Hi Alexander, this looks very good. I failed to understand just one thing: why in Item_cond_and::build_equal_items() there're no calls to used_tables_and_const_cache_init/used_tables_and_const_cache_join like in Item_cond::build_equal_items? They were also present in original code. Regards, Sergey On Thu, Apr 23, 2015 at 07:17:50PM +0400, Alexander Barkov wrote:
Hi Sergey,
Can you please review the "step 2" part of MDEV-7950?
This is rather a mechanical cut-and-paste change.
It does the following things:
1. Removes the function build_equal_items_for_cond() and introduces a new method Item::build_equal_items() instead, with specific implementations in the following Items:
Item (the default implementation) Item_ident_or_func_or_sum Item_cond Item_cond_and
2. Adds a new abstract class Item_ident_or_func_or_sum, a common parent for Item_ident and Item_func_or_sum, as they have exactly the same build_equal_items().
3. Renames Item_cond_and::cond_equal to Item_cond_and::m_cond_equal, to avoid confusion between the member and local variables named "cond_equal".
The main purpose of this patch is to prepare to the next step in MDEV-7950. But it already improves performance per se: it gets rid of some virtual calls:
- The former call for "((Item_cond*) cond)->functype()" is not needed any more, because Item_cond and Item_cond_and now have different implementations of the method build_equal_items().
- This condition: "else if (cond->type() == Item::FUNC_ITEM || cond->real_item()->type() == Item::FIELD_ITEM)"
(which used to cover Item_func, Item_ident and Item_ref) consisted of three virtual calls.
It's now replaced by a single virtual call for Item_ident_or_func_or_sum::build_equal_items(), which covers all three item types.
Thanks.
diff --git a/sql/item.cc b/sql/item.cc index 5433f1e..8392032 100644 --- a/sql/item.cc +++ b/sql/item.cc @@ -739,7 +739,7 @@ Item_ident::Item_ident(TABLE_LIST *view_arg, const char *field_name_arg) */
Item_ident::Item_ident(THD *thd, Item_ident *item) - :Item_result_field(thd, item), + :Item_ident_or_func_or_sum(thd, item), orig_db_name(item->orig_db_name), orig_table_name(item->orig_table_name), orig_field_name(item->orig_field_name), diff --git a/sql/item.h b/sql/item.h index 4b42db2..225686f 100644 --- a/sql/item.h +++ b/sql/item.h @@ -1094,6 +1094,12 @@ class Item { void print_item_w_name(String *, enum_query_type query_type); void print_value(String *); virtual void update_used_tables() {} + virtual COND *build_equal_items(THD *thd, COND_EQUAL *inherited, + bool link_item_fields) + { + update_used_tables(); + return this; + } virtual void split_sum_func(THD *thd, Item **ref_pointer_array, List<Item> &fields) {} /* Called for items that really have to be split */ @@ -2095,7 +2101,19 @@ class Item_result_field :public Item /* Item with result field */ };
-class Item_ident :public Item_result_field +class Item_ident_or_func_or_sum: public Item_result_field +{ +public: + Item_ident_or_func_or_sum(): Item_result_field() { } + Item_ident_or_func_or_sum(THD *thd, Item_ident_or_func_or_sum *item) + :Item_result_field(thd, item) + { } + COND *build_equal_items(THD *thd, COND_EQUAL *inherited, + bool link_item_fields); +}; + + +class Item_ident :public Item_ident_or_func_or_sum { protected: /* @@ -3398,25 +3416,20 @@ class Used_tables_and_const_cache An abstract class representing common features of regular functions and aggregate functions. */ -class Item_func_or_sum: public Item_result_field, public Item_args +class Item_func_or_sum: public Item_ident_or_func_or_sum, public Item_args { public: - Item_func_or_sum() - :Item_result_field(), Item_args() {} - Item_func_or_sum(Item *a) - :Item_result_field(), Item_args(a) { } - Item_func_or_sum(Item *a, Item *b) - :Item_result_field(), Item_args(a, b) { } - Item_func_or_sum(Item *a, Item *b, Item *c) - :Item_result_field(), Item_args(a, b, c) { } + Item_func_or_sum() :Item_args() {} + Item_func_or_sum(Item *a) :Item_args(a) { } + Item_func_or_sum(Item *a, Item *b) :Item_args(a, b) { } + Item_func_or_sum(Item *a, Item *b, Item *c) :Item_args(a, b, c) { } Item_func_or_sum(Item *a, Item *b, Item *c, Item *d) - :Item_result_field(), Item_args(a, b, c, d) { } + :Item_args(a, b, c, d) { } Item_func_or_sum(Item *a, Item *b, Item *c, Item *d, Item *e) - :Item_result_field(), Item_args(a, b, c, d, e) { } + :Item_args(a, b, c, d, e) { } Item_func_or_sum(THD *thd, Item_func_or_sum *item) - :Item_result_field(thd, item), Item_args(thd, item) { } - Item_func_or_sum(List<Item> &list) - :Item_result_field(), Item_args(list) { } + :Item_ident_or_func_or_sum(thd, item), Item_args(thd, item) { } + Item_func_or_sum(List<Item> &list) :Item_args(list) { } /* This method is used for debug purposes to print the name of an item to the debug log. The second use of this method is as diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h index bf388ef..ae7bac0 100644 --- a/sql/item_cmpfunc.h +++ b/sql/item_cmpfunc.h @@ -1768,6 +1768,8 @@ class Item_cond :public Item_bool_func used_tables_and_const_cache_init(); used_tables_and_const_cache_update_and_join(list); } + COND *build_equal_items(THD *thd, COND_EQUAL *inherited, + bool link_item_fields); virtual void print(String *str, enum_query_type query_type); void split_sum_func(THD *thd, Item **ref_pointer_array, List<Item> &fields); friend int setup_conds(THD *thd, TABLE_LIST *tables, TABLE_LIST *leaves, @@ -2078,9 +2080,9 @@ class Item_equal_fields_iterator_slow class Item_cond_and :public Item_cond { public: - COND_EQUAL cond_equal; /* contains list of Item_equal objects for - the current and level and reference - to multiple equalities of upper and levels */ + COND_EQUAL m_cond_equal; /* contains list of Item_equal objects for + the current and level and reference + to multiple equalities of upper and levels */ Item_cond_and() :Item_cond() {} Item_cond_and(Item *i1,Item *i2) :Item_cond(i1,i2) {} Item_cond_and(THD *thd, Item_cond_and *item) :Item_cond(thd, item) {} @@ -2101,6 +2103,8 @@ class Item_cond_and :public Item_cond void mark_as_condition_AND_part(TABLE_LIST *embedding); virtual uint exists2in_reserved_items() { return list.elements; }; bool walk_top_and(Item_processor processor, uchar *arg); + COND *build_equal_items(THD *thd, COND_EQUAL *inherited, + bool link_item_fields); };
inline bool is_cond_and(Item *item) diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 476adb7..d0e0fae 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -3865,7 +3865,7 @@ make_join_statistics(JOIN *join, List
&tables_list, conds= remove_eq_conds(join->thd, conds, &join->cond_value); if (conds && conds->type() == Item::COND_ITEM && ((Item_cond*) conds)->functype() == Item_func::COND_AND_FUNC) - join->cond_equal= &((Item_cond_and*) conds)->cond_equal; + join->cond_equal= &((Item_cond_and*) conds)->m_cond_equal; join->select_lex->where= conds; if (join->cond_value == Item::COND_FALSE) { @@ -3878,7 +3878,7 @@ make_join_statistics(JOIN *join, List &tables_list, { if (conds->type() == Item::COND_ITEM && ((Item_cond*) conds)->functype() == Item_func::COND_AND_FUNC) - join->cond_equal= (&((Item_cond_and *) conds)->cond_equal); + join->cond_equal= (&((Item_cond_and *) conds)->m_cond_equal); else if (conds->type() == Item::FUNC_ITEM && ((Item_func*) conds)->functype() == Item_func::MULT_EQUAL_FUNC) { @@ -4050,7 +4050,7 @@ make_join_statistics(JOIN *join, List &tables_list, ((Item_cond*) (join->conds))->functype() == Item_func::COND_AND_FUNC && join->cond_equal == - &((Item_cond_and *) (join->conds))->cond_equal) || + &((Item_cond_and *) (join->conds))->m_cond_equal) || (join->conds->type() == Item::FUNC_ITEM && ((Item_func*) (join->conds))->functype() == Item_func::MULT_EQUAL_FUNC && @@ -12377,7 +12377,7 @@ Item_equal *find_item_equal(COND_EQUAL *cond_equal, Field *field, general case, its own constant for each fields from the multiple equality. But at the same time it would allow us to get rid of constant propagation completely: it would be done by the call - to build_equal_items_for_cond. + to cond->build_equal_items(). The implementation does not follow exactly the above rules to @@ -12710,7 +12710,10 @@ static bool check_equality(THD *thd, Item *item, COND_EQUAL *cond_equal,
/** - Replace all equality predicates in a condition by multiple equality items. + Item_xxx::build_equal_items() + + Replace all equality predicates in a condition referenced by "this" + by multiple equality items.
At each 'and' level the function detects items for equality predicates and replaced them by a set of multiple equality items of class Item_equal, @@ -12766,7 +12769,6 @@ static bool check_equality(THD *thd, Item *item, COND_EQUAL *cond_equal, all possible Item_equal objects in upper levels.
@param thd thread handle - @param cond condition(expression) where to make replacement @param inherited path to all inherited multiple equality items
@return @@ -12775,180 +12777,195 @@ static bool check_equality(THD *thd, Item *item, COND_EQUAL *cond_equal, so no additional update_used_tables() is needed on the result. */
-static COND *build_equal_items_for_cond(THD *thd, COND *cond, - COND_EQUAL *inherited, - bool link_item_fields) +COND *Item_cond_and::build_equal_items(THD *thd, + COND_EQUAL *inherited, + bool link_item_fields) { Item_equal *item_equal; COND_EQUAL cond_equal; cond_equal.upper_levels= inherited;
- if (cond->type() == Item::COND_ITEM) + List<Item> eq_list; + List<Item> *args= argument_list(); + + List_iterator<Item> li(*args); + Item *item; + + /* + Retrieve all conjuncts of this level detecting the equality + that are subject to substitution by multiple equality items and + removing each such predicate from the conjunction after having + found/created a multiple equality whose inference the predicate is. + */ + while ((item= li++)) { - List<Item> eq_list; - Item_cond *cond_item= (Item_cond*) cond; - bool and_level= cond_item->functype() == Item_func::COND_AND_FUNC; - List<Item> *args= cond_item->argument_list(); - - List_iterator<Item> li(*args); - Item *item; + /* + PS/SP note: we can safely remove a node from AND-OR + structure here because it's restored before each + re-execution of any prepared statement/stored procedure. + */ + if (check_equality(thd, item, &cond_equal, &eq_list)) + li.remove(); + }
- if (and_level) + /* + Check if we eliminated all the predicates of the level, e.g. + (a=a AND b=b AND a=a). + */ + if (!args->elements && + !cond_equal.current_level.elements && + !eq_list.elements) + return new Item_int((longlong) 1, 1); + + List_iterator_fast
it(cond_equal.current_level); + while ((item_equal= it++)) + { + item_equal->set_link_equal_fields(link_item_fields); + item_equal->fix_fields(thd, NULL); + item_equal->update_used_tables(); + set_if_bigger(thd->lex->current_select->max_equal_elems, + item_equal->n_field_items()); + } + + m_cond_equal.copy(cond_equal); + cond_equal.current_level= m_cond_equal.current_level; + inherited= &m_cond_equal; + + /* + Make replacement of equality predicates for lower levels + of the condition expression. + */ + li.rewind(); + while ((item= li++)) + { + Item *new_item; + if ((new_item= item->build_equal_items(thd, inherited, FALSE)) + != item) { + /* This replacement happens only for standalone equalities */ /* - Retrieve all conjuncts of this level detecting the equality - that are subject to substitution by multiple equality items and - removing each such predicate from the conjunction after having - found/created a multiple equality whose inference the predicate is. - */ - while ((item= li++)) - { - /* - PS/SP note: we can safely remove a node from AND-OR - structure here because it's restored before each - re-execution of any prepared statement/stored procedure. - */ - if (check_equality(thd, item, &cond_equal, &eq_list)) - li.remove(); - } + This is ok with PS/SP as the replacement is done for + arguments of an AND/OR item, which are restored for each + execution of PS/SP. + */ + li.replace(new_item); + } + } + args->append(&eq_list); + args->append((List<Item> *)&cond_equal.current_level); + update_used_tables(); + return this; +} + +COND *Item_cond::build_equal_items(THD *thd, + COND_EQUAL *inherited, + bool link_item_fields) +{ + List<Item> *args= argument_list(); + + List_iterator<Item> li(*args); + Item *item; + + /* + Make replacement of equality predicates for lower levels + of the condition expression. + Update used_tables_cache and const_item_cache on the way. + */ + used_tables_and_const_cache_init(); + while ((item= li++)) + { + Item *new_item; + if ((new_item= item->build_equal_items(thd, inherited, FALSE)) + != item) + { + /* This replacement happens only for standalone equalities */ /* - Check if we eliminated all the predicates of the level, e.g. - (a=a AND b=b AND a=a). + This is ok with PS/SP as the replacement is done for + arguments of an AND/OR item, which are restored for each + execution of PS/SP. */ - if (!args->elements && - !cond_equal.current_level.elements && - !eq_list.elements) - return new Item_int((longlong) 1, 1); + li.replace(new_item); + } + used_tables_and_const_cache_join(new_item); + } + return this; +}
- List_iterator_fast
it(cond_equal.current_level); - while ((item_equal= it++)) + +COND *Item_ident_or_func_or_sum::build_equal_items(THD *thd, + COND_EQUAL *inherited, + bool link_item_fields) +{ + COND_EQUAL cond_equal; + cond_equal.upper_levels= inherited; + List<Item> eq_list; + /* + If an equality predicate forms the whole and level, + we call it standalone equality and it's processed here. + E.g. in the following where condition + WHERE a=5 AND (b=5 or a=c) + (b=5) and (a=c) are standalone equalities. + In general we can't leave alone standalone eqalities: + for WHERE a=b AND c=d AND (b=c OR d=5) + b=c is replaced by =(a,b,c,d). + */ + if (check_equality(thd, this, &cond_equal, &eq_list)) + { + Item_equal *item_equal; + int n= cond_equal.current_level.elements + eq_list.elements; + if (n == 0) + return new Item_int((longlong) 1,1); + else if (n == 1) + { + if ((item_equal= cond_equal.current_level.pop())) { - item_equal->set_link_equal_fields(link_item_fields); item_equal->fix_fields(thd, NULL); item_equal->update_used_tables(); set_if_bigger(thd->lex->current_select->max_equal_elems, item_equal->n_field_items()); + item_equal->upper_levels= inherited; + return item_equal; } - - ((Item_cond_and*)cond)->cond_equal.copy(cond_equal); - cond_equal.current_level= - ((Item_cond_and*)cond)->cond_equal.current_level; - inherited= &(((Item_cond_and*)cond)->cond_equal); - } - /* - Make replacement of equality predicates for lower levels - of the condition expression. - Update used_tables_cache and const_item_cache on the way. - */ - li.rewind(); - cond_item->used_tables_and_const_cache_init(); - while ((item= li++)) - { - Item *new_item; - if ((new_item= build_equal_items_for_cond(thd, item, inherited, FALSE)) - != item) - { - /* This replacement happens only for standalone equalities */ - /* - This is ok with PS/SP as the replacement is done for - arguments of an AND/OR item, which are restored for each - execution of PS/SP. - */ - li.replace(new_item); - } - cond_item->used_tables_and_const_cache_join(new_item); + Item *res= eq_list.pop(); + res->update_used_tables(); + return res; } - if (and_level) + else { - args->append(&eq_list); - args->append((List<Item> *)&cond_equal.current_level); - /* - Instead of the cond_item->update_used_tables() call below, - we could do this: - - cond_item->used_tables_and_const_cache_update_and_join(eq_list); - cond_item->used_tables_and_const_cache_update_and_join( - *(List<Item> *) &cond_equal.current_level); - - But initializing 2 iterators will probably be even slower than - redundant iterations over the topmost elements in "args", - which were already processed in the "while" loop above. + /* + Here a new AND level must be created. It can happen only + when a row equality is processed as a standalone predicate. */ - cond_item->update_used_tables(); - } - return cond_item; - } - else if (cond->type() == Item::FUNC_ITEM || - cond->real_item()->type() == Item::FIELD_ITEM) - { - List<Item> eq_list; - /* - If an equality predicate forms the whole and level, - we call it standalone equality and it's processed here. - E.g. in the following where condition - WHERE a=5 AND (b=5 or a=c) - (b=5) and (a=c) are standalone equalities. - In general we can't leave alone standalone eqalities: - for WHERE a=b AND c=d AND (b=c OR d=5) - b=c is replaced by =(a,b,c,d). - */ - if (check_equality(thd, cond, &cond_equal, &eq_list)) - { - int n= cond_equal.current_level.elements + eq_list.elements; - if (n == 0) - return new Item_int((longlong) 1,1); - else if (n == 1) - { - if ((item_equal= cond_equal.current_level.pop())) - { - item_equal->fix_fields(thd, NULL); - item_equal->update_used_tables(); - set_if_bigger(thd->lex->current_select->max_equal_elems, - item_equal->n_field_items()); - item_equal->upper_levels= inherited; - return item_equal; - } - Item *res= eq_list.pop(); - res->update_used_tables(); - return res; - } - else + Item_cond_and *and_cond= new Item_cond_and(eq_list); + and_cond->quick_fix_field(); + List<Item> *args= and_cond->argument_list(); + List_iterator_fast it(cond_equal.current_level); + while ((item_equal= it++)) { - /* - Here a new AND level must be created. It can happen only - when a row equality is processed as a standalone predicate. - */ - Item_cond_and *and_cond= new Item_cond_and(eq_list); - and_cond->quick_fix_field(); - List<Item> *args= and_cond->argument_list(); - List_iterator_fast it(cond_equal.current_level); - while ((item_equal= it++)) - { - item_equal->fix_length_and_dec(); - item_equal->update_used_tables(); - set_if_bigger(thd->lex->current_select->max_equal_elems, - item_equal->n_field_items()); - } - and_cond->cond_equal.copy(cond_equal); - cond_equal.current_level= and_cond->cond_equal.current_level; - args->append((List<Item> *)&cond_equal.current_level); - and_cond->update_used_tables(); - return and_cond; + item_equal->fix_length_and_dec(); + item_equal->update_used_tables(); + set_if_bigger(thd->lex->current_select->max_equal_elems, + item_equal->n_field_items()); } + and_cond->m_cond_equal.copy(cond_equal); + cond_equal.current_level= and_cond->m_cond_equal.current_level; + args->append((List<Item> *)&cond_equal.current_level); + and_cond->update_used_tables(); + return and_cond; } - /* - For each field reference in cond, not from equal item predicates, - set a pointer to the multiple equality it belongs to (if there is any) - as soon the field is not of a string type or the field reference is - an argument of a comparison predicate. - */ - uchar* is_subst_valid= (uchar *) Item::ANY_SUBST; - cond= cond->compile(&Item::subst_argument_checker, - &is_subst_valid, - &Item::equal_fields_propagator, - (uchar *) inherited); } + /* + For each field reference in cond, not from equal item predicates, + set a pointer to the multiple equality it belongs to (if there is any) + as soon the field is not of a string type or the field reference is + an argument of a comparison predicate. + */ + uchar* is_subst_valid= (uchar *) Item::ANY_SUBST; + COND *cond= compile(&Item::subst_argument_checker, + &is_subst_valid, + &Item::equal_fields_propagator, + (uchar *) inherited); cond->update_used_tables(); return cond; } @@ -12958,7 +12975,7 @@ static COND *build_equal_items_for_cond(THD *thd, COND *cond, Build multiple equalities for a condition and all on expressions that inherit these multiple equalities. - The function first applies the build_equal_items_for_cond function + The function first applies the cond->build_equal_items() method to build all multiple equalities for condition cond utilizing equalities referred through the parameter inherited. The extended set of equalities is returned in the structure referred by the cond_equal_ref @@ -13035,10 +13052,10 @@ static COND *build_equal_items(JOIN *join, COND *cond,
