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Commit388e71a

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Make timetz_zone() stable, and correct a bug for DYNTZ abbreviations.
Historically, timetz_zone() has used time(NULL) as the reference pointfor deciding whether DST is active. That means its result can changeintra-statement, requiring it to be marked VOLATILE (cf.35979e6).But that definition is pretty inconsistent with the way we deal withtimestamps elsewhere. Let's make it use the transaction start time("now()") as the reference point instead. That lets it be markedSTABLE, and also saves a kernel call per invocation.While at it, remove the function's use of pg_time_t and pg_localtime.Those are inconsistent with the other code in this area, which indeedcreated a bug: timetz_zone() delivered completely wrong answers ifthe zone was specified by a dynamic TZ abbreviation. (We need to dosomething about that in the back branches, but the fix will lookdifferent from this.)Aleksander Alekseev and Tom LaneDiscussion:https://postgr.es/m/CAJ7c6TOMG8zSNEZtCn5SPe+cCk3Lfxb71ZaQwT2F4T7PJ_t=KA@mail.gmail.com
1 parent78aa616 commit388e71a

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3 files changed

+16
-16
lines changed

3 files changed

+16
-16
lines changed

‎src/backend/utils/adt/date.c

Lines changed: 14 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -1481,9 +1481,7 @@ float_time_overflows(int hour, int min, double sec)
14811481
/* time2tm()
14821482
* Convert time data type to POSIX time structure.
14831483
*
1484-
* For dates within the range of pg_time_t, convert to the local time zone.
1485-
* If out of this range, leave as UTC (in practice that could only happen
1486-
* if pg_time_t is just 32 bits) - thomas 97/05/27
1484+
* Note that only the hour/min/sec/fractional-sec fields are filled in.
14871485
*/
14881486
int
14891487
time2tm(TimeADTtime,structpg_tm*tm,fsec_t*fsec)
@@ -3029,7 +3027,7 @@ extract_timetz(PG_FUNCTION_ARGS)
30293027

30303028
/* timetz_zone()
30313029
* Encode time with time zone type with specified time zone.
3032-
* Applies DST rules as of thecurrent date.
3030+
* Applies DST rules as of thetransaction start time.
30333031
*/
30343032
Datum
30353033
timetz_zone(PG_FUNCTION_ARGS)
@@ -3068,25 +3066,27 @@ timetz_zone(PG_FUNCTION_ARGS)
30683066
}
30693067
elseif (type==DYNTZ)
30703068
{
3071-
/* dynamic-offset abbreviation, resolve usingcurrent time */
3072-
pg_time_tnow=(pg_time_t)time(NULL);
3073-
structpg_tm*tm;
3069+
/* dynamic-offset abbreviation, resolve usingtransaction start time */
3070+
TimestampTznow=GetCurrentTransactionStartTimestamp();
3071+
intisdst;
30743072

3075-
tm=pg_localtime(&now,tzp);
3076-
tz=DetermineTimeZoneAbbrevOffset(tm,tzname,tzp);
3073+
tz=DetermineTimeZoneAbbrevOffsetTS(now,tzname,tzp,&isdst);
30773074
}
30783075
else
30793076
{
30803077
/* try it as a full zone name */
30813078
tzp=pg_tzset(tzname);
30823079
if (tzp)
30833080
{
3084-
/* Get the offset-from-GMT that is valid today for the zone */
3085-
pg_time_tnow= (pg_time_t)time(NULL);
3086-
structpg_tm*tm;
3081+
/* Get the offset-from-GMT that is valid now for the zone */
3082+
TimestampTznow=GetCurrentTransactionStartTimestamp();
3083+
structpg_tmtm;
3084+
fsec_tfsec;
30873085

3088-
tm=pg_localtime(&now,tzp);
3089-
tz=-tm->tm_gmtoff;
3086+
if (timestamp2tm(now,&tz,&tm,&fsec,NULL,tzp)!=0)
3087+
ereport(ERROR,
3088+
(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
3089+
errmsg("timestamp out of range")));
30903090
}
30913091
else
30923092
{

‎src/include/catalog/catversion.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,6 @@
5353
*/
5454

5555
/*yyyymmddN */
56-
#defineCATALOG_VERSION_NO202109032
56+
#defineCATALOG_VERSION_NO202109061
5757

5858
#endif

‎src/include/catalog/pg_proc.dat

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -5953,7 +5953,7 @@
59535953
proname => 'timestamp_larger', prorettype => 'timestamp',
59545954
proargtypes => 'timestamp timestamp', prosrc => 'timestamp_larger' },
59555955
{ oid => '2037', descr => 'adjust time with time zone to new zone',
5956-
proname => 'timezone', provolatile => 'v', prorettype => 'timetz',
5956+
proname => 'timezone', provolatile => 's', prorettype => 'timetz',
59575957
proargtypes => 'text timetz', prosrc => 'timetz_zone' },
59585958
{ oid => '2038', descr => 'adjust time with time zone to new zone',
59595959
proname => 'timezone', prorettype => 'timetz',

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