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

5 files changed, 185 insertions, 93 deletions

diff --git a/src/timezone/localtime.c b/src/timezone/localtime.c
index 8e64f065b4..28b8f289a2 100644
--- a/src/timezone/localtime.c
+++ b/src/timezone/localtime.c
@@ -3,7 +3,7 @@
  * 1996-06-05 by Arthur David Olson (arthur_david_olson@nih.gov).
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/timezone/localtime.c,v 1.9 2004/11/01 21:34:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/timezone/localtime.c,v 1.10 2005/04/19 03:13:59 momjian Exp $
  */
 
 /*
@@ -16,8 +16,8 @@
 
 #include <fcntl.h>
 
-#include "pgtz.h"
 #include "private.h"
+#include "pgtz.h"
 #include "tzfile.h"
 
 
@@ -58,37 +58,6 @@ static const char gmt[] = "GMT";
  */
 #define TZDEFRULESTRING ",M4.1.0,M10.5.0"
 
-struct ttinfo
-{								/* time type information */
-	long		tt_gmtoff;		/* UTC offset in seconds */
-	int			tt_isdst;		/* used to set tm_isdst */
-	int			tt_abbrind;		/* abbreviation list index */
-	int			tt_ttisstd;		/* TRUE if transition is std time */
-	int			tt_ttisgmt;		/* TRUE if transition is UTC */
-};
-
-struct lsinfo
-{								/* leap second information */
-	pg_time_t	ls_trans;		/* transition time */
-	long		ls_corr;		/* correction to apply */
-};
-
-#define BIGGEST(a, b)	(((a) > (b)) ? (a) : (b))
-
-struct state
-{
-	int			leapcnt;
-	int			timecnt;
-	int			typecnt;
-	int			charcnt;
-	pg_time_t	ats[TZ_MAX_TIMES];
-	unsigned char types[TZ_MAX_TIMES];
-	struct ttinfo ttis[TZ_MAX_TYPES];
-	char		chars[BIGGEST(BIGGEST(TZ_MAX_CHARS + 1, sizeof gmt),
-										  (2 * (TZ_STRLEN_MAX + 1)))];
-	struct lsinfo lsis[TZ_MAX_LEAPS];
-};
-
 struct rule
 {
 	int			r_type;			/* type of rule--see below */
@@ -115,22 +84,19 @@ static const char *getoffset(const char *strp, long *offsetp);
 static const char *getrule(const char *strp, struct rule * rulep);
 static void gmtload(struct state * sp);
 static void gmtsub(const pg_time_t *timep, long offset, struct pg_tm * tmp);
-static void localsub(const pg_time_t *timep, long offset, struct pg_tm * tmp);
+static void localsub(const pg_time_t *timep, long offset, struct pg_tm * tmp, const pg_tz *tz);
 static void timesub(const pg_time_t *timep, long offset,
 		const struct state * sp, struct pg_tm * tmp);
 static pg_time_t transtime(pg_time_t janfirst, int year,
-		  const struct rule * rulep, long offset);
-static int	tzload(const char *name, struct state * sp);
-static int	tzparse(const char *name, struct state * sp, int lastditch);
+						   const struct rule * rulep, long offset);
+int	tzparse(const char *name, struct state * sp, int lastditch);
 
-static struct state lclmem;
+/* GMT timezone */
 static struct state gmtmem;
 
-#define lclptr		(&lclmem)
 #define gmtptr		(&gmtmem)
 
-static char lcl_TZname[TZ_STRLEN_MAX + 1];
-static int	lcl_is_set = 0;
+
 static int	gmt_is_set = 0;
 
 /*
@@ -156,7 +122,7 @@ detzcode(const char *codep)
 	return result;
 }
 
-static int
+int
 tzload(register const char *name, register struct state * sp)
 {
 	register const char *p;
@@ -589,7 +555,7 @@ transtime(const pg_time_t janfirst, const int year,
  * appropriate.
  */
 
-static int
+int
 tzparse(const char *name, register struct state * sp, const int lastditch)
 {
 	const char *stdname;
@@ -839,30 +805,6 @@ gmtload(struct state * sp)
 }
 
