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Diffstat (limited to 'sql/sql_derived.cc')
| -rw-r--r-- | sql/sql_derived.cc | 1671 |
1 files changed, 1671 insertions, 0 deletions
diff --git a/sql/sql_derived.cc b/sql/sql_derived.cc new file mode 100644 index 00000000..f8ee3475 --- /dev/null +++ b/sql/sql_derived.cc @@ -0,0 +1,1671 @@ +/* + Copyright (c) 2002, 2011, Oracle and/or its affiliates. + Copyright (c) 2010, 2021, 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 02110-1335 USA */ + + +/* + Derived tables + These were introduced by Sinisa <sinisa@mysql.com> +*/ + + +#include "mariadb.h" /* NO_EMBEDDED_ACCESS_CHECKS */ +#include "sql_priv.h" +#include "unireg.h" +#include "sql_select.h" +#include "derived_handler.h" +#include "sql_base.h" +#include "sql_view.h" // check_duplicate_names +#include "sql_acl.h" // SELECT_ACL +#include "sql_class.h" +#include "sql_derived.h" +#include "sql_cte.h" +#include "my_json_writer.h" +#include "opt_trace.h" + +typedef bool (*dt_processor)(THD *thd, LEX *lex, TABLE_LIST *derived); + +static bool mysql_derived_init(THD *thd, LEX *lex, TABLE_LIST *derived); +static bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived); +static bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived); +static bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived); +static bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived); +static bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived); +static bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived); +static bool mysql_derived_merge_for_insert(THD *thd, LEX *lex, + TABLE_LIST *derived); + +dt_processor processors[]= +{ + &mysql_derived_init, + &mysql_derived_prepare, + &mysql_derived_optimize, + &mysql_derived_merge, + &mysql_derived_merge_for_insert, + &mysql_derived_create, + &mysql_derived_fill, + &mysql_derived_reinit, +}; + +/* + Run specified phases on all derived tables/views in given LEX. + + @param lex LEX for this thread + @param phases phases to run derived tables/views through + + @return FALSE OK + @return TRUE Error +*/ +bool +mysql_handle_derived(LEX *lex, uint phases) +{ + bool res= FALSE; + DBUG_ENTER("mysql_handle_derived"); + DBUG_PRINT("enter", ("phases: 0x%x", phases)); + if (!lex->derived_tables) + DBUG_RETURN(FALSE); + + lex->thd->derived_tables_processing= TRUE; + + for (uint phase= 0; phase < DT_PHASES && !res; phase++) + { + uint phase_flag= DT_INIT << phase; + if (phase_flag > phases) + break; + if (!(phases & phase_flag)) + continue; + + for (SELECT_LEX *sl= lex->all_selects_list; + sl && !res; + sl= sl->next_select_in_list()) + { + TABLE_LIST *cursor= sl->get_table_list(); + sl->changed_elements|= TOUCHED_SEL_DERIVED; + /* + DT_MERGE_FOR_INSERT is not needed for views/derived tables inside + subqueries. Views and derived tables of subqueries should be + processed normally. + */ + if (phases == DT_MERGE_FOR_INSERT && + cursor && (cursor->top_table()->select_lex != + lex->first_select_lex())) + continue; + for (; + cursor && !res; + cursor= cursor->next_local) + { + if (!cursor->is_view_or_derived() && phases == DT_MERGE_FOR_INSERT) + continue; + uint8 allowed_phases= (cursor->is_merged_derived() ? DT_PHASES_MERGE : + DT_PHASES_MATERIALIZE | DT_MERGE_FOR_INSERT); + /* + Skip derived tables to which the phase isn't applicable. + TODO: mark derived at the parse time, later set it's type + (merged or materialized) + */ + if ((phase_flag != DT_PREPARE && !(allowed_phases & phase_flag)) || + (cursor->merged_for_insert && phase_flag != DT_REINIT && + phase_flag != DT_PREPARE)) + continue; + res= (*processors[phase])(lex->thd, lex, cursor); + } + if (lex->describe) + { + /* + Force join->join_tmp creation, because we will use this JOIN + twice for EXPLAIN and we have to have unchanged join for EXPLAINing + */ + sl->uncacheable|= UNCACHEABLE_EXPLAIN; + sl->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN; + } + } + } + lex->thd->derived_tables_processing= FALSE; + DBUG_RETURN(res); +} + +/* + Run through phases for the given derived table/view. + + @param lex LEX for this thread + @param derived the derived table to handle + @param phase_map phases to process tables/views through + + @details + + This function process the derived table (view) 'derived' to performs all + actions that are to be done on the table at the phases specified by + phase_map. The processing is carried out starting from the actions + performed at the earlier phases (those