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Properly round months into days and into seconds for interval

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multiplication/division queries like select '41 mon 10:00:00'::interval
/ 10 as "pos".

Report from Michael Glaesemann
This commit is contained in:
Bruce Momjian 2006-09-03 03:34:04 +00:00
parent 5120f88c88
commit fc51c9186a
2 changed files with 44 additions and 36 deletions
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76
src/backend/utils/adt/timestamp.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.165 2006/07/13 16:49:16 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.166 2006/09/03 03:34:04 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -2492,19 +2492,14 @@ interval_mul(PG_FUNCTION_ARGS)
{
Interval *span = PG_GETARG_INTERVAL_P(0);
float8 factor = PG_GETARG_FLOAT8(1);
double month_remainder,
day_remainder,
month_remainder_days;
double month_remainder_days, sec_remainder;
int32 orig_month = span->month, orig_day = span->day;
Interval *result;
result = (Interval *) palloc(sizeof(Interval));
month_remainder = span->month * factor;
day_remainder = span->day * factor;
result->month = (int32) month_remainder;
result->day = (int32) day_remainder;
month_remainder -= result->month;
day_remainder -= result->day;
result->month = (int32) (span->month * factor);
result->day = (int32) (span->day * factor);
/*
* The above correctly handles the whole-number part of the month and day
@ -2516,16 +2511,31 @@ interval_mul(PG_FUNCTION_ARGS)
* using justify_hours and/or justify_days.
*/
/* fractional months full days into days */
month_remainder_days = month_remainder * DAYS_PER_MONTH;
result->day += (int32) month_remainder_days;
/* fractional months partial days into time */
day_remainder += month_remainder_days - (int32) month_remainder_days;
/*
* Fractional months full days into days.
*
* The remainders suffer from float rounding, so instead of
* doing the computation using just the remainder, we calculate
* the total number of days and subtract. Specifically, we are
* multipling by DAYS_PER_MONTH before dividing by factor.
* This greatly reduces rounding errors.
*/
month_remainder_days = (orig_month * (double)DAYS_PER_MONTH) * factor -
result->month * (double)DAYS_PER_MONTH;
sec_remainder = (orig_day * (double)SECS_PER_DAY) * factor -
result->day * (double)SECS_PER_DAY +
(month_remainder_days - (int32) month_remainder_days) * SECS_PER_DAY;
/* cascade units down */
result->day += (int32) month_remainder_days;
#ifdef HAVE_INT64_TIMESTAMP
result->time = rint(span->time * factor + day_remainder * USECS_PER_DAY);
result->time = rint(span->time * factor + sec_remainder * USECS_PER_SEC);
#else
result->time = span->time * factor + day_remainder * SECS_PER_DAY;
/*
* TSROUND() needed to prevent -146:23:60.00 output on PowerPC for
* SELECT interval '-41 mon -12 days -360:00' * 0.3;
*/
result->time = span->time * factor + TSROUND(sec_remainder);
#endif
PG_RETURN_INTERVAL_P(result);
@ -2546,9 +2556,8 @@ interval_div(PG_FUNCTION_ARGS)
{
Interval *span = PG_GETARG_INTERVAL_P(0);
float8 factor = PG_GETARG_FLOAT8(1);
double month_remainder,
day_remainder,
month_remainder_days;
double month_remainder_days, sec_remainder;
int32 orig_month = span->month, orig_day = span->day;
Interval *result;
result = (Interval *) palloc(sizeof(Interval));
@ -2558,27 +2567,26 @@ interval_div(PG_FUNCTION_ARGS)
(errcode(ERRCODE_DIVISION_BY_ZERO),
errmsg("division by zero")));
month_remainder = span->month / factor;
day_remainder = span->day / factor;
result->month = (int32) month_remainder;
result->day = (int32) day_remainder;
month_remainder -= result->month;
day_remainder -= result->day;
result->month = (int32) (span->month / factor);
result->day = (int32) (span->day / factor);
/*
* Handle any fractional parts the same way as in interval_mul.
* Fractional months full days into days. See comment in
* interval_mul().
*/
month_remainder_days = (orig_month * (double)DAYS_PER_MONTH) / factor -
result->month * (double)DAYS_PER_MONTH;
sec_remainder = (orig_day * (double)SECS_PER_DAY) / factor -
result->day * (double)SECS_PER_DAY +
(month_remainder_days - (int32) month_remainder_days) * SECS_PER_DAY;
/* fractional months full days into days */
month_remainder_days = month_remainder * DAYS_PER_MONTH;
/* cascade units down */
result->day += (int32) month_remainder_days;
/* fractional months partial days into time */
day_remainder += month_remainder_days - (int32) month_remainder_days;
#ifdef HAVE_INT64_TIMESTAMP
result->time = rint(span->time / factor + day_remainder * USECS_PER_DAY);
result->time = rint(span->time / factor + sec_remainder * USECS_PER_SEC);
#else
result->time = span->time / factor + day_remainder * SECS_PER_DAY;
/* See TSROUND comment in interval_mul(). */
result->time = span->time / factor + TSROUND(sec_remainder);
#endif
PG_RETURN_INTERVAL_P(result);

2
src/test/regress/expected/interval.out
View File

@ -218,7 +218,7 @@ SELECT '' AS ten, * FROM INTERVAL_TBL;
select avg(f1) from interval_tbl;
avg
-------------------------------------------------
@ 4 years 1 mon 9 days 28 hours 18 mins 23 secs
@ 4 years 1 mon 10 days 4 hours 18 mins 23 secs
(1 row)
-- test long interval input