Fix sorting of NULL values (Should always be first)

Fix problem with HAVING and MAX() IS NOT NULL


Docs/manual.texi:
  Changelog & NULL usage with ORDER BY
client/mysqldump.c:
  Cleanup disable keys
mysql-test/r/distinct.result:
  Fix results after ORDER BY with NULL fix
mysql-test/r/group_by.result:
  Fix results after ORDER BY with NULL fix
mysql-test/r/having.result:
  Testcase for bug with HAVING
mysql-test/t/distinct.test:
  Test for DISTINCT + ORDER BY DESC bug
mysql-test/t/having.test:
  Test of HAVING and MAX IS NOT NULL
sql/filesort.cc:
  Fix sorting of NULL values (Should always be first)
sql/item.h:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/item_sum.h:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/opt_range.cc:
  Fix problem with HAVING and MAX() IS NOT NULL
sql/opt_range.h:
  Fix sorting of NULL values
sql/sql_select.cc:
  Fix sorting of ORDER BY ... DESC on NULL values.

1 files changed, 8 insertions, 7 deletions

diff --git a/sql/opt_range.cc b/sql/opt_range.cc
index c3f4c91b718..20f198182f4 100644
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -2523,13 +2523,13 @@ int QUICK_SELECT::cmp_next(QUICK_RANGE *range)
 
 
 /*
- * This is a hack: we inherit from QUICK_SELECT so that we can use the
- * get_next() interface, but we have to hold a pointer to the original
- * QUICK_SELECT because its data are used all over the place.  What
- * should be done is to factor out the data that is needed into a base
- * class (QUICK_SELECT), and then have two subclasses (_ASC and _DESC)
- * which handle the ranges and implement the get_next() function.  But
- * for now, this seems to work right at least.
+  This is a hack: we inherit from QUICK_SELECT so that we can use the
+  get_next() interface, but we have to hold a pointer to the original
+  QUICK_SELECT because its data are used all over the place.  What
+  should be done is to factor out the data that is needed into a base
+  class (QUICK_SELECT), and then have two subclasses (_ASC and _DESC)
+  which handle the ranges and implement the get_next() function.  But
+  for now, this seems to work right at least.
  */
 
 QUICK_SELECT_DESC::QUICK_SELECT_DESC(QUICK_SELECT *q, uint used_key_parts)
@@ -2538,6 +2538,7 @@ QUICK_SELECT_DESC::QUICK_SELECT_DESC(QUICK_SELECT *q, uint used_key_parts)
   bool not_read_after_key = file->option_flag() & HA_NOT_READ_AFTER_KEY;
   QUICK_RANGE *r;
 
+  it.rewind();
   for (r = it++; r; r = it++)
   {
     rev_ranges.push_front(r);