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postgresql/src/include/utils/datetime.h
Tom Lane b2cbced9ee Support timezone abbreviations that sometimes change. 
Up to now, PG has assumed that any given timezone abbreviation (such as
"EDT") represents a constant GMT offset in the usage of any particular
region; we had a way to configure what that offset was, but not for it
to be changeable over time.  But, as with most things horological, this
view of the world is too simplistic: there are numerous regions that have
at one time or another switched to a different GMT offset but kept using
the same timezone abbreviation.  Almost the entire Russian Federation did
that a few years ago, and later this month they're going to do it again.
And there are similar examples all over the world.

To cope with this, invent the notion of a "dynamic timezone abbreviation",
which is one that is referenced to a particular underlying timezone
(as defined in the IANA timezone database) and means whatever it currently
means in that zone.  For zones that use or have used daylight-savings time,
the standard and DST abbreviations continue to have the property that you
can specify standard or DST time and get that time offset whether or not
DST was theoretically in effect at the time.  However, the abbreviations
mean what they meant at the time in question (or most recently before that
time) rather than being absolutely fixed.

The standard abbreviation-list files have been changed to use this behavior
for abbreviations that have actually varied in meaning since 1970.  The
old simple-numeric definitions are kept for abbreviations that have not
changed, since they are a bit faster to resolve.

While this is clearly a new feature, it seems necessary to back-patch it
into all active branches, because otherwise use of Russian zone
abbreviations is going to become even more problematic than it already was.
This change supersedes the changes in commit 513d06ded et al to modify the
fixed meanings of the Russian abbreviations; since we've not shipped that
yet, this will avoid an undesirably incompatible (not to mention incorrect)
change in behavior for timestamps between 2011 and 2014.

This patch makes some cosmetic changes in ecpglib to keep its usage of
datetime lookup tables as similar as possible to the backend code, but
doesn't do anything about the increasingly obsolete set of timezone
abbreviation definitions that are hard-wired into ecpglib.  Whatever we
do about that will likely not be appropriate material for back-patching.
Also, a potential free() of a garbage pointer after an out-of-memory
failure in ecpglib has been fixed.

This patch also fixes pre-existing bugs in DetermineTimeZoneOffset() that
caused it to produce unexpected results near a timezone transition, if
both the "before" and "after" states are marked as standard time.  We'd
only ever thought about or tested transitions between standard and DST
time, but that's not what's happening when a zone simply redefines their
base GMT offset.

In passing, update the SGML documentation to refer to the Olson/zoneinfo/
zic timezone database as the "IANA" database, since it's now being
maintained under the auspices of IANA.
2014-10-16 15:22:10 -04:00

