Arrange for the postmaster (and standalone backends, initdb, etc) to

chdir into PGDATA and subsequently use relative paths instead of absolute
paths to access all files under PGDATA.  This seems to give a small
performance improvement, and it should make the system more robust
against naive DBAs doing things like moving a database directory that
has a live postmaster in it.  Per recent discussion.

Author: tglsfdc

contrib/dbsize/dbsize.c

@@ -5,7 +5,7 @@
  * Copyright (c) 2002-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/contrib/dbsize/dbsize.c,v 1.18 2005/06/19 21:34:00 tgl Exp $
+ *	  $PostgreSQL: pgsql/contrib/dbsize/dbsize.c,v 1.19 2005/07/04 04:51:43 tgl Exp $
  *
  */
 
@@ -24,9 +24,6 @@
 #include "utils/syscache.h"
 
 
-/* hack to make it compile under Win32 */
-extern DLLIMPORT char *DataDir;
-
 Datum pg_tablespace_size(PG_FUNCTION_ARGS);
 Datum pg_database_size(PG_FUNCTION_ARGS);
 Datum pg_relation_size(PG_FUNCTION_ARGS);
@@ -91,11 +88,11 @@ calculate_database_size(Oid dbOid)
 	/* Shared storage in pg_global is not counted */
 
 	/* Include pg_default storage */
-	snprintf(pathname, MAXPGPATH, "%s/base/%u", DataDir, dbOid);
+	snprintf(pathname, MAXPGPATH, "base/%u", dbOid);
 	totalsize += db_dir_size(pathname);
 
 	/* Scan the non-default tablespaces */
-	snprintf(pathname, MAXPGPATH, "%s/pg_tblspc", DataDir);
+	snprintf(pathname, MAXPGPATH, "pg_tblspc");
 	dirdesc = AllocateDir(pathname);
 
 	while ((direntry = ReadDir(dirdesc, pathname)) != NULL)
@@ -104,8 +101,8 @@ calculate_database_size(Oid dbOid)
 			strcmp(direntry->d_name, "..") == 0)
 		    continue;
 
-		snprintf(pathname, MAXPGPATH, "%s/pg_tblspc/%s/%u",
-				 DataDir, direntry->d_name, dbOid);
+		snprintf(pathname, MAXPGPATH, "pg_tblspc/%s/%u",
+				 direntry->d_name, dbOid);
 		totalsize += db_dir_size(pathname);
 	}
 
@@ -134,11 +131,11 @@ pg_tablespace_size(PG_FUNCTION_ARGS)
     struct dirent *direntry;
 
 	if (tblspcOid == DEFAULTTABLESPACE_OID)
-	    snprintf(tblspcPath, MAXPGPATH, "%s/base", DataDir);
+	    snprintf(tblspcPath, MAXPGPATH, "base");
 	else if (tblspcOid == GLOBALTABLESPACE_OID)
-	    snprintf(tblspcPath, MAXPGPATH, "%s/global", DataDir);
+	    snprintf(tblspcPath, MAXPGPATH, "global");
 	else
-		snprintf(tblspcPath, MAXPGPATH, "%s/pg_tblspc/%u", DataDir, tblspcOid);
+		snprintf(tblspcPath, MAXPGPATH, "pg_tblspc/%u", tblspcOid);
 
 	dirdesc = AllocateDir(tblspcPath);
 
@@ -208,12 +205,12 @@ calculate_relation_size(Oid tblspcOid, Oid relnodeOid)
 		tblspcOid = MyDatabaseTableSpace;
 
 	if (tblspcOid == DEFAULTTABLESPACE_OID)
-	    snprintf(dirpath, MAXPGPATH, "%s/base/%u", DataDir, MyDatabaseId);
+	    snprintf(dirpath, MAXPGPATH, "base/%u", MyDatabaseId);
 	else if (tblspcOid == GLOBALTABLESPACE_OID)
-	    snprintf(dirpath, MAXPGPATH, "%s/global", DataDir);
+	    snprintf(dirpath, MAXPGPATH, "global");
 	else
-	    snprintf(dirpath, MAXPGPATH, "%s/pg_tblspc/%u/%u",
-				 DataDir, tblspcOid, MyDatabaseId);
+	    snprintf(dirpath, MAXPGPATH, "pg_tblspc/%u/%u",
+				 tblspcOid, MyDatabaseId);
 
 	for (segcount = 0 ;; segcount++)
 	{

src/backend/access/transam/slru.c

@@ -48,7 +48,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/slru.c,v 1.25 2005/06/19 21:34:01 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/slru.c,v 1.26 2005/07/04 04:51:44 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -190,7 +190,7 @@ SimpleLruInit(SlruCtl ctl, const char *name,
 	 */
 	ctl->shared = shared;
 	ctl->do_fsync = true;		/* default behavior */
-	snprintf(ctl->Dir, MAXPGPATH, "%s/%s", DataDir, subdir);
+	StrNCpy(ctl->Dir, subdir, sizeof(ctl->Dir));
 }
 
 /*

src/backend/access/transam/twophase.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *		$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.7 2005/06/28 05:08:51 tgl Exp $
+ *		$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.8 2005/07/04 04:51:44 tgl Exp $
  *
  * NOTES
  *		Each global transaction is associated with a global transaction
@@ -661,7 +661,7 @@ TwoPhaseGetDummyProc(TransactionId xid)
 /************************************************************************/
 
 #define TwoPhaseFilePath(path, xid) \
-	snprintf(path, MAXPGPATH, "%s/%s/%08X", DataDir, TWOPHASE_DIR, xid)
+	snprintf(path, MAXPGPATH, TWOPHASE_DIR "/%08X", xid)
 
 /*
  * 2PC state file format:
@@ -1434,14 +1434,11 @@ PrescanPreparedTransactions(void)
 {
 	TransactionId origNextXid = ShmemVariableCache->nextXid;
 	TransactionId result = origNextXid;
-	char	dir[MAXPGPATH];
 	DIR		*cldir;
 	struct dirent *clde;
 
-	snprintf(dir, MAXPGPATH, "%s/%s", DataDir, TWOPHASE_DIR);
-
-	cldir = AllocateDir(dir);
-	while ((clde = ReadDir(cldir, dir)) != NULL)
+	cldir = AllocateDir(TWOPHASE_DIR);
+	while ((clde = ReadDir(cldir, TWOPHASE_DIR)) != NULL)
 	{
 		if (strlen(clde->d_name) == 8 &&
 			strspn(clde->d_name, "0123456789ABCDEF") == 8)
@@ -1540,7 +1537,7 @@ RecoverPreparedTransactions(void)
 	DIR		*cldir;
 	struct dirent *clde;
 
-	snprintf(dir, MAXPGPATH, "%s/%s", DataDir, TWOPHASE_DIR);
+	snprintf(dir, MAXPGPATH, "%s", TWOPHASE_DIR);
 
 	cldir = AllocateDir(dir);
 	while ((clde = ReadDir(cldir, dir)) != NULL)