MWL#17: Table elimination

- More dbug printouts
- More testcases

mysql-test/r/table_elim.result

@@ -202,3 +202,20 @@ t2.pk3=t2.pk1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	
 drop table t1, t2;
+create table t1 (pk int primary key, col int);
+insert into t1 values (1,1),(2,2);
+create table t2 like t1;
+insert into t2 select * from t1;
+create table t3 like t1;
+insert into t3 select * from t1;
+explain 
+select t1.* from t1 left join ( t2 left join t3 on t3.pk=t2.col) on t2.col=t1.col;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	2	
+explain 
+select t1.*, t2.* from t1 left join (t2 left join t3 on t3.pk=t2.col) on t2.pk=t1.col;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	
+1	SIMPLE	t2	eq_ref	PRIMARY	PRIMARY	4	test.t1.col	1	
+drop table t1, t2;

mysql-test/t/table_elim.test

@@ -157,4 +157,23 @@ explain select t1.* from t1 left join t2 on t2.pk2=t1.a and
                                             t2.pk3=t2.pk1;
 
 drop table t1, t2;
+#
+# Check that equality propagation is taken into account
+#
+create table t1 (pk int primary key, col int);
+insert into t1 values (1,1),(2,2);
+
+create table t2 like t1;
+insert into t2 select * from t1;
+
+create table t3 like t1;
+insert into t3 select * from t1;
+
+explain 
+select t1.* from t1 left join ( t2 left join t3 on t3.pk=t2.col) on t2.col=t1.col;
+
+explain 
+select t1.*, t2.* from t1 left join (t2 left join t3 on t3.pk=t2.col) on t2.pk=t1.col;
+
+drop table t1, t2;
 

sql/opt_table_elimination.cc

@@ -136,7 +136,8 @@ class Table_elimination;
 
 
 /*
-  A value. 
+  A value, something that can be bound or not bound. Also, values can be linked
+  in a list.
 */
 
 class Value_dep : public Sql_alloc
@@ -203,7 +204,7 @@ public:
 
 
 /*
-  A 'module'
+  A 'module'. Module has dependencies
 */
 
 class Module_dep : public Sql_alloc
@@ -227,7 +228,6 @@ public:
 };
 
 
-
 /*
   A "tbl.column= expr" equality dependency.  tbl.column depends on fields 
   used in expr.
@@ -333,6 +333,9 @@ Equality_module *merge_func_deps(Equality_module *start, Equality_module *new_fi
 
 static Table_value *get_table_value(Table_elimination *te, TABLE *table);
 static Field_value *get_field_value(Table_elimination *te, Field *field);
+static Outer_join_module *get_outer_join_dep(Table_elimination *te, 
+                                             TABLE_LIST *outer_join, 
+                                             table_map deps_map);
 static 
 void run_elimination_wave(Table_elimination *te, Module_dep *bound_modules);
 void eliminate_tables(JOIN *join);
@@ -1212,15 +1215,19 @@ void run_elimination_wave(Table_elimination *te, Module_dep *bound_modules)
             - expressions that depend on us.
           */
           Field_value *field_dep= (Field_value*)bound_values;
+          DBUG_PRINT("info", ("field %s.%s is now bound",
+                               field_dep->field->table->alias,
+                               field_dep->field->field_name));
+
           for (Key_module *key_dep= field_dep->table->keys; key_dep;
                key_dep= key_dep->next_table_key)
           {
-            DBUG_PRINT("info", ("key %s.%s is now bound",
-                                key_dep->table->table->alias, 
-                                key_dep->table->table->key_info[key_dep->keyno].name));
             if (field_dep->field->part_of_key.is_set(key_dep->keyno) && 
                 key_dep->unknown_args && !--key_dep->unknown_args)
             {
+              DBUG_PRINT("info", ("key %s.%s is now bound",
+                                  key_dep->table->table->alias, 
+                                  key_dep->table->table->key_info[key_dep->keyno].name));
               /* Mark as bound and add to the list */
               key_dep->next= bound_modules;
               bound_modules= key_dep;