Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commitb36df04

Browse files
committed
Guard against roundoff errors in new selectivity-estimation code,
per bug report from Laurette Cisneros.
1 parentbb2bff4 commitb36df04

File tree

1 file changed

+34
-22
lines changed

1 file changed

+34
-22
lines changed

‎src/backend/utils/adt/selfuncs.c

Lines changed: 34 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@
1515
*
1616
*
1717
* IDENTIFICATION
18-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.102 2001/11/05 17:46:29 momjian Exp $
18+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.103 2002/01/03 04:02:34 tgl Exp $
1919
*
2020
*-------------------------------------------------------------------------
2121
*/
@@ -124,6 +124,19 @@
124124
#defineDEFAULT_NOT_UNK_SEL(1.0 - DEFAULT_UNK_SEL)
125125
#defineDEFAULT_BOOL_SEL0.5
126126

127+
/*
128+
* Clamp a computed probability estimate (which may suffer from roundoff or
129+
* estimation errors) to valid range. Argument must be a float variable.
130+
*/
131+
#defineCLAMP_PROBABILITY(p) \
132+
do { \
133+
if (p < 0.0) \
134+
p = 0.0; \
135+
else if (p > 1.0) \
136+
p = 1.0; \
137+
} while (0)
138+
139+
127140
staticboolconvert_to_scalar(Datumvalue,Oidvaluetypid,double*scaledvalue,
128141
Datumlobound,Datumhibound,Oidboundstypid,
129142
double*scaledlobound,double*scaledhibound);
@@ -285,6 +298,7 @@ eqsel(PG_FUNCTION_ARGS)
285298
for (i=0;i<nnumbers;i++)
286299
sumcommon+=numbers[i];
287300
selec=1.0-sumcommon-stats->stanullfrac;
301+
CLAMP_PROBABILITY(selec);
288302

289303
/*
290304
* and in fact it's probably a good deal less. We
@@ -356,10 +370,7 @@ eqsel(PG_FUNCTION_ARGS)
356370
}
357371

358372
/* result should be in range, but make sure... */
359-
if (selec<0.0)
360-
selec=0.0;
361-
elseif (selec>1.0)
362-
selec=1.0;
373+
CLAMP_PROBABILITY(selec);
363374

364375
PG_RETURN_FLOAT8((float8)selec);
365376
}
@@ -669,10 +680,7 @@ scalarineqsel(Query *root, Oid operator, bool isgt,
669680
ReleaseSysCache(statsTuple);
670681

671682
/* result should be in range, but make sure... */
672-
if (selec<0.0)
673-
selec=0.0;
674-
elseif (selec>1.0)
675-
selec=1.0;
683+
CLAMP_PROBABILITY(selec);
676684

677685
returnselec;
678686
}
@@ -867,10 +875,7 @@ patternsel(PG_FUNCTION_ARGS, Pattern_Type ptype)
867875
restsel=pattern_selectivity(rest,ptype);
868876
selec=prefixsel*restsel;
869877
/* result should be in range, but make sure... */
870-
if (selec<0.0)
871-
selec=0.0;
872-
elseif (selec>1.0)
873-
selec=1.0;
878+
CLAMP_PROBABILITY(selec);
874879
result=selec;
875880
}
876881

@@ -1179,10 +1184,7 @@ booltestsel(Query *root, BooleanTest *clause, int varRelid)
11791184
}
11801185

11811186
/* result should be in range, but make sure... */
1182-
if (selec<0.0)
1183-
selec=0.0;
1184-
elseif (selec>1.0)
1185-
selec=1.0;
1187+
CLAMP_PROBABILITY(selec);
11861188

11871189
return (Selectivity)selec;
11881190
}
@@ -1285,10 +1287,7 @@ nulltestsel(Query *root, NullTest *clause, int varRelid)
12851287
}
12861288

12871289
/* result should be in range, but make sure... */
1288-
if (selec<0.0)
1289-
selec=0.0;
1290-
elseif (selec>1.0)
1291-
selec=1.0;
1290+
CLAMP_PROBABILITY(selec);
12921291

12931292
return (Selectivity)selec;
12941293
}
@@ -1448,6 +1447,7 @@ eqjoinsel(PG_FUNCTION_ARGS)
14481447
}
14491448
}
14501449
}
1450+
CLAMP_PROBABILITY(matchprodfreq);
14511451
/* Sum up frequencies of matched and unmatched MCVs */
14521452
matchfreq1=unmatchfreq1=0.0;
14531453
for (i=0;i<nvalues1;i++)
@@ -1457,6 +1457,8 @@ eqjoinsel(PG_FUNCTION_ARGS)
14571457
else
14581458
unmatchfreq1+=numbers1[i];
14591459
}
1460+
CLAMP_PROBABILITY(matchfreq1);
1461+
CLAMP_PROBABILITY(unmatchfreq1);
14601462
matchfreq2=unmatchfreq2=0.0;
14611463
for (i=0;i<nvalues2;i++)
14621464
{
@@ -1465,6 +1467,8 @@ eqjoinsel(PG_FUNCTION_ARGS)
14651467
else
14661468
unmatchfreq2+=numbers2[i];
14671469
}
1470+
CLAMP_PROBABILITY(matchfreq2);
1471+
CLAMP_PROBABILITY(unmatchfreq2);
14681472
pfree(hasmatch1);
14691473
pfree(hasmatch2);
14701474

@@ -1474,6 +1478,8 @@ eqjoinsel(PG_FUNCTION_ARGS)
14741478
*/
14751479
otherfreq1=1.0-stats1->stanullfrac-matchfreq1-unmatchfreq1;
14761480
otherfreq2=1.0-stats2->stanullfrac-matchfreq2-unmatchfreq2;
1481+
CLAMP_PROBABILITY(otherfreq1);
1482+
CLAMP_PROBABILITY(otherfreq2);
14771483

14781484
/*
14791485
* We can estimate the total selectivity from the point of
@@ -1544,6 +1550,9 @@ eqjoinsel(PG_FUNCTION_ARGS)
15441550
if (HeapTupleIsValid(statsTuple2))
15451551
ReleaseSysCache(statsTuple2);
15461552
}
1553+
1554+
CLAMP_PROBABILITY(selec);
1555+
15471556
PG_RETURN_FLOAT8((float8)selec);
15481557
}
15491558

@@ -2213,6 +2222,9 @@ convert_timevalue_to_scalar(Datum value, Oid typid)
22132222
*
22142223
* var: identifies the attribute to examine.
22152224
* stats: pg_statistic tuple for attribute, or NULL if not available.
2225+
*
2226+
* NB: be careful to produce an integral result, since callers may compare
2227+
* the result to exact integer counts.
22162228
*/
22172229
staticdouble
22182230
get_att_numdistinct(Query*root,Var*var,Form_pg_statisticstats)
@@ -2254,7 +2266,7 @@ get_att_numdistinct(Query *root, Var *var, Form_pg_statistic stats)
22542266
if (stats->stadistinct>0.0)
22552267
returnstats->stadistinct;
22562268
if (stats->stadistinct<0.0)
2257-
return-stats->stadistinct*ntuples;
2269+
returnfloor((-stats->stadistinct*ntuples)+0.5);
22582270
}
22592271

22602272
/*

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp