MDEV-406: ANALYZE $stmt

- Support tracking for UNIONs, temporary-table based ORDER BYs,
  and both.

mysql-test/r/ps.result

 call mtr.add_suppression('Unsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT.');
 drop table if exists t1,t2,t3,t4;
+drop database if exists mysqltest1;
 drop database if exists client_test_db;
 create table t1
 (

mysql-test/t/ps.test

@@ -7,6 +7,7 @@ call mtr.add_suppression('Unsafe statement written to the binary log using state
 --disable_warnings
 drop table if exists t1,t2,t3,t4;
 
+drop database if exists mysqltest1;
 # Avoid wrong warnings if mysql_client_test fails
 drop database if exists client_test_db;
 --enable_warnings

sql/sql_explain.cc

@@ -542,7 +542,7 @@ int Explain_table_access::print_explain(select_result_sink *output, uint8 explai
   /* `r_rows` */
   if (is_analyze)
   {
-    ha_rows avg_rows= r_scans ? round((double) r_rows / r_scans): 0;
+    ha_rows avg_rows= tracker.r_scans ? round((double) tracker.r_rows / tracker.r_scans): 0;
     item_list.push_back(new Item_int((longlong) (ulonglong) avg_rows, 
                                       MY_INT64_NUM_DECIMAL_DIGITS));
   }
@@ -562,8 +562,8 @@ int Explain_table_access::print_explain(select_result_sink *output, uint8 explai
   if (is_analyze)
   {
     double r_filtered;
-    if (r_rows > 0)
-      r_filtered= 100.0 * (double)r_rows_after_table_cond / r_rows;
+    if (tracker.r_rows > 0)
+      r_filtered= 100.0 * (double)tracker.r_rows_after_table_cond / tracker.r_rows;
     else
       r_filtered= 100.0;
     item_list.push_back(new Item_float(r_filtered, 2));

sql/sql_explain.h

@@ -14,6 +14,21 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
+/* Data structures for ANALYZE */
+class Table_access_tracker 
+{
+public:
+  Table_access_tracker() :
+    r_scans(0), r_rows(0), r_rows_after_table_cond(0),
+    r_rows_after_where(0)
+  {}
+
+  ha_rows r_scans; /* How many scans were ran on this join_tab */
+  ha_rows r_rows; /* How many rows we've got after that */
+  ha_rows r_rows_after_table_cond; /* Rows after applying the table condition */
+  ha_rows r_rows_after_where; /* Rows after applying attached part of WHERE */
+};
+
 
 /**************************************************************************************
  
@@ -135,6 +150,13 @@ public:
   
   int print_explain(Explain_query *query, select_result_sink *output, 
                     uint8 explain_flags, bool is_analyze);
+  
+  Table_access_tracker *get_using_temporary_read_tracker()
+  {
+    return &using_temporary_read_tracker;
+  }
+private:
+  Table_access_tracker using_temporary_read_tracker;
 };
 
 
@@ -176,6 +198,19 @@ public:
 
   const char *fake_select_type;
   bool using_filesort;
+
+  Table_access_tracker *get_fake_select_lex_tracker()
+  {
+    return &fake_select_lex_tracker;
+  }
+  Table_access_tracker *get_tmptable_read_tracker()
+  {
+    return &tmptable_read_tracker;
+  }
+private:
+  Table_access_tracker fake_select_lex_tracker;
+  /* This one is for reading after ORDER BY */
+  Table_access_tracker tmptable_read_tracker; 
 };
 
 
@@ -183,6 +218,7 @@ class Explain_update;
 class Explain_delete;
 class Explain_insert;
 
+
 /*
   Explain structure for a query (i.e. a statement).
 
