MWL#90: Code cleanup: Unification of merged and non-merged SJM nests processing

- Make join buffering code to take into account that JOIN_TABs are not a 
  linear array anymore.

mysql-test/r/subselect.result

@@ -1360,7 +1360,7 @@ explain extended select * from t2 where t2.a in (select t1.a from t1,t3 where t1
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t2	index	a	a	5	NULL	4	100.00	Using index
 1	PRIMARY	t3	index	a	a	5	NULL	3	100.00	Using index
-1	PRIMARY	t1	ref	a	a	10	test.t2.a,test.t3.a	116	100.61	Using index; FirstMatch(t2)
+1	PRIMARY	t1	ref	a	a	10	test.t2.a,test.t3.a	116	100.00	Using index; FirstMatch(t2)
 Warnings:
 Note	1003	select `test`.`t2`.`a` AS `a` from `test`.`t2` semi join (`test`.`t1` join `test`.`t3`) where ((`test`.`t1`.`a` = `test`.`t2`.`a`) and (`test`.`t1`.`b` = `test`.`t3`.`a`))
 insert into t1 values (3,31);

sql/opt_subselect.cc

@@ -3983,6 +3983,7 @@ bool join_tab_execution_startup(JOIN_TAB *tab)
     JOIN *join= tab->join;
     SJ_MATERIALIZATION_INFO *sjm= tab->bush_children->start->emb_sj_nest->sj_mat_info;
     JOIN_TAB *join_tab= tab->bush_children->start;
+    JOIN_TAB *save_return_tab= join->return_tab;
 
     if (!sjm->materialized)
     {
@@ -3995,29 +3996,14 @@ bool join_tab_execution_startup(JOIN_TAB *tab)
           (rc= sub_select(join, join_tab, TRUE/* now EOF */)) < 0)
       {
         //psergey3-todo: set sjm->materialized=TRUE here, too??
+        join->return_tab= save_return_tab;
         DBUG_RETURN(rc); /* it's NESTED_LOOP_(ERROR|KILLED)*/
       }
       /*
         Ok, materialization finished. Initialize the access to the temptable
       */
+      join->return_tab= save_return_tab;
       sjm->materialized= TRUE;
-#if 0 
-      psergey3: already done at setup:
-      if (sjm->is_sj_scan)
-      {
-        /* Initialize full scan */
-        JOIN_TAB *last_tab= join_tab + (sjm->tables - 1);
-        init_read_record(&last_tab->read_record, join->thd,
-                         sjm->table, NULL, TRUE, TRUE, FALSE);
-
-        DBUG_ASSERT(last_tab->read_record.read_record == rr_sequential);
-        last_tab->read_first_record= join_read_record_no_init;
-        last_tab->read_record.copy_field= sjm->copy_field;
-        last_tab->read_record.copy_field_end= sjm->copy_field +
-                                              sjm->sjm_table_cols.elements;
-        last_tab->read_record.read_record= rr_sequential_and_unpack;
-      }
-#endif       
     }
   }
 

sql/sql_join_cache.cc

@@ -137,6 +137,7 @@ uint add_table_data_fields_to_join_cache(JOIN_TAB *tab,
   return len;
 }
     
+JOIN_TAB *next_linear_tab(JOIN* join, JOIN_TAB* tab, bool include_bush_roots);
 
 /* 
   Determine different counters of fields associated with a record in the cache  
@@ -157,10 +158,61 @@ uint add_table_data_fields_to_join_cache(JOIN_TAB *tab,
 
 void JOIN_CACHE::calc_record_fields()
 {
-  JOIN_TAB *tab = prev_cache ? prev_cache->join_tab :
+  //psergey4-todo: prev_cache, or
+  //  - first non-const table if on top level
+  //  - first table inside SJM nest if within sjm nest
+  // this->join_tab is 'our' join_tab
+
+  // No. the right idea: start from ... and walk to the current join_tab 
+  /// with an iterator, skipping
+  // join nests (can do so for now)
+
+  /*
+    The above sucks, too.
+     The right idea: 
+      - for SJM-inner tables, walk only within the nest
+      - for SJM-outer tables, use all preceding tables, including inner ones.
+      eof
+  */
+
+/*  JOIN_TAB *tab = prev_cache ? prev_cache->join_tab :
                                join->join_tab+join->const_tables;
-  tables= join_tab-tab;
+*/
 
+/*  JOIN_TAB *tab;
+  if (prev_cache)
+    tab= prev_cache->join_tab;
+  else
+  {
+    if (tab->bush_root_tab)
+    {
+      ;
+    }
+    else
+    {
+      / * top-level * /
+      tab= join->join_tab+join->const_tables;
+    }
+  }*/
+  JOIN_TAB *tab;
+  if (prev_cache)
+    tab= prev_cache->join_tab;
+  else
+  {
+    if (join_tab->bush_root_tab)
+    {
+      // inside SJM-Mat nest: pick first one
+      tab= join_tab->bush_root_tab->bush_children->start;
+    }
+    else
+    {
+      // outside SJM-Mat nest: start from first non-const table
+      tab= join->join_tab + join->const_tables;
+    }
+  }
+  start_tab= tab;
+  //tables= join_tab-tab;
+  //tables= 0;
   fields= 0;
   blobs= 0;
   flag_fields= 0;
@@ -168,7 +220,7 @@ void JOIN_CACHE::calc_record_fields()
   data_field_ptr_count= 0;
   referenced_fields= 0;
 