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/*-------------------------------------------------------------------------
*
* datetime.h
* Definitions for date/time support code.
* The support code is shared with other date data types,
* including abstime, reltime, date, and time.
*
*
* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/utils/datetime.h
*
*-------------------------------------------------------------------------
*/
#ifndef DATETIME_H
#define DATETIME_H
#include "nodes/nodes.h"
#include "utils/timestamp.h"
/* this struct is declared in utils/tzparser.h: */
struct tzEntry;
/* ----------------------------------------------------------------
* time types + support macros
*
* String definitions for standard time quantities.
*
* These strings are the defaults used to form output time strings.
* Other alternative forms are hardcoded into token tables in datetime.c.
* ----------------------------------------------------------------
*/
#define DAGO "ago"
#define DCURRENT "current"
#define EPOCH "epoch"
#define INVALID "invalid"
#define EARLY "-infinity"
#define LATE "infinity"
#define NOW "now"
#define TODAY "today"
#define TOMORROW "tomorrow"
#define YESTERDAY "yesterday"
#define ZULU "zulu"
#define DMICROSEC "usecond"
#define DMILLISEC "msecond"
#define DSECOND "second"
#define DMINUTE "minute"
#define DHOUR "hour"
#define DDAY "day"
#define DWEEK "week"
#define DMONTH "month"
#define DQUARTER "quarter"
#define DYEAR "year"
#define DDECADE "decade"
#define DCENTURY "century"
#define DMILLENNIUM "millennium"
#define DA_D "ad"
#define DB_C "bc"
#define DTIMEZONE "timezone"
/*
* Fundamental time field definitions for parsing.
*
* Meridian: am, pm, or 24-hour style.
* Millennium: ad, bc
*/
#define AM 0
#define PM 1
#define HR24 2
#define AD 0
#define BC 1
/*
* Field types for time decoding.
*
* Can't have more of these than there are bits in an unsigned int
* since these are turned into bit masks during parsing and decoding.
*
* Furthermore, the values for YEAR, MONTH, DAY, HOUR, MINUTE, SECOND
* must be in the range 0..14 so that the associated bitmasks can fit
* into the left half of an INTERVAL's typmod value. Since those bits
* are stored in typmods, you can't change them without initdb!
*/
#define RESERV 0
#define MONTH 1
#define YEAR 2
#define DAY 3
#define JULIAN 4
#define TZ 5 /* fixed-offset timezone abbreviation */
#define DTZ 6 /* fixed-offset timezone abbrev, DST */
#define DYNTZ 7 /* dynamic timezone abbreviation */
#define IGNORE_DTF 8
#define AMPM 9
#define HOUR 10
#define MINUTE 11
#define SECOND 12
#define MILLISECOND 13
#define MICROSECOND 14
#define DOY 15
#define DOW 16
#define UNITS 17
#define ADBC 18
/* these are only for relative dates */
#define AGO 19
#define ABS_BEFORE 20
#define ABS_AFTER 21
/* generic fields to help with parsing */
#define ISODATE 22
#define ISOTIME 23
/* these are only for parsing intervals */
#define WEEK 24
#define DECADE 25
#define CENTURY 26
#define MILLENNIUM 27
/* hack for parsing two-word timezone specs "MET DST" etc */
#define DTZMOD 28 /* "DST" as a separate word */
/* reserved for unrecognized string values */
#define UNKNOWN_FIELD 31
/*
* Token field definitions for time parsing and decoding.
*
* Some field type codes (see above) use these as the "value" in datetktbl[].
* These are also used for bit masks in DecodeDateTime and friends
* so actually restrict them to within [0,31] for now.
* - thomas 97/06/19
* Not all of these fields are used for masks in DecodeDateTime
* so allow some larger than 31. - thomas 1997-11-17
*
* Caution: there are undocumented assumptions in the code that most of these
* values are not equal to IGNORE_DTF nor RESERV. Be very careful when
* renumbering values in either of these apparently-independent lists :-(
*/
#define DTK_NUMBER 0
#define DTK_STRING 1
#define DTK_DATE 2
#define DTK_TIME 3
#define DTK_TZ 4
#define DTK_AGO 5
#define DTK_SPECIAL 6
#define DTK_INVALID 7
#define DTK_CURRENT 8
#define DTK_EARLY 9
#define DTK_LATE 10
#define DTK_EPOCH 11
#define DTK_NOW 12
#define DTK_YESTERDAY 13
#define DTK_TODAY 14
#define DTK_TOMORROW 15
#define DTK_ZULU 16
#define DTK_DELTA 17
#define DTK_SECOND 18
#define DTK_MINUTE 19
#define DTK_HOUR 20
#define DTK_DAY 21
#define DTK_WEEK 22
#define DTK_MONTH 23
#define DTK_QUARTER 24
#define DTK_YEAR 25
#define DTK_DECADE 26
#define DTK_CENTURY 27
#define DTK_MILLENNIUM 28
#define DTK_MILLISEC 29
#define DTK_MICROSEC 30
#define DTK_JULIAN 31
#define DTK_DOW 32
#define DTK_DOY 33
#define DTK_TZ_HOUR 34
#define DTK_TZ_MINUTE 35
#define DTK_ISOYEAR 36
#define DTK_ISODOW 37
/*
* Bit mask definitions for time parsing.
*/
#define DTK_M(t) (0x01 << (t))
/* Convenience: a second, plus any fractional component */
#define DTK_ALL_SECS_M (DTK_M(SECOND) | DTK_M(MILLISECOND) | DTK_M(MICROSECOND))
#define DTK_DATE_M (DTK_M(YEAR) | DTK_M(MONTH) | DTK_M(DAY))
#define DTK_TIME_M (DTK_M(HOUR) | DTK_M(MINUTE) | DTK_ALL_SECS_M)
/*
* Working buffer size for input and output of interval, timestamp, etc.