@@ -389,6 +425,7 @@ private:
 /*
   EXPLAIN data structure for a single JOIN_TAB.
 */
+
 class Explain_table_access : public Sql_alloc
 {
 public:
@@ -467,15 +504,7 @@ public:
                     bool using_temporary, bool using_filesort);
 
   /* ANALYZE members*/
-  ha_rows r_scans; /* How many scans were ran on this join_tab */
-  ha_rows r_rows; /* How many rows we've got after that */
-  ha_rows r_rows_after_table_cond; /* Rows after applying the table condition */
-  ha_rows r_rows_after_where; /* Rows after applying attached part of WHERE */
-
-  Explain_table_access():
-    r_scans(0), r_rows(0), r_rows_after_table_cond(0),
-    r_rows_after_where(0)
-  {}
+  Table_access_tracker tracker;
 
 private:
   void append_tag_name(String *str, enum explain_extra_tag tag);

sql/sql_select.cc

@@ -1032,6 +1032,9 @@ int JOIN::optimize()
         subquery), returns 1
       - another JOIN::optimize() call made, and now join->optimize() will
         return 0, even though we never had a query plan.
+
+    Can have QEP_NOT_PRESENT_YET for degenerate queries (for example,
+    SELECT * FROM tbl LIMIT 0)
   */
   if (was_optimized != optimized && !res && have_query_plan != QEP_DELETED)
   {
@@ -2350,6 +2353,20 @@ void JOIN::save_explain_data(Explain_query *output, bool can_overwrite,
     }
     save_explain_data_intern(thd->lex->explain, need_tmp_table, need_order,
                              distinct, message);
+    return;
+  }
+  
+  /*
+    Can have join_tab==NULL for degenerate cases (e.g. SELECT .. UNION ... SELECT LIMIT 0)
+  */
+  if (select_lex == select_lex->master_unit()->fake_select_lex && join_tab)
+  {
+    /* 
+      This is fake_select_lex. It has no query plan, but we need to set up a
+      tracker for ANALYZE 
+    */
+    Explain_union *eu= output->get_union(select_lex->master_unit()->first_select()->select_number);
+    join_tab[0].tracker= eu->get_fake_select_lex_tracker();
   }
 }
 
@@ -8958,6 +8975,20 @@ 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;
+  
+  uint select_nr= select_lex->select_number;
+  if (select_nr == INT_MAX) 
+  {
+    /* this is a fake_select_lex of a union */
+    select_nr= select_lex->master_unit()->first_select()->select_number;
+    join_tab->tracker= thd->lex->explain->get_union(select_nr)->
+                       get_tmptable_read_tracker();
+  }
+  else
+  {
+    join_tab->tracker= thd->lex->explain->get_select(select_nr)->
+                       get_using_temporary_read_tracker();
+  }
   bzero((char*) &join_tab->read_record,sizeof(join_tab->read_record));
   temp_table->status=0;
   temp_table->null_row=0;
@@ -17532,7 +17563,7 @@ sub_select(JOIN *join,JOIN_TAB *join_tab,bool end_of_records)
       (*join_tab->next_select)(join,join_tab+1,end_of_records);
     DBUG_RETURN(nls);
   }
-  join_tab->explain->r_scans++;
+  join_tab->tracker->r_scans++;
 
   int error;
   enum_nested_loop_state rc= NESTED_LOOP_OK;
@@ -17669,7 +17700,7 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
     DBUG_RETURN(NESTED_LOOP_KILLED);            /* purecov: inspected */
   }
 
-  join_tab->explain->r_rows++;
+  join_tab->tracker->r_rows++;
 
   if (join_tab->table->vfield)
     update_virtual_fields(join->thd, join_tab->table);
@@ -17689,7 +17720,7 @@ evaluate_join_record(JOIN *join, JOIN_TAB *join_tab,
       There is no select condition or the attached pushed down
       condition is true => a match is found.
     */
-    join_tab->explain->r_rows_after_table_cond++;
+    join_tab->tracker->r_rows_after_table_cond++;
     bool found= 1;
     while (join_tab->first_unmatched && found)
     {
@@ -23315,7 +23346,7 @@ int JOIN::save_explain_data_intern(Explain_query *output, bool need_tmp_table,
       eta->key.set(thd->mem_root, NULL, (uint)-1);
       eta->quick_info= NULL;
       
-      tab->explain= eta;
+      tab->tracker= &eta->tracker;
       
       /* id */
       if (tab->bush_root_tab)

sql/sql_select.h

@@ -251,7 +251,7 @@ typedef struct st_join_table {
   /* Special content for EXPLAIN 'Extra' column or NULL if none */
   enum explain_extra_tag info;
   
-  Explain_table_access *explain;
+  Table_access_tracker *tracker;
   /* 
     Bitmap of TAB_INFO_* bits that encodes special line for EXPLAIN 'Extra'
     column, or 0 if there is no info.