having smaller ordinal numbers). + + @note + This function runs specified phases of the derived tables handling on the + given derived table/view. This function is used in the chain of calls: + SELECT_LEX::handle_derived -> + TABLE_LIST::handle_derived -> + mysql_handle_single_derived + This chain of calls implements the bottom-up handling of the derived tables: + i.e. most inner derived tables/views are handled first. This order is + required for the all phases except the merge and the create steps. + For the sake of code simplicity this order is kept for all phases. + + @return FALSE ok + @return TRUE error +*/ + +bool +mysql_handle_single_derived(LEX *lex, TABLE_LIST *derived, uint phases) +{ + bool res= FALSE; + uint8 allowed_phases= (derived->is_merged_derived() ? DT_PHASES_MERGE : + DT_PHASES_MATERIALIZE); + DBUG_ENTER("mysql_handle_single_derived"); + DBUG_PRINT("enter", ("phases: 0x%x allowed: 0x%x alias: '%s'", + phases, allowed_phases, + (derived->alias.str ? derived->alias.str : "<NULL>"))); + if (!lex->derived_tables) + DBUG_RETURN(FALSE); + + if (derived->select_lex) + derived->select_lex->changed_elements|= TOUCHED_SEL_DERIVED; + else + DBUG_ASSERT(derived->prelocking_placeholder); + lex->thd->derived_tables_processing= TRUE; + + for (uint phase= 0; phase < DT_PHASES; phase++) + { + uint phase_flag= DT_INIT << phase; + if (phase_flag > phases) + break; + if (!(phases & phase_flag)) + continue; + /* Skip derived tables to which the phase isn't applicable. */ + if (phase_flag != DT_PREPARE && + !(allowed_phases & phase_flag)) + continue; + + if ((res= (*processors[phase])(lex->thd, lex, derived))) + break; + } + + lex->thd->derived_tables_processing= FALSE; + DBUG_RETURN(res); +} + + +/** + Merge a derived table/view into the embedding select + + @param thd thread handle + @param lex LEX of the embedding query. + @param derived reference to the derived table. + + @details + This function merges the given derived table / view into the parent select + construction. Any derived table/reference to view occurred in the FROM + clause of the embedding select is represented by a TABLE_LIST structure a + pointer to which is passed to the function as in the parameter 'derived'. + This structure contains the number/map, alias, a link to SELECT_LEX of the + derived table and other info. If the 'derived' table is used in a nested join + then additionally the structure contains a reference to the ON expression + for this join. + + The merge process results in elimination of the derived table (or the + reference to a view) such that: + - the FROM list of the derived table/view is wrapped into a nested join + after which the nest is added to the FROM list of the embedding select + - the WHERE condition of the derived table (view) is ANDed with the ON + condition attached to the table. + + @note + Tables are merged into the leaf_tables list, original derived table is removed + from this list also. SELECT_LEX::table_list list is left untouched. + Where expression is merged with derived table's on_expr and can be found after + the merge through the SELECT_LEX::table_list. + + Examples of the derived table/view merge: + + Schema: + Tables: t1(f1), t2(f2), t3(f3) + View v1: SELECT f1 FROM t1 WHERE f1 < 1 + + Example with a view: + Before merge: + + The query (Q1): SELECT f1,f2 FROM t2 LEFT JOIN v1 ON f1 = f2 + + (LEX of the main query) + | + (select_lex) + | + (FROM table list) + | + (join list)= t2, v1 + / \ + / (on_expr)= (f1 = f2) + | + (LEX of the v1 view) + | + (select_lex)= SELECT f1 FROM t1 WHERE f1 < 1 + + + After merge: + + The rewritten query Q1 (Q1'): + SELECT f1,f2 FROM t2 LEFT JOIN (t1) ON ((f1 = f2) and (f1 < 1)) + + (LEX of the main query) + | + (select_lex) + | + (FROM table list) + | + (join list)= t2, (t1) + \ + (on_expr)= (f1 = f2) and (f1 < 1) + + In this example table numbers are assigned as follows: + (outer select): t2 - 1, v1 - 2 + (inner select): t1 - 1 + After the merge table numbers will be: + (outer select): t2 - 1, t1 - 2 + + Example with a derived table: + The query Q2: + SELECT f1,f2 + FROM (SELECT f1 FROM t1, t3 WHERE f1=f3 and f1 < 1) tt, t2 + WHERE f1 = f2 + + Before merge: + (LEX of the main query) + | + (select_lex) + / \ + (FROM table list) (WHERE clause)= (f1 = f2) + | + (join list)= tt, t2 + / \ + / (on_expr)= (empty) + / + (select_lex)= SELECT f1 FROM t1, t3 WHERE f1 = f3 and f1 < 1 + + After merge: + + The rewritten query Q2 (Q2'): + SELECT f1,f2 + FROM (t1, t3) JOIN t2 ON (f1 = f3 and f1 < 1) + WHERE f1 = f2 + + (LEX of the main query) + | + (select_lex) + / \ + (FROM table list) (WHERE clause)= (f1 = f2) + | + (join list)= t2, (t1, t3) + \ + (on_expr)= (f1 = f3 and f1 < 1) + + In this example table numbers are assigned as follows: + (outer select): tt - 1, t2 - 2 + (inner select): t1 - 1, t3 - 2 + After the merge table numbers will be: + (outer select): t1 - 1, t2 - 2, t3 - 3 + + @return FALSE if derived table/view were successfully merged. + @return TRUE if an error occur. +*/ + +static +bool mysql_derived_merge(THD *thd, LEX *lex, TABLE_LIST *derived) +{ + bool res= FALSE; + SELECT_LEX *dt_select= derived->get_single_select(); + table_map map; + uint tablenr; + SELECT_LEX *parent_lex= derived->select_lex; + Query_arena *arena, backup; + DBUG_ENTER("mysql_derived_merge"); + DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", + (derived->alias.str ? derived->alias.str : "<NULL>"), + derived->get_unit())); + const char *cause= NULL; + + if (derived->merged) + { + + DBUG_PRINT("info", ("Irreversibly merged: exit")); + DBUG_RETURN(FALSE); + } + + if (dt_select->uncacheable & UNCACHEABLE_RAND) + { + /* There is random function => fall back to materialization. */ + cause= "Random function in the select"; + if (unlikely(thd->trace_started())) + { + OPT_TRACE_VIEWS_TRANSFORM(thd, trace_wrapper, trace_derived, + derived->is_derived() ? "derived" : "view", + derived->alias.str ? derived->alias.str : "<NULL>", + derived->get_unit()->first_select()->select_number, + "materialized"); + trace_derived.add("cause", cause); + } + derived->change_refs_to_fields(); + derived->set_materialized_derived(); + DBUG_RETURN(FALSE); + } + + if (derived->dt_handler) + { + derived->change_refs_to_fields(); + derived->set_materialized_derived(); + DBUG_RETURN(FALSE); + } + + arena= thd->activate_stmt_arena_if_needed(&backup); // For easier test + + if (!derived->merged_for_insert || + (derived->is_multitable() && + (thd->lex->sql_command == SQLCOM_UPDATE_MULTI || + thd->lex->sql_command == SQLCOM_DELETE_MULTI))) + { + /* + Check whether there is enough free bits in table map to merge subquery. + If not - materialize it. This check isn't cached so when there is a big + and small subqueries, and the bigger one can't be merged it wouldn't + block the smaller one. + */ + if (parent_lex->get_free_table_map(&map, &tablenr) || + dt_select->leaf_tables.elements + tablenr > MAX_TABLES) + { + /* There is no enough table bits, fall back to materialization. */ + cause= "Not enough table bits to merge subquery"; + goto unconditional_materialization; + } + + if (dt_select->options & OPTION_SCHEMA_TABLE) + parent_lex->options |= OPTION_SCHEMA_TABLE; + + if (!derived->get_unit()->prepared) + { + dt_select->leaf_tables.empty(); + make_leaves_list(thd, dt_select->leaf_tables, derived, TRUE, 0); + } + + derived->nested_join= (NESTED_JOIN*) thd->calloc(sizeof(NESTED_JOIN)); + if (!derived->nested_join) + { + res= TRUE; + goto exit_merge; + } + + /* Merge derived table's subquery in the parent select. */ + if (parent_lex->merge_subquery(thd, derived, dt_select, tablenr, map)) + { + res= TRUE; + goto exit_merge; + } + + /* + exclude select lex so it doesn't show up in explain. + do this only for derived table as for views this is already done. + + From sql_view.cc + Add subqueries units to SELECT into which we merging current view. + unit(->next)* chain starts with subqueries that are used by this + view and continues with subqueries that are used by other views. + We must not add any subquery twice (otherwise we'll form a loop), + to do this we remember in end_unit the first subquery that has + been already added. + */ + derived->get_unit()->exclude_level(); + if (parent_lex->join) + parent_lex->join->table_count+= dt_select->join->table_count - 1; + } + derived->merged= TRUE; + if (derived->get_unit()->prepared) + { + Item *expr= derived->on_expr; + expr= and_conds(thd, expr, dt_select->join ? dt_select->join->conds : 0); + if (expr) + expr->top_level_item(); + + if (expr && (derived->prep_on_expr || expr != derived->on_expr)) + { + derived->on_expr= expr; + derived->prep_on_expr= expr->copy_andor_structure(thd); + } + thd->where= "on clause"; + if (derived->on_expr && + derived->on_expr->fix_fields_if_needed_for_bool(thd, &derived->on_expr)) + { + res= TRUE; /* purecov: inspected */ + goto exit_merge; + } + // Update used tables cache according to new table