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Commit5832be6

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Fix edge-case crashes and misestimation in range containment selectivity.
When estimating the selectivity of "range_var <@ range_constant" or"range_var @> range_constant", if the upper (or respectively lower)bound of the range_constant was above the last bin of the range_var'shistogram, the code would access uninitialized memory and potentiallycrash (though it seems the probability of a crash is quite low).Handle the endpoint cases explicitly to fix that.While at it, be more paranoid about the possibility of getting NaNor other silly results from the range type's subdiff function.And improve some comments.Ordinarily we'd probably add a regression test case demonstratingthe bug in unpatched code. But it's too hard to get it to crashreliably because of the uninitialized-memory dependence, so skip that.Per bug #16122 from Adam Scott. It's been broken from the beginning,apparently, so backpatch to all supported branches.Diagnosis by Michael Paquier, patch by Andrey Borodin and Tom Lane.Discussion:https://postgr.es/m/16122-eb35bc248c806c15@postgresql.org
1 parent7eb6217 commit5832be6

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1 file changed

+72
-28
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1 file changed

+72
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‎src/backend/utils/adt/rangetypes_selfuncs.c

Lines changed: 72 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,8 @@
1717
*/
1818
#include"postgres.h"
1919

20+
#include<math.h>
21+
2022
#include"access/htup_details.h"
2123
#include"catalog/pg_operator.h"
2224
#include"catalog/pg_statistic.h"
@@ -397,6 +399,13 @@ calc_hist_selectivity(TypeCacheEntry *typcache, VariableStatData *vardata,
397399
ATTSTATSSLOT_VALUES)))
398400
return-1.0;
399401

402+
/* check that it's a histogram, not just a dummy entry */
403+
if (hslot.nvalues<2)
404+
{
405+
free_attstatsslot(&hslot);
406+
return-1.0;
407+
}
408+
400409
/*
401410
* Convert histogram of ranges into histograms of its lower and upper
402411
* bounds.
@@ -683,7 +692,8 @@ get_position(TypeCacheEntry *typcache, RangeBound *value, RangeBound *hist1,
683692
/*
684693
* Both bounds are finite. Assuming the subtype's comparison function
685694
* works sanely, the value must be finite, too, because it lies
686-
* somewhere between the bounds. If it doesn't, just return something.
695+
* somewhere between the bounds. If it doesn't, arbitrarily return
696+
* 0.5.
687697
*/
688698
if (value->infinite)
689699
return0.5;
@@ -693,21 +703,22 @@ get_position(TypeCacheEntry *typcache, RangeBound *value, RangeBound *hist1,
693703
return0.5;
694704

695705
/* Calculate relative position using subdiff function. */
696-
bin_width=DatumGetFloat8(FunctionCall2Coll(
697-
&typcache->rng_subdiff_finfo,
706+
bin_width=DatumGetFloat8(FunctionCall2Coll(&typcache->rng_subdiff_finfo,
698707
typcache->rng_collation,
699708
hist2->val,
700709
hist1->val));
701-
if (bin_width <=0.0)
702-
return0.5;/*zerowidth bin */
710+
if (isnan(bin_width)||bin_width <=0.0)
711+
return0.5;/*punt for NaN or zero-width bin */
703712

704-
position=DatumGetFloat8(FunctionCall2Coll(
705-
&typcache->rng_subdiff_finfo,
713+
position=DatumGetFloat8(FunctionCall2Coll(&typcache->rng_subdiff_finfo,
706714
typcache->rng_collation,
707715
value->val,
708716
hist1->val))
709717
/bin_width;
710718

719+
if (isnan(position))
720+
return0.5;/* punt for NaN from subdiff, Inf/Inf, etc */
721+
711722
/* Relative position must be in [0,1] range */
712723
position=Max(position,0.0);
713724
position=Min(position,1.0);
@@ -799,15 +810,23 @@ get_distance(TypeCacheEntry *typcache, RangeBound *bound1, RangeBound *bound2)
799810
if (!bound1->infinite&& !bound2->infinite)
800811
{
801812
/*
802-
*No bounds are infinite, use subdiff function or return default
813+
*Neither bound is infinite, use subdiff function or return default
803814
* value of 1.0 if no subdiff is available.
804815
*/
805816
if (has_subdiff)
806-
return
807-
DatumGetFloat8(FunctionCall2Coll(&typcache->rng_subdiff_finfo,
808-
typcache->rng_collation,
809-
bound2->val,
810-
bound1->val));
817+
{
818+
float8res;
819+
820+
res=DatumGetFloat8(FunctionCall2Coll(&typcache->rng_subdiff_finfo,
821+
typcache->rng_collation,
822+
bound2->val,
823+
bound1->val));
824+
/* Reject possible NaN result, also negative result */
825+
if (isnan(res)||res<0.0)
826+
return1.0;
827+
else
828+
returnres;
829+
}
811830
else
812831
return1.0;
813832
}
@@ -821,7 +840,7 @@ get_distance(TypeCacheEntry *typcache, RangeBound *bound1, RangeBound *bound2)
821840
}
822841
else
823842
{
824-
/* One bound is infinite,another is not */
843+
/* One bound is infinite,the other is not */
825844
returnget_float8_infinity();
826845
}
827846
}
@@ -1017,17 +1036,31 @@ calc_hist_selectivity_contained(TypeCacheEntry *typcache,
10171036
upper_index=rbound_bsearch(typcache,upper,hist_lower,hist_nvalues,
10181037
false);
10191038

