From 015c320a75e830deafcd51fdda00504c4d642b60 Mon Sep 17 00:00:00 2001
From: Jorgen Loland <jorgen.loland@oracle.com>
Date: Wed, 20 Mar 2013 11:20:12 +0100
Subject: [PATCH] Bug#16394084: LOOSE INDEX SCAN WITH QUOTED INT PREDICATE     
          RETURNS RANDOM DATA

MySQL 5.5 specific version of bugfix.

When Loose Index Scan Range access is used, MySQL execution needs
to copy non-aggregated fields. end_send() checked if this was
necessary by checking if join_tab->select->quick had type
QS_TYPE_GROUP_MIN_MAX.

In this bug, however, MySQL created a sort index to sort the rows
read from this range access method. create_sort_index() deletes
join_tab->select->quick which makes it impossible to inquire
the join_tab if LIS has been used.

The fix for MySQL 5.5 is to introduce a variable in JOIN_TAB
that stores whether or not LIS has been used. There is no need
for this variable in later MySQL versions because the relevant
code has been refactored.
---
 sql/sql_select.cc | 15 +++++++++++++++
 sql/sql_select.h  | 34 +++++++++++++++++++++++++++++-----
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index d40c7cb7c81..2f20d7aad17 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -2713,6 +2713,8 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables_arg, COND *conds,
     s->const_keys.init();
     s->checked_keys.init();
     s->needed_reg.init();
+    s->filesort_used_loose_index_scan= false;
+    s->filesort_used_loose_index_scan_agg_distinct= false;
     table_vector[i]=s->table=table=tables->table;
     table->pos_in_table_list= tables;
     error= table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);
@@ -6163,6 +6165,8 @@ JOIN::make_simple_join(JOIN *parent, TABLE *temp_table)
   join_tab->read_first_record= join_init_read_record;
   join_tab->join= this;
   join_tab->ref.key_parts= 0;
+  join_tab->filesort_used_loose_index_scan= false;
+  join_tab->filesort_used_loose_index_scan_agg_distinct= false;
   bzero((char*) &join_tab->read_record,sizeof(join_tab->read_record));
   temp_table->status=0;
   temp_table->null_row=0;
@@ -14240,6 +14244,17 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
     tablesort_result_cache= table->sort.io_cache;
     table->sort.io_cache= NULL;
 
+    if (select->quick &&
+        select->quick->get_type() == QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX)
+    {
+      tab->filesort_used_loose_index_scan= true;
+
+      QUICK_GROUP_MIN_MAX_SELECT *minmax_quick=
+        static_cast<QUICK_GROUP_MIN_MAX_SELECT*>(select->quick);
+      if (minmax_quick->is_agg_distinct())
+        tab->filesort_used_loose_index_scan_agg_distinct= true;
+    }
+
     /*
       If a quick object was created outside of create_sort_index()
       that might be reused, then do not call select->cleanup() since
diff --git a/sql/sql_select.h b/sql/sql_select.h
index 6732eb354d6..fc39eb30984 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -243,16 +243,40 @@ typedef struct st_join_table {
   nested_join_map embedding_map;
 
   void cleanup();
+  /*
+    In cases where filesort reads rows from a table using Loose Index
+    Scan, the fact that LIS was used is lost because
+    create_sort_index() deletes join_tab->select->quick. MySQL needs
+    this information during JOIN::exec().
+
+    This variable is a hack for MySQL 5.5 only. A value of true means
+    that filesort used LIS to read from the table. In MySQL 5.6 and
+    later, join_tab->filesort is a separate structure with it's own
+    select that can be inquired to get the same information. There is
+    no need for this variable in MySQL 5.6 and later.
+  */
+  bool		filesort_used_loose_index_scan;
+  /*
+    Similar hack as for filesort_used_loose_index_scan. Not needed for
+    MySQL 5.6 and later.
+  */
+  bool		filesort_used_loose_index_scan_agg_distinct;
   inline bool is_using_loose_index_scan()
   {
-    return (select && select->quick &&
-            (select->quick->get_type() ==
-             QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX));
+    return (filesort_used_loose_index_scan || 
+            (select && select->quick &&
+             (select->quick->get_type() ==
+              QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX))
+            );
   }
   bool is_using_agg_loose_index_scan ()
   {
-    return (is_using_loose_index_scan() &&
-            ((QUICK_GROUP_MIN_MAX_SELECT *)select->quick)->is_agg_distinct());
+    return (filesort_used_loose_index_scan_agg_distinct ||
+            (select && select->quick &&
+             (select->quick->get_type() ==
+              QUICK_SELECT_I::QS_TYPE_GROUP_MIN_MAX) &&
+             ((QUICK_GROUP_MIN_MAX_SELECT *)select->quick)->is_agg_distinct())
+            );
   }
 } JOIN_TAB;