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Add functions to do timestamptz arithmetic in a non-default timezone.

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Add versions of timestamptz + interval, timestamptz - interval, and
generate_series(timestamptz, ...) in which a timezone can be specified
explicitly instead of defaulting to the TimeZone GUC setting.

The new functions for the first two are named date_add and
date_subtract.  This might seem too generic, but we could use
overloading to add additional variants if that seems useful.

Along the way, improve the docs' pretty inadequate explanation
of how timestamptz +- interval works.

Przemysław Sztoch and Gurjeet Singh; cosmetic changes and most of
the docs work by me

Discussion: https://postgr.es/m/01a84551-48dd-1359-bf7e-f6b0203a6bd0@sztoch.pl
This commit is contained in:
Tom Lane
2023-03-18 14:12:14 -04:00
parent 0e681cf039
commit 75bd846b68
6 changed files with 292 additions and 45 deletions
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148
src/backend/utils/adt/timestamp.c
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@ -69,6 +69,7 @@ typedef struct
TimestampTz finish;
Interval step;
int step_sign;
pg_tz *attimezone;
} generate_series_timestamptz_fctx;
@ -531,6 +532,21 @@ parse_sane_timezone(struct pg_tm *tm, text *zone)
return tz;
}
/*
* Look up the requested timezone, returning a pg_tz struct.
*
* This is the same as DecodeTimezoneNameToTz, but starting with a text Datum.
*/
static pg_tz *
lookup_timezone(text *zone)
{
char tzname[TZ_STRLEN_MAX + 1];
text_to_cstring_buffer(zone, tzname, sizeof(tzname));
return DecodeTimezoneNameToTz(tzname);
}
/*
* make_timestamp_internal
* workhorse for make_timestamp and make_timestamptz
@ -2998,20 +3014,22 @@ timestamp_mi_interval(PG_FUNCTION_ARGS)
}
/* timestamptz_pl_interval()
* Add an interval to a timestamp with time zone data type.
* Note that interval has provisions for qualitative year/month
/* timestamptz_pl_interval_internal()
* Add an interval to a timestamptz, in the given (or session) timezone.
*
* Note that interval has provisions for qualitative year/month and day
* units, so try to do the right thing with them.
* To add a month, increment the month, and use the same day of month.
* Then, if the next month has fewer days, set the day of month
* to the last day of month.
* To add a day, increment the mday, and use the same time of day.
* Lastly, add in the "quantitative time".
*/
Datum
timestamptz_pl_interval(PG_FUNCTION_ARGS)
static TimestampTz
timestamptz_pl_interval_internal(TimestampTz timestamp,
Interval *span,
pg_tz *attimezone)
{
TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
Interval *span = PG_GETARG_INTERVAL_P(1);
TimestampTz result;
int tz;
@ -3019,13 +3037,17 @@ timestamptz_pl_interval(PG_FUNCTION_ARGS)
result = timestamp;
else
{
/* Use session timezone if caller asks for default */
if (attimezone == NULL)
attimezone = session_timezone;
if (span->month != 0)
{
struct pg_tm tt,
*tm = &tt;
fsec_t fsec;
if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, attimezone) != 0)
ereport(ERROR,
(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
errmsg("timestamp out of range")));
@ -3046,7 +3068,7 @@ timestamptz_pl_interval(PG_FUNCTION_ARGS)
if (tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
tm->tm_mday = (day_tab[isleap(tm->tm_year)][tm->tm_mon - 1]);
tz = DetermineTimeZoneOffset(tm, session_timezone);
tz = DetermineTimeZoneOffset(tm, attimezone);
if (tm2timestamp(tm, fsec, &tz, &timestamp) != 0)
ereport(ERROR,
@ -3061,7 +3083,7 @@ timestamptz_pl_interval(PG_FUNCTION_ARGS)
fsec_t fsec;
int julian;
if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, attimezone) != 0)
ereport(ERROR,
(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
errmsg("timestamp out of range")));
@ -3070,7 +3092,7 @@ timestamptz_pl_interval(PG_FUNCTION_ARGS)
julian = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) + span->day;
j2date(julian, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
tz = DetermineTimeZoneOffset(tm, session_timezone);
tz = DetermineTimeZoneOffset(tm, attimezone);
if (tm2timestamp(tm, fsec, &tz, &timestamp) != 0)
ereport(ERROR,
@ -3088,7 +3110,36 @@ timestamptz_pl_interval(PG_FUNCTION_ARGS)
result = timestamp;
}
PG_RETURN_TIMESTAMP(result);
return result;
}
/* timestamptz_mi_interval_internal()
* As above, but subtract the interval.
*/
static TimestampTz
timestamptz_mi_interval_internal(TimestampTz timestamp,
Interval *span,
pg_tz *attimezone)
{
Interval tspan;
tspan.month = -span->month;
tspan.day = -span->day;
tspan.time = -span->time;
