270 lines
9.4 KiB
C
270 lines
9.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* timestamp.h
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* Timestamp and Interval typedefs and related macros.
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*
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* Note: this file must be includable in both frontend and backend contexts.
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*
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* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/datatype/timestamp.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef DATATYPE_TIMESTAMP_H
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#define DATATYPE_TIMESTAMP_H
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/*
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* Timestamp represents absolute time.
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*
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* Interval represents delta time. Keep track of months (and years), days,
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* and hours/minutes/seconds separately since the elapsed time spanned is
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* unknown until instantiated relative to an absolute time.
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*
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* Note that Postgres uses "time interval" to mean a bounded interval,
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* consisting of a beginning and ending time, not a time span - thomas 97/03/20
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*
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* Timestamps, as well as the h/m/s fields of intervals, are stored as
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* int64 values with units of microseconds. (Once upon a time they were
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* double values with units of seconds.)
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*
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* TimeOffset and fsec_t are convenience typedefs for temporary variables.
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* Do not use fsec_t in values stored on-disk.
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* Also, fsec_t is only meant for *fractional* seconds; beware of overflow
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* if the value you need to store could be many seconds.
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*/
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typedef int64 Timestamp;
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typedef int64 TimestampTz;
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typedef int64 TimeOffset;
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typedef int32 fsec_t; /* fractional seconds (in microseconds) */
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/*
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* Storage format for type interval.
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*/
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typedef struct
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{
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TimeOffset time; /* all time units other than days, months and
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* years */
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int32 day; /* days, after time for alignment */
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int32 month; /* months and years, after time for alignment */
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} Interval;
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/*
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* Data structure representing a broken-down interval.
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*
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* For historical reasons, this is modeled on struct pg_tm for timestamps.
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* Unlike the situation for timestamps, there's no magic interpretation
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* needed for months or years: they're just zero or not. Note that fields
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* can be negative; however, because of the divisions done while converting
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* from struct Interval, only tm_mday could be INT_MIN. This is important
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* because we may need to negate the values in some code paths.
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*/
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struct pg_itm
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{
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int tm_usec;
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int tm_sec;
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int tm_min;
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int64 tm_hour; /* needs to be wide */
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int tm_mday;
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int tm_mon;
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int tm_year;
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};
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/*
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* Data structure for decoding intervals. We could just use struct pg_itm,
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* but then the requirement for tm_usec to be 64 bits would propagate to
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* places where it's not really needed. Also, omitting the fields that
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* aren't used during decoding seems like a good error-prevention measure.
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*/
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struct pg_itm_in
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{
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int64 tm_usec; /* needs to be wide */
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int tm_mday;
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int tm_mon;
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int tm_year;
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};
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/* Limits on the "precision" option (typmod) for these data types */
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#define MAX_TIMESTAMP_PRECISION 6
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#define MAX_INTERVAL_PRECISION 6
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/*
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* Round off to MAX_TIMESTAMP_PRECISION decimal places.
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* Note: this is also used for rounding off intervals.
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*/
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#define TS_PREC_INV 1000000.0
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#define TSROUND(j) (rint(((double) (j)) * TS_PREC_INV) / TS_PREC_INV)
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/*
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* Assorted constants for datetime-related calculations
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*/
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#define DAYS_PER_YEAR 365.25 /* assumes leap year every four years */
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#define MONTHS_PER_YEAR 12
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/*
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* DAYS_PER_MONTH is very imprecise. The more accurate value is
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* 365.2425/12 = 30.436875, or '30 days 10:29:06'. Right now we only
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* return an integral number of days, but someday perhaps we should
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* also return a 'time' value to be used as well. ISO 8601 suggests
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* 30 days.
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*/
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#define DAYS_PER_MONTH 30 /* assumes exactly 30 days per month */
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#define DAYS_PER_WEEK 7
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#define HOURS_PER_DAY 24 /* assume no daylight savings time changes */
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/*
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* This doesn't adjust for uneven daylight savings time intervals or leap
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* seconds, and it crudely estimates leap years. A more accurate value
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* for days per years is 365.2422.
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*/
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#define SECS_PER_YEAR (36525 * 864) /* avoid floating-point computation */
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#define SECS_PER_DAY 86400
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#define SECS_PER_HOUR 3600
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#define SECS_PER_MINUTE 60
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#define MINS_PER_HOUR 60
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#define USECS_PER_DAY INT64CONST(86400000000)
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#define USECS_PER_HOUR INT64CONST(3600000000)
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#define USECS_PER_MINUTE INT64CONST(60000000)
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#define USECS_PER_SEC INT64CONST(1000000)
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/*
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* We allow numeric timezone offsets up to 15:59:59 either way from Greenwich.
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* Currently, the record holders for wackiest offsets in actual use are zones
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* Asia/Manila, at -15:56:00 until 1844, and America/Metlakatla, at +15:13:42
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* until 1867. If we were to reject such values we would fail to dump and
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* restore old timestamptz values with these zone settings.
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*/
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#define MAX_TZDISP_HOUR 15 /* maximum allowed hour part */
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#define TZDISP_LIMIT ((MAX_TZDISP_HOUR + 1) * SECS_PER_HOUR)
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/*
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* We reserve the minimum and maximum integer values to represent
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* timestamp (or timestamptz) -infinity and +infinity.
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*/
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#define TIMESTAMP_MINUS_INFINITY PG_INT64_MIN
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#define TIMESTAMP_INFINITY PG_INT64_MAX
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/*
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* Historically these aliases for infinity have been used.