1039+
/*
1040+
* If the upper bound value is below the histogram's lower limit, there
1041+
* are no matches.
1042+
*/
1043+
if (upper_index<0)
1044+
return0.0;
1045+
1046+
/*
1047+
* If the upper bound value is at or beyond the histogram's upper limit,
1048+
* start our loop at the last actual bin, as though the upper bound were
1049+
* within that bin; get_position will clamp its result to 1.0 anyway.
1050+
* (This corresponds to assuming that the data population above the
1051+
* histogram's upper limit is empty, exactly like what we just assumed for
1052+
* the lower limit.)
1053+
*/
1054+
upper_index=Min(upper_index,hist_nvalues-2);
1055+
10201056
/*
10211057
* Calculate upper_bin_width, ie. the fraction of the (upper_index,
10221058
* upper_index + 1) bin which is greater than upper bound of query range
10231059
* using linear interpolation of subdiff function.
10241060
*/
1025-
if (upper_index >=0&&upper_index<hist_nvalues-1)
1026-
upper_bin_width=get_position(typcache,upper,
1027-
&hist_lower[upper_index],
1028-
&hist_lower[upper_index+1]);
1029-
else
1030-
upper_bin_width=0.0;
1061+
upper_bin_width=get_position(typcache,upper,
1062+
&hist_lower[upper_index],
1063+
&hist_lower[upper_index+1]);
10311064

10321065
/*
10331066
* In the loop, dist and prev_dist are the distance of the "current" bin's
@@ -1100,9 +1133,6 @@ calc_hist_selectivity_contained(TypeCacheEntry *typcache,
11001133
* of ranges that contain the constant lower and upper bounds. This uses
11011134
* the histograms of range lower bounds and range lengths, on the assumption
11021135
* that the range lengths are independent of the lower bounds.
1103-
*
1104-
* Note, this is "var @> const", ie. estimate the fraction of ranges that
1105-
* contain the constant lower and upper bounds.
11061136
*/
11071137
staticdouble
11081138
calc_hist_selectivity_contains(TypeCacheEntry*typcache,
@@ -1121,16 +1151,30 @@ calc_hist_selectivity_contains(TypeCacheEntry *typcache,
11211151
lower_index=rbound_bsearch(typcache,lower,hist_lower,hist_nvalues,
11221152
true);
11231153

1154+
/*
1155+
* If the lower bound value is below the histogram's lower limit, there
1156+
* are no matches.
1157+
*/
1158+
if (lower_index<0)
1159+
return0.0;
1160+
1161+
/*
1162+
* If the lower bound value is at or beyond the histogram's upper limit,
1163+
* start our loop at the last actual bin, as though the upper bound were
1164+
* within that bin; get_position will clamp its result to 1.0 anyway.
1165+
* (This corresponds to assuming that the data population above the
1166+
* histogram's upper limit is empty, exactly like what we just assumed for
1167+
* the lower limit.)
1168+
*/
1169+
lower_index=Min(lower_index,hist_nvalues-2);
1170+
11241171
/*
11251172
* Calculate lower_bin_width, ie. the fraction of the of (lower_index,
11261173
* lower_index + 1) bin which is greater than lower bound of query range
11271174
* using linear interpolation of subdiff function.
11281175
*/
1129-
if (lower_index >=0&&lower_index<hist_nvalues-1)
1130-
lower_bin_width=get_position(typcache,lower,&hist_lower[lower_index],
1131-
&hist_lower[lower_index+1]);
1132-
else
1133-
lower_bin_width=0.0;
1176+
lower_bin_width=get_position(typcache,lower,&hist_lower[lower_index],
1177+
&hist_lower[lower_index+1]);
11341178

11351179
/*
11361180
* Loop through all the lower bound bins, smaller than the query lower

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