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, 1 insertions, 1 deletions

diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 6cbe98fe862..b6e41788ef0 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -1476,7 +1476,7 @@ static int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
     DBUG_RETURN(-1);
   }
   /* Sort keys in optimized order */
-  qsort((gptr) *key_info_buffer, *key_count, sizeof(KEY),
+  my_qsort((gptr) *key_info_buffer, *key_count, sizeof(KEY),
 	(qsort_cmp) sort_keys);
   create_info->null_bits= null_fields;