Cleanups for: 0762dd928 Improve pruning in greedy_search by sorting tables during searchbb-10.10-spetrunia

2 files changed, 17 insertions, 9 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index b9d606eac1f..96c53b360a7 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -5441,13 +5441,19 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
     }
   }
 
+  /* Set JOIN_TAB::embedded_dependent for tables inside semi-joins */
   {
     for (JOIN_TAB *s= stat ; s < stat_end ; s++)
     {
-      TABLE_LIST *tl= s->table->pos_in_table_list;
-      if (tl->embedding && tl->embedding->sj_subq_pred)
+      TABLE_LIST *emb= s->table->pos_in_table_list->embedding;
+      while (emb)
       {
-        s->embedded_dependent= tl->embedding->original_subq_pred_used_tables;
+        if (emb->sj_subq_pred)
+        {
+          s->embedded_dependent= emb->original_subq_pred_used_tables;
+          break;
+        }
+        emb= emb->embedding;
       }
     }
   }
@@ -8366,7 +8372,7 @@ best_access_path(JOIN      *join,
     */
     if (s->key_start_dependent)
       key_dependent= s->key_dependent;
-    /* Add dependencey for sub queries */
+    /* Add dependency from semi-join subquery */
     key_dependent|= s->embedded_dependent;
   }
   /* Check that s->key_dependent contains all used_tables found in s->keyuse */
@@ -9953,8 +9959,8 @@ check_if_edge_table(POSITION *pos,
 
 struct SORT_POSITION
 {
-  JOIN_TAB **join_tab;
-  POSITION *position;
+  JOIN_TAB **join_tab; /* Position of the JOIN_TAB in join->best_ref array */
+  POSITION *position; /* Pointer to how we read the table */
 };
 
 
diff --git a/sql/sql_select.h b/sql/sql_select.h
index 46a359c746f..a6e4c752f9b 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -359,9 +359,11 @@ typedef struct st_join_table {
 
   table_map	dependent,key_dependent;
   /*
-    This is set for embedded sub queries.  It contains the table map of
-    the outer expression, like 'A' in the following expression:
-    WHERE A in (SELECT ....)
+    This is non-zero for tables in semi-join nests. It contains bits
+    of tables that the subquery depends on.
+    For example, for
+       WHERE t1.col in (SELECT t10.col FROM t10 WHERE t10.col<t2.col)
+    t10->embedded_dependent= {t1, t2}
   */
   table_map     embedded_dependent;