* Inputs that need more working space will be rejected early. Longer outputs
* will overrun buffers, so this must suffice for all possible output. As of
* this writing, interval_out() needs the most space at ~90 bytes.
*/
#define MAXDATELEN 128
/* maximum possible number of fields in a date string */
#define MAXDATEFIELDS 25
/* only this many chars are stored in datetktbl */
#define TOKMAXLEN 10
/* keep this struct small; it gets used a lot */
typedef struct
{
char token[TOKMAXLEN + 1]; /* always NUL-terminated */
char type; /* see field type codes above */
int32 value; /* meaning depends on type */
} datetkn;
/* one of its uses is in tables of time zone abbreviations */
typedef struct TimeZoneAbbrevTable
{
Size tblsize; /* size in bytes of TimeZoneAbbrevTable */
int numabbrevs; /* number of entries in abbrevs[] array */
datetkn abbrevs[1]; /* VARIABLE LENGTH ARRAY */
/* DynamicZoneAbbrev(s) may follow the abbrevs[] array */
} TimeZoneAbbrevTable;
/* auxiliary data for a dynamic time zone abbreviation (non-fixed-offset) */
typedef struct DynamicZoneAbbrev
{
pg_tz *tz; /* NULL if not yet looked up */
char zone[1]; /* zone name (var length, NUL-terminated) */
} DynamicZoneAbbrev;
/* FMODULO()
* Macro to replace modf(), which is broken on some platforms.
* t = input and remainder
* q = integer part
* u = divisor
*/
#define FMODULO(t,q,u) \
do { \
(q) = (((t) < 0) ? ceil((t) / (u)) : floor((t) / (u))); \
if ((q) != 0) (t) -= rint((q) * (u)); \
} while(0)
/* TMODULO()
* Like FMODULO(), but work on the timestamp datatype (either int64 or float8).
* We assume that int64 follows the C99 semantics for division (negative
* quotients truncate towards zero).
*/
#ifdef HAVE_INT64_TIMESTAMP
#define TMODULO(t,q,u) \
do { \
(q) = ((t) / (u)); \
if ((q) != 0) (t) -= ((q) * (u)); \
} while(0)
#else
#define TMODULO(t,q,u) \
do { \
(q) = (((t) < 0) ? ceil((t) / (u)) : floor((t) / (u))); \
if ((q) != 0) (t) -= rint((q) * (u)); \
} while(0)
#endif
/*
* Date/time validation
* Include check for leap year.
*/
extern const char *const months[]; /* months (3-char abbreviations) */
extern const char *const days[]; /* days (full names) */
extern const int day_tab[2][13];
#define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
/*
* Datetime input parsing routines (ParseDateTime, DecodeDateTime, etc)
* return zero or a positive value on success. On failure, they return
* one of these negative code values. DateTimeParseError may be used to
* produce a correct ereport.
*/
#define DTERR_BAD_FORMAT (-1)
#define DTERR_FIELD_OVERFLOW (-2)
#define DTERR_MD_FIELD_OVERFLOW (-3) /* triggers hint about DateStyle */
#define DTERR_INTERVAL_OVERFLOW (-4)
#define DTERR_TZDISP_OVERFLOW (-5)
extern void GetCurrentDateTime(struct pg_tm * tm);
extern void GetCurrentTimeUsec(struct pg_tm * tm, fsec_t *fsec, int *tzp);
extern void j2date(int jd, int *year, int *month, int *day);
extern int date2j(int year, int month, int day);
extern int ParseDateTime(const char *timestr, char *workbuf, size_t buflen,
char **field, int *ftype,
int maxfields, int *numfields);
extern int DecodeDateTime(char **field, int *ftype,
int nf, int *dtype,
struct pg_tm * tm, fsec_t *fsec, int *tzp);
extern int DecodeTimezone(char *str, int *tzp);
extern int DecodeTimeOnly(char **field, int *ftype,
int nf, int *dtype,
struct pg_tm * tm, fsec_t *fsec, int *tzp);
extern int DecodeInterval(char **field, int *ftype, int nf, int range,
int *dtype, struct pg_tm * tm, fsec_t *fsec);
extern int DecodeISO8601Interval(char *str,
int *dtype, struct pg_tm * tm, fsec_t *fsec);
extern void DateTimeParseError(int dterr, const char *str,
const char *datatype) __attribute__((noreturn));
extern int DetermineTimeZoneOffset(struct pg_tm * tm, pg_tz *tzp);
extern int DetermineTimeZoneAbbrevOffset(struct pg_tm * tm, const char *abbr, pg_tz *tzp);
extern int DetermineTimeZoneAbbrevOffsetTS(TimestampTz ts, const char *abbr,
pg_tz *tzp, int *isdst);
extern void EncodeDateOnly(struct pg_tm * tm, int style, char *str);
extern void EncodeTimeOnly(struct pg_tm * tm, fsec_t fsec, bool print_tz, int tz, int style, char *str);
extern void EncodeDateTime(struct pg_tm * tm, fsec_t fsec, bool print_tz, int tz, const char *tzn, int style, char *str);
extern void EncodeInterval(struct pg_tm * tm, fsec_t fsec, int style, char *str);
extern int ValidateDate(int fmask, bool isjulian, bool is2digits, bool bc,
struct pg_tm * tm);
extern int DecodeTimezoneAbbrev(int field, char *lowtoken,
int *offset, pg_tz **tz);
extern int DecodeSpecial(int field, char *lowtoken, int *val);
extern int DecodeUnits(int field, char *lowtoken, int *val);
extern int j2day(int jd);
extern Node *TemporalTransform(int32 max_precis, Node *node);
extern bool CheckDateTokenTables(void);
extern TimeZoneAbbrevTable *ConvertTimeZoneAbbrevs(struct tzEntry *abbrevs,
int n);
extern void InstallTimeZoneAbbrevs(TimeZoneAbbrevTable *tbl);
extern Datum pg_timezone_abbrevs(PG_FUNCTION_ARGS);
extern Datum pg_timezone_names(PG_FUNCTION_ARGS);
#endif /* DATETIME_H */
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