1 files changed, 95 insertions, 30 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index cbb5868623c..90c3110b63a 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -291,18 +291,18 @@ static double table_cond_selectivity(JOIN *join, uint idx, JOIN_TAB *s,
 void dbug_serve_apcs(THD *thd, int n_calls)
 {
   const char *save_proc_info= thd->proc_info;
-  /* This is so that mysqltest knows we're ready to serve requests: */
-  thd_proc_info(thd, "show_explain_trap");
   
   /* Busy-wait for n_calls APC requests to arrive and be processed */
   int n_apcs= thd->apc_target.n_calls_processed + n_calls;
   while (thd->apc_target.n_calls_processed < n_apcs)
   {
-    my_sleep(300);
+    /* This is so that mysqltest knows we're ready to serve requests: */
+    thd_proc_info(thd, "show_explain_trap");
+    my_sleep(30000);
+    thd_proc_info(thd, save_proc_info);
     if (thd->check_killed())
       break;
   }
-  thd_proc_info(thd, save_proc_info);
 }
 
 
@@ -3043,6 +3043,7 @@ void JOIN::exec_inner()
       const ha_rows select_limit_arg=
         select_options & OPTION_FOUND_ROWS
         ? HA_POS_ERROR : unit->select_limit_cnt;
+      curr_join->filesort_found_rows= filesort_limit_arg != HA_POS_ERROR;
 
       DBUG_PRINT("info", ("has_group_by %d "
                           "curr_join->table_count %d "
@@ -3089,7 +3090,8 @@ void JOIN::exec_inner()
                                     *curr_fields_list),
                                    Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF);
   error= do_select(curr_join, curr_fields_list, NULL, procedure);
-  if (curr_join->order && curr_join->filesort_found_rows)
+  if (curr_join->order && curr_join->sortorder &&
+      curr_join->filesort_found_rows)
   {
     /* Use info provided by filesort. */
     DBUG_ASSERT(curr_join->table_count > curr_join->const_tables);
@@ -10066,7 +10068,7 @@ bool generate_derived_keys_for_table(KEYUSE *keyuse, uint count, uint keys)
       else
       {
         /* Mark keyuses for this key to be excluded */
-        for (KEYUSE *curr=save_first_keyuse; curr < first_keyuse; curr++)
+        for (KEYUSE *curr=save_first_keyuse; curr < keyuse; curr++)
 	{
           curr->key= MAX_KEY;
         }
@@ -12295,8 +12297,8 @@ public:
   { TRASH(ptr, size); }
 
   Item *and_level;
-  Item_func *cmp_func;
-  COND_CMP(Item *a,Item_func *b) :and_level(a),cmp_func(b) {}
+  Item_bool_func2 *cmp_func;
+  COND_CMP(Item *a,Item_bool_func2 *b) :and_level(a),cmp_func(b) {}
 };
 
 /**
@@ -13685,6 +13687,75 @@ static void update_const_equal_items(COND *cond, JOIN_TAB *tab, bool const_key)
 }
 
 
+/**
+  Check if
+    WHERE expr=value AND expr=const
+  can be rewritten as:
+    WHERE const=value AND expr=const
+
+  @param target       - the target operator whose "expr" argument will be
+                        replaced to "const".
+  @param target_expr  - the target's "expr" which will be replaced to "const".
+  @param target_value - the target's second argument, it will remain unchanged.
+  @param source       - the equality expression ("=" or "<=>") that
+                        can be used to rewrite the "target" part
+                        (under certain conditions, see the code).
+  @param source_expr  - the source's "expr". It should be exactly equal to 
+                        the target's "expr" to make condition rewrite possible.
+  @param source_const - the source's "const" argument, it will be inserted
+                        into "target" instead of "expr".
+*/
+static bool
+can_change_cond_ref_to_const(Item_bool_func2 *target,
+                             Item *target_expr, Item *target_value,
+                             Item_bool_func2 *source,
+                             Item *source_expr, Item *source_const)
+{
+  if (!target_expr->eq(source_expr,0) ||
+       target_value == source_const ||
+       target_expr->cmp_context != source_expr->cmp_context)
+    return false;
+  if (target_expr->cmp_context == STRING_RESULT)
+  {
+    /*
+      In this example:
+        SET NAMES utf8 COLLATE utf8_german2_ci;
+        DROP TABLE IF EXISTS t1;
+        CREATE TABLE t1 (a CHAR(10) CHARACTER SET utf8);
+        INSERT INTO t1 VALUES ('o-umlaut'),('oe');
+        SELECT * FROM t1 WHERE a='oe' COLLATE utf8_german2_ci AND a='oe';
+
+      the query should return only the row with 'oe'.
+      It should not return 'o-umlaut', because 'o-umlaut' does not match
+      the right part of the condition: a='oe'
+      ('o-umlaut' is not equal to 'oe' in utf8_general_ci,
+       which is the collation of the field "a").
+
+      If we change the right part from:
+         ... AND a='oe'
+      to
+         ... AND 'oe' COLLATE utf8_german2_ci='oe'
+      it will be evalulated to TRUE and removed from the condition,
+      so the overall query will be simplified to:
+
+        SELECT * FROM t1 WHERE a='oe' COLLATE utf8_german2_ci;
+
+      which will erroneously start to return both 'oe' and 'o-umlaut'.
+      So changing "expr" to "const" is not possible if the effective
+      collations of "target" and "source" are not exactly the same.
+
+      Note, the code before the fix for MDEV-7152 only checked that
+      collations of "source_const" and "target_value" are the same.
+      This was not enough, as the bug report demonstrated.
+    */
+    return
+      target->compare_collation() == source->compare_collation() &&
+      target_value->collation.collation == source_const->collation.collation;
+  }
+  return true; // Non-string comparison
+}
+
+
 /*
   change field = field to field = const for each found field = const in the
   and_level
@@ -13693,6 +13764,7 @@ static void update_const_equal_items(COND *cond, JOIN_TAB *tab, bool const_key)
 static void
 change_cond_ref_to_const(THD *thd, I_List<COND_CMP> *save_list,
                          Item *and_father, Item *cond,
+                         Item_bool_func2 *field_value_owner,
                          Item *field, Item *value)
 {
   if (cond->type() == Item::COND_ITEM)
@@ -13703,7 +13775,7 @@ change_cond_ref_to_const(THD *thd, I_List<COND_CMP> *save_list,
     Item *item;
     while ((item=li++))
       change_cond_ref_to_const(thd, save_list,and_level ? cond : item, item,
-			       field, value);
+			       field_value_owner, field, value);
     return;
   }
   if (cond->eq_cmp_result() == Item::COND_OK)
@@ -13715,11 +13787,8 @@ change_cond_ref_to_const(THD *thd, I_List<COND_CMP> *save_list,
   Item *right_item= args[1];
   Item_func::Functype functype=  func->functype();
 
