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Protect GIST logic that assumes penalty values can't be negative.

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Apparently sane-looking penalty code might return small negative values,
for example because of roundoff error.  This will confuse places like
gistchoose().  Prevent problems by clamping negative penalty values to
zero.  (Just to be really sure, I also made it force NaNs to zero.)
Back-patch to all supported branches.

Alexander Korotkov
This commit is contained in:
Tom Lane 2011-05-31 17:54:01 -04:00
parent 0699d053ba
commit 8057b7554b
2 changed files with 13 additions and 3 deletions
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2
doc/src/sgml/gist.sgml
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@ -374,6 +374,8 @@ my_decompress(PG_FUNCTION_ARGS)
Returns a value indicating the <quote>cost</quote> of inserting the new
entry into a particular branch of the tree. Items will be inserted
down the path of least <function>penalty</function> in the tree.
Values returned by <function>penalty</function> should be non-negative.
If a negative value is returned, it will be treated as zero.
</para>
<para>

14
src/backend/access/gist/gistutil.c
View File

@ -13,6 +13,8 @@
*/
#include "postgres.h"
#include <math.h>
#include "access/gist_private.h"
#include "access/reloptions.h"
#include "storage/freespace.h"
@ -532,16 +534,22 @@ gistpenalty(GISTSTATE *giststate, int attno,
{
float penalty = 0.0;
if (giststate->penaltyFn[attno].fn_strict == FALSE || (isNullOrig == FALSE && isNullAdd == FALSE))
if (giststate->penaltyFn[attno].fn_strict == FALSE ||
(isNullOrig == FALSE && isNullAdd == FALSE))
{
FunctionCall3(&giststate->penaltyFn[attno],
PointerGetDatum(orig),
PointerGetDatum(add),
PointerGetDatum(&penalty));
/* disallow negative or NaN penalty */
if (isnan(penalty) || penalty < 0.0)
penalty = 0.0;
}
else if (isNullOrig && isNullAdd)
penalty = 0.0;
else
penalty = 1e10; /* try to prevent to mix null and non-null
* value */
penalty = 1e10; /* try to prevent mixing null and non-null
* values */
return penalty;
}