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If a time zone abbreviation used in datetime input is defined in the currently active timezone, use that definition in preference to looking in the timezone_abbreviations list. That allows us to correctly handle abbreviations that have different meanings in different timezones. Also, it eliminates an inconsistency between datetime input and datetime output: the non-ISO datestyles for timestamptz have always printed abbreviations taken from the IANA data, not from timezone_abbreviations. Before this fix, it was possible to demonstrate cases where casting a timestamp to text and back fails or changes the value significantly because of that inconsistency. While this change removes the ability to override the IANA data about an abbreviation known in the current zone, it's not clear that there's any real use-case for doing so. But it is clear that this makes life a lot easier for dealing with abbreviations that have conflicts across different time zones. Also update the pg_timezone_abbrevs view to report abbreviations that are recognized via the IANA data, and *not* report any timezone_abbreviations entries that are thereby overridden. Under the hood, there are now two SRFs, one that pulls the IANA data and one that pulls timezone_abbreviations entries. They're combined by logic in the view. This approach was useful for debugging (since the functions can be called on their own). While I don't intend to document the functions explicitly, they might be useful to call directly. Also improve DecodeTimezoneAbbrev's caching logic so that it can cache zone abbreviations found in the IANA data. Without that, this patch would have caused a noticeable degradation of the runtime of timestamptz_in. Per report from Aleksander Alekseev and additional investigation. Discussion: https://postgr.es/m/CAJ7c6TOATjJqvhnYsui0=CO5XFMF4dvTGH+skzB--jNhqSQu5g@mail.gmail.com
102 lines
3.0 KiB
C
102 lines
3.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* pgtime.h
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* PostgreSQL internal timezone library
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*
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* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/include/pgtime.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef _PGTIME_H
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#define _PGTIME_H
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/*
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* The API of this library is generally similar to the corresponding
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* C library functions, except that we use pg_time_t which (we hope) is
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* 64 bits wide, and which is most definitely signed not unsigned.
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*/
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typedef int64 pg_time_t;
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/*
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* Data structure representing a broken-down timestamp.
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*
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* CAUTION: the IANA timezone library (src/timezone/) follows the POSIX
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* convention that tm_mon counts from 0 and tm_year is relative to 1900.
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* However, Postgres' datetime functions generally treat tm_mon as counting
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* from 1 and tm_year as relative to 1 BC. Be sure to make the appropriate
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* adjustments when moving from one code domain to the other.
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*/
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struct pg_tm
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{
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int tm_sec;
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int tm_min;
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int tm_hour;
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int tm_mday;
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int tm_mon; /* see above */
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int tm_year; /* see above */
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int tm_wday;
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int tm_yday;
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int tm_isdst;
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long int tm_gmtoff;
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const char *tm_zone;
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};
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/* These structs are opaque outside the timezone library */
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typedef struct pg_tz pg_tz;
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typedef struct pg_tzenum pg_tzenum;
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/* Maximum length of a timezone name (not including trailing null) */
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#define TZ_STRLEN_MAX 255
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/* these functions are in localtime.c */
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extern struct pg_tm *pg_localtime(const pg_time_t *timep, const pg_tz *tz);
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extern struct pg_tm *pg_gmtime(const pg_time_t *timep);
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extern int pg_next_dst_boundary(const pg_time_t *timep,
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long int *before_gmtoff,
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int *before_isdst,
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pg_time_t *boundary,
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long int *after_gmtoff,
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int *after_isdst,
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const pg_tz *tz);
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extern bool pg_interpret_timezone_abbrev(const char *abbrev,
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const pg_time_t *timep,
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long int *gmtoff,
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int *isdst,
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const pg_tz *tz);
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extern bool pg_timezone_abbrev_is_known(const char *abbrev,
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bool *isfixed,
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long int *gmtoff,
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int *isdst,
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const pg_tz *tz);
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extern const char *pg_get_next_timezone_abbrev(int *indx,
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const pg_tz *tz);
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extern bool pg_get_timezone_offset(const pg_tz *tz, long int *gmtoff);
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extern const char *pg_get_timezone_name(pg_tz *tz);
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extern bool pg_tz_acceptable(pg_tz *tz);
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/* these functions are in strftime.c */
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extern size_t pg_strftime(char *s, size_t maxsize, const char *format,
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const struct pg_tm *t);
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/* these functions and variables are in pgtz.c */
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extern PGDLLIMPORT pg_tz *session_timezone;
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extern PGDLLIMPORT pg_tz *log_timezone;
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extern void pg_timezone_initialize(void);
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extern pg_tz *pg_tzset(const char *tzname);
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extern pg_tz *pg_tzset_offset(long gmtoffset);
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extern pg_tzenum *pg_tzenumerate_start(void);
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extern pg_tz *pg_tzenumerate_next(pg_tzenum *dir);
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extern void pg_tzenumerate_end(pg_tzenum *dir);
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#endif /* _PGTIME_H */
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