-  if (right_item->eq(field,0) && left_item != value &&
-      right_item->cmp_context == field->cmp_context &&
-      (left_item->result_type() != STRING_RESULT ||
-       value->result_type() != STRING_RESULT ||
-       left_item->collation.collation == value->collation.collation))
+  if (can_change_cond_ref_to_const(func, right_item, left_item,
+                                   field_value_owner, field, value))
   {
     Item *tmp=value->clone_item();
     if (tmp)
@@ -13738,11 +13807,8 @@ change_cond_ref_to_const(THD *thd, I_List<COND_CMP> *save_list,
       func->set_cmp_func();
     }
   }
-  else if (left_item->eq(field,0) && right_item != value &&
-           left_item->cmp_context == field->cmp_context &&
-           (right_item->result_type() != STRING_RESULT ||
-            value->result_type() != STRING_RESULT ||
-            right_item->collation.collation == value->collation.collation))
+  else if (can_change_cond_ref_to_const(func, left_item, right_item,
+                                        field_value_owner, field, value))
   {
     Item *tmp= value->clone_item();
     if (tmp)
@@ -13791,7 +13857,8 @@ propagate_cond_constants(THD *thd, I_List<COND_CMP> *save_list,
         Item **args= cond_cmp->cmp_func->arguments();
         if (!args[0]->const_item())
           change_cond_ref_to_const(thd, &save,cond_cmp->and_level,
-                                   cond_cmp->and_level, args[0], args[1]);
+                                   cond_cmp->and_level,
+                                   cond_cmp->cmp_func, args[0], args[1]);
       }
     }
   }
@@ -13813,14 +13880,14 @@ propagate_cond_constants(THD *thd, I_List<COND_CMP> *save_list,
           resolve_const_item(thd, &args[1], args[0]);
 	  func->update_used_tables();
           change_cond_ref_to_const(thd, save_list, and_father, and_father,
-                                   args[0], args[1]);
+                                   func, args[0], args[1]);
 	}
 	else if (left_const)
 	{
           resolve_const_item(thd, &args[0], args[1]);
 	  func->update_used_tables();
           change_cond_ref_to_const(thd, save_list, and_father, and_father,
-                                   args[1], args[0]);
+                                   func, args[1], args[0]);
 	}
       }
     }
@@ -18931,7 +18998,8 @@ end_send(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
         records are read. Because of optimization in some cases it can
         provide only select_limit_cnt+1 records.
       */
-      if (join->order && join->filesort_found_rows &&
+      if (join->order && join->sortorder &&
+          join->filesort_found_rows &&
           join->select_options & OPTION_FOUND_ROWS)
       {
         DBUG_PRINT("info", ("filesort NESTED_LOOP_QUERY_LIMIT"));
@@ -18953,8 +19021,9 @@ end_send(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
 	  /* Join over all rows in table;  Return number of found rows */
 	  TABLE *table=jt->table;
 
-          join->select_options ^= OPTION_FOUND_ROWS;
-          if (join->filesort_found_rows)
+	  join->select_options ^= OPTION_FOUND_ROWS;
+	  if (table->sort.record_pointers ||
+	      (table->sort.io_cache && my_b_inited(table->sort.io_cache)))
 	  {
 	    /* Using filesort */
 	    join->send_records= table->sort.found_records;
@@ -20808,11 +20877,7 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
                             select, filesort_limit, 0,
                             &examined_rows, &found_rows);
   table->sort.found_records= filesort_retval;
-  if (found_rows != HA_POS_ERROR)
-  {
-    tab->records= found_rows;                     // For SQL_CALC_ROWS
-    join->filesort_found_rows= true;
-  }
+  tab->records= found_rows;                     // For SQL_CALC_ROWS
 
   if (quick_created)
   {