src/include/datatype/timestamp.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * timestamp.h
   4  *        Timestamp and Interval typedefs and related macros.
   5  *
   6  * Note: this file must be includable in both frontend and backend contexts.
   7  *
   8  * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
   9  * Portions Copyright (c) 1994, Regents of the University of California
  10  *
  11  * src/include/datatype/timestamp.h
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #ifndef DATATYPE_TIMESTAMP_H
  16 #define DATATYPE_TIMESTAMP_H
  17
  18 /*
  19  * Timestamp represents absolute time.
  20  *
  21  * Interval represents delta time. Keep track of months (and years), days,
  22  * and hours/minutes/seconds separately since the elapsed time spanned is
  23  * unknown until instantiated relative to an absolute time.
  24  *
  25  * Note that Postgres uses "time interval" to mean a bounded interval,
  26  * consisting of a beginning and ending time, not a time span - thomas 97/03/20
  27  *
  28  * Timestamps, as well as the h/m/s fields of intervals, are stored as
  29  * int64 values with units of microseconds.  (Once upon a time they were
  30  * double values with units of seconds.)
  31  *
  32  * TimeOffset and fsec_t are convenience typedefs for temporary variables.
  33  * Do not use fsec_t in values stored on-disk.
  34  * Also, fsec_t is only meant for *fractional* seconds; beware of overflow
  35  * if the value you need to store could be many seconds.
  36  */
  37
  38 typedef int64 Timestamp;
  39 typedef int64 TimestampTz;
  40 typedef int64 TimeOffset;
  41 typedef int32 fsec_t;                   /* fractional seconds (in microseconds) */
  42
  43 typedef struct
  44 {
  45         TimeOffset      time;                   /* all time units other than days, months and
  46                                                                  * years */
  47         int32           day;                    /* days, after time for alignment */
  48         int32           month;                  /* months and years, after time for alignment */
  49 } Interval;
  50
  51
  52 /* Limits on the "precision" option (typmod) for these data types */
  53 #define MAX_TIMESTAMP_PRECISION 6
  54 #define MAX_INTERVAL_PRECISION 6
  55
  56 /*
  57  *      Round off to MAX_TIMESTAMP_PRECISION decimal places.
  58  *      Note: this is also used for rounding off intervals.
  59  */
  60 #define TS_PREC_INV 1000000.0
  61 #define TSROUND(j) (rint(((double) (j)) * TS_PREC_INV) / TS_PREC_INV)
  62
  63
  64 /*
  65  * Assorted constants for datetime-related calculations
  66  */
  67
  68 #define DAYS_PER_YEAR   365.25  /* assumes leap year every four years */
  69 #define MONTHS_PER_YEAR 12
  70 /*
  71  *      DAYS_PER_MONTH is very imprecise.  The more accurate value is
  72  *      365.2425/12 = 30.436875, or '30 days 10:29:06'.  Right now we only
  73  *      return an integral number of days, but someday perhaps we should
  74  *      also return a 'time' value to be used as well.  ISO 8601 suggests
  75  *      30 days.
  76  */
  77 #define DAYS_PER_MONTH  30              /* assumes exactly 30 days per month */
  78 #define HOURS_PER_DAY   24              /* assume no daylight savings time changes */
  79
  80 /*
  81  *      This doesn't adjust for uneven daylight savings time intervals or leap
  82  *      seconds, and it crudely estimates leap years.  A more accurate value
  83  *      for days per years is 365.2422.
  84  */
  85 #define SECS_PER_YEAR   (36525 * 864)   /* avoid floating-point computation */
  86 #define SECS_PER_DAY    86400
  87 #define SECS_PER_HOUR   3600
  88 #define SECS_PER_MINUTE 60
  89 #define MINS_PER_HOUR   60
  90
  91 #define USECS_PER_DAY   INT64CONST(86400000000)
  92 #define USECS_PER_HOUR  INT64CONST(3600000000)
  93 #define USECS_PER_MINUTE INT64CONST(60000000)
  94 #define USECS_PER_SEC   INT64CONST(1000000)
  95
  96 /*
  97  * We allow numeric timezone offsets up to 15:59:59 either way from Greenwich.
  98  * Currently, the record holders for wackiest offsets in actual use are zones
  99  * Asia/Manila, at -15:56:00 until 1844, and America/Metlakatla, at +15:13:42
 100  * until 1867.  If we were to reject such values we would fail to dump and
 101  * restore old timestamptz values with these zone settings.
 102  */
 103 #define MAX_TZDISP_HOUR         15      /* maximum allowed hour part */
 104 #define TZDISP_LIMIT            ((MAX_TZDISP_HOUR + 1) * SECS_PER_HOUR)
 105
 106 /*
 107  * DT_NOBEGIN represents timestamp -infinity; DT_NOEND represents +infinity
 108  */
 109 #define DT_NOBEGIN              PG_INT64_MIN
 110 #define DT_NOEND                PG_INT64_MAX
 111
 112 #define TIMESTAMP_NOBEGIN(j)    \
 113         do {(j) = DT_NOBEGIN;} while (0)
 114
 115 #define TIMESTAMP_IS_NOBEGIN(j) ((j) == DT_NOBEGIN)
 116
 117 #define TIMESTAMP_NOEND(j)              \
 118         do {(j) = DT_NOEND;} while (0)
 119
 120 #define TIMESTAMP_IS_NOEND(j)   ((j) == DT_NOEND)
 121
 122 #define TIMESTAMP_NOT_FINITE(j) (TIMESTAMP_IS_NOBEGIN(j) || TIMESTAMP_IS_NOEND(j))
 123
 124
 125 /*
 126  * Julian date support.
 127  *
 128  * date2j() and j2date() nominally handle the Julian date range 0..INT_MAX,
 129  * or 4714-11-24 BC to 5874898-06-03 AD.  In practice, date2j() will work and
 130  * give correct negative Julian dates for dates before 4714-11-24 BC as well.
 131  * We rely on it to do so back to 4714-11-01 BC.  Allowing at least one day's
 132  * slop is necessary so that timestamp rotation doesn't produce dates that
 133  * would be rejected on input.  For example, '4714-11-24 00:00 GMT BC' is a
 134  * legal timestamptz value, but in zones east of Greenwich it would print as
 135  * sometime in the afternoon of 4714-11-23 BC; if we couldn't process such a
 136  * date we'd have a dump/reload failure.  So the idea is for IS_VALID_JULIAN
 137  * to accept a slightly wider range of dates than we really support, and
 138  * then we apply the exact checks in IS_VALID_DATE or IS_VALID_TIMESTAMP,
 139  * after timezone rotation if any.  To save a few cycles, we can make
 140  * IS_VALID_JULIAN check only to the month boundary, since its exact cutoffs
 141  * are not very critical in this scheme.
 142  *
 143  * It is correct that JULIAN_MINYEAR is -4713, not -4714; it is defined to
 144  * allow easy comparison to tm_year values, in which we follow the convention
 145  * that tm_year <= 0 represents abs(tm_year)+1 BC.
 146  */
 147
 148 #define JULIAN_MINYEAR (-4713)
 149 #define JULIAN_MINMONTH (11)
 150 #define JULIAN_MINDAY (24)
 151 #define JULIAN_MAXYEAR (5874898)
 152 #define JULIAN_MAXMONTH (6)
 153 #define JULIAN_MAXDAY (3)
 154
 155 #define IS_VALID_JULIAN(y,m,d) \
 156         (((y) > JULIAN_MINYEAR || \
 157           ((y) == JULIAN_MINYEAR && ((m) >= JULIAN_MINMONTH))) && \
 158          ((y) < JULIAN_MAXYEAR || \
 159           ((y) == JULIAN_MAXYEAR && ((m) < JULIAN_MAXMONTH))))
 160
 161 /* Julian-date equivalents of Day 0 in Unix and Postgres reckoning */
 162 #define UNIX_EPOCH_JDATE                2440588 /* == date2j(1970, 1, 1) */
 163 #define POSTGRES_EPOCH_JDATE    2451545 /* == date2j(2000, 1, 1) */
 164
 165 /*
 166  * Range limits for dates and timestamps.
 167  *
 168  * We have traditionally allowed Julian day zero as a valid datetime value,
 169  * so that is the lower bound for both dates and timestamps.
 170  *
 171  * The upper limit for dates is 5874897-12-31, which is a bit less than what
 172  * the Julian-date code can allow.  For timestamps, the upper limit is
 173  * 294276-12-31.  The int64 overflow limit would be a few days later; again,
 174  * leaving some slop avoids worries about corner-case overflow, and provides
 175  * a simpler user-visible definition.
 176  */
 177
 178 /* First allowed date, and first disallowed date, in Julian-date form */
 179 #define DATETIME_MIN_JULIAN (0)
 180 #define DATE_END_JULIAN (2147483494)    /* == date2j(JULIAN_MAXYEAR, 1, 1) */
 181 #define TIMESTAMP_END_JULIAN (109203528)        /* == date2j(294277, 1, 1) */
 182
 183 /* Timestamp limits */
 184 #define MIN_TIMESTAMP   INT64CONST(-211813488000000000)
 185 /* == (DATETIME_MIN_JULIAN - POSTGRES_EPOCH_JDATE) * USECS_PER_DAY */
 186 #define END_TIMESTAMP   INT64CONST(9223371331200000000)
 187 /* == (TIMESTAMP_END_JULIAN - POSTGRES_EPOCH_JDATE) * USECS_PER_DAY */
 188
 189 /* Range-check a date (given in Postgres, not Julian, numbering) */
 190 #define IS_VALID_DATE(d) \
 191         ((DATETIME_MIN_JULIAN - POSTGRES_EPOCH_JDATE) <= (d) && \
 192          (d) < (DATE_END_JULIAN - POSTGRES_EPOCH_JDATE))
 193
 194 /* Range-check a timestamp */
 195 #define IS_VALID_TIMESTAMP(t)  (MIN_TIMESTAMP <= (t) && (t) < END_TIMESTAMP)
 196
 197 #endif                                                  /* DATATYPE_TIMESTAMP_H */