 
-bool
-pg_tzset(const char *name)
-{
-	if (lcl_is_set && strcmp(lcl_TZname, name) == 0)
-		return true;			/* no change */
-
-	if (strlen(name) >= sizeof(lcl_TZname))
-		return false;			/* not gonna fit */
-
-	if (tzload(name, lclptr) != 0)
-	{
-		if (name[0] == ':' || tzparse(name, lclptr, FALSE) != 0)
-		{
-			/* Unknown timezone. Fail our call instead of loading GMT! */
-			return false;
-		}
-	}
-
-	strcpy(lcl_TZname, name);
-	lcl_is_set = true;
-
-	return true;
-}
-
 /*
  * The easy way to behave "as if no library function calls" localtime
  * is to not call it--so we drop its guts into "localsub", which can be
@@ -872,14 +814,14 @@ pg_tzset(const char *name)
  * The unused offset argument is for the benefit of mktime variants.
  */
 static void
-localsub(const pg_time_t *timep, const long offset, struct pg_tm * tmp)
+localsub(const pg_time_t *timep, const long offset, struct pg_tm * tmp, const pg_tz *tz)
 {
-	register struct state *sp;
+ 	register const struct state *sp;
 	register const struct ttinfo *ttisp;
 	register int i;
 	const pg_time_t t = *timep;
 
-	sp = lclptr;
+	sp = &tz->state;
 	if (sp->timecnt == 0 || t < sp->ats[0])
 	{
 		i = 0;
@@ -906,9 +848,9 @@ localsub(const pg_time_t *timep, const long offset, struct pg_tm * tmp)
 
 
 struct pg_tm *
-pg_localtime(const pg_time_t *timep)
+pg_localtime(const pg_time_t *timep, const pg_tz *tz)
 {
-	localsub(timep, 0L, &tm);
+	localsub(timep, 0L, &tm, tz);
 	return &tm;
 }
 
@@ -1084,15 +1026,16 @@ pg_next_dst_boundary(const pg_time_t *timep,
 					 int *before_isdst,
 					 pg_time_t *boundary,
 					 long int *after_gmtoff,
-					 int *after_isdst)
+					 int *after_isdst,
+	                 const pg_tz *tz)
 {
-	register struct state *sp;
+	register const struct state *sp;
 	register const struct ttinfo *ttisp;
 	int i;
 	int j;
 	const pg_time_t t = *timep;
 
-	sp = lclptr;
+	sp = &tz->state;
 	if (sp->timecnt == 0)
 	{
 		/* non-DST zone, use lowest-numbered standard type */
@@ -1158,9 +1101,9 @@ pg_next_dst_boundary(const pg_time_t *timep,
  * Return the name of the current timezone
  */
 const char *
-pg_get_current_timezone(void)
+pg_get_timezone_name(pg_tz *tz)
 {
-	if (lcl_is_set)
-		return lcl_TZname;
+	if (tz)
+		return tz->TZname;
 	return NULL;
 }
diff --git a/src/timezone/pgtz.c b/src/timezone/pgtz.c
index 599aaac4ef..f228ed5bac 100644
--- a/src/timezone/pgtz.c
+++ b/src/timezone/pgtz.c
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.29 2004/12/31 22:03:59 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.30 2005/04/19 03:13:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -26,12 +26,18 @@
 #include "utils/datetime.h"
 #include "utils/elog.h"
 #include "utils/guc.h"
+#include "utils/hsearch.h"
+
+/* Current global timezone */
+pg_tz *global_timezone = NULL;
 
 
 static char tzdir[MAXPGPATH];
 static int	done_tzdir = 0;
 
 static const char *identify_system_timezone(void);
+static const char *select_default_timezone(void);
+static bool set_global_timezone(const char *tzname);
 
 
 /*
@@ -156,12 +162,14 @@ score_timezone(const char *tzname, struct tztry * tt)
 	struct tm  *systm;
 	struct pg_tm *pgtm;
 	char		cbuf[TZ_STRLEN_MAX + 1];
+	pg_tz       *tz;
 
-	if (!pg_tzset(tzname))
+	tz = pg_tzset(tzname);
+	if (!tz)
 		return -1;				/* can't handle the TZ name at all */
 
