Rename the recently-added pg_timezonenames view to pg_timezone_abbrevs,

and create a new view pg_timezone_names that provides information about
the zones known in the 'zic' database.  Magnus Hagander, with some
additional work by Tom Lane.

doc/src/sgml/catalogs.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.131 2006/09/16 00:30:11 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.132 2006/09/16 20:14:32 tgl Exp $ -->
 <!--
  Documentation of the system catalogs, directed toward PostgreSQL developers
  -->
@@ -4564,10 +4564,15 @@
      </row>
 
      <row>
-      <entry><link linkend="view-pg-timezonenames"><structname>pg_timezonenames</structname></link></entry>
+      <entry><link linkend="view-pg-timezone-abbrevs"><structname>pg_timezone_abbrevs</structname></link></entry>
       <entry>time zone abbreviations</entry>
      </row>
 
+     <row>
+      <entry><link linkend="view-pg-timezone-names"><structname>pg_timezone_names</structname></link></entry>
+      <entry>time zone names</entry>
+     </row>
+
      <row>
       <entry><link linkend="view-pg-user"><structname>pg_user</structname></link></entry>
       <entry>database users</entry>
@@ -5884,22 +5889,74 @@
 
  </sect1>
 
- <sect1 id="view-pg-timezonenames">
-  <title><structname>pg_timezonenames</structname></title>
+ <sect1 id="view-pg-timezone-abbrevs">
+  <title><structname>pg_timezone_abbrevs</structname></title>
 
-  <indexterm zone="view-pg-timezonenames">
-   <primary>pg_timezonenames</primary>
+  <indexterm zone="view-pg-timezone-abbrevs">
+   <primary>pg_timezone_abbrevs</primary>
   </indexterm>
 
   <para>
-   The view <structname>pg_timezonenames</structname> provides a list
+   The view <structname>pg_timezone_abbrevs</structname> provides a list
    of time zone abbreviations that are currently recognized by the datetime
    input routines.  The contents of this view change when the
    <xref linkend="guc-timezone-abbreviations"> run-time parameter is modified.
   </para>
 
   <table>
-   <title><structname>pg_timezonenames</> Columns</title>
+   <title><structname>pg_timezone_abbrevs</> Columns</title>
+
+   <tgroup cols=3>
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+    <tbody>
+     <row>
+      <entry><structfield>abbrev</structfield></entry>
+      <entry><type>text</type></entry>
+      <entry>time zone abbreviation</entry>
+     </row>
+     <row>
+      <entry><structfield>utc_offset</structfield></entry>
+      <entry><type>interval</type></entry>
+      <entry>offset from UTC (positive means east of Greenwich)</entry>
+     </row>
+     <row>
+      <entry><structfield>is_dst</structfield></entry>
+      <entry><type>boolean</type></entry>
+      <entry>true if this is a daylight-savings abbreviation</entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect1>
+
+ <sect1 id="view-pg-timezone-names">
+  <title><structname>pg_timezone_names</structname></title>
+
+  <indexterm zone="view-pg-timezone-names">
+   <primary>pg_timezone_names</primary>
+  </indexterm>
+
+  <para>
+   The view <structname>pg_timezone_names</structname> provides a list
+   of time zone names that are recognized by <command>SET TIMEZONE</>,
+   along with their associated abbreviations, UTC offsets,
+   and daylight-savings status.
+   Unlike the abbreviations shown in <link
+   linkend="view-pg-timezone-abbrevs"><structname>pg_timezone_abbrevs</structname></link>, many of these names imply a set of daylight-savings transition
+   date rules.  Therefore, the associated information changes across local DST
+   boundaries.  The displayed information is computed based on the current
+   value of <function>CURRENT_TIMESTAMP</>.
+  </para>
+
+  <table>
+   <title><structname>pg_timezone_names</> Columns</title>
 
    <tgroup cols=3>
     <thead>
@@ -5913,6 +5970,11 @@
      <row>
       <entry><structfield>name</structfield></entry>
       <entry><type>text</type></entry>
+      <entry>time zone name</entry>
+     </row>
+     <row>
+      <entry><structfield>abbrev</structfield></entry>
+      <entry><type>text</type></entry>
       <entry>time zone abbreviation</entry>
      </row>
      <row>
@@ -5923,7 +5985,7 @@
      <row>
       <entry><structfield>is_dst</structfield></entry>
       <entry><type>boolean</type></entry>
-      <entry>true if this is a daylight-savings zone</entry>
+      <entry>true if currently observing daylight savings</entry>
      </row>
     </tbody>
    </tgroup>

src/backend/catalog/system_views.sql

@@ -3,7 +3,7 @@
  *
  * Copyright (c) 1996-2006, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.30 2006/08/19 01:36:24 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.31 2006/09/16 20:14:33 tgl Exp $
  */
 
 CREATE VIEW pg_roles AS 
@@ -186,10 +186,11 @@ CREATE RULE pg_settings_n AS
 
 GRANT SELECT, UPDATE ON pg_settings TO PUBLIC;
 
-CREATE VIEW pg_timezonenames AS
-    SELECT *
-    FROM pg_timezonenames() AS T
-    (name text, utc_offset interval, is_dst boolean);
+CREATE VIEW pg_timezone_abbrevs AS
+    SELECT * FROM pg_timezone_abbrevs();
+
+CREATE VIEW pg_timezone_names AS
+    SELECT * FROM pg_timezone_names();
 
 -- Statistics views
 

src/backend/utils/adt/datetime.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/datetime.c,v 1.170 2006/09/04 01:26:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/datetime.c,v 1.171 2006/09/16 20:14:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3839,21 +3839,21 @@ InstallTimeZoneAbbrevs(tzEntry *abbrevs, int n)
 
 /*
  * This set-returning function reads all the available time zone abbreviations
- * and returns a set of (name, utc_offset, is_dst).
+ * and returns a set of (abbrev, utc_offset, is_dst).
  */
 Datum
-pg_timezonenames(PG_FUNCTION_ARGS)
+pg_timezone_abbrevs(PG_FUNCTION_ARGS)
 {
 	FuncCallContext	   *funcctx;
 	int				   *pindex;
 	Datum				result;
-	Interval		   *resInterval;
 	HeapTuple			tuple;
 	Datum				values[3];
 	bool				nulls[3];
 	char				buffer[TOKMAXLEN + 1];
 	unsigned char	   *p;
 	struct pg_tm		tm;
+	Interval		   *resInterval;
 
 	/* stuff done only on the first call of the function */
 	if (SRF_IS_FIRSTCALL())
@@ -3876,11 +3876,11 @@ pg_timezonenames(PG_FUNCTION_ARGS)
 		funcctx->user_fctx = (void *) pindex;
 
 		/*
-		 * build tupdesc for result tuples. This must match the
-		 * definition of the pg_timezonenames view in system_views.sql
+		 * build tupdesc for result tuples. This must match this function's
+		 * pg_proc entry!
 		 */
 		tupdesc = CreateTemplateTupleDesc(3, false);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
+		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "abbrev",
 						   TEXTOID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "utc_offset",
 						   INTERVALOID, -1, 0);
@@ -3928,3 +3928,114 @@ pg_timezonenames(PG_FUNCTION_ARGS)
 
 	SRF_RETURN_NEXT(funcctx, result);
 }
+
+/*
+ * This set-returning function reads all the available full time zones
+ * and returns a set of (name, abbrev, utc_offset, is_dst).
+ */
+Datum
+pg_timezone_names(PG_FUNCTION_ARGS)
+{
+	MemoryContext	oldcontext;
+	FuncCallContext	   *funcctx;
+	pg_tzenum          *tzenum;
+	pg_tz              *tz;
+	Datum				result;
+	HeapTuple			tuple;
+	Datum				values[4];
+	bool				nulls[4];
+	int			tzoff;
+	struct pg_tm		tm;
+	fsec_t		fsec;
+	char	   *tzn;
+	Interval		   *resInterval;
+	struct pg_tm		itm;
+
+	/* stuff done only on the first call of the function */
+	if (SRF_IS_FIRSTCALL())
+	{
+		TupleDesc		tupdesc;
+
+		/* create a function context for cross-call persistence */
+		funcctx = SRF_FIRSTCALL_INIT();
+
+		/*
+		 * switch to memory context appropriate for multiple function
+		 * calls
+		 */
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
+		/* initialize timezone scanning code */
+		tzenum = pg_tzenumerate_start();
+		funcctx->user_fctx = (void *) tzenum;
+
+		/*
+		 * build tupdesc for result tuples. This must match this function's
+		 * pg_proc entry!
+		 */
+		tupdesc = CreateTemplateTupleDesc(4, false);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
+						   TEXTOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "abbrev",
+						   TEXTOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "utc_offset",
+						   INTERVALOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 4, "is_dst",
+						   BOOLOID, -1, 0);
+
+		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	/* stuff done on every call of the function */
+	funcctx = SRF_PERCALL_SETUP();
+	tzenum = (pg_tzenum *) funcctx->user_fctx;
+
+	/* search for another zone to display */
+	for (;;)
+	{
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+		tz = pg_tzenumerate_next(tzenum);
+		MemoryContextSwitchTo(oldcontext);
+
+		if (!tz)
+		{
+			pg_tzenumerate_end(tzenum);
+			funcctx->user_fctx = NULL;
+			SRF_RETURN_DONE(funcctx);
+		}
+
+		/* Convert now() to local time in this zone */
+		if (timestamp2tm(GetCurrentTransactionStartTimestamp(),
+						 &tzoff, &tm, &fsec, &tzn, tz) != 0)
+			continue;			/* ignore if conversion fails */
+
+		/* Ignore zic's rather silly "Factory" time zone */
+		if (tzn && strcmp(tzn, "Local time zone must be set--see zic manual page") == 0)
+			continue;
+
+		/* Found a displayable zone */
+		break;
+	}
+
+	MemSet(nulls, 0, sizeof(nulls));
+
+	values[0] = DirectFunctionCall1(textin,
+									CStringGetDatum(pg_get_timezone_name(tz)));
+
+	values[1] = DirectFunctionCall1(textin,
+									CStringGetDatum(tzn ? tzn : ""));
+
+	MemSet(&itm, 0, sizeof(struct pg_tm));
+	itm.tm_sec = -tzoff;
+	resInterval = (Interval *) palloc(sizeof(Interval));
+	tm2interval(&itm, 0, resInterval);
+	values[2] = IntervalPGetDatum(resInterval);
+
+	values[3] = BoolGetDatum(tm.tm_isdst > 0);
+
+	tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
+	result = HeapTupleGetDatum(tuple);
+
+	SRF_RETURN_NEXT(funcctx, result);
+}

src/include/catalog/catversion.h

@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.356 2006/09/14 22:05:06 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.357 2006/09/16 20:14:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200609141
+#define CATALOG_VERSION_NO	200609161
 
 #endif

src/include/catalog/pg_proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.424 2006/09/14 22:05:06 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.425 2006/09/16 20:14:33 tgl Exp $
  *
  * NOTES
  *	  The script catalog/genbki.sh reads this file and generates .bki
@@ -3791,7 +3791,9 @@ DATA(insert OID = 2510 (  pg_prepared_statement PGNSP PGUID 12 f f t t s 0 2249
 DESCR("get the prepared statements for this session");
 DATA(insert OID = 2511 (  pg_cursor PGNSP PGUID 12 f f t t s 0 2249 "" _null_ _null_ _null_ pg_cursor - _null_ ));
 DESCR("get the open cursors for this session");
-DATA(insert OID = 2599 (  pg_timezonenames PGNSP PGUID 12 f f t t s 0 2249 "" _null_ _null_ _null_ pg_timezonenames - _null_ ));
+DATA(insert OID = 2599 (  pg_timezone_abbrevs	PGNSP PGUID 12 f f t t s 0 2249 "" "{25,1186,16}" "{o,o,o}" "{abbrev,utc_offset,is_dst}" pg_timezone_abbrevs - _null_ ));
+DESCR("get the available time zone abbreviations");
+DATA(insert OID = 2856 (  pg_timezone_names		PGNSP PGUID 12 f f t t s 0 2249 "" "{25,25,1186,16}" "{o,o,o,o}" "{name,abbrev,utc_offset,is_dst}" pg_timezone_names - _null_ ));
 DESCR("get the available time zone names");
 
 /* non-persistent series generator */

src/include/pgtime.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/include/pgtime.h,v 1.12 2006/03/05 15:58:53 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/include/pgtime.h,v 1.13 2006/09/16 20:14:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -38,6 +38,7 @@ struct pg_tm
 };
 
 typedef struct pg_tz pg_tz;
+typedef struct pg_tzenum pg_tzenum;
 
 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);
@@ -56,6 +57,10 @@ 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_tzenum *pg_tzenumerate_start(void);
+extern pg_tz *pg_tzenumerate_next(pg_tzenum *dir);
+extern void pg_tzenumerate_end(pg_tzenum *dir);
+
 extern pg_tz *global_timezone;
 
 /* Maximum length of a timezone name (not including trailing null) */

src/include/utils/datetime.h

@@ -9,7 +9,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/datetime.h,v 1.60 2006/07/25 03:51:22 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/datetime.h,v 1.61 2006/09/16 20:14:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -303,6 +303,7 @@ extern int	j2day(int jd);
 extern bool CheckDateTokenTables(void);
 extern void InstallTimeZoneAbbrevs(tzEntry *abbrevs, int n);
 
-extern Datum pg_timezonenames(PG_FUNCTION_ARGS);
+extern Datum pg_timezone_abbrevs(PG_FUNCTION_ARGS);
+extern Datum pg_timezone_names(PG_FUNCTION_ARGS);
 
