Adjust initialization sequence for timezone_abbreviations so that

it's handled just about like timezone; in particular, don't try
to read anything during InitializeGUCOptions.  Should solve current
startup failure on Windows, and avoid wasted cycles if a nondefault
setting is specified in postgresql.conf too.  Possibly we need to
think about a more general solution for handling 'expensive to set'
GUC options.

src/backend/bootstrap/bootstrap.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootstrap.c,v 1.220 2006/07/14 14:52:17 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/bootstrap/bootstrap.c,v 1.221 2006/07/29 03:02:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -358,6 +358,8 @@ BootstrapMain(int argc, char *argv[])
 			proc_exit(1);
 		/* If timezone is not set, determine what the OS uses */
 		pg_timezone_initialize();
+		/* If timezone_abbreviations is not set, select default */
+		pg_timezone_abbrev_initialize();
 	}
 
 	/* Validate we have been given a reasonable-looking DataDir */

src/backend/postmaster/postmaster.c

@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.496 2006/07/25 01:23:34 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.497 2006/07/29 03:02:55 tgl Exp $
  *
  * NOTES
  *
@@ -691,10 +691,16 @@ PostmasterMain(int argc, char *argv[])
 	 * should be done during GUC initialization, but because it can take as
 	 * much as several seconds, we delay it until after we've created the
 	 * postmaster.pid file.  This prevents problems with boot scripts that
-	 * expect the pidfile to appear quickly.)
+	 * expect the pidfile to appear quickly.  Also, we avoid problems with
+	 * trying to locate the timezone files too early in initialization.)
 	 */
 	pg_timezone_initialize();
 
+	/*
+	 * Likewise, init timezone_abbreviations if not already set.
+	 */
+	pg_timezone_abbrev_initialize();
+
 	/*
 	 * Initialize SSL library, if specified.
 	 */

src/backend/tcop/postgres.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.492 2006/07/14 14:52:23 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.493 2006/07/29 03:02:56 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -2758,6 +2758,8 @@ PostgresMain(int argc, char *argv[], const char *username)
 			proc_exit(1);
 		/* If timezone is not set, determine what the OS uses */
 		pg_timezone_initialize();
+		/* If timezone_abbreviations is not set, select default */
+		pg_timezone_abbrev_initialize();
 	}
 
 	if (PostAuthDelay)

src/backend/utils/misc/guc.c

@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.332 2006/07/27 08:30:41 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.333 2006/07/29 03:02:56 tgl Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -221,10 +221,10 @@ static char *regex_flavor_string;
 static char *server_encoding_string;
 static char *server_version_string;
 static char *timezone_string;
+static char *timezone_abbreviations_string;
 static char *XactIsoLevel_string;
 static char *data_directory;
 static char *custom_variable_classes;
-static char *timezone_abbreviations;
 static int	max_function_args;
 static int	max_index_keys;
 static int	max_identifier_length;
@@ -2101,8 +2101,8 @@ static struct config_string ConfigureNamesString[] =
 			gettext_noop("Selects a file of timezone abbreviations"),
 			NULL,
 		},
-		&timezone_abbreviations,
+		&timezone_abbreviations_string,
-		"Default", assign_timezone_abbreviations, NULL
+		"UNKNOWN", assign_timezone_abbreviations, NULL
 	},
 
 	{
@@ -6288,9 +6288,27 @@ assign_backslash_quote(const char *newval, bool doit, GucSource source)
 static const char *
 assign_timezone_abbreviations(const char *newval, bool doit, GucSource source)
 {
+	/*
+	 * The powerup value shown above for timezone_abbreviations is "UNKNOWN".
+	 * When we see this we just do nothing.  If this value isn't overridden
+	 * from the config file then pg_timezone_abbrev_initialize() will
+	 * eventually replace it with "Default".  This hack has two purposes:
+	 * to avoid wasting cycles loading values that might soon be overridden
+	 * from the config file, and to avoid trying to read the timezone abbrev
+	 * files during InitializeGUCOptions().  The latter doesn't work in an
+	 * EXEC_BACKEND subprocess because my_exec_path hasn't been set yet and
+	 * so we can't locate PGSHAREDIR.  (Essentially the same hack is used
+	 * to delay initializing TimeZone ... if we have any more, we should
+	 * try to clean up and centralize this mechanism ...)
+	 */
+	if (strcmp(newval, "UNKNOWN") == 0)
+	{
+		return newval;
+	}
+
 	/* Loading abbrev file is expensive, so only do it when value changes */
-	if (timezone_abbreviations == NULL ||
+	if (timezone_abbreviations_string == NULL ||
-		strcmp(timezone_abbreviations, newval) != 0)
+		strcmp(timezone_abbreviations_string, newval) != 0)
 	{
 		int		elevel;
 
@@ -6309,6 +6327,22 @@ assign_timezone_abbreviations(const char *newval, bool doit, GucSource source)
 	return newval;
 }
 
+/*
+ * pg_timezone_abbrev_initialize --- set default value if not done already
+ *
+ * This is called after initial loading of postgresql.conf.  If no
+ * timezone_abbreviations setting was found therein, select default.
+ */
+void
+pg_timezone_abbrev_initialize(void)
+{
+	if (strcmp(timezone_abbreviations_string, "UNKNOWN") == 0)
+	{
+		SetConfigOption("timezone_abbreviations", "Default",
+						PGC_POSTMASTER, PGC_S_ARGV);
+	}
+}
+
 static bool
 assign_tcp_keepalives_idle(int newval, bool doit, GucSource source)
 {

src/include/utils/guc.h

@@ -7,7 +7,7 @@
  * Copyright (c) 2000-2006, PostgreSQL Global Development Group
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
- * $PostgreSQL: pgsql/src/include/utils/guc.h,v 1.70 2006/07/25 03:51:22 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/guc.h,v 1.71 2006/07/29 03:02:56 tgl Exp $
  *--------------------------------------------------------------------
  */
 #ifndef GUC_H
@@ -208,6 +208,8 @@ extern void ProcessGUCArray(ArrayType *array, GucSource source);
 extern ArrayType *GUCArrayAdd(ArrayType *array, const char *name, const char *value);
 extern ArrayType *GUCArrayDelete(ArrayType *array, const char *name);
 
+extern void pg_timezone_abbrev_initialize(void);
+
 #ifdef EXEC_BACKEND
 extern void write_nondefault_variables(GucContext context);
 extern void read_nondefault_variables(void);