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MWL#89: Cost-based choice between Materialization and IN->EXISTS transformation

Browse source 
Merge 5.3-mwl89 into 5.3 main.

There is one remaining test failure in this merge:
innodb_mysql_lock2. All other tests have been checked to
deliver the same results/explains as 5.3-mwl89, including
the few remaining wrong results.
This commit is contained in:
unknown 2010-11-05 14:42:58 +02:00
commit bc7369b74b
26 changed files with 5804 additions and 791 deletions
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100
sql/item_subselect.h
View file

@ -71,6 +71,13 @@ protected:
bool inside_first_fix_fields;
bool done_first_fix_fields;
/*
Set to TRUE if at optimization or execution time we determine that this
item's value is a constant. We need this member because it is not possible
to substitute 'this' with a constant item.
*/
bool forced_const;
public:
/* A reference from inside subquery predicate to somewhere outside of it */
class Ref_to_outside : public Sql_alloc
@ -119,6 +126,12 @@ public:
Item_subselect();
virtual subs_type substype() { return UNKNOWN_SUBS; }
bool is_in_predicate()
{
return (substype() == Item_subselect::IN_SUBS ||
substype() == Item_subselect::ALL_SUBS ||
substype() == Item_subselect::ANY_SUBS);
}
/*
We need this method, because some compilers do not allow 'this'
@ -149,12 +162,21 @@ public:
void fix_after_pullout(st_select_lex *new_parent, Item **ref);
void recalc_used_tables(st_select_lex *new_parent, bool after_pullout);
virtual bool exec();
/*
If subquery optimization or execution determines that the subquery has
an empty result, mark the subquery predicate as a constant value.
*/
void make_const()
{
used_tables_cache= 0;
const_item_cache= 0;
forced_const= TRUE;
}
virtual void fix_length_and_dec();
table_map used_tables() const;
table_map not_null_tables() const { return 0; }
bool const_item() const;
inline table_map get_used_tables_cache() { return used_tables_cache; }
inline bool get_const_item_cache() { return const_item_cache; }
Item *get_tmp_table_item(THD *thd);
void update_used_tables();
virtual void print(String *str, enum_query_type query_type);
@ -181,6 +203,8 @@ public:
enum_parsing_place place() { return parsing_place; }
bool walk(Item_processor processor, bool walk_subquery, uchar *arg);
bool mark_as_eliminated_processor(uchar *arg);
bool eliminate_subselect_processor(uchar *arg);
bool set_fake_select_as_master_processor(uchar *arg);
bool enumerate_field_refs_processor(uchar *arg);
bool check_vcol_func_processor(uchar *int_arg)
{
@ -313,6 +337,18 @@ public:
};
/*
Possible methods to execute an IN predicate. These are set by the optimizer
based on user-set optimizer switches, semantic analysis and cost comparison.
*/
#define SUBS_NOT_TRANSFORMED 0 /* No execution method was chosen for this IN. */
#define SUBS_SEMI_JOIN 1 /* IN was converted to semi-join. */
#define SUBS_IN_TO_EXISTS 2 /* IN was converted to correlated EXISTS. */
#define SUBS_MATERIALIZATION 4 /* Execute IN via subquery materialization. */
/* Partial matching substrategies of MATERIALIZATION. */
#define SUBS_PARTIAL_MATCH_ROWID_MERGE 8
#define SUBS_PARTIAL_MATCH_TABLE_SCAN 16
/**
Representation of IN subquery predicates of the form
"left_expr IN (SELECT ...)".
@ -330,8 +366,6 @@ public:
class Item_in_subselect :public Item_exists_subselect
{
public:
Item *left_expr;
protected:
/*
Cache of the left operand of the subquery predicate. Allocated in the
@ -339,12 +373,6 @@ protected:
*/
List<Cached_item> *left_expr_cache;
bool first_execution;
/*
Set to TRUE if at query execution time we determine that this item's
value is a constant during this execution. We need this member because
it is not possible to substitute 'this' with a constant item.
*/
bool is_constant;
/*
expr & optimizer used in subselect rewriting to store Item for
@ -354,10 +382,24 @@ protected:
Item_in_optimizer *optimizer;
bool was_null;
bool abort_on_null;
public:
/* Used to trigger on/off conditions that were pushed down to subselect */
bool *pushed_cond_guards;
Comp_creator *func;
protected:
bool init_cond_guards();
trans_res select_in_like_transformer(JOIN *join);
trans_res single_value_transformer(JOIN *join);
trans_res row_value_transformer(JOIN * join);
bool fix_having(Item *having, st_select_lex *select_lex);
trans_res create_single_in_to_exists_cond(JOIN * join,
Item **where_item,
Item **having_item);
trans_res create_row_in_to_exists_cond(JOIN * join,
Item **where_item,
Item **having_item);
public:
Item *left_expr;
/* Priority of this predicate in the convert-to-semi-join-nest process. */
int sj_convert_priority;
/*
@ -388,14 +430,8 @@ public:
*/
bool sjm_scan_allowed;
/* The method chosen to execute the IN predicate. */
enum enum_exec_method {
NOT_TRANSFORMED, /* No execution method was chosen for this IN. */
SEMI_JOIN, /* IN was converted to semi-join nest and should be removed. */
IN_TO_EXISTS, /* IN was converted to correlated EXISTS. */
MATERIALIZATION /* IN will be executed via subquery materialization. */
};
enum_exec_method exec_method;
/* A bitmap of possible execution strategies for an IN predicate. */
uchar in_strategy;
bool *get_cond_guard(int i)
{
@ -413,9 +449,10 @@ public:
Item_in_subselect(Item * left_expr, st_select_lex *select_lex);
Item_in_subselect()
:Item_exists_subselect(), left_expr_cache(0), first_execution(TRUE),
is_constant(FALSE), optimizer(0), abort_on_null(0),
pushed_cond_guards(NULL), exec_method(NOT_TRANSFORMED), upper_item(0)
{}
optimizer(0), abort_on_null(0),
pushed_cond_guards(NULL), func(NULL), in_strategy(0),
upper_item(0)
{}
void cleanup();
subs_type substype() { return IN_SUBS; }
void reset()
@ -426,12 +463,9 @@ public:
was_null= 0;
}
trans_res select_transformer(JOIN *join);
trans_res select_in_like_transformer(JOIN *join, Comp_creator *func);
trans_res single_value_transformer(JOIN *join, Comp_creator *func);
trans_res row_value_transformer(JOIN * join);
trans_res single_value_in_to_exists_transformer(JOIN * join,
Comp_creator *func);
trans_res row_value_in_to_exists_transformer(JOIN * join);
bool create_in_to_exists_cond(JOIN *join_arg);
bool inject_in_to_exists_cond(JOIN *join_arg);
virtual bool exec();
longlong val_int();
double val_real();
@ -446,11 +480,12 @@ public:
bool fix_fields(THD *thd, Item **ref);
void fix_after_pullout(st_select_lex *new_parent, Item **ref);
void update_used_tables();
bool setup_engine();
bool setup_mat_engine();
bool init_left_expr_cache();
/* Inform 'this' that it was computed, and contains a valid result. */
void set_first_execution() { if (first_execution) first_execution= FALSE; }
bool is_expensive_processor(uchar *arg);
bool is_expensive() { return TRUE; }
bool expr_cache_is_needed(THD *thd);
/*
@ -472,7 +507,6 @@ class Item_allany_subselect :public Item_in_subselect
{
public:
chooser_compare_func_creator func_creator;
Comp_creator *func;
bool all;
Item_allany_subselect(Item * left_expr, chooser_compare_func_creator fc,
@ -481,6 +515,7 @@ public:
// only ALL subquery has upper not
subs_type substype() { return all?ALL_SUBS:ANY_SUBS; }
trans_res select_transformer(JOIN *join);
void create_comp_func(bool invert) { func= func_creator(invert); }
virtual void print(String *str, enum_query_type query_type);
};
@ -821,10 +856,9 @@ public:
}
~subselect_hash_sj_engine();
bool init_permanent(List<Item> *tmp_columns);
bool init_runtime();
bool init(List<Item> *tmp_columns);
void cleanup();
int prepare() { return 0; } /* Override virtual function in base class. */
int prepare();
int exec();
virtual void print(String *str, enum_query_type query_type);
uint cols()