-  for ( ; tab < join_tab ; tab++)
+  for ( ; tab != join_tab ; tab= next_linear_tab(join, tab, TRUE))
   {	    
     calc_used_field_length(join->thd, tab);
     flag_fields+= test(tab->used_null_fields || tab->used_uneven_bit_fields);
@@ -177,6 +229,7 @@ void JOIN_CACHE::calc_record_fields()
     blobs+= tab->used_blobs;
 
     fields+= tab->check_rowid_field();
+    //tables++;
   }
   if ((with_match_flag= join_tab->use_match_flag()))
     flag_fields++;
@@ -271,7 +324,8 @@ void JOIN_CACHE::create_flag_fields()
 	                                  &copy);
 
   /* Create fields for all null bitmaps and null row flags that are needed */
-  for (tab= join_tab-tables; tab < join_tab; tab++)
+  //for (tab= join_tab-tables; tab < join_tab; tab++)
+  for (tab= start_tab; tab != join_tab; tab= next_linear_tab(join, tab, TRUE))
   {
     TABLE *table= tab->table;
 
@@ -336,7 +390,8 @@ void JOIN_CACHE:: create_remaining_fields(bool all_read_fields)
   CACHE_FIELD *copy= field_descr+flag_fields+data_field_count;
   CACHE_FIELD **copy_ptr= blob_ptr+data_field_ptr_count;
 
-  for (tab= join_tab-tables; tab < join_tab; tab++)
+  for (tab= start_tab; tab != join_tab; tab= next_linear_tab(join, tab, TRUE))
+  //for (tab= join_tab-tables; tab < join_tab; tab++)
   {
     MY_BITMAP *rem_field_set;
     TABLE *table= tab->table;
@@ -557,7 +612,9 @@ int JOIN_CACHE_BKA::init()
       of the counting 'in local_key_arg_fields' and 'external_key_arg_fields'
       respectively.
     */ 
-    for (tab= cache->join_tab-cache->tables; tab < cache->join_tab ; tab++)
+   // for (tab= cache->join_tab-cache->tables; tab < cache->join_tab ; tab++)
+    for (tab= cache->start_tab; tab != cache->join_tab; tab=
+         next_linear_tab(cache->join, tab, TRUE))
     { 
       uint key_args;
       bitmap_clear_all(&tab->table->tmp_set);
@@ -597,7 +654,9 @@ int JOIN_CACHE_BKA::init()
   while (ext_key_arg_cnt)
   {
     cache= cache->prev_cache;
-    for (tab= cache->join_tab-cache->tables; tab < cache->join_tab ; tab++)
+    for (tab= cache->start_tab; tab != cache->join_tab; tab=
+         next_linear_tab(cache->join, tab, TRUE))
+    //for (tab= cache->join_tab-cache->tables; tab < cache->join_tab ; tab++)
     { 
       CACHE_FIELD *copy_end;
       MY_BITMAP *key_read_set= &tab->table->tmp_set;
@@ -640,7 +699,8 @@ int JOIN_CACHE_BKA::init()
   
   /* Now create local fields that are used to build ref for this key access */
   copy= field_descr+flag_fields;
-  for (tab= join_tab-tables; tab < join_tab ; tab++)
+  //for (tab= join_tab-tables; tab < join_tab ; tab++)
+  for (tab= start_tab; tab != join_tab; tab= next_linear_tab(join, tab, TRUE))
   {
     length+= add_table_data_fields_to_join_cache(tab, &tab->table->tmp_set,
                                                  &data_field_count, &copy,

sql/sql_select.cc

@@ -5883,7 +5883,7 @@ JOIN_TAB *first_linear_tab(JOIN *join, bool after_const_tables)
     Depending on include_bush_roots parameter, JOIN_TABS that represent
     SJM-scan/lookups are produced or omitted.
 
-    SJM Bush children are returned right after (or in place of) their container
+    SJM-Bush children are returned right after (or in place of) their container
     join tab (TODO: does anybody depend on this? A: make_join_readinfo() seems
     to.)
 */
@@ -6095,8 +6095,8 @@ get_best_combination(JOIN *join)
     }
     else if (create_ref_for_key(join, j, keyuse, used_tables))
       DBUG_RETURN(TRUE);                        // Something went wrong
-    j->records_read= join->best_positions[tablenr].records_read;
   loop_end:
+    j->records_read= join->best_positions[tablenr].records_read;
     join->map2table[j->table->tablenr]= j;
 
     // If we've reached the end of sjm nest, switch back to main sequence

sql/sql_select.h

@@ -500,12 +500,14 @@ class JOIN_CACHE :public Sql_alloc
     context can be accessed.  
   */   
   JOIN *join;  
-
+#if 0
   /* 
     Cardinality of the range of join tables whose fields can be put into the
     cache. (A table from the range not necessarily contributes to the cache.)
   */
   uint tables;
+#endif
+  JOIN_TAB *start_tab;
 
   /* 
     The total number of flag and data fields that can appear in a record