 #endif   /* DATETIME_H */

src/test/regress/expected/rules.out

@@ -1306,7 +1306,8 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_statio_user_tables    | SELECT pg_statio_all_tables.relid, pg_statio_all_tables.schemaname, pg_statio_all_tables.relname, pg_statio_all_tables.heap_blks_read, pg_statio_all_tables.heap_blks_hit, pg_statio_all_tables.idx_blks_read, pg_statio_all_tables.idx_blks_hit, pg_statio_all_tables.toast_blks_read, pg_statio_all_tables.toast_blks_hit, pg_statio_all_tables.tidx_blks_read, pg_statio_all_tables.tidx_blks_hit FROM pg_statio_all_tables WHERE (pg_statio_all_tables.schemaname <> ALL (ARRAY['pg_catalog'::name, 'pg_toast'::name, 'information_schema'::name]));
  pg_stats                 | SELECT n.nspname AS schemaname, c.relname AS tablename, a.attname, s.stanullfrac AS null_frac, s.stawidth AS avg_width, s.stadistinct AS n_distinct, CASE 1 WHEN s.stakind1 THEN s.stavalues1 WHEN s.stakind2 THEN s.stavalues2 WHEN s.stakind3 THEN s.stavalues3 WHEN s.stakind4 THEN s.stavalues4 ELSE NULL::"unknown" END AS most_common_vals, CASE 1 WHEN s.stakind1 THEN s.stanumbers1 WHEN s.stakind2 THEN s.stanumbers2 WHEN s.stakind3 THEN s.stanumbers3 WHEN s.stakind4 THEN s.stanumbers4 ELSE NULL::real[] END AS most_common_freqs, CASE 2 WHEN s.stakind1 THEN s.stavalues1 WHEN s.stakind2 THEN s.stavalues2 WHEN s.stakind3 THEN s.stavalues3 WHEN s.stakind4 THEN s.stavalues4 ELSE NULL::"unknown" END AS histogram_bounds, CASE 3 WHEN s.stakind1 THEN s.stanumbers1[1] WHEN s.stakind2 THEN s.stanumbers2[1] WHEN s.stakind3 THEN s.stanumbers3[1] WHEN s.stakind4 THEN s.stanumbers4[1] ELSE NULL::real END AS correlation FROM (((pg_statistic s JOIN pg_class c ON ((c.oid = s.starelid))) JOIN pg_attribute a ON (((c.oid = a.attrelid) AND (a.attnum = s.staattnum)))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE has_table_privilege(c.oid, 'select'::text);
  pg_tables                | SELECT n.nspname AS schemaname, c.relname AS tablename, pg_get_userbyid(c.relowner) AS tableowner, t.spcname AS "tablespace", c.relhasindex AS hasindexes, c.relhasrules AS hasrules, (c.reltriggers > 0) AS hastriggers FROM ((pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) LEFT JOIN pg_tablespace t ON ((t.oid = c.reltablespace))) WHERE (c.relkind = 'r'::"char");
- pg_timezonenames         | SELECT t.name, t.utc_offset, t.is_dst FROM pg_timezonenames() t(name text, utc_offset interval, is_dst boolean);
+ pg_timezone_abbrevs      | SELECT pg_timezone_abbrevs.abbrev, pg_timezone_abbrevs.utc_offset, pg_timezone_abbrevs.is_dst FROM pg_timezone_abbrevs() pg_timezone_abbrevs(abbrev, utc_offset, is_dst);
+ pg_timezone_names        | SELECT pg_timezone_names.name, pg_timezone_names.abbrev, pg_timezone_names.utc_offset, pg_timezone_names.is_dst FROM pg_timezone_names() pg_timezone_names(name, abbrev, utc_offset, is_dst);
  pg_user                  | SELECT pg_shadow.usename, pg_shadow.usesysid, pg_shadow.usecreatedb, pg_shadow.usesuper, pg_shadow.usecatupd, '********'::text AS passwd, pg_shadow.valuntil, pg_shadow.useconfig FROM pg_shadow;
  pg_views                 | SELECT n.nspname AS schemaname, c.relname AS viewname, pg_get_userbyid(c.relowner) AS viewowner, pg_get_viewdef(c.oid) AS definition FROM (pg_class c LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (c.relkind = 'v'::"char");
  rtest_v1                 | SELECT rtest_t1.a, rtest_t1.b FROM rtest_t1;
@@ -1323,7 +1324,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  shoelace_obsolete        | SELECT shoelace.sl_name, shoelace.sl_avail, shoelace.sl_color, shoelace.sl_len, shoelace.sl_unit, shoelace.sl_len_cm FROM shoelace WHERE (NOT (EXISTS (SELECT shoe.shoename FROM shoe WHERE (shoe.slcolor = shoelace.sl_color))));
  street                   | SELECT r.name, r.thepath, c.cname FROM ONLY road r, real_city c WHERE (c.outline ## r.thepath);
  toyemp                   | SELECT emp.name, emp.age, emp."location", (12 * emp.salary) AS annualsal FROM emp;
-(47 rows)
+(48 rows)
 
