WL#3527: Extend IGNORE INDEX so places where index is ignored

         can be specified
Currently MySQL allows one to specify what indexes to ignore during
join optimization. The scope of the current USE/FORCE/IGNORE INDEX 
statement is only the FROM clause, while all other clauses are not 
affected.

However, in certain cases, the optimizer
may incorrectly choose an index for sorting and/or grouping, and
produce an inefficient query plan.

This task provides the means to specify what indexes are
ignored/used for what operation in a more fine-grained manner, thus
making it possible to manually force a better plan. We do this
by extending the current IGNORE/USE/FORCE INDEX syntax to:

IGNORE/USE/FORCE INDEX [FOR {JOIN | ORDER | GROUP BY}]

so that:
- if no FOR is specified, the index hint will apply everywhere.
- if MySQL is started with the compatibility option --old_mode then
  an index hint without a FOR clause works as in 5.0 (i.e, the 
  index will only be ignored for JOINs, but can still be used to
  compute ORDER BY).

See the WL#3527 for further details.


BitKeeper/deleted/.del-mysqld.cc.rej:
  Rename: sql/mysqld.cc.rej -> BitKeeper/deleted/.del-mysqld.cc.rej
BitKeeper/deleted/.del-sql_parse.cc.rej:
  Rename: sql/sql_parse.cc.rej -> BitKeeper/deleted/.del-sql_parse.cc.rej
BitKeeper/deleted/.del-table.cc.rej:
  Rename: sql/table.cc.rej -> BitKeeper/deleted/.del-table.cc.rej
mysql-test/r/endspace.result:
  WL3527 : fixed undeterministic test
mysql-test/r/group_by.result:
  WL#3527: test cases
mysql-test/t/endspace.test:
  WL3527 : fixed undeterministic test
mysql-test/t/group_by.test:
  WL#3527: test cases
sql/item.cc:
  WL#3527: renames
sql/mysql_priv.h:
  WL#3527: corrected initialization
sql/mysqld.cc:
  WL#3527: added old_mode command line option
sql/opt_range.cc:
  WL#3527: renames
sql/sql_base.cc:
  WL#3527: 
   - renames
   - correct initialization
   - extended the processing of USE/FORCE/IGNORE index
sql/sql_class.h:
  WL#3527: added old_mode command line option
sql/sql_delete.cc:
  WL#3527: renames
sql/sql_help.cc:
  WL#3527: renames
sql/sql_lex.cc:
  WL#3527: extended parsing of USE/FORCE/IGNORE index
sql/sql_lex.h:
  WL#3527: extended parsing of USE/FORCE/IGNORE index
sql/sql_parse.cc:
  WL#3527: extended parsing of USE/FORCE/IGNORE index
sql/sql_select.cc:
  WL#3527:
   - renames
   - passing additional info to support the extended 
     USE/FORCE/IGNORE INDEX syntax
   - If there is a covering index, and we have 
     IGNORE INDEX FOR GROUP/ORDER, and this index is 
     used for the JOIN part, then we have to ignore the
     IGNORE INDEX FOR GROUP/ORDER.
sql/sql_show.cc:
  WL#3527: passing additional info to support the extended 
     USE/FORCE/IGNORE INDEX syntax
sql/sql_update.cc:
  WL#3527: renames
sql/sql_yacc.yy:
  WL#3527: extended parsing of USE/FORCE/IGNORE index
sql/table.cc:
  WL#3527: extended the processing of USE/FORCE/IGNORE index
sql/table.h:
  WL#3527: extended the processing of USE/FORCE/IGNORE index
storage/myisam/ha_myisam.cc:
  WL#3527: extended the processing of USE/FORCE/IGNORE index

1 files changed, 71 insertions, 10 deletions

diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index 7fd60cbfa58..0e91b2a786b 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -209,6 +209,47 @@ enum tablespace_op_type
 };
 
