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Commit1c2d408

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Rewrite interval_hash() so that the hashcodes are equal for values that
interval_eq() considers equal. I'm not sure how that fundamental requirementescaped us through multiple revisions of this hash function, but there it is;it's been wrong since interval_hash was first written for PG 7.1.Per bug #4748 from Roman Kononov.Backpatch to all supported releases.This patch changes the contents of hash indexes for interval columns. That'sno particular problem for PG 8.4, since we've broken on-disk compatibilityof hash indexes already; but it will require a migration warning note inthe next minor releases of all existing branches: "if you have any hashindexes on columns of type interval, REINDEX them after updating".
1 parent1c855f0 commit1c2d408

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3 files changed

+46
-34
lines changed

3 files changed

+46
-34
lines changed

‎src/backend/utils/adt/timestamp.c‎

Lines changed: 29 additions & 34 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 1.197 2009/03/15 20:31:19 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/utils/adt/timestamp.c,v 1.198 2009/04/04 04:53:25 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -2041,27 +2041,30 @@ timestamptz_cmp_timestamp(PG_FUNCTION_ARGS)
20412041
*
20422042
*collate invalid interval at the end
20432043
*/
2044-
staticint
2045-
interval_cmp_internal(Interval*interval1,Interval*interval2)
2044+
staticinlineTimeOffset
2045+
interval_cmp_value(constInterval*interval)
20462046
{
2047-
TimeOffsetspan1,
2048-
span2;
2047+
TimeOffsetspan;
20492048

2050-
span1=interval1->time;
2051-
span2=interval2->time;
2049+
span=interval->time;
20522050

20532051
#ifdefHAVE_INT64_TIMESTAMP
2054-
span1+=interval1->month*INT64CONST(30)*USECS_PER_DAY;
2055-
span1+=interval1->day*INT64CONST(24)*USECS_PER_HOUR;
2056-
span2+=interval2->month*INT64CONST(30)*USECS_PER_DAY;
2057-
span2+=interval2->day*INT64CONST(24)*USECS_PER_HOUR;
2052+
span+=interval->month*INT64CONST(30)*USECS_PER_DAY;
2053+
span+=interval->day*INT64CONST(24)*USECS_PER_HOUR;
20582054
#else
2059-
span1+=interval1->month* ((double)DAYS_PER_MONTH*SECS_PER_DAY);
2060-
span1+=interval1->day* ((double)HOURS_PER_DAY*SECS_PER_HOUR);
2061-
span2+=interval2->month* ((double)DAYS_PER_MONTH*SECS_PER_DAY);
2062-
span2+=interval2->day* ((double)HOURS_PER_DAY*SECS_PER_HOUR);
2055+
span+=interval->month* ((double)DAYS_PER_MONTH*SECS_PER_DAY);
2056+
span+=interval->day* ((double)HOURS_PER_DAY*SECS_PER_HOUR);
20632057
#endif
20642058

2059+
returnspan;
2060+
}
2061+
2062+
staticint
2063+
interval_cmp_internal(Interval*interval1,Interval*interval2)
2064+
{
2065+
TimeOffsetspan1=interval_cmp_value(interval1);
2066+
TimeOffsetspan2=interval_cmp_value(interval2);
2067+
20652068
return ((span1<span2) ?-1 : (span1>span2) ?1 :0);
20662069
}
20672070

@@ -2128,32 +2131,24 @@ interval_cmp(PG_FUNCTION_ARGS)
21282131
PG_RETURN_INT32(interval_cmp_internal(interval1,interval2));
21292132
}
21302133

2134+
/*
2135+
* Hashing for intervals
2136+
*
2137+
* We must produce equal hashvals for values that interval_cmp_internal()
2138+
* considers equal. So, compute the net span the same way it does,
2139+
* and then hash that, using either int64 or float8 hashing.
2140+
*/
21312141
Datum
21322142
interval_hash(PG_FUNCTION_ARGS)
21332143
{
2134-
Interval*key=PG_GETARG_INTERVAL_P(0);
2135-
uint32thash;
2136-
uint32mhash;
2144+
Interval*interval=PG_GETARG_INTERVAL_P(0);
2145+
TimeOffsetspan=interval_cmp_value(interval);
21372146

2138-
/*
2139-
* To avoid any problems with padding bytes in the struct, we figure the
2140-
* field hashes separately and XOR them. This also provides a convenient
2141-
* framework for dealing with the fact that the time field might be either
2142-
* double or int64.
2143-
*/
21442147
#ifdefHAVE_INT64_TIMESTAMP
2145-
thash=DatumGetUInt32(DirectFunctionCall1(hashint8,
2146-
Int64GetDatumFast(key->time)));
2148+
returnDirectFunctionCall1(hashint8,Int64GetDatumFast(span));
21472149
#else
2148-
thash=DatumGetUInt32(DirectFunctionCall1(hashfloat8,
2149-
Float8GetDatumFast(key->time)));
2150+
returnDirectFunctionCall1(hashfloat8,Float8GetDatumFast(span));
21502151
#endif
2151-
thash ^=DatumGetUInt32(hash_uint32(key->day));
2152-
/* Shift so "k days" and "k months" don't hash to the same thing */
2153-
mhash=DatumGetUInt32(hash_uint32(key->month));
2154-
thash ^=mhash <<24;
2155-
thash ^=mhash >>8;
2156-
PG_RETURN_UINT32(thash);
21572152
}
21582153

21592154
/* overlaps_timestamp() --- implements the SQL92 OVERLAPS operator.

‎src/test/regress/expected/interval.out‎

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -717,3 +717,16 @@ select interval '0:0:0.7', interval '@ 0.70 secs', interval '0.7 seconds';
717717
@ 0.7 secs | @ 0.7 secs | @ 0.7 secs
718718
(1 row)
719719

720+
-- check that '30 days' equals '1 month' according to the hash function
721+
select '30 days'::interval = '1 month'::interval as t;
722+
t
723+
---
724+
t
725+
(1 row)
726+
727+
select interval_hash('30 days'::interval) = interval_hash('1 month'::interval) as t;
728+
t
729+
---
730+
t
731+
(1 row)
732+

‎src/test/regress/sql/interval.sql‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -241,3 +241,7 @@ SET IntervalStyle to postgres_verbose;
241241
select interval'-10 mons -3 days +03:55:06.70';
242242
select interval'1 year 2 mons 3 days 04:05:06.699999';
243243
select interval'0:0:0.7', interval'@ 0.70 secs', interval'0.7 seconds';
244+
245+
-- check that '30 days' equals '1 month' according to the hash function
246+
select'30 days'::interval='1 month'::intervalas t;
247+
select interval_hash('30 days'::interval)= interval_hash('1 month'::interval)as t;

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