return timestamptz_pl_interval_internal(timestamp, &tspan, attimezone);
}
/* timestamptz_pl_interval()
* Add an interval to a timestamptz, in the session timezone.
*/
Datum
timestamptz_pl_interval(PG_FUNCTION_ARGS)
{
TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
Interval *span = PG_GETARG_INTERVAL_P(1);
PG_RETURN_TIMESTAMP(timestamptz_pl_interval_internal(timestamp, span, NULL));
}
Datum
@ -3096,17 +3147,34 @@ timestamptz_mi_interval(PG_FUNCTION_ARGS)
{
TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
Interval *span = PG_GETARG_INTERVAL_P(1);
Interval tspan;
tspan.month = -span->month;
tspan.day = -span->day;
tspan.time = -span->time;
return DirectFunctionCall2(timestamptz_pl_interval,
TimestampGetDatum(timestamp),
PointerGetDatum(&tspan));
PG_RETURN_TIMESTAMP(timestamptz_mi_interval_internal(timestamp, span, NULL));
}
/* timestamptz_pl_interval_at_zone()
* Add an interval to a timestamptz, in the specified timezone.
*/
Datum
timestamptz_pl_interval_at_zone(PG_FUNCTION_ARGS)
{
TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
Interval *span = PG_GETARG_INTERVAL_P(1);
text *zone = PG_GETARG_TEXT_PP(2);
pg_tz *attimezone = lookup_timezone(zone);
PG_RETURN_TIMESTAMP(timestamptz_pl_interval_internal(timestamp, span, attimezone));
}
Datum
timestamptz_mi_interval_at_zone(PG_FUNCTION_ARGS)
{
TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
Interval *span = PG_GETARG_INTERVAL_P(1);
text *zone = PG_GETARG_TEXT_PP(2);
pg_tz *attimezone = lookup_timezone(zone);
PG_RETURN_TIMESTAMP(timestamptz_mi_interval_internal(timestamp, span, attimezone));
}
Datum
interval_um(PG_FUNCTION_ARGS)
@ -3396,13 +3464,9 @@ in_range_timestamptz_interval(PG_FUNCTION_ARGS)
/* We don't currently bother to avoid overflow hazards here */
if (sub)
sum = DatumGetTimestampTz(DirectFunctionCall2(timestamptz_mi_interval,
TimestampTzGetDatum(base),
IntervalPGetDatum(offset)));
sum = timestamptz_mi_interval_internal(base, offset, NULL);
else
sum = DatumGetTimestampTz(DirectFunctionCall2(timestamptz_pl_interval,
TimestampTzGetDatum(base),
IntervalPGetDatum(offset)));
sum = timestamptz_pl_interval_internal(base, offset, NULL);
if (less)
PG_RETURN_BOOL(val <= sum);
@ -4284,7 +4348,6 @@ timestamptz_trunc_zone(PG_FUNCTION_ARGS)
TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
text *zone = PG_GETARG_TEXT_PP(2);
TimestampTz result;
char tzname[TZ_STRLEN_MAX + 1];
pg_tz *tzp;
/*
@ -4297,9 +4360,7 @@ timestamptz_trunc_zone(PG_FUNCTION_ARGS)
/*
* Look up the requested timezone.
*/
text_to_cstring_buffer(zone, tzname, sizeof(tzname));
tzp = DecodeTimezoneNameToTz(tzname);
tzp = lookup_timezone(zone);
result = timestamptz_trunc_internal(units, timestamp, tzp);
@ -5776,10 +5837,11 @@ generate_series_timestamp(PG_FUNCTION_ARGS)
}
/* generate_series_timestamptz()
* Generate the set of timestamps from start to finish by step
* Generate the set of timestamps from start to finish by step,
* doing arithmetic in the specified or session timezone.
*/
Datum
generate_series_timestamptz(PG_FUNCTION_ARGS)
static Datum
generate_series_timestamptz_internal(FunctionCallInfo fcinfo)
{
FuncCallContext *funcctx;
generate_series_timestamptz_fctx *fctx;
@ -5791,6 +5853,7 @@ generate_series_timestamptz(PG_FUNCTION_ARGS)
TimestampTz start = PG_GETARG_TIMESTAMPTZ(0);
TimestampTz finish = PG_GETARG_TIMESTAMPTZ(1);
Interval *step = PG_GETARG_INTERVAL_P(2);
text *zone = (PG_NARGS() == 4) ? PG_GETARG_TEXT_PP(3) : NULL;
MemoryContext oldcontext;
const Interval interval_zero = {0};
@ -5813,6 +5876,7 @@ generate_series_timestamptz(PG_FUNCTION_ARGS)
fctx->current = start;
fctx->finish = finish;
fctx->step = *step;
fctx->attimezone = zone ? lookup_timezone(zone) : session_timezone;
/* Determine sign of the interval */
fctx->step_sign = interval_cmp_internal(&fctx->step, &interval_zero);
@ -5840,9 +5904,9 @@ generate_series_timestamptz(PG_FUNCTION_ARGS)
timestamp_cmp_internal(result, fctx->finish) >= 0)
{
/* increment current in preparation for next iteration */
fctx->current = DatumGetTimestampTz(DirectFunctionCall2(timestamptz_pl_interval,
TimestampTzGetDatum(fctx->current),
PointerGetDatum(&fctx->step)));
fctx->current = timestamptz_pl_interval_internal(fctx->current,
&fctx->step,
fctx->attimezone);
/* do when there is more left to send */
SRF_RETURN_NEXT(funcctx, TimestampTzGetDatum(result));
@ -5853,3 +5917,15 @@ generate_series_timestamptz(PG_FUNCTION_ARGS)
SRF_RETURN_DONE(funcctx);
}
}
Datum
generate_series_timestamptz(PG_FUNCTION_ARGS)
{
return generate_series_timestamptz_internal(fcinfo);
}
Datum
generate_series_timestamptz_at_zone(PG_FUNCTION_ARGS)
{
return generate_series_timestamptz_internal(fcinfo);
}