Re: Report error position in partition bound check

Thank you Daniel. Here's the rebased patch. I also squashed the two
patches into one so it's easier to review.

@@ -3320,7 +3338,9 @@ make_one_partition_rbound(PartitionKey key, int index, List *datums, bool lower)
  * partition_rbound_cmp
  *
  * Return for two range bounds whether the 1st one (specified in datums1,

I think it's better to reword it as. "For two range bounds decide whether ...

- * kind1, and lower1) is <, =, or > the bound specified in *b2.
+ * kind1, and lower1) is <, =, or > the bound specified in *b2. 0 is returned if
+ * equal and the 1-based index of the first mismatching bound if unequal;
+ * multiplied by -1 if the 1st bound is smaller.

This sentence makes sense after the above correction. I liked this change,
requires very small changes in other parts.

 
 /*
@@ -3495,7 +3518,7 @@ static int
 partition_range_bsearch(int partnatts, FmgrInfo *partsupfunc,
                        Oid *partcollation,
                        PartitionBoundInfo boundinfo,
-                       PartitionRangeBound *probe, bool *is_equal)
+                       PartitionRangeBound *probe, bool *is_equal, int32 *cmpval)