# name       : optimizer_fix.patch
# introduced : 11 or before
# maintainer : Yasufumi
#
#!!! notice !!!
# Any small change to this file in the main branch
# should be done or reviewed by the maintainer!
--- /dev/null
+++ b/patch_info/optimizer_fix.info
@@ -0,0 +1,8 @@
+File=optimizer_fix.patch
+Name=Unofficial optimizer fixes
+Version=1.0
+Author=Percona <info@percona.com>
+License=GPL
+Comment=
+2010-01
+Ported to 5.1.42
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -434,6 +434,7 @@
 MYSQL_PLUGIN_IMPORT uint    opt_debug_sync_timeout= 0;
 #endif /* defined(ENABLED_DEBUG_SYNC) */
 my_bool opt_old_style_user_limits= 0, trust_function_creators= 0;
+my_bool opt_optimizer_fix= 0;
 /*
   True if there is at least one per-hour limit for some user, so we should
   check them before each query (and possibly reset counters when hour is
--- a/sql/mysqld.h
+++ b/sql/mysqld.h
@@ -109,6 +109,7 @@
 extern ulonglong slave_type_conversions_options;
 extern my_bool read_only, opt_readonly;
 extern my_bool lower_case_file_system;
+extern my_bool opt_optimizer_fix;
 extern my_bool opt_enable_named_pipe, opt_sync_frm, opt_allow_suspicious_udfs;
 extern my_bool opt_secure_auth;
 extern char* opt_secure_file_priv;
--- a/sql/opt_range.cc
+++ b/sql/opt_range.cc
@@ -727,7 +727,7 @@
 static TRP_RANGE *get_key_scans_params(PARAM *param, SEL_TREE *tree,
                                        bool index_read_must_be_used,
                                        bool update_tbl_stats,
-                                       double read_time);
+                                       double read_time, ha_rows *estimated_records);
 static
 TRP_ROR_INTERSECT *get_best_ror_intersect(const PARAM *param, SEL_TREE *tree,
                                           double read_time,
@@ -2151,6 +2151,7 @@
 				  ha_rows limit, bool force_quick_range)
 {
   uint idx;
+  ha_rows estimated_records=0;
   double scan_time;
   DBUG_ENTER("SQL_SELECT::test_quick_select");
   DBUG_PRINT("enter",("keys_to_use: %lu  prev_tables: %lu  const_tables: %lu",
@@ -2319,12 +2320,17 @@
 
         /* Get best 'range' plan and prepare data for making other plans */
         if ((range_trp= get_key_scans_params(&param, tree, FALSE, TRUE,
-                                             best_read_time)))
+                                             best_read_time, &estimated_records)))
         {
           best_trp= range_trp;
           best_read_time= best_trp->read_cost;
         }
 
+        if (opt_optimizer_fix && estimated_records)
+        {
+          records = estimated_records;
+        }
+
         /*
           Simultaneous key scans and row deletes on several handler
           objects are not allowed so don't use ROR-intersection for
@@ -3820,7 +3826,7 @@
   {
     DBUG_EXECUTE("info", print_sel_tree(param, *ptree, &(*ptree)->keys_map,
                                         "tree in SEL_IMERGE"););
-    if (!(*cur_child= get_key_scans_params(param, *ptree, TRUE, FALSE, read_time)))
+    if (!(*cur_child= get_key_scans_params(param, *ptree, TRUE, FALSE, read_time, NULL)))
     {
       /*
         One of index scans in this index_merge is more expensive than entire
@@ -4923,11 +4929,12 @@
 static TRP_RANGE *get_key_scans_params(PARAM *param, SEL_TREE *tree,
                                        bool index_read_must_be_used, 
                                        bool update_tbl_stats,
-                                       double read_time)
+                                       double read_time, ha_rows *estimated_records)
 {
   int idx;
   SEL_ARG **key,**end, **key_to_read= NULL;
   ha_rows UNINIT_VAR(best_records);              /* protected by key_to_read */
+  ha_rows min_records= HA_POS_ERROR;
   TRP_RANGE* read_plan= NULL;
   bool pk_is_clustered= param->table->file->primary_key_is_clustered();
   DBUG_ENTER("get_key_scans_params");
@@ -4998,6 +5005,11 @@
         key_to_read=  key;
       }
 
+      if (estimated_records && found_records
+          && min_records > found_records)
+      {
+        min_records = found_records;
+      }
     }
   }
 
@@ -5020,6 +5032,12 @@
   else
     DBUG_PRINT("info", ("No 'range' table read plan found"));
 
+  /* minimum number of records (not 0) as estimated number of records */
+  if (estimated_records && min_records != HA_POS_ERROR)
+  {
+    *estimated_records = min_records;
+  }
+
   DBUG_RETURN(read_plan);
 }
 
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -2619,6 +2619,11 @@
       table->reginfo.impossible_range=1;
       DBUG_RETURN(0);
     }
+    if (opt_optimizer_fix && error == 0)
+    {
+      /* quick select is not effective. but the estimated value is used. */
+      DBUG_RETURN(select->records);
+    }
     DBUG_PRINT("warning",("Couldn't use record count on const keypart"));
   }
   DBUG_RETURN(HA_POS_ERROR);			/* This shouldn't happend */
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -2259,6 +2259,12 @@
        VALID_RANGE(1, IF_WIN(INT_MAX32/1000, LONG_TIMEOUT)),
        DEFAULT(NET_WAIT_TIMEOUT), BLOCK_SIZE(1));
 
+static Sys_var_mybool Sys_optimizer_fix(
+       "optimizer_fix",
+       "Enable unofficial optimizer fixes.",
+       GLOBAL_VAR(opt_optimizer_fix),
+       NO_CMD_LINE, DEFAULT(TRUE));
+
 /** propagates changes to the relevant flag of @@optimizer_switch */
 static bool fix_engine_condition_pushdown(sys_var *self, THD *thd,
                                           enum_var_type type)