 	/* Reject if leap seconds involved */
-	if (!tz_acceptable())
+	if (!tz_acceptable(tz))
 	{
 		elog(DEBUG4, "Reject TZ \"%s\": uses leap seconds", tzname);
 		return -1;
@@ -171,7 +179,7 @@ score_timezone(const char *tzname, struct tztry * tt)
 	for (i = 0; i < tt->n_test_times; i++)
 	{
 		pgtt = (pg_time_t) (tt->test_times[i]);
-		pgtm = pg_localtime(&pgtt);
+		pgtm = pg_localtime(&pgtt, tz);
 		if (!pgtm)
 			return -1;			/* probably shouldn't happen */
 		systm = localtime(&(tt->test_times[i]));
@@ -957,6 +965,82 @@ identify_system_timezone(void)
 #endif   /* WIN32 */
 
 
+
+/*
+ * We keep loaded timezones in a hashtable so we don't have to
+ * load and parse the TZ definition file every time it is selected.
+ */
+static HTAB *timezone_cache = NULL;
+static bool
+init_timezone_hashtable(void)
+{
+	HASHCTL		hash_ctl;
+
+	MemSet(&hash_ctl, 0, sizeof(hash_ctl));
+
+	hash_ctl.keysize = TZ_STRLEN_MAX;
+	hash_ctl.entrysize = sizeof(pg_tz);
+
+	timezone_cache = hash_create("Timezones",
+								 31,
+								 &hash_ctl,
+								 HASH_ELEM);
+	if (!timezone_cache)
+		return false;
+
+	return true;
+}
+
+/*
+ * Load a timezone from file or from cache.
+ * Does not verify that the timezone is acceptable!
+ */
+struct pg_tz *
+pg_tzset(const char *name)
+{
+	pg_tz *tzp;
+	pg_tz tz;
+	
+	if (strlen(name) >= TZ_STRLEN_MAX)
+		return NULL;			/* not going to fit */
+
+	if (!timezone_cache)
+		if (!init_timezone_hashtable())
+			return NULL;
+
+	tzp = (pg_tz *)hash_search(timezone_cache,
+							  name,
+							  HASH_FIND,
+							  NULL);
+	if (tzp)
+		/* Timezone found in cache, nothing more to do */
+		return tzp;
+
+	if (tzload(name, &tz.state) != 0)
+	{
+		if (name[0] == ':' || tzparse(name, &tz.state, FALSE) != 0)
+			/* Unknown timezone. Fail our call instead of loading GMT! */
+			return NULL;
+	}
+
+	strcpy(tz.TZname, name);
+
+	/* Save timezone in the cache */
+	tzp = hash_search(timezone_cache,
+					  name,
+					  HASH_ENTER,
+					  NULL);
+	
+	if (!tzp)
+		return NULL;
+	
+	strcpy(tzp->TZname, tz.TZname);
+	memcpy(&tzp->state, &tz.state, sizeof(tz.state));
+
+	return tzp;
+}
+
+
 /*
  * Check whether timezone is acceptable.
  *
@@ -968,7 +1052,7 @@ identify_system_timezone(void)
  * it can restore the old value of TZ if we don't like the new one.
  */
 bool
-tz_acceptable(void)
+tz_acceptable(pg_tz *tz)
 {
 	struct pg_tm *tt;
 	pg_time_t	time2000;
@@ -979,13 +1063,36 @@ tz_acceptable(void)
 	 * any other result has to be due to leap seconds.
 	 */
 	time2000 = (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * 86400;
-	tt = pg_localtime(&time2000);
+	tt = pg_localtime(&time2000, tz);
 	if (!tt || tt->tm_sec != 0)
 		return false;
 
 	return true;
 }
 
+
+/*
+ * Set the global timezone. Verify that it's acceptable first.
+ */
+static bool
+set_global_timezone(const char *tzname)
+{
+	pg_tz *tznew;
+
+	if (!tzname || !tzname[0])
+		return false;
+	
+	tznew = pg_tzset(tzname);
+	if (!tznew)
+		return false;
+
+	if (!tz_acceptable(tznew))
+		return false;
+
+	global_timezone = tznew;
+	return true;
+}
+
 /*
  * Identify a suitable default timezone setting based on the environment,
  * and make it active.
@@ -995,20 +1102,20 @@ tz_acceptable(void)
  * from the behavior of the system timezone library.  When all else fails,
  * fall back to GMT.
  */
-const char *
+static const char *
 select_default_timezone(void)
 {
 	const char *def_tz;
 
 	def_tz = getenv("TZ");
-	if (def_tz && pg_tzset(def_tz) && tz_acceptable())
+	if (set_global_timezone(def_tz))
 		return def_tz;
 
 	def_tz = identify_system_timezone();
-	if (def_tz && pg_tzset(def_tz) && tz_acceptable())
+	if (set_global_timezone(def_tz))
 		return def_tz;
 