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*/
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#define DT_NOBEGIN TIMESTAMP_MINUS_INFINITY
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#define DT_NOEND TIMESTAMP_INFINITY
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#define TIMESTAMP_NOBEGIN(j) \
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do {(j) = DT_NOBEGIN;} while (0)
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#define TIMESTAMP_IS_NOBEGIN(j) ((j) == DT_NOBEGIN)
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#define TIMESTAMP_NOEND(j) \
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do {(j) = DT_NOEND;} while (0)
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#define TIMESTAMP_IS_NOEND(j) ((j) == DT_NOEND)
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#define TIMESTAMP_NOT_FINITE(j) (TIMESTAMP_IS_NOBEGIN(j) || TIMESTAMP_IS_NOEND(j))
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/*
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* Infinite intervals are represented by setting all fields to the minimum or
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* maximum integer values.
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*/
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#define INTERVAL_NOBEGIN(i) \
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do { \
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(i)->time = PG_INT64_MIN; \
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(i)->day = PG_INT32_MIN; \
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(i)->month = PG_INT32_MIN; \
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} while (0)
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#define INTERVAL_IS_NOBEGIN(i) \
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((i)->month == PG_INT32_MIN && (i)->day == PG_INT32_MIN && (i)->time == PG_INT64_MIN)
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#define INTERVAL_NOEND(i) \
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do { \
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(i)->time = PG_INT64_MAX; \
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(i)->day = PG_INT32_MAX; \
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(i)->month = PG_INT32_MAX; \
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} while (0)
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#define INTERVAL_IS_NOEND(i) \
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((i)->month == PG_INT32_MAX && (i)->day == PG_INT32_MAX && (i)->time == PG_INT64_MAX)
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#define INTERVAL_NOT_FINITE(i) (INTERVAL_IS_NOBEGIN(i) || INTERVAL_IS_NOEND(i))
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/*
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* Julian date support.
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*
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* date2j() and j2date() nominally handle the Julian date range 0..INT_MAX,
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* or 4714-11-24 BC to 5874898-06-03 AD. In practice, date2j() will work and
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* give correct negative Julian dates for dates before 4714-11-24 BC as well.
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* We rely on it to do so back to 4714-11-01 BC. Allowing at least one day's
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* slop is necessary so that timestamp rotation doesn't produce dates that
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* would be rejected on input. For example, '4714-11-24 00:00 GMT BC' is a
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* legal timestamptz value, but in zones east of Greenwich it would print as
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* sometime in the afternoon of 4714-11-23 BC; if we couldn't process such a
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* date we'd have a dump/reload failure. So the idea is for IS_VALID_JULIAN
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* to accept a slightly wider range of dates than we really support, and
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* then we apply the exact checks in IS_VALID_DATE or IS_VALID_TIMESTAMP,
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* after timezone rotation if any. To save a few cycles, we can make
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* IS_VALID_JULIAN check only to the month boundary, since its exact cutoffs
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* are not very critical in this scheme.
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*
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* It is correct that JULIAN_MINYEAR is -4713, not -4714; it is defined to
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* allow easy comparison to tm_year values, in which we follow the convention
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* that tm_year <= 0 represents abs(tm_year)+1 BC.
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*/
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#define JULIAN_MINYEAR (-4713)
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#define JULIAN_MINMONTH (11)
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#define JULIAN_MINDAY (24)
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#define JULIAN_MAXYEAR (5874898)
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#define JULIAN_MAXMONTH (6)
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#define JULIAN_MAXDAY (3)
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#define IS_VALID_JULIAN(y,m,d) \
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(((y) > JULIAN_MINYEAR || \
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((y) == JULIAN_MINYEAR && ((m) >= JULIAN_MINMONTH))) && \
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((y) < JULIAN_MAXYEAR || \
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((y) == JULIAN_MAXYEAR && ((m) < JULIAN_MAXMONTH))))
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/* Julian-date equivalents of Day 0 in Unix and Postgres reckoning */
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#define UNIX_EPOCH_JDATE 2440588 /* == date2j(1970, 1, 1) */
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#define POSTGRES_EPOCH_JDATE 2451545 /* == date2j(2000, 1, 1) */
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/*
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* Range limits for dates and timestamps.
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*
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* We have traditionally allowed Julian day zero as a valid datetime value,
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* so that is the lower bound for both dates and timestamps.
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*
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* The upper limit for dates is 5874897-12-31, which is a bit less than what
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* the Julian-date code can allow. For timestamps, the upper limit is
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* 294276-12-31. The int64 overflow limit would be a few days later; again,
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* leaving some slop avoids worries about corner-case overflow, and provides
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* a simpler user-visible definition.
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*/
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/* First allowed date, and first disallowed date, in Julian-date form */
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#define DATETIME_MIN_JULIAN (0)
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#define DATE_END_JULIAN (2147483494) /* == date2j(JULIAN_MAXYEAR, 1, 1) */
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#define TIMESTAMP_END_JULIAN (109203528) /* == date2j(294277, 1, 1) */
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/* Timestamp limits */
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#define MIN_TIMESTAMP INT64CONST(-211813488000000000)
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/* == (DATETIME_MIN_JULIAN - POSTGRES_EPOCH_JDATE) * USECS_PER_DAY */
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#define END_TIMESTAMP INT64CONST(9223371331200000000)
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/* == (TIMESTAMP_END_JULIAN - POSTGRES_EPOCH_JDATE) * USECS_PER_DAY */
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/* Range-check a date (given in Postgres, not Julian, numbering) */
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#define IS_VALID_DATE(d) \
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((DATETIME_MIN_JULIAN - POSTGRES_EPOCH_JDATE) <= (d) && \
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(d) < (DATE_END_JULIAN - POSTGRES_EPOCH_JDATE))
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/* Range-check a timestamp */
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#define IS_VALID_TIMESTAMP(t) (MIN_TIMESTAMP <= (t) && (t) < END_TIMESTAMP)
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#endif /* DATATYPE_TIMESTAMP_H */
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