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Commitfc51c91

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Properly round months into days and into seconds for interval
multiplication/division queries like select '41 mon 10:00:00'::interval/ 10 as "pos".Report from Michael Glaesemann
1 parent5120f88 commitfc51c91

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2 files changed

+44
-36
lines changed

2 files changed

+44
-36
lines changed

‎src/backend/utils/adt/timestamp.c

Lines changed: 43 additions & 35 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.165 2006/07/13 16:49:16 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.166 2006/09/03 03:34:04 momjian Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -2492,19 +2492,14 @@ interval_mul(PG_FUNCTION_ARGS)
24922492
{
24932493
Interval*span=PG_GETARG_INTERVAL_P(0);
24942494
float8factor=PG_GETARG_FLOAT8(1);
2495-
doublemonth_remainder,
2496-
day_remainder,
2497-
month_remainder_days;
2495+
doublemonth_remainder_days,sec_remainder;
2496+
int32orig_month=span->month,orig_day=span->day;
24982497
Interval*result;
24992498

25002499
result= (Interval*)palloc(sizeof(Interval));
25012500

2502-
month_remainder=span->month*factor;
2503-
day_remainder=span->day*factor;
2504-
result->month= (int32)month_remainder;
2505-
result->day= (int32)day_remainder;
2506-
month_remainder-=result->month;
2507-
day_remainder-=result->day;
2501+
result->month= (int32) (span->month*factor);
2502+
result->day= (int32) (span->day*factor);
25082503

25092504
/*
25102505
* The above correctly handles the whole-number part of the month and day
@@ -2516,16 +2511,31 @@ interval_mul(PG_FUNCTION_ARGS)
25162511
* using justify_hours and/or justify_days.
25172512
*/
25182513

2519-
/* fractional months full days into days */
2520-
month_remainder_days=month_remainder*DAYS_PER_MONTH;
2521-
result->day+= (int32)month_remainder_days;
2522-
/* fractional months partial days into time */
2523-
day_remainder+=month_remainder_days- (int32)month_remainder_days;
2514+
/*
2515+
*Fractional months full days into days.
2516+
*
2517+
*The remainders suffer from float rounding, so instead of
2518+
*doing the computation using just the remainder, we calculate
2519+
*the total number of days and subtract. Specifically, we are
2520+
*multipling by DAYS_PER_MONTH before dividing by factor.
2521+
*This greatly reduces rounding errors.
2522+
*/
2523+
month_remainder_days= (orig_month* (double)DAYS_PER_MONTH)*factor-
2524+
result->month* (double)DAYS_PER_MONTH;
2525+
sec_remainder= (orig_day* (double)SECS_PER_DAY)*factor-
2526+
result->day* (double)SECS_PER_DAY+
2527+
(month_remainder_days- (int32)month_remainder_days)*SECS_PER_DAY;
25242528

2529+
/* cascade units down */
2530+
result->day+= (int32)month_remainder_days;
25252531
#ifdefHAVE_INT64_TIMESTAMP
2526-
result->time=rint(span->time*factor+day_remainder*USECS_PER_DAY);
2532+
result->time=rint(span->time*factor+sec_remainder*USECS_PER_SEC);
25272533
#else
2528-
result->time=span->time*factor+day_remainder*SECS_PER_DAY;
2534+
/*
2535+
*TSROUND() needed to prevent -146:23:60.00 output on PowerPC for
2536+
*SELECT interval '-41 mon -12 days -360:00' * 0.3;
2537+
*/
2538+
result->time=span->time*factor+TSROUND(sec_remainder);
25292539
#endif
25302540

25312541
PG_RETURN_INTERVAL_P(result);
@@ -2546,39 +2556,37 @@ interval_div(PG_FUNCTION_ARGS)
25462556
{
25472557
Interval*span=PG_GETARG_INTERVAL_P(0);
25482558
float8factor=PG_GETARG_FLOAT8(1);
2549-
doublemonth_remainder,
2550-
day_remainder,
2551-
month_remainder_days;
2559+
doublemonth_remainder_days,sec_remainder;
2560+
int32orig_month=span->month,orig_day=span->day;
25522561
Interval*result;
2553-
2562+
25542563
result= (Interval*)palloc(sizeof(Interval));
25552564

25562565
if (factor==0.0)
25572566
ereport(ERROR,
25582567
(errcode(ERRCODE_DIVISION_BY_ZERO),
25592568
errmsg("division by zero")));
25602569

2561-
month_remainder=span->month /factor;
2562-
day_remainder=span->day /factor;
2563-
result->month= (int32)month_remainder;
2564-
result->day= (int32)day_remainder;
2565-
month_remainder-=result->month;
2566-
day_remainder-=result->day;
2570+
result->month= (int32) (span->month /factor);
2571+
result->day= (int32) (span->day /factor);
25672572

25682573
/*
2569-
* Handle any fractional parts the same way as in interval_mul.
2574+
*Fractional months full days into days. See comment in
2575+
*interval_mul().
25702576
*/
2577+
month_remainder_days= (orig_month* (double)DAYS_PER_MONTH) /factor-
2578+
result->month* (double)DAYS_PER_MONTH;
2579+
sec_remainder= (orig_day* (double)SECS_PER_DAY) /factor-
2580+
result->day* (double)SECS_PER_DAY+
2581+
(month_remainder_days- (int32)month_remainder_days)*SECS_PER_DAY;
25712582

2572-
/* fractional months full days into days */
2573-
month_remainder_days=month_remainder*DAYS_PER_MONTH;
2583+
/* cascade units down */
25742584
result->day+= (int32)month_remainder_days;
2575-
/* fractional months partial days into time */
2576-
day_remainder+=month_remainder_days- (int32)month_remainder_days;
2577-
25782585
#ifdefHAVE_INT64_TIMESTAMP
2579-
result->time=rint(span->time /factor+day_remainder*USECS_PER_DAY);
2586+
result->time=rint(span->time /factor+sec_remainder*USECS_PER_SEC);
25802587
#else
2581-
result->time=span->time /factor+day_remainder*SECS_PER_DAY;
2588+
/* See TSROUND comment in interval_mul(). */
2589+
result->time=span->time /factor+TSROUND(sec_remainder);
25822590
#endif
25832591

25842592
PG_RETURN_INTERVAL_P(result);

‎src/test/regress/expected/interval.out

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -218,7 +218,7 @@ SELECT '' AS ten, * FROM INTERVAL_TBL;
218218
select avg(f1) from interval_tbl;
219219
avg
220220
-------------------------------------------------
221-
@ 4 years 1 mon9 days28 hours 18 mins 23 secs
221+
@ 4 years 1 mon10 days4 hours 18 mins 23 secs
222222
(1 row)
223223

224224
-- test long interval input

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