 /* 
+  String names used to print a statement with index hints.
+  Keep in sync with index_hint_type.
+*/
+extern const char * index_hint_type_name[];
+typedef byte index_clause_map;
+
+/*
+  Bits in index_clause_map : one for each possible FOR clause in
+  USE/FORCE/IGNORE INDEX index hint specification
+*/
+#define INDEX_HINT_MASK_JOIN  (1)
+#define INDEX_HINT_MASK_GROUP (1 << 1)
+#define INDEX_HINT_MASK_ORDER (1 << 2)
+
+#define INDEX_HINT_MASK_ALL (INDEX_HINT_MASK_JOIN | INDEX_HINT_MASK_GROUP | \
+                             INDEX_HINT_MASK_ORDER)
+
+/* Single element of an USE/FORCE/IGNORE INDEX list specified as a SQL hint  */
+class index_hint : public Sql_alloc
+{
+public:
+  /* The type of the hint : USE/FORCE/IGNORE */
+  enum index_hint_type type;
+  /* Where the hit applies to. A bitmask of INDEX_HINT_MASK_<place> values */
+  index_clause_map clause;
+  /* 
+    The index name. Empty (str=NULL) name represents an empty list 
+    USE INDEX () clause 
+  */ 
+  LEX_STRING key_name;
+
+  index_hint (enum index_hint_type type_arg, index_clause_map clause_arg,
+              char *str, uint length) :
+    type(type_arg), clause(clause_arg)
+  {
+    key_name.str= str;
+    key_name.length= length;
+  }
+}; 
+
+/* 
   The state of the lex parsing for selects 
    
    master and slaves are pointers to select_lex.
@@ -386,15 +427,12 @@ public:
   virtual uint get_in_sum_expr();
   virtual TABLE_LIST* get_table_list();
   virtual List<Item>* get_item_list();
-  virtual List<String>* get_use_index();
-  virtual List<String>* get_ignore_index();
   virtual ulong get_table_join_options();
   virtual TABLE_LIST *add_table_to_list(THD *thd, Table_ident *table,
 					LEX_STRING *alias,
 					ulong table_options,
 					thr_lock_type flags= TL_UNLOCK,
-					List<String> *use_index= 0,
-					List<String> *ignore_index= 0,
+					List<index_hint> *hints= 0,
                                         LEX_STRING *option= 0);
   virtual void set_lock_for_tables(thr_lock_type lock_type) {}
 
@@ -521,8 +559,7 @@ public:
   SQL_LIST	      table_list;
   SQL_LIST	      group_list; /* GROUP BY clause. */
   List<Item>          item_list;  /* list of fields & expressions */
-  List<String>        interval_list, use_index, *use_index_ptr,
-		      ignore_index, *ignore_index_ptr;
+  List<String>        interval_list;
   bool	              is_item_list_lookup;
   /* 
     Usualy it is pointer to ftfunc_list_alloc, but in union used to create fake
@@ -645,8 +682,7 @@ public:
 				LEX_STRING *alias,
 				ulong table_options,
 				thr_lock_type flags= TL_UNLOCK,
-				List<String> *use_index= 0,
-				List<String> *ignore_index= 0,
+				List<index_hint> *hints= 0,
                                 LEX_STRING *option= 0);
   TABLE_LIST* get_table_list();
   bool init_nested_join(THD *thd);
@@ -655,8 +691,6 @@ public:
   void add_joined_table(TABLE_LIST *table);
   TABLE_LIST *convert_right_join();
   List<Item>* get_item_list();
-  List<String>* get_use_index();
-  List<String>* get_ignore_index();
   ulong get_table_join_options();
   void set_lock_for_tables(thr_lock_type lock_type);
   inline void init_order()
@@ -696,6 +730,33 @@ public:
     select lexes.
   */
   void cleanup_all_joins(bool full);
+
+  void set_index_hint_type(enum index_hint_type type, index_clause_map clause);
+
+  /* 
+   Add a index hint to the tagged list of hints. The type and clause of the
+   hint will be the current ones (set by set_index_hint()) 
+  */
+  bool add_index_hint (THD *thd, char *str, uint length);
+
+  /* make a list to hold index hints */
+  void alloc_index_hints (THD *thd);
+  /* read and clear the index hints */
+  List<index_hint>* pop_index_hints(void) 
+  {
+    List<index_hint> *hints= index_hints;
+    index_hints= NULL;
+    return hints;
+  }
+
+  void clear_index_hints(void) { index_hints= NULL; }
+
+private:  
+  /* current index hint kind. used in filling up index_hints */
+  enum index_hint_type current_index_hint_type;
+  index_clause_map current_index_hint_clause;
+  /* a list of USE/FORCE/IGNORE INDEX */
+  List<index_hint> *index_hints;
 };
 typedef class st_select_lex SELECT_LEX;