Attached patch gets rid of the global timezone in the following steps:

* Changes the APIs to the timezone functions to take a pg_tz pointer as
an argument, representing the timezone to use for the selected
operation.

* Adds a global_timezone variable that represents the current timezone
in the backend as set by SET TIMEZONE (or guc, or env, etc).

* Implements a hash-table cache of loaded tables, so we don't have to
read and parse the TZ file everytime we change a timezone. While not
necesasry now (we don't change timezones very often), I beleive this
will be necessary (or at least good) when "multiple timezones in the
same query" is eventually implemented. And code-wise, this was the time
to do it.


There are no user-visible changes at this time. Implementing the
"multiple zones in one query" is a later step...

This also gets rid of some of the cruft needed to "back out a timezone
change", since we previously couldn't check a timezone unless it was
activated first.

Passes regression tests on win32, linux (slackware 10) and solaris x86.

Magnus Hagander

Author: bmomjian

src/backend/commands/variable.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/variable.c,v 1.105 2004/12/31 21:59:42 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/variable.c,v 1.106 2005/04/19 03:13:58 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -315,104 +315,50 @@ assign_timezone(const char *value, bool doit, GucSource source)
 			 * UNKNOWN as the canonical spelling.
 			 *
 			 * During GUC initialization, since the timezone library isn't
-			 * set up yet, pg_get_current_timezone will return NULL and we
+			 * set up yet, pg_get_timezone_name will return NULL and we
 			 * will leave the setting as UNKNOWN.  If this isn't
 			 * overridden from the config file then
 			 * pg_timezone_initialize() will eventually select a default
 			 * value from the environment.
 			 */
-			const char *curzone = pg_get_current_timezone();
+			const char *curzone = pg_get_timezone_name(global_timezone);
 
 			if (curzone)
 				value = curzone;
 		}
 		else
 		{
 			/*
-			 * Otherwise assume it is a timezone name.
-			 *
-			 * We have to actually apply the change before we can have any
-			 * hope of checking it.  So, save the old value in case we
-			 * have to back out.  We have to copy since
-			 * pg_get_current_timezone returns a pointer to its static
-			 * state.
-			 *
-			 * This would all get a lot simpler if the TZ library had a
-			 * better API that would let us look up and test a timezone
-			 * name without making it the default.
+			 * Otherwise assume it is a timezone name, and try to load it.
 			 */
-			const char *cur_tz;
-			char	   *save_tz;
-			bool		known,
-						acceptable;
+			pg_tz *new_tz;
 
-			cur_tz = pg_get_current_timezone();
-			if (cur_tz)
-				save_tz = pstrdup(cur_tz);
-			else
-				save_tz = NULL;
+			new_tz = pg_tzset(value);
 
-			known = pg_tzset(value);
-			acceptable = known ? tz_acceptable() : false;
+			if (!new_tz)
+			{
+				ereport((source >= PGC_S_INTERACTIVE) ? ERROR : LOG,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("unrecognized time zone name: \"%s\"",
+								value)));
+				return NULL;
+			}
 
-			if (doit && known && acceptable)
+			if (!tz_acceptable(new_tz))
 			{
-				/* Keep the changed TZ */
-				HasCTZSet = false;
+				ereport((source >= PGC_S_INTERACTIVE) ? ERROR : LOG,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("time zone \"%s\" appears to use leap seconds",
+								value),
+						 errdetail("PostgreSQL does not support leap seconds.")));
+				return NULL;
 			}
-			else
+
+			if (doit)
 			{
-				/*
-				 * Revert to prior TZ setting; note we haven't changed
-				 * HasCTZSet in this path, so if we were previously using
-				 * a fixed offset, we still are.
-				 */
-				if (save_tz)
-					pg_tzset(save_tz);
-				else
-				{
-					/*
-					 * TZ library wasn't initialized yet.  Annoyingly, we
-					 * will come here during startup because guc-file.l
-					 * checks the value with doit = false before actually
-					 * applying. The best approach seems to be as follows:
-					 *
-					 * 1. known && acceptable: leave the setting in place,
-					 * since we'll apply it soon anyway.  This is mainly
-					 * so that any log messages printed during this
-					 * interval are timestamped with the user's requested
-					 * timezone.
-					 *
-					 * 2. known && !acceptable: revert to GMT for lack of any
-					 * better idea.  (select_default_timezone() may get
-					 * called later to undo this.)
-					 *
-					 * 3. !known: no need to do anything since TZ library did
-					 * not change its state.
-					 *
-					 * Again, this should all go away sometime soon.
-					 */
-					if (known && !acceptable)
-						pg_tzset("GMT");
-				}
-				/* Complain if it was bad */
-				if (!known)
-				{
-					ereport((source >= PGC_S_INTERACTIVE) ? ERROR : LOG,
-							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-							 errmsg("unrecognized time zone name: \"%s\"",
-									value)));
-					return NULL;
-				}
-				if (!acceptable)
-				{
-					ereport((source >= PGC_S_INTERACTIVE) ? ERROR : LOG,
-							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					errmsg("time zone \"%s\" appears to use leap seconds",
-						   value),
-							 errdetail("PostgreSQL does not support leap seconds.")));
-					return NULL;
-				}
+				/* Save the changed TZ */
+				global_timezone = new_tz;
+				HasCTZSet = false;
 			}
 		}
 	}
@@ -459,7 +405,7 @@ show_timezone(void)
 										  IntervalPGetDatum(&interval)));
 	}
 	else
-		tzn = pg_get_current_timezone();
+		tzn = pg_get_timezone_name(global_timezone);
 
 	if (tzn != NULL)
 		return tzn;

src/backend/postmaster/syslogger.c

@@ -18,7 +18,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/syslogger.c,v 1.14 2005/03/12 01:54:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/syslogger.c,v 1.15 2005/04/19 03:13:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -833,7 +833,7 @@ logfile_getname(pg_time_t timestamp)
 	if (strchr(Log_filename, '%'))
 	{
 		/* treat it as a strftime pattern */
-		tm = pg_localtime(&timestamp);
+		tm = pg_localtime(&timestamp, global_timezone);
 		pg_strftime(filename + len, MAXPGPATH - len, Log_filename, tm);
 	}
 	else 
@@ -868,7 +868,7 @@ set_next_rotation_time(void)
 	 */
 	rotinterval = Log_RotationAge * 60; /* convert to seconds */
 	now = time(NULL);
-	tm = pg_localtime(&now);
+	tm = pg_localtime(&now, global_timezone);
 	now += tm->tm_gmtoff;
 	now -= now % rotinterval;
 	now += rotinterval;

src/backend/utils/adt/datetime.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/datetime.c,v 1.137 2005/01/11 18:33:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/datetime.c,v 1.138 2005/04/19 03:13:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1634,7 +1634,8 @@ DetermineLocalTimeZone(struct pg_tm * tm)
 	res = pg_next_dst_boundary(&prevtime,
 							   &before_gmtoff, &before_isdst,
 							   &boundary,
-							   &after_gmtoff, &after_isdst);
+							   &after_gmtoff, &after_isdst,
+		                       global_timezone);
 	if (res < 0)
 		goto overflow;			/* failure? */
 

src/backend/utils/adt/nabstime.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/nabstime.c,v 1.127 2004/12/31 22:01:22 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/nabstime.c,v 1.128 2005/04/19 03:13:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -192,7 +192,7 @@ abstime2tm(AbsoluteTime _time, int *tzp, struct pg_tm * tm, char **tzn)
 		time -= CTimeZone;
 
 	if ((!HasCTZSet) && (tzp != NULL))
-		tx = pg_localtime(&time);
+		tx = pg_localtime(&time,global_timezone);
 	else
 		tx = pg_gmtime(&time);
 
@@ -1677,7 +1677,7 @@ timeofday(PG_FUNCTION_ARGS)
 	gettimeofday(&tp, &tpz);
 	tt = (pg_time_t) tp.tv_sec;
 	pg_strftime(templ, sizeof(templ), "%a %b %d %H:%M:%S.%%06d %Y %Z",
-				pg_localtime(&tt));
+				pg_localtime(&tt,global_timezone));
 	snprintf(buf, sizeof(buf), templ, tp.tv_usec);
 
 	len = VARHDRSZ + strlen(buf);

src/backend/utils/adt/timestamp.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.118 2005/04/01 14:25:23 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.119 2005/04/19 03:13:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1078,7 +1078,7 @@ timestamp2tm(Timestamp dt, int *tzp, struct pg_tm * tm, fsec_t *fsec, char **tzn
 	utime = (pg_time_t) dt;
 	if ((Timestamp) utime == dt)
 	{
-		struct pg_tm *tx = pg_localtime(&utime);
+		struct pg_tm *tx = pg_localtime(&utime, global_timezone);
 
 		tm->tm_year = tx->tm_year + 1900;
 		tm->tm_mon = tx->tm_mon + 1;

src/include/pgtime.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/include/pgtime.h,v 1.6 2004/12/31 22:03:19 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/include/pgtime.h,v 1.7 2005/04/19 03:13:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -37,21 +37,24 @@ struct pg_tm
 	const char *tm_zone;
 };
 
-extern struct pg_tm *pg_localtime(const pg_time_t *timep);
+typedef struct pg_tz pg_tz;
+
+extern struct pg_tm *pg_localtime(const pg_time_t *timep, const pg_tz *tz);
 extern struct pg_tm *pg_gmtime(const pg_time_t *timep);
 extern int	pg_next_dst_boundary(const pg_time_t *timep,
 								 long int *before_gmtoff,
 								 int *before_isdst,
 								 pg_time_t *boundary,
 								 long int *after_gmtoff,
-								 int *after_isdst);
+								 int *after_isdst,
+	                             const pg_tz *tz);
 extern size_t pg_strftime(char *s, size_t max, const char *format,
 			const struct pg_tm * tm);
 
 extern void pg_timezone_initialize(void);
-extern bool pg_tzset(const char *tzname);
-extern bool tz_acceptable(void);
-extern const char *select_default_timezone(void);
-extern const char *pg_get_current_timezone(void);
+extern pg_tz *pg_tzset(const char *tzname);
+extern bool tz_acceptable(pg_tz *tz);
+extern const char *pg_get_timezone_name(pg_tz *tz);
 
+extern pg_tz *global_timezone;
 #endif   /* _PGTIME_H */