo()
  * Pull database information from pg_database.
@@ -153,24 +149,13 @@ ExpandDatabasePath(char *dbpath)
  *		cache.	To get around this problem, this code opens and scans the
  *		pg_database relation by hand.
  *
- *		This algorithm relies on the fact that first attribute in the
- *		pg_database relation schema is the database name.  It also knows
- *		about the internal format of tuples on disk and the length of
- *		the datname attribute.	It knows the location of the pg_database
- *		file.
- *		Actually, the code looks as though it is using the pg_database
- *		tuple definition to locate the database name, so the above statement
- *		seems to be no longer correct. - thomas 1997-11-01
- *
- *		This code is called from InitPostgres(), before we chdir() to the
- *		local database directory and before we open any relations.
- *		Used to be called after the chdir(), but we now want to confirm
- *		the location of the target database using pg_database info.
- *		- thomas 1997-11-01
+ *		This code knows way more than it should about the layout of
+ *		tuples on disk, but there seems to be no help for that.
+ *		We're pulling ourselves up by the bootstraps here...
  * --------------------------------
  */
 void
-GetRawDatabaseInfo(char *name, int4 *owner, Oid *db_id, char *path, int *encoding)
+GetRawDatabaseInfo(char *name, Oid *db_id, char *path)
 {
 	int			dbfd;
 	int			fileflags;
@@ -238,48 +223,38 @@ GetRawDatabaseInfo(char *name, int4 *owner, Oid *db_id, char *path, int *encodin
 			 * skip this tuple.  XXX warning, will robinson:  violation of
 			 * transaction semantics happens right here.  we should check
 			 * to be sure that the xact that deleted this tuple actually
-			 * committed.  only way to do this at init time is to paw over
-			 * the log relation by hand, too.  let's be optimistic.
+			 * committed.  Only way to do that at init time is to paw over
+			 * the log relation by hand, too.  Instead we take the
+			 * conservative assumption that if someone tried to delete it,
+			 * it's gone.  The other side of the coin is that we might
+			 * accept a tuple that was stored and never committed.  All in
+			 * all, this code is pretty shaky.  We will cross-check our
+			 * result in ReverifyMyDatabase() in postinit.c.
 			 *
-			 * XXX This is an evil type cast.  tup->t_xmax is char[5] while
-			 * TransactionId is struct * { char data[5] }.	It works but
-			 * if data is ever moved and no longer the first field this
-			 * will be broken!! -mer 11 Nov 1991.
+			 * NOTE: if a bogus tuple in pg_database prevents connection
+			 * to a valid database, a fix is to connect to another database
+			 * and do "select * from pg_database".  That should cause
+			 * committed and dead tuples to be marked with correct states.
+			 *
+			 * XXX wouldn't it be better to let new backends read the
+			 * database OID from a flat file, handled the same way
+			 * we handle the password relation?
 			 */
 			if (TransactionIdIsValid((TransactionId) tup.t_data->t_xmax))
 				continue;
 
 			/*
-			 * Okay, see if this is the one we want. XXX 1 july 91:  mao
-			 * and mer discover that tuples now squash t_bits.	Why is
-			 * this?
-			 *
-			 * 24 july 92:	mer realizes that the t_bits field is only used
-			 * in the event of null values.  If no fields are null we
-			 * reduce the header size by doing the squash.	t_hoff tells
-			 * you exactly how big the header actually is. use the PC
-			 * means of getting at sys cat attrs.
+			 * Okay, see if this is the one we want.
 			 */
 			tup_db = (Form_pg_database) GETSTRUCT(&tup);
-#ifdef MULTIBYTE
 
-			/*
-			 * get encoding from template database. This is the "default
-			 * for default" for create database command.
-			 */
-			if (strcmp("template1", tup_db->datname.data) == 0)
-				SetTemplateEncoding(tup_db->encoding);
-#endif
 			if (strcmp(name, tup_db->datname.data) == 0)
 			{
+				/* Found it; extract the OID and the database path. */
 				*db_id = tup.t_data->t_oid;
 				strncpy(path, VARDATA(&(tup_db->datpath)),
 						(VARSIZE(&(tup_db->datpath)) - VARHDRSZ));
 				*(path + VARSIZE(&(tup_db->datpath)) - VARHDRSZ) = '\0';
-#ifdef MULTIBYTE
-				*encoding = tup_db->encoding;
-#endif
-
 				goto done;
 			}
 		}