Fix for bug #31207: Test "join_nested" shows different strategy on IA64

CPUs / Intel's ICC compile

The bug is a combination of two problems:

1. IA64/ICC MySQL binaries use glibc's qsort(), not the one in mysys.

2. The order relation implemented by join_tab_cmp() is not transitive,
i.e. it is possible to choose such a, b and c that (a < b) && (b < c)
but (c < a). This implies that result of a sort using the relation
implemented by join_tab_cmp() depends on the order in which
elements are compared, i.e. the result is implementation-specific. Since
choose_plan() uses qsort() to pre-sort the
join tables using join_tab_cmp() as a compare function, the results of
the sorting may vary depending on qsort() implementation.

It is neither possible nor important to implement a better ordering
algorithm in join_tab_cmp(). Therefore the only way to fix it is to
force our own qsort() to be used by renaming it to my_qsort(), so we don't depend
on linker to decide that.

This patch also "fixes" bug #20530: qsort redefinition violates the
standard.

1 files changed, 2 insertions, 1 deletions

diff --git a/sql/records.cc b/sql/records.cc
index 3a833c87b7b..f61efc13034 100644
--- a/sql/records.cc
+++ b/sql/records.cc
@@ -497,7 +497,8 @@ static int rr_from_cache(READ_RECORD *info)
       int3store(ref_position,(long) i);
       ref_position+=3;
     }
-    qsort(info->read_positions,length,info->struct_length,(qsort_cmp) rr_cmp);
+    my_qsort(info->read_positions, length, info->struct_length,
+             (qsort_cmp) rr_cmp);
 
     position=info->read_positions;
     for (i=0 ; i < length ; i++)