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timestamp.h
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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 */
int64 TimestampTz
Definition: timestamp.h:39
signed int int32
Definition: c.h:246
int32 day
Definition: timestamp.h:47
TimeOffset time
Definition: timestamp.h:45
int32 fsec_t
Definition: timestamp.h:41
int32 month
Definition: timestamp.h:48
int64 Timestamp
Definition: timestamp.h:38
int64 TimeOffset
Definition: timestamp.h:40