rdelaage/postgresql
1
0
Fork 0
mirror of https://git.postgresql.org/git/postgresql.git synced 2024-10-01 09:51:18 +02:00
Code Issues Packages Projects Releases Wiki Activity

Make timetz_zone() stable, and correct a bug for DYNTZ abbreviations.

Browse Source 
Historically, timetz_zone() has used time(NULL) as the reference point
for deciding whether DST is active.  That means its result can change
intra-statement, requiring it to be marked VOLATILE (cf. 35979e6c3).
But that definition is pretty inconsistent with the way we deal with
timestamps elsewhere.  Let's make it use the transaction start time
("now()") as the reference point instead.  That lets it be marked
STABLE, 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 indeed
created a bug: timetz_zone() delivered completely wrong answers if
the zone was specified by a dynamic TZ abbreviation.  (We need to do
something about that in the back branches, but the fix will look
different from this.)

Aleksander Alekseev and Tom Lane

Discussion: https://postgr.es/m/CAJ7c6TOMG8zSNEZtCn5SPe+cCk3Lfxb71ZaQwT2F4T7PJ_t=KA@mail.gmail.com
This commit is contained in:
Tom Lane 2021-09-06 11:03:56 -04:00
parent 78aa616be7
commit 388e71af88
3 changed files with 16 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
src/backend/utils/adt/date.c
View File

@ -1481,9 +1481,7 @@ float_time_overflows(int hour, int min, double sec)
/* time2tm()
* Convert time data type to POSIX time structure.
*
* For dates within the range of pg_time_t, convert to the local time zone.
* If out of this range, leave as UTC (in practice that could only happen
* if pg_time_t is just 32 bits) - thomas 97/05/27
* Note that only the hour/min/sec/fractional-sec fields are filled in.
*/
int
time2tm(TimeADT time, struct pg_tm *tm, fsec_t *fsec)
@ -3029,7 +3027,7 @@ extract_timetz(PG_FUNCTION_ARGS)
/* timetz_zone()
* Encode time with time zone type with specified time zone.
* Applies DST rules as of the current date.
* Applies DST rules as of the transaction start time.
*/
Datum
timetz_zone(PG_FUNCTION_ARGS)
@ -3068,12 +3066,11 @@ timetz_zone(PG_FUNCTION_ARGS)
}
else if (type == DYNTZ)
{
/* dynamic-offset abbreviation, resolve using current time */
pg_time_t now = (pg_time_t) time(NULL);
struct pg_tm *tm;
/* dynamic-offset abbreviation, resolve using transaction start time */
TimestampTz now = GetCurrentTransactionStartTimestamp();
int isdst;
tm = pg_localtime(&now, tzp);
tz = DetermineTimeZoneAbbrevOffset(tm, tzname, tzp);
tz = DetermineTimeZoneAbbrevOffsetTS(now, tzname, tzp, &isdst);
}
else
{
@ -3081,12 +3078,15 @@ timetz_zone(PG_FUNCTION_ARGS)
tzp = pg_tzset(tzname);
if (tzp)
{
/* Get the offset-from-GMT that is valid today for the zone */
pg_time_t now = (pg_time_t) time(NULL);
struct pg_tm *tm;
/* Get the offset-from-GMT that is valid now for the zone */
TimestampTz now = GetCurrentTransactionStartTimestamp();
struct pg_tm tm;
fsec_t fsec;
tm = pg_localtime(&now, tzp);
tz = -tm->tm_gmtoff;
if (timestamp2tm(now, &tz, &tm, &fsec, NULL, tzp) != 0)
ereport(ERROR,
(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
errmsg("timestamp out of range")));
}
else
{

2
src/include/catalog/catversion.h
View File

@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 202109032
#define CATALOG_VERSION_NO 202109061
#endif

2
src/include/catalog/pg_proc.dat
View File

@ -5953,7 +5953,7 @@
proname => 'timestamp_larger', prorettype => 'timestamp',
proargtypes => 'timestamp timestamp', prosrc => 'timestamp_larger' },
{ oid => '2037', descr => 'adjust time with time zone to new zone',
proname => 'timezone', provolatile => 'v', prorettype => 'timetz',
proname => 'timezone', provolatile => 's', prorettype => 'timetz',
proargtypes => 'text timetz', prosrc => 'timetz_zone' },
{ oid => '2038', descr => 'adjust time with time zone to new zone',
proname => 'timezone', prorettype => 'timetz',