MWL#182: SHOW EXPLAIN: Merge 5.3->5.5

1 files changed, 89 insertions, 3 deletions

diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 6fd6e53424f..4c19217a99d 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -1872,6 +1872,7 @@ void st_select_lex::init_query()
   nest_level= 0;
   link_next= 0;
   is_prep_leaf_list_saved= FALSE;
+  have_merged_subqueries= FALSE;
   bzero((char*) expr_cache_may_be_used, sizeof(expr_cache_may_be_used));
   m_non_agg_field_used= false;
   m_agg_func_used= false;
@@ -3440,7 +3441,7 @@ bool st_select_lex::optimize_unflattened_subqueries()
         if (options & SELECT_DESCRIBE)
         {
           /* Optimize the subquery in the context of EXPLAIN. */
-          sl->set_explain_type();
+          sl->set_explain_type(FALSE);
           sl->options|= SELECT_DESCRIBE;
           inner_join->select_options|= SELECT_DESCRIBE;
         }
@@ -3832,7 +3833,7 @@ void SELECT_LEX::update_used_tables()
   Set the EXPLAIN type for this subquery.
 */
 
-void st_select_lex::set_explain_type()
+void st_select_lex::set_explain_type(bool on_the_fly)
 {
   bool is_primary= FALSE;
   if (next_select())
@@ -3854,6 +3855,9 @@ void st_select_lex::set_explain_type()
     }
   }
 
+  if (on_the_fly && !is_primary && have_merged_subqueries)
+    is_primary= TRUE;
+
   SELECT_LEX *first= master_unit()->first_select();
   /* drop UNCACHEABLE_EXPLAIN, because it is for internal usage only */
   uint8 is_uncacheable= (uncacheable & ~UNCACHEABLE_EXPLAIN);
@@ -3906,10 +3910,15 @@ void st_select_lex::set_explain_type()
       else
       {
         type= is_uncacheable ? "UNCACHEABLE UNION": "UNION";
+        if (this == master_unit()->fake_select_lex)
+          type= "UNION RESULT";
+
       }
     }
   }
-  options|= SELECT_DESCRIBE;
+
+  if (!on_the_fly)
+    options|= SELECT_DESCRIBE;
 }
 
 
@@ -4056,6 +4065,83 @@ bool st_select_lex::is_merged_child_of(st_select_lex *ancestor)
 }
 
 
+int print_explain_message_line(select_result_sink *result, 
+                               SELECT_LEX *select_lex,
+                               bool on_the_fly,
+                               uint8 options,
+                               const char *message);
+
+
+int st_select_lex::print_explain(select_result_sink *output)
+{
+  int res;
+  if (join && join->have_query_plan == JOIN::QEP_AVAILABLE)
+  {
+    res= join->print_explain(output, TRUE,
+                             FALSE, // need_tmp_table, 
+                             FALSE, // bool need_order,
+                             FALSE, // bool distinct,
+                             NULL); //const char *message
+    if (res)
+      goto err;
+
+    for (SELECT_LEX_UNIT *unit= join->select_lex->first_inner_unit();
+         unit;
+         unit= unit->next_unit())
+    {
+      /* 
+        Display subqueries only if they are not parts of eliminated WHERE/ON
+        clauses.
+      */
+      if (!(unit->item && unit->item->eliminated))
+      {
+        unit->print_explain(output);
+      }
+    }
+  }
+  else
+  {
+    const char *msg;
+    if (!join)
+      DBUG_ASSERT(0); // psergey: TODO: can this happen or not?
+    if (join->have_query_plan == JOIN::QEP_NOT_PRESENT_YET)
+      msg= "Not yet optimized";
+    else
+    {
+      DBUG_ASSERT(join->have_query_plan == JOIN::QEP_DELETED);
+      msg= "Query plan already deleted";
+    }
+    res= print_explain_message_line(output, this, TRUE /* on_the_fly */,
+                                    0, msg);
+  }
+err:
+  return 0;
+}
+
+
+int st_select_lex_unit::print_explain(select_result_sink *output)
+{
+  int res= 0;
+  SELECT_LEX *first= first_select();
+
+  for (SELECT_LEX *sl= first; sl; sl= sl->next_select())
+  {
+    if ((res= sl->print_explain(output)))
+      break;
+  }
+
+  /* 
+    Note: it could be that fake_select_lex->join == NULL still at this point
+  */
+  if (fake_select_lex && !fake_select_lex->join)
+  {
+    res= print_fake_select_lex_join(output, TRUE /* on the fly */,
+                                    fake_select_lex, 0 /* flags */);
+  }
+  return res;
+}
+
+
 /**
   A routine used by the parser to decide whether we are specifying a full
   partitioning or if only partitions to add or to split.