postgres.git / summary / log / commit / refs

commit    08779dc699634858d4940158f5de12e1c7ff1448
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Tue May 31 21:54:11 2011 +0000

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


 doc/src/sgml/gist.sgml             |  2 ++
 src/backend/access/gist/gistutil.c | 14 +++++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/doc/src/sgml/gist.sgml b/doc/src/sgml/gist.sgml
index 2418c72aa2a..4442ae37a12 100644
--- a/doc/src/sgml/gist.sgml
+++ b/doc/src/sgml/gist.sgml
@@ -147,6 +147,8 @@
        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>
      </listitem>
     </varlistentry>
diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index fda7c5df2ee..176783b5a56 100644
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -13,6 +13,8 @@
  */
 #include "postgres.h"
 
+#include <math.h>
+
 #include "access/gist_private.h"
 #include "access/heapam.h"
 #include "access/reloptions.h"
@@ -530,16 +532,22 @@ 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;
 }


[parent: fccef77183af]