bzr commit into mysql-6.0-opt branch (epotemkin:2822) WL#3485

[Evgeny Potemkin]

#At file:///work/bzr_trees/wl3485-merge-6.0/ based on revid:epotemkin@stripped

 2822 Evgeny Potemkin	2009-03-02
      WL#3485 Subquery optimization: FROM (SELECT)
      A small fix for EXPLAIN to correctly show select's type when
      derived tables/views are involved.
modified:
  sql/sql_cache.cc
  sql/sql_select.cc
  sql/table.cc

=== modified file 'sql/sql_cache.cc'
--- a/sql/sql_cache.cc	2008-12-17 18:40:14 +0000
+++ b/sql/sql_cache.cc	2009-03-02 21:37:55 +0000
@@ -3390,16 +3390,17 @@ Query_cache::process_and_count_tables(TH
     }
     else
     {
-      DBUG_PRINT("qcache", ("table: %s  db:  %s  type: %u",
-                            tables_used->table->s->table_name.str,
-                            tables_used->table->s->db.str,
-                            tables_used->table->s->db_type()->db_type));
       if (tables_used->derived)
       {
+        DBUG_PRINT("qcache", ("table: %s", tables_used->alias));
         table_count--;
         DBUG_PRINT("qcache", ("derived table skipped"));
         continue;
       }
+      DBUG_PRINT("qcache", ("table: %s  db:  %s  type: %u",
+                            tables_used->table->s->table_name.str,
+                            tables_used->table->s->db.str,
+                            tables_used->table->s->db_type()->db_type));
       *tables_type|= tables_used->table->file->table_cache_type();
 
       /*

=== modified file 'sql/sql_select.cc'
--- a/sql/sql_select.cc	2009-02-26 21:27:14 +0000
+++ b/sql/sql_select.cc	2009-03-02 21:37:55 +0000
@@ -21795,13 +21795,32 @@ bool mysql_explain_union(THD *thd, SELEC
        sl;
        sl= sl->next_select())
   {
+    bool is_primary= FALSE;
+    if (sl->next_select())
+      is_primary= TRUE;
+
+    if (!is_primary && sl->first_inner_unit())
+    {
+      /*
+        If there is at least one materialized derived|view then it's a PRIMARY select.
+        Otherwise, all derived tables/views were merged and this select is a SIMPLE one.
+      */
+      for (SELECT_LEX_UNIT *un= sl->first_inner_unit();
+           un;
+           un= un->next_unit())
+      {
+        if ((!un->derived ||
+            un->derived->is_materialized_derived()))
+        {
+          is_primary= TRUE;
+          break;
+        }
+      }
+    }
     // drop UNCACHEABLE_EXPLAIN, because it is for internal usage only
     uint8 uncacheable= (sl->uncacheable & ~UNCACHEABLE_EXPLAIN);
     sl->type= (((&thd->lex->select_lex)==sl)?
-	       ((sl->first_inner_unit() || sl->next_select()) &&
-                 (!sl->master_unit()->derived ||
-                 sl->master_unit()->derived->is_materialized_derived())
-                ? "PRIMARY" : "SIMPLE"):
+	       (is_primary ? "PRIMARY" : "SIMPLE"):
 	       ((sl == first)?
 		((sl->linkage == DERIVED_TABLE_TYPE) ?
 		 "DERIVED":

=== modified file 'sql/table.cc'
--- a/sql/table.cc	2009-02-26 21:27:14 +0000
+++ b/sql/table.cc	2009-03-02 21:37:55 +0000
@@ -5189,12 +5189,7 @@ bool TABLE_LIST::init_derived(THD *thd, 
   SELECT_LEX *first_select= get_single_select();
   SELECT_LEX_UNIT *unit= get_unit();
 
-  /*
-    Initialization is split for views and derived tables. Views
-    are initialized after tables are opened, derived tables - prior to
-    JOIN::prepare.
-  */
-  if (!unit || (!init_view && view))
+  if (!unit)
     return FALSE;
   /*
     Check whether we can merge this derived table into main select.
@@ -5204,11 +5199,11 @@ bool TABLE_LIST::init_derived(THD *thd, 
   if (first_select->table_list.elements > 1)
     set_multitable();
 
+  unit->derived= this;
   if (init_view && !view)
   {
     /* This is all what we can do for a derived table for now. */
     set_derived();
-    unit->derived= this;
   }
 
   if (!is_view())