-	if (pg_tzset("GMT") && tz_acceptable())
+	if (set_global_timezone("GMT"))
 		return "GMT";
 
 	ereport(FATAL,
diff --git a/src/timezone/pgtz.h b/src/timezone/pgtz.h
index 6c05198aed..e325dec483 100644
--- a/src/timezone/pgtz.h
+++ b/src/timezone/pgtz.h
@@ -9,15 +9,57 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/timezone/pgtz.h,v 1.10 2004/12/31 22:03:59 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/timezone/pgtz.h,v 1.11 2005/04/19 03:13:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef _PGTZ_H
 #define _PGTZ_H
 
+#include "tzfile.h"
+
 #define TZ_STRLEN_MAX 255
 
 extern char *pg_TZDIR(void);
 
+#define BIGGEST(a, b)	(((a) > (b)) ? (a) : (b))
+
+struct ttinfo
+{								/* time type information */
+	long		tt_gmtoff;		/* UTC offset in seconds */
+	int			tt_isdst;		/* used to set tm_isdst */
+	int			tt_abbrind;		/* abbreviation list index */
+	int			tt_ttisstd;		/* TRUE if transition is std time */
+	int			tt_ttisgmt;		/* TRUE if transition is UTC */
+};
+
+struct lsinfo
+{								/* leap second information */
+	pg_time_t	ls_trans;		/* transition time */
+	long		ls_corr;		/* correction to apply */
+};
+
+struct state
+{
+	int			leapcnt;
+	int			timecnt;
+	int			typecnt;
+	int			charcnt;
+	pg_time_t	ats[TZ_MAX_TIMES];
+	unsigned char types[TZ_MAX_TIMES];
+	struct ttinfo ttis[TZ_MAX_TYPES];
+	char		chars[BIGGEST(BIGGEST(TZ_MAX_CHARS + 1, 3 /* sizeof gmt */),
+										  (2 * (TZ_STRLEN_MAX + 1)))];
+	struct lsinfo lsis[TZ_MAX_LEAPS];
+};
+
+
+struct pg_tz {
+	char TZname[TZ_STRLEN_MAX + 1];
+	struct state state;
+};
+
+int	tzload(const char *name, struct state * sp);
+int	tzparse(const char *name, struct state * sp, int lastditch);
+
 #endif   /* _PGTZ_H */
diff --git a/src/timezone/strftime.c b/src/timezone/strftime.c
index c23ae7cb6f..cc45527fe4 100644
--- a/src/timezone/strftime.c
+++ b/src/timezone/strftime.c
@@ -15,7 +15,7 @@
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/timezone/strftime.c,v 1.5 2004/08/29 05:07:02 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/timezone/strftime.c,v 1.6 2005/04/19 03:13:59 momjian Exp $
  */
 
 #include "postgres.h"
@@ -23,8 +23,8 @@
 #include <fcntl.h>
 #include <locale.h>
 
-#include "pgtz.h"
 #include "private.h"
+#include "pgtz.h"
 #include "tzfile.h"
 
 
diff --git a/src/timezone/zic.c b/src/timezone/zic.c
index 5cc2432998..1d3695b659 100644
--- a/src/timezone/zic.c
+++ b/src/timezone/zic.c
@@ -3,7 +3,7 @@
  * 1996-06-05 by Arthur David Olson (arthur_david_olson@nih.gov).
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/timezone/zic.c,v 1.13 2004/09/27 19:16:03 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/timezone/zic.c,v 1.14 2005/04/19 03:13:59 momjian Exp $
  */
 
 #include "postgres.h"
@@ -14,8 +14,8 @@
 #include <limits.h>
 #include <locale.h>
 
-#include "pgtz.h"
 #include "private.h"
+#include "pgtz.h"
 #include "tzfile.h"
 
 #ifdef HAVE_SYS_STAT_H