 SELECT tablename, rulename, definition FROM pg_rules 
 	ORDER BY tablename, rulename;

src/timezone/pgtz.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.44 2006/07/14 14:52:27 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.45 2006/09/16 20:14:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1136,3 +1136,120 @@ pg_timezone_initialize(void)
 		SetConfigOption("timezone", def_tz, PGC_POSTMASTER, PGC_S_ARGV);
 	}
 }
+
+
+/*
+ * Functions to enumerate available timezones
+ *
+ * Note that pg_tzenumerate_next() will return a pointer into the pg_tzenum
+ * structure, so the data is only valid up to the next call.
+ *
+ * All data is allocated using palloc in the current context.
+ */
+#define MAX_TZDIR_DEPTH 10
+
+struct pg_tzenum {
+   int baselen;
+   int depth;
+   DIR *dirdesc[MAX_TZDIR_DEPTH];
+   char *dirname[MAX_TZDIR_DEPTH];
+   struct pg_tz tz;
+};
+/* typedef pg_tzenum is declared in pgtime.h */
+
+pg_tzenum *
+pg_tzenumerate_start(void) 
+{
+	pg_tzenum *ret = (pg_tzenum *) palloc0(sizeof(pg_tzenum));
+	char *startdir = pstrdup(pg_TZDIR());
+
+	ret->baselen = strlen(startdir) + 1;
+	ret->depth = 0;
+	ret->dirname[0] = startdir;
+	ret->dirdesc[0] = AllocateDir(startdir);
+	if (!ret->dirdesc[0]) 
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open directory \"%s\": %m", startdir)));
+	return ret;
+}
+
+void
+pg_tzenumerate_end(pg_tzenum *dir)
+{
+	while (dir->depth >= 0)
+	{
+		FreeDir(dir->dirdesc[dir->depth]);
+		pfree(dir->dirname[dir->depth]);
+		dir->depth--;
+	}
+	pfree(dir);
+}
+
+pg_tz *
+pg_tzenumerate_next(pg_tzenum *dir)
+{
+	while (dir->depth >= 0)
+	{
+		struct dirent *direntry;
+		char fullname[MAXPGPATH];
+		struct stat statbuf;
+
+		direntry = ReadDir(dir->dirdesc[dir->depth], dir->dirname[dir->depth]);
+
+		if (!direntry)
+		{
+			/* End of this directory */
+			FreeDir(dir->dirdesc[dir->depth]);
+			pfree(dir->dirname[dir->depth]);
+			dir->depth--;
+			continue;
+		}
+
+		if (direntry->d_name[0] == '.')
+			continue;
+
+		snprintf(fullname, MAXPGPATH, "%s/%s",
+				 dir->dirname[dir->depth], direntry->d_name);
+		if (stat(fullname, &statbuf) != 0)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not stat \"%s\": %m", fullname)));
+
+		if (S_ISDIR(statbuf.st_mode))
+		{
+			/* Step into the subdirectory */
+			if (dir->depth >= MAX_TZDIR_DEPTH-1)
+				ereport(ERROR,
+						(errmsg("timezone directory stack overflow")));
+			dir->depth++;
+			dir->dirname[dir->depth] = pstrdup(fullname);
+			dir->dirdesc[dir->depth] = AllocateDir(fullname);
+			if (!dir->dirdesc[dir->depth]) 
+				ereport(ERROR,
+						(errcode_for_file_access(),
+						 errmsg("could not open directory \"%s\": %m",
+								fullname)));
+
+			/* Start over reading in the new directory */
+			continue;
+		}
+
+		/*
+		 * Load this timezone using tzload() not pg_tzset(),
+		 * so we don't fill the cache
+		 */
+		if (tzload(fullname + dir->baselen, &dir->tz.state) != 0)
+		{
+			/* Zone could not be loaded, ignore it */
+			continue;
+		}
+
+		/* Timezone loaded OK. */
+		strcpy(dir->tz.TZname, fullname + dir->baselen);
+		return &dir->tz;
+	}
+
+	/* Nothing more found */
+	return NULL;
+}