if (cond) { - cond= build_equal_items_for_cond(thd, cond, inherited, link_equal_fields); + cond= cond->build_equal_items(thd, inherited, link_equal_fields); if (cond->type() == Item::COND_ITEM && ((Item_cond*) cond)->functype() == Item_func::COND_AND_FUNC) - cond_equal= &((Item_cond_and*) cond)->cond_equal; + cond_equal= &((Item_cond_and*) cond)->m_cond_equal;
else if (cond->type() == Item::FUNC_ITEM && ((Item_cond*) cond)->functype() == Item_func::MULT_EQUAL_FUNC) @@ -13516,7 +13533,7 @@ static COND* substitute_for_best_equal_field(JOIN_TAB *context_tab, Item_func::COND_AND_FUNC; if (and_level) { - cond_equal= &((Item_cond_and *) cond)->cond_equal; + cond_equal= &((Item_cond_and *) cond)->m_cond_equal; cond_list->disjoin((List<Item> *) &cond_equal->current_level);/* remove Item_equal objects from the AND. */
List_iterator_fast
it(cond_equal->current_level); @@ -14667,7 +14684,7 @@ optimize_cond(JOIN *join, COND *conds, conds= remove_eq_conds(thd, conds, cond_value); if (conds && conds->type() == Item::COND_ITEM && ((Item_cond*) conds)->functype() == Item_func::COND_AND_FUNC) - *cond_equal= &((Item_cond_and*) conds)->cond_equal; + *cond_equal= &((Item_cond_and*) conds)->m_cond_equal; DBUG_EXECUTE("info",print_where(conds,"after remove", QT_ORDINARY);); } DBUG_RETURN(conds); @@ -14708,8 +14725,8 @@ void propagate_new_equalities(THD *thd, Item *cond, if (and_level) { Item_cond_and *cond_and= (Item_cond_and *) cond; - List *cond_equalities= &cond_and->cond_equal.current_level; - cond_and->cond_equal.upper_levels= inherited; + List *cond_equalities= &cond_and->m_cond_equal.current_level; + cond_and->m_cond_equal.upper_levels= inherited; if (!cond_equalities->is_empty() && cond_equalities != new_equalities) { Item_equal *equal_item; @@ -14735,7 +14752,7 @@ void propagate_new_equalities(THD *thd, Item *cond, while ((item= li++)) { COND_EQUAL *new_inherited= and_level && item->type() == Item::COND_ITEM ? - &((Item_cond_and *) cond)->cond_equal : + &((Item_cond_and *) cond)->m_cond_equal : inherited; propagate_new_equalities(thd, item, new_equalities, new_inherited, is_simplifiable_cond); @@ -14920,7 +14937,7 @@ internal_remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value) So it's easier to do it at one pass through the list of the equalities. */ List *cond_equalities= - &((Item_cond_and *) cond)->cond_equal.current_level; + &((Item_cond_and *) cond)->m_cond_equal.current_level; cond_arg_list->disjoin((List<Item> *) cond_equalities); List_iterator it(*cond_equalities); Item_equal *eq_item; @@ -14976,7 +14993,7 @@ internal_remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value) of cond_arg_list. */ List *new_item_equalities= - &((Item_cond_and *) new_item)->cond_equal.current_level; + &((Item_cond_and *) new_item)->m_cond_equal.current_level; if (!new_item_equalities->is_empty()) { /* @@ -15062,7 +15079,7 @@ internal_remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value) These multiple equalities are to be merged into the multiple equalities of cond_arg_list. */ - COND_EQUAL *cond_equal= &((Item_cond_and *) cond)->cond_equal; + COND_EQUAL *cond_equal= &((Item_cond_and *) cond)->m_cond_equal; List *cond_equalities= &cond_equal->current_level; cond_arg_list->disjoin((List<Item> *) cond_equalities); Item_equal *equality;