map + if (derived->on_expr) + { + derived->on_expr->fix_after_pullout(parent_lex, &derived->on_expr, + TRUE); + fix_list_after_tbl_changes(parent_lex, &derived->nested_join->join_list); + } + } + +exit_merge: + if (arena) + thd->restore_active_arena(arena, &backup); + DBUG_RETURN(res); + +unconditional_materialization: + + if (unlikely(thd->trace_started())) + { + OPT_TRACE_VIEWS_TRANSFORM(thd,trace_wrapper, trace_derived, + derived->is_derived() ? "derived" : "view", + derived->alias.str ? derived->alias.str : "<NULL>", + derived->get_unit()->first_select()->select_number, + "materialized"); + trace_derived.add("cause", cause); + } + + derived->change_refs_to_fields(); + derived->set_materialized_derived(); + if (!derived->table || !derived->table->is_created()) + res= mysql_derived_create(thd, lex, derived); + goto exit_merge; +} + + +/** + Merge a view for the embedding INSERT/UPDATE/DELETE + + @param thd thread handle + @param lex LEX of the embedding query. + @param derived reference to the derived table. + + @details + This function substitutes the derived table for the first table from + the query of the derived table thus making it a correct target table for the + INSERT/UPDATE/DELETE statements. As this operation is correct only for + single table views only, for multi table views this function does nothing. + The derived parameter isn't checked to be a view as derived tables aren't + allowed for INSERT/UPDATE/DELETE statements. + + @return FALSE if derived table/view were successfully merged. + @return TRUE if an error occur. +*/ + +static +bool mysql_derived_merge_for_insert(THD *thd, LEX *lex, TABLE_LIST *derived) +{ + DBUG_ENTER("mysql_derived_merge_for_insert"); + DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", + (derived->alias.str ? derived->alias.str : "<NULL>"), + derived->get_unit())); + DBUG_PRINT("info", ("merged_for_insert: %d is_materialized_derived: %d " + "is_multitable: %d single_table_updatable: %d " + "merge_underlying_list: %d", + derived->merged_for_insert, + derived->is_materialized_derived(), + derived->is_multitable(), + derived->single_table_updatable(), + derived->merge_underlying_list != 0)); + if (derived->merged_for_insert) + DBUG_RETURN(FALSE); + if (derived->init_derived(thd, FALSE)) + DBUG_RETURN(TRUE); + if (derived->is_materialized_derived()) + DBUG_RETURN(mysql_derived_prepare(thd, lex, derived)); + if ((thd->lex->sql_command == SQLCOM_UPDATE_MULTI || + thd->lex->sql_command == SQLCOM_DELETE_MULTI)) + DBUG_RETURN(FALSE); + if (!derived->is_multitable()) + { + if (!derived->single_table_updatable()) + DBUG_RETURN(derived->create_field_translation(thd)); + if (derived->merge_underlying_list) + { + derived->table= derived->merge_underlying_list->table; + derived->schema_table= derived->merge_underlying_list->schema_table; + derived->merged_for_insert= TRUE; + DBUG_ASSERT(derived->table); + } + } + DBUG_RETURN(FALSE); +} + + +/* + Initialize a derived table/view + + @param thd Thread handle + @param lex LEX of the embedding query. + @param derived reference to the derived table. + + @detail + Fill info about derived table/view without preparing an + underlying select. Such as: create a field translation for views, mark it as + a multitable if it is and so on. + + @return + false OK + true Error +*/ + +static +bool mysql_derived_init(THD *thd, LEX *lex, TABLE_LIST *derived) +{ + SELECT_LEX_UNIT *unit= derived->get_unit(); + DBUG_ENTER("mysql_derived_init"); + DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", + (derived->alias.str ? derived->alias.str : "<NULL>"), + derived->get_unit())); + + // Skip already prepared views/DT + if (!unit || unit->prepared) + DBUG_RETURN(FALSE); + + bool res= derived->init_derived(thd, TRUE); + + derived->updatable= derived->updatable && derived->is_view(); + + DBUG_RETURN(res); +} + + +/** + @brief + Prevent name resolution out of context of ON expressions in derived tables + + @param + join_list list of tables used in from list of a derived + + @details + The function sets the Name_resolution_context::outer_context to NULL + for all ON expressions contexts in the given join list. It does this + recursively for all nested joins the list contains. +*/ + +static void nullify_outer_context_for_on_clauses(List<TABLE_LIST>& join_list) +{ + List_iterator<TABLE_LIST> li(join_list); + while (TABLE_LIST *table= li++) + { + if (table->on_context) + table->on_context->outer_context= NULL; + if (table->nested_join) + nullify_outer_context_for_on_clauses(table->nested_join->join_list); + } +} + + +/* + Create temporary table structure (but do not fill it) + + @param thd Thread handle + @param lex LEX of the embedding query. + @param derived reference to the derived table. + + @detail + Prepare underlying select for a derived table/view. To properly resolve + names in the embedding query the TABLE structure is created. Actual table + is created later by the mysql_derived_create function. + + This function is called before any command containing derived table + is executed. All types of derived tables are handled by this function: + - Anonymous derived tables, or + - Named derived tables (aka views). + + The table reference, contained in @c derived, is updated with the + fields of a new temporary table. + Derived tables are stored in @c thd->derived_tables and closed by + close_thread_tables(). + + This function is part of the procedure that starts in + open_and_lock_tables(), a procedure that - among other things - introduces + new table and table reference objects (to represent derived tables) that + don't exist in the privilege database. This means that normal privilege + checking cannot handle them. Hence this function does some extra tricks in + order to bypass normal privilege checking, by exploiting the fact that the + current state of privilege verification is attached as GRANT_INFO structures + on the relevant TABLE and TABLE_REF objects. + + For table references, the current state of accrued access is stored inside + TABLE_LIST::grant. Hence this function must update the state of fulfilled + privileges for the new TABLE_LIST, an operation which is normally performed + exclusively by the table and database access checking functions, + check_access() and check_grant(), respectively. This modification is done + for both views and anonymous derived tables: The @c SELECT privilege is set + as fulfilled by the user. However, if a view is referenced and the table + reference is queried against directly (see TABLE_LIST::referencing_view), + the state of privilege checking (GRANT_INFO struct) is copied as-is to the + temporary table. + + Only the TABLE structure is created here, actual table is created by the + mysql_derived_create function. + + @note This function sets @c SELECT_ACL for @c TEMPTABLE views as well as + anonymous derived tables, but this is ok since later access checking will + distinguish between them. + + @see mysql_handle_derived(), mysql_derived_fill(), GRANT_INFO + + @return + false OK + true Error +*/ + +static +bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived) +{ + SELECT_LEX_UNIT *unit= derived->get_unit(); + bool res= FALSE; + DBUG_ENTER("mysql_derived_prepare"); + DBUG_PRINT("enter", ("unit: %p table_list: %p alias: '%s'", + unit, derived, derived->alias.str)); + if (!unit) + DBUG_RETURN(FALSE); + + SELECT_LEX *first_select= unit->first_select(); + + if (derived->is_recursive_with_table() && + !derived->is_with_table_recursive_reference() && + !derived->with->rec_result && derived->with->get_sq_rec_ref()) + { + /* + This is a non-recursive reference to a recursive CTE whose + specification unit has not been prepared at the regular processing of + derived table references. This can happen only in the case when + the specification unit has no recursive references at the top level. + Force the preparation of the specification unit. Use a recursive + table reference from a subquery for this. + */ + DBUG_ASSERT(derived->with->get_sq_rec_ref()); + if (unlikely(mysql_derived_prepare(lex->thd, lex, + derived->with->get_sq_rec_ref()))) + DBUG_RETURN(TRUE); + } + + if (unit->prepared && derived->is_recursive_with_table() && + !derived->table) + { + /* + Here 'derived' is either a non-recursive table reference to a recursive + with table or a recursive table reference to a recursvive table whose + specification has been already prepared (a secondary recursive table + reference. + */ + if (!(derived->derived_result= new (thd->mem_root) select_unit(thd))) + DBUG_RETURN(TRUE); // out of memory + thd->create_tmp_table_for_derived= TRUE; + res= derived->derived_result->create_result_table( + thd, &unit->types, FALSE, + (first_select->options | + thd->variables.option_bits | + TMP_TABLE_ALL_COLUMNS), + &derived->alias, FALSE, FALSE, FALSE, 0); + thd->create_tmp_table_for_derived= FALSE; + + if (likely(!res) && !derived->table) + { + derived->derived_result->set_unