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Diffstat (limited to '')
| -rw-r--r-- | sql/sql_tvc.cc | 1187 |
1 files changed, 1187 insertions, 0 deletions
diff --git a/sql/sql_tvc.cc b/sql/sql_tvc.cc new file mode 100644 index 00000000..6984fdd6 --- /dev/null +++ b/sql/sql_tvc.cc @@ -0,0 +1,1187 @@ +/* Copyright (c) 2017, 2020, MariaDB + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; version 2 of the License. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ + +#include "mariadb.h" +#include "sql_list.h" +#include "sql_tvc.h" +#include "sql_class.h" +#include "opt_range.h" +#include "sql_select.h" +#include "sql_explain.h" +#include "sql_parse.h" +#include "sql_cte.h" +#include "my_json_writer.h" + + +/** + @brief + Walk through all VALUES items. + @param + @param processor - the processor to call for each Item + @param walk_qubquery - if should dive into subquery items + @param argument - the argument to pass recursively + @retval + true on error + false on success +*/ +bool table_value_constr::walk_values(Item_processor processor, + bool walk_subquery, + void *argument) +{ + List_iterator_fast<List_item> list_item_it(lists_of_values); + while (List_item *list= list_item_it++) + { + List_iterator_fast<Item> item_it(*list); + while (Item *item= item_it++) + { + if (item->walk(&Item::unknown_splocal_processor, false, argument)) + return true; + } + } + return false; +} + + +/** + @brief + Fix fields for TVC values + + @param + @param thd The context of the statement + @param li The iterator on the list of lists + + @details + Call fix_fields procedure for TVC values. + + @retval + true if an error was reported + false otherwise +*/ + +bool fix_fields_for_tvc(THD *thd, List_iterator_fast<List_item> &li) +{ + DBUG_ENTER("fix_fields_for_tvc"); + List_item *lst; + li.rewind(); + + while ((lst= li++)) + { + List_iterator<Item> it(*lst); + Item *item; + + while ((item= it++)) + { + /* + Some items have already been fixed. + For example Item_splocal items get fixed in + Item_splocal::append_for_log(), which is called from subst_spvars() + while replacing their values to NAME_CONST()s. + So fix only those that have not been. + */ + if (item->fix_fields_if_needed_for_scalar(thd, it.ref()) || + item->check_is_evaluable_expression_or_error()) + DBUG_RETURN(true); + } + } + DBUG_RETURN(false); +} + + +/** + @brief + Defines types of matrix columns elements where matrix rows are defined by + some lists of values. + + @param + @param thd The context of the statement + @param li The iterator on the list of lists + @param holders The structure where types of matrix columns are stored + @param first_list_el_count Count of the list values. It should be the same + for each list of lists elements. It contains + number of elements of the first list from list of + lists. + + @details + For each list list_a from list of lists the procedure gets its elements + types and aggregates them with the previous ones stored in holders. If + list_a is the first one in the list of lists its elements types are put in + holders. The errors can be reported when count of list_a elements is + different from the first_list_el_count. Also error can be reported whe + n aggregation can't be made. + + @retval + true if an error was reported + false otherwise +*/ + +bool join_type_handlers_for_tvc(THD *thd, List_iterator_fast<List_item> &li, + Type_holder *holders, uint first_list_el_count) +{ + DBUG_ENTER("join_type_handlers_for_tvc"); + List_item *lst; + li.rewind(); + bool first= true; + + while ((lst= li++)) + { + List_iterator_fast<Item> it(*lst); + Item *item; + + if (first_list_el_count != lst->elements) + { + my_message(ER_WRONG_NUMBER_OF_VALUES_IN_TVC, + ER_THD(thd, ER_WRONG_NUMBER_OF_VALUES_IN_TVC), + MYF(0)); + DBUG_RETURN(true); + } + for (uint pos= 0; (item=it++); pos++) + { + const Type_handler *item_type_handler= item->real_type_handler(); + if (first) + holders[pos].set_handler(item_type_handler); + else if (holders[pos].aggregate_for_result(item_type_handler)) + { + my_error(ER_ILLEGAL_PARAMETER_DATA_TYPES2_FOR_OPERATION, MYF(0), + holders[pos].type_handler()->name().ptr(), + item_type_handler->name().ptr(), + "TABLE VALUE CONSTRUCTOR"); + DBUG_RETURN(true); + } + } + first= false; + } + DBUG_RETURN(false); +} + + +/** + @brief + Define attributes of matrix columns elements where matrix rows are defined + by some lists of values. + + @param + @param thd The context of the statement + @param li The iterator on the list of lists + @param holders The structure where names of matrix columns are stored + @param count_of_lists Count of list of lists elements + @param first_list_el_count Count of the list values. It should be the same + for each list of lists elements. It contains + number of elements of the first list from list + of lists. + + @details + For each list list_a from list of lists the procedure gets its elements + attributes and aggregates them with the previous ones stored in holders. + The errors can be reported when aggregation can't be made. + + @retval + true if an error was reported + false otherwise +*/ + +bool get_type_attributes_for_tvc(THD *thd, + List_iterator_fast<List_item> &li, + Type_holder *holders, uint count_of_lists, + uint first_list_el_count) +{ + DBUG_ENTER("get_type_attributes_for_tvc"); + List_item *lst; + li.rewind(); + + for (uint pos= 0; pos < first_list_el_count; pos++) + { + if (holders[pos].alloc_arguments(thd, count_of_lists)) + DBUG_RETURN(true); + } + + while ((lst= li++)) + { + List_iterator_fast<Item> it(*lst); + Item *item; + for (uint holder_pos= 0 ; (item= it++); holder_pos++) + { + DBUG_ASSERT(item->is_fixed()); + holders[holder_pos].add_argument(item); + } + } + + for (uint pos= 0; pos < first_list_el_count; pos++) + { + if (holders[pos].aggregate_attributes(thd)) + DBUG_RETURN(true); + } + DBUG_RETURN(false); +} + + +/** + @brief + Prepare of TVC + + @param + @param thd The context of the statement + @param sl The select where this TVC is defined + @param tmp_result Structure that contains the information + about where to send the result of the query + @param unit_arg The union where sl is defined + + @details + Gets types and attributes of values of this TVC that will be used + for temporary table creation for this TVC. It creates Item_type_holders + for each element of the first list from list of lists (VALUES from tvc), + using its elements name, defined type and attribute. + + @retval + true if an error was reported + false otherwise +*/ + +bool table_value_constr::prepare(THD *thd, SELECT_LEX *sl, + select_result *tmp_result, + st_select_lex_unit *unit_arg) +{ + DBUG_ENTER("table_value_constr::prepare"); + select_lex->in_tvc= true; + List_iterator_fast<List_item> li(lists_of_values); + + List_item *first_elem= li++; + uint cnt= first_elem->elements; + Type_holder *holders; + + if (cnt == 0) + { + my_error(ER_EMPTY_ROW_IN_TVC, MYF(0)); + DBUG_RETURN(true); + } + + if (fix_fields_for_tvc(thd, li)) + DBUG_RETURN(true); + + if (!(holders= new (thd->stmt_arena->mem_root) Type_holder[cnt]) || + join_type_handlers_for_tvc(thd, li, holders, cnt) || + get_type_attributes_for_tvc(thd, li, holders, + lists_of_values.elements, cnt)) + DBUG_RETURN(true); + + List_iterator_fast<Item> it(*first_elem); + Item *item; + Query_arena *arena, backup; + arena=thd->activate_stmt_arena_if_needed(&backup); + + sl->item_list.empty(); + for (uint pos= 0; (item= it++); pos++) + { + /* Error's in 'new' will be detected after loop */ + Item_type_holder *new_holder= new (thd->mem_root) + Item_type_holder(thd, item, holders[pos].type_handler(), + &holders[pos]/*Type_all_attributes*/, + holders[pos].get_maybe_null()); + sl->item_list.push_back(new_holder); + } + if (arena) + thd->restore_active_arena(arena, &backup); + + if (unlikely(thd->is_fatal_error)) + DBUG_RETURN(true); // out of memory + + result= tmp_result; + + if (result && result->prepare(sl->item_list, unit_arg)) + DBUG_RETURN(true); + + /* + setup_order() for a TVC is not called when the following is true + (thd->lex->context_analysis_only & CONTEXT_ANALYSIS_ONLY_VIEW) + */ + + thd->where="order clause"; + ORDER *order= sl->order_list.first; + for (; order; order=order->next) + { + Item *order_item= *order->item; + if (order_item->is_order_clause_position()) + { + uint count= 0; + if (order->counter_used) + count= order->counter; // counter was once resolved + else + count= (uint) order_item->val_int(); + if (!count || count > first_elem->elements) + { + my_error(ER_BAD_FIELD_ERROR, MYF(0), + order_item->full_name(), thd->where); + DBUG_RETURN(true); + } + order->in_field_list= 1; + order->counter= count; + order->counter_used= 1; + } + } + + select_lex->in_tvc= false; + DBUG_RETURN(false); +} + + +/** + Save Query Plan Footprint +*/ + +int table_value_constr::save_explain_data_intern(THD *thd, + Explain_query *output) +{ + const char *message= "No tables used"; + DBUG_ENTER("table_value_constr::save_explain_data_intern"); + DBUG_PRINT("info", ("Select %p, type %s, message %s", + select_lex, select_lex->type, + message)); + DBUG_ASSERT(have_query_plan == QEP_AVAILABLE); + + /* There should be no attempts to save query plans for merged selects */ + DBUG_ASSERT(!select_lex->master_unit()->derived || + select_lex->master_unit()->derived->is_materialized_derived() || + select_lex->master_unit()->derived->is_with_table()); + + explain= new (output->mem_root) Explain_select(output->mem_root, + thd->lex->analyze_stmt); + if (!explain) + DBUG_RETURN(1); + + select_lex->set_explain_type(true); + + explain->select_id= select_lex->select_number; + explain->select_type= select_lex->type; + explain->linkage= select_lex->get_linkage(); + explain->using_temporary= false; + explain->using_filesort= false; + /* Setting explain->message means that all other members are invalid */ + explain->message= message; + + if (select_lex->master_unit()->derived) + explain->connection_type= Explain_node::EXPLAIN_NODE_DERIVED; + + for (SELECT_LEX_UNIT *unit= select_lex->first_inner_unit(); + unit; + unit= unit->next_unit()) + { + explain->add_child(unit->first_select()->select_number); + } + + output->add_node(explain); + + if (select_lex->is_top_level_node()) + output->query_plan_ready(); + + DBUG_RETURN(0); +} + + +/** + Optimization of TVC +*/ + +bool table_value_constr::optimize(THD *thd) +{ + create_explain_query_if_not_exists(thd->lex, thd->mem_root); + have_query_plan= QEP_AVAILABLE; + + if (select_lex->select_number != UINT_MAX && + select_lex->select_number != INT_MAX /* this is not a UNION's "fake select */ && + have_query_plan != QEP_NOT_PRESENT_YET && + thd->lex->explain && // for "SET" command in SPs. + (!thd->lex->explain->get_select(select_lex->select_number))) + { + if (save_explain_data_intern(thd, thd->lex->explain)) + return true; + } + + if (select_lex->optimize_unflattened_subqueries(true)) + return true; + + return false; +} + + +/** + Execute of TVC +*/ + +bool table_value_constr::exec(SELECT_LEX *sl) +{ + DBUG_ENTER("table_value_constr::exec"); + List_iterator_fast<List_item> li(lists_of_values); + List_item *elem; + ha_rows send_records= 0; + + if (select_options & SELECT_DESCRIBE) + DBUG_RETURN(false); + + if (result->send_result_set_metadata(sl->item_list, + Protocol::SEND_NUM_ROWS | + Protocol::SEND_EOF)) + { + DBUG_RETURN(true); + } + + while ((elem= li++)) + { + if (send_records >= sl->master_unit()->lim.get_select_limit()) + break; + int rc= + result->send_data_with_check(*elem, sl->master_unit(), send_records); + if (!rc) + send_records++; + else if (rc > 0) + DBUG_RETURN(true); + } + + if (result->send_eof()) + DBUG_RETURN(true); + + DBUG_RETURN(false); +} + + +/** + @brief + Print list + + @param str The reference on the string representation of the list + @param list The list that needed to be print + @param query_type The mode of printing + + @details + The method saves a string representation of list in the + string str. +*/ + +void print_list_item(String *str, List_item *list, + enum_query_type query_type) +{ + bool is_first_elem= true; + List_iterator_fast<Item> it(*list); + Item *item; + + str->append('('); + + while ((item= it++)) + { + if (is_first_elem) + is_first_elem= false; + else + str->append(','); + + item->print(str, query_type); + } + + str->append(')'); +} + + +/** + @brief + Print this TVC + + @param thd The context of the statement + @param str The reference on the string representation of this TVC + @param query_type The mode of printing + + @details + The method saves a string representation of this TVC in the + string str. +*/ + +void table_value_constr::print(THD *thd, String *str, + enum_query_type query_type) +{ + DBUG_ASSERT(thd); + + str->append(STRING_WITH_LEN("values ")); + + bool is_first_elem= true; + List_iterator_fast<List_item> li(lists_of_values); + List_item *list; + + while ((list= li++)) + { + if (is_first_elem) + is_first_elem= false; + else + str->append(','); + + print_list_item(str, list, query_type); + } + if (select_lex->order_list.elements) + { + str->append(STRING_WITH_LEN(" order by ")); + select_lex->print_order(str, select_lex->order_list.first, query_type); + } + select_lex->print_limit(thd, str, query_type); +} + + +/** + @brief + Create list of lists for TVC from the list of this IN predicate + + @param thd The context of the statement + @param values TVC list of values + + @details + The method uses the list of values of this IN predicate to build + an equivalent list of values that can be used in TVC. + + E.g.: + + <value_list> = 5,2,7 + <transformed_value_list> = (5),(2),(7) + + <value_list> = (5,2),(7,1) + <transformed_value_list> = (5,2),(7,1) + + @retval + false if the method succeeds + true otherwise +*/ + +bool Item_func_in::create_value_list_for_tvc(THD *thd, + List< List<Item> > *values) +{ + bool is_list_of_rows= args[1]->type() == Item::ROW_ITEM; + + for (uint i=1; i < arg_count; i++) + { + char col_name[8]; + List<Item> *tvc_value; + if (!(tvc_value= new (thd->mem_root) List<Item>())) + return true; + + if (is_list_of_rows) + { + Item_row *row_list= (Item_row *)(args[i]); + + for (uint j=0; j < row_list->cols(); j++) + { + if (i == 1) + { + sprintf(col_name, "_col_%i", j+1); + row_list->element_index(j)->set_name(thd, col_name, strlen(col_name), + thd->charset()); + } + if (tvc_value->push_back(row_list->element_index(j), + thd->mem_root)) + return true; + } + } + else + { + if (i == 1) + { + sprintf(col_name, "_col_%i", 1); + args[i]->set_name(thd, col_name, strlen(col_name), thd->charset()); + } + if (tvc_value->push_back(args[i]->real_item())) + return true; + } + + if (values->push_back(tvc_value, thd->mem_root)) + return true; + } + return false; +} + + +/** + @brief + Create name for the derived table defined by TVC + + @param thd The context of the statement + @param parent_select The SELECT where derived table is used + @param alias The returned created name + + @details + Create name for the derived table using current TVC number + for this parent_select stored in parent_select + + @retval + true if creation fails + false otherwise +*/ + +static bool create_tvc_name(THD *thd, st_select_lex *parent_select, + LEX_CSTRING *alias) +{ + char buff[6]; + + alias->length= my_snprintf(buff, sizeof(buff), + "tvc_%u", + parent_select ? parent_select->curr_tvc_name : 0); + alias->str= thd->strmake(buff, alias->length); + if (!alias->str) + return true; + + return false; +} + + +/** + @brief + Check whether TVC used in unit is to be wrapped into select + + @details + TVC used in unit that contains more than one members is to be wrapped + into select if it is tailed with ORDER BY ... LIMIT n [OFFSET m] + + @retval + true if TVC is to be wrapped + false otherwise +*/ + +bool table_value_constr::to_be_wrapped_as_with_tail() +{ + return select_lex->master_unit()->first_select()->next_select() && + select_lex->order_list.elements && select_lex->explicit_limit; +} + + +/** + @brief + Wrap table value constructor into a select + + @param thd The context handler + @param tvc_sl The TVC to wrap + @parent_select The parent select if tvc_sl used in a subquery + + @details + The function wraps the TVC tvc_sl into a select: + the function transforms the TVC of the form VALUES (v1), ... (vn) into + the select of the form + SELECT * FROM (VALUES (v1), ... (vn)) tvc_x + + @retval pointer to the result of of the transformation if successful + NULL - otherwise +*/ + +static +st_select_lex *wrap_tvc(THD *thd, st_select_lex *tvc_sl, + st_select_lex *parent_select) +{ + LEX *lex= thd->lex; + select_result *save_result= lex->result; + uint8 save_derived_tables= lex->derived_tables; + thd->lex->result= NULL; + + Query_arena backup; + Query_arena *arena= thd->activate_stmt_arena_if_needed(&backup); + + Item *item; + SELECT_LEX *wrapper_sl; + SELECT_LEX_UNIT *derived_unit; + + /* + Create SELECT_LEX wrapper_sl of the select used in the result + of the transformation + */ + if (!(wrapper_sl= new (thd->mem_root) SELECT_LEX())) + goto err; + wrapper_sl->select_number= ++thd->lex->stmt_lex->current_select_number; + wrapper_sl->parent_lex= lex; /* Used in init_query. */ + wrapper_sl->init_query(); + wrapper_sl->init_select(); + + wrapper_sl->nest_level= tvc_sl->nest_level; + wrapper_sl->parsing_place= tvc_sl->parsing_place; + wrapper_sl->set_linkage(tvc_sl->get_linkage()); + wrapper_sl->exclude_from_table_unique_test= + tvc_sl->exclude_from_table_unique_test; + + lex->current_select= wrapper_sl; + item= new (thd->mem_root) Item_field(thd, &wrapper_sl->context, + star_clex_str); + if (item == NULL || add_item_to_list(thd, item)) + goto err; + (wrapper_sl->with_wild)++; + + /* Include the newly created select into the global list of selects */ + wrapper_sl->include_global((st_select_lex_node**)&lex->all_selects_list); + + /* Substitute select node used of TVC for the newly created select */ + tvc_sl->substitute_in_tree(wrapper_sl); + + /* + Create a unit for the substituted select used for TVC and attach it + to the the wrapper select wrapper_sl as the only unit. The created + unit is the unit for the derived table tvc_x of the transformation. + */ + if (!(derived_unit= new (thd->mem_root) SELECT_LEX_UNIT())) + goto err; + derived_unit->init_query(); + derived_unit->thd= thd; + derived_unit->include_down(wrapper_sl); + + /* + Attach the select used of TVC as the only slave to the unit for + the derived table tvc_x of the transformation + */ + derived_unit->add_slave(tvc_sl); + tvc_sl->set_linkage(DERIVED_TABLE_TYPE); + + /* + Generate the name of the derived table created for TVC and + add it to the FROM list of the wrapping select + */ + Table_ident *ti; + LEX_CSTRING alias; + TABLE_LIST *derived_tab; + if (!(ti= new (thd->mem_root) Table_ident(derived_unit)) || + create_tvc_name(thd, parent_select, &alias)) + goto err; + if (!(derived_tab= + wrapper_sl->add_table_to_list(thd, + ti, &alias, 0, + TL_READ, MDL_SHARED_READ))) + goto err; + wrapper_sl->add_joined_table(derived_tab); + wrapper_sl->add_where_field(derived_unit->first_select()); + wrapper_sl->context.table_list= wrapper_sl->table_list.first; + wrapper_sl->context.first_name_resolution_table= wrapper_sl->table_list.first; + wrapper_sl->table_list.first->derived_type= DTYPE_TABLE | DTYPE_MATERIALIZE; + lex->derived_tables|= DERIVED_SUBQUERY; + + if (arena) + thd->restore_active_arena(arena, &backup); + lex->result= save_result; + return wrapper_sl; + +err: + if (arena) + thd->restore_active_arena(arena, &backup); + lex->result= save_result; + lex->derived_tables= save_derived_tables; + return 0; +} + + +/** + @brief + Wrap TVC with ORDER BY ... LIMIT tail into a select + + @param thd The context handler + @param tvc_sl The TVC to wrap + + @details + The function wraps the TVC tvc_sl into a select: + the function transforms the TVC with tail of the form + VALUES (v1), ... (vn) ORDER BY ... LIMIT n [OFFSET m] + into the select with the same tail of the form + SELECT * FROM (VALUES (v1), ... (vn)) tvc_x + ORDER BY ... LIMIT n [OFFSET m] + + @retval pointer to the result of of the transformation if successful + NULL - otherwise +*/ + +st_select_lex *wrap_tvc_with_tail(THD *thd, st_select_lex *tvc_sl) +{ + st_select_lex *wrapper_sl= wrap_tvc(thd, tvc_sl, NULL); + if (!wrapper_sl) + return NULL; + + wrapper_sl->order_list= tvc_sl->order_list; + wrapper_sl->select_limit= tvc_sl->select_limit; + wrapper_sl->offset_limit= tvc_sl->offset_limit; + wrapper_sl->braces= tvc_sl->braces; + wrapper_sl->explicit_limit= tvc_sl->explicit_limit; + tvc_sl->order_list.empty(); + tvc_sl->select_limit= NULL; + tvc_sl->offset_limit= NULL; + tvc_sl->braces= 0; + tvc_sl->explicit_limit= false; + if (tvc_sl->select_number == 1) + { + tvc_sl->select_number= wrapper_sl->select_number; + wrapper_sl->select_number= 1; + } + if (tvc_sl->master_unit()->union_distinct == tvc_sl) + { + wrapper_sl->master_unit()->union_distinct= wrapper_sl; + } + wrapper_sl->distinct= tvc_sl->distinct; + thd->lex->current_select= wrapper_sl; + return wrapper_sl; +} + + +/** + @brief + Wrap TVC in a subselect into a select + + @param thd The context handler + @param tvc_sl The TVC to wrap + + @details + The function wraps the TVC tvc_sl used in a subselect into a select + the function transforms the TVC of the form VALUES (v1), ... (vn) + into the select the form + SELECT * FROM (VALUES (v1), ... (vn)) tvc_x + and replaces the subselect with the result of the transformation. + + @retval wrapping select if successful + 0 otherwise +*/ + +st_select_lex * +Item_subselect::wrap_tvc_into_select(THD *thd, st_select_lex *tvc_sl) +{ + LEX *lex= thd->lex; + /* SELECT_LEX object where the transformation is performed */ + SELECT_LEX *parent_select= lex->current_select; + SELECT_LEX *wrapper_sl= wrap_tvc(thd, tvc_sl, parent_select); + if (wrapper_sl) + { + if (engine->engine_type() == subselect_engine::SINGLE_SELECT_ENGINE) + ((subselect_single_select_engine *) engine)->change_select(wrapper_sl); + } + lex->current_select= parent_select; + return wrapper_sl; +} + + +/* + @brief + Check whether the items are of comparable type or not + + @details + This check are done because materialization is not performed + if the left expr and right expr are of the same types. + @see subquery_types_allow_materialization() + + @retval + 0 comparable + 1 not comparable +*/ + +static bool cmp_row_types(Item* item1, Item* item2) +{ + uint n= item1->cols(); + if (item2->check_cols(n)) + return true; + + for (uint i=0; i < n; i++) + { + Item *inner= item1->element_index(i); + Item *outer= item2->element_index(i); + if (!inner->type_handler()->subquery_type_allows_materialization(inner, + outer, + true)) + return true; + } + return false; +} + + +/** + @brief + Transform IN predicate into IN subquery + + @param thd The context of the statement + @param arg Not used + + @details + The method transforms this IN predicate into in equivalent IN subquery: + + <left_expr> IN (<value_list>) + => + <left_expr> IN (SELECT * FROM (VALUES <transformed_value_list>) AS tvc_#) + + E.g.: + + <value_list> = 5,2,7 + <transformed_value_list> = (5),(2),(7) + + <value_list> = (5,2),(7,1) + <transformed_value_list> = (5,2),(7,1) + + If the transformation succeeds the method returns the result IN subquery, + otherwise this IN predicate is returned. + + @retval + pointer to the result of transformation if succeeded + pointer to this IN predicate otherwise +*/ + +Item *Item_func_in::in_predicate_to_in_subs_transformer(THD *thd, + uchar *arg) +{ + if (!transform_into_subq) + return this; + + Json_writer_object trace_wrapper(thd); + Json_writer_object trace_conv(thd, "in_to_subquery_conversion"); + trace_conv.add("item", this); + + transform_into_subq= false; + + List<List_item> values; + + LEX *lex= thd->lex; + /* SELECT_LEX object where the transformation is performed */ + SELECT_LEX *parent_select= lex->current_select; + uint8 save_derived_tables= lex->derived_tables; + + /* + Make sure that create_tmp_table will not fail due to too long keys. + Here the strategy would mainly use materialization, so we need to make + sure that the materialized table can be created. + + The checks here are the same as in subquery_type_allows_materialization() + */ + uint32 length= max_length_of_left_expr(); + if (!length || length > tmp_table_max_key_length() || + args[0]->cols() > tmp_table_max_key_parts()) + { + trace_conv.add("done", false); + trace_conv.add("reason", "key is too long"); + return this; + } + + for (uint i=1; i < arg_count; i++) + { + if (!args[i]->const_item()) + { + trace_conv.add("done", false); + trace_conv.add("reason", "non-constant element in the IN-list"); + return this; + } + + if (cmp_row_types(args[i], args[0])) + { + trace_conv.add("done", false); + trace_conv.add("reason", "type mismatch"); + return this; + } + } + Json_writer_array trace_nested_obj(thd, "conversion"); + + Query_arena backup; + Query_arena *arena= thd->activate_stmt_arena_if_needed(&backup); + + /* + Create SELECT_LEX of the subquery SQ used in the result of transformation + */ + if (mysql_new_select(lex, 1, NULL)) + goto err; + mysql_init_select(lex); + /* Create item list as '*' for the subquery SQ */ + Item *item; + SELECT_LEX *sq_select; // select for IN subquery; + sq_select= lex->current_select; + sq_select->parsing_place= SELECT_LIST; + item= new (thd->mem_root) Item_field(thd, &sq_select->context, + star_clex_str); + if (item == NULL || add_item_to_list(thd, item)) + goto err; + (sq_select->with_wild)++; + /* + Create derived table DT that will wrap TVC in the result of transformation + */ + SELECT_LEX *tvc_select; // select for tvc + SELECT_LEX_UNIT *derived_unit; // unit for tvc_select + if (mysql_new_select(lex, 1, NULL)) + goto err; + mysql_init_select(lex); + tvc_select= lex->current_select; + derived_unit= tvc_select->master_unit(); + tvc_select->set_linkage(DERIVED_TABLE_TYPE); + + /* Create TVC used in the transformation */ + if (create_value_list_for_tvc(thd, &values)) + goto err; + if (!(tvc_select->tvc= + new (thd->mem_root) + table_value_constr(values, + tvc_select, + tvc_select->options))) + goto err; + + lex->current_select= sq_select; + + /* + Create the name of the wrapping derived table and + add it to the FROM list of the subquery SQ + */ + Table_ident *ti; + LEX_CSTRING alias; + TABLE_LIST *derived_tab; + if (!(ti= new (thd->mem_root) Table_ident(derived_unit)) || + create_tvc_name(thd, parent_select, &alias)) + goto err; + if (!(derived_tab= + sq_select->add_table_to_list(thd, + ti, &alias, 0, + TL_READ, MDL_SHARED_READ))) + goto err; + sq_select->add_joined_table(derived_tab); + sq_select->add_where_field(derived_unit->first_select()); + sq_select->context.table_list= sq_select->table_list.first; + sq_select->context.first_name_resolution_table= sq_select->table_list.first; + sq_select->table_list.first->derived_type= DTYPE_TABLE | DTYPE_MATERIALIZE; + lex->derived_tables|= DERIVED_SUBQUERY; + + sq_select->where= 0; + sq_select->set_braces(false); + derived_unit->set_with_clause(0); + + /* Create IN subquery predicate */ + sq_select->parsing_place= parent_select->parsing_place; + Item_in_subselect *in_subs; + Item *sq; + if (!(in_subs= + new (thd->mem_root) Item_in_subselect(thd, args[0], sq_select))) + goto err; + in_subs->converted_from_in_predicate= TRUE; + sq= in_subs; + if (negated) + sq= negate_expression(thd, in_subs); + else + in_subs->emb_on_expr_nest= emb_on_expr_nest; + + if (arena) + thd->restore_active_arena(arena, &backup); + thd->lex->current_select= parent_select; + + if (sq->fix_fields(thd, (Item **)&sq)) + goto err; + + parent_select->curr_tvc_name++; + + return sq; + +err: + if (arena) + thd->restore_active_arena(arena, &backup); + lex->derived_tables= save_derived_tables; + thd->lex->current_select= parent_select; + return NULL; +} + + +uint32 Item_func_in::max_length_of_left_expr() +{ + uint n= args[0]->cols(); + uint32 length= 0; + for (uint i=0; i < n; i++) + length+= args[0]->element_index(i)->max_length; + return length; +} + + +/** + @brief + Check if this IN-predicate can be transformed in IN-subquery + with TVC + + @param thd The context of the statement + + @details + Compare the number of elements in the list of + values in this IN-predicate with the + in_subquery_conversion_threshold special variable + + @retval + true if transformation can be made + false otherwise +*/ + +bool Item_func_in::to_be_transformed_into_in_subq(THD *thd) +{ + uint values_count= arg_count-1; + + if (args[1]->type() == Item::ROW_ITEM) + values_count*= ((Item_row *)(args[1]))->cols(); + + if (thd->variables.in_subquery_conversion_threshold == 0 || + thd->variables.in_subquery_conversion_threshold > values_count) + return false; + + return true; +} + + +/** + @brief + Transform IN predicates into IN subqueries in WHERE and ON expressions + + @param thd The context of the statement + + @details + For each IN predicate from AND parts of the WHERE condition and/or + ON expressions of the SELECT for this join the method performs + the intransformation into an equivalent IN sunquery if it's needed. + + @retval + false always +*/ + +bool JOIN::transform_in_predicates_into_in_subq(THD *thd) +{ + DBUG_ENTER("JOIN::transform_in_predicates_into_in_subq"); + if (!select_lex->in_funcs.elements) + DBUG_RETURN(false); + + SELECT_LEX *save_current_select= thd->lex->current_select; + enum_parsing_place save_parsing_place= select_lex->parsing_place; + thd->lex->current_select= select_lex; + if (conds) + { + select_lex->parsing_place= IN_WHERE; + conds= + conds->transform(thd, + &Item::in_predicate_to_in_subs_transformer, + (uchar*) 0); + if (!conds) + DBUG_RETURN(true); + select_lex->prep_where= conds ? conds->copy_andor_structure(thd) : 0; + select_lex->where= conds; + } + + if (join_list) + { + TABLE_LIST *table; + List_iterator<TABLE_LIST> li(*join_list); + select_lex->parsing_place= IN_ON; + + while ((table= li++)) + { + if (table->on_expr) + { + table->on_expr= + table->on_expr->transform(thd, + &Item::in_predicate_to_in_subs_transformer, + (uchar*) 0); + if (!table->on_expr) + DBUG_RETURN(true); + table->prep_on_expr= table->on_expr ? + table->on_expr->copy_andor_structure(thd) : 0; + } + } + } + + select_lex->in_funcs.empty(); + select_lex->parsing_place= save_parsing_place; + thd->lex->current_select= save_current_select; + DBUG_RETURN(false); +} + |