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) 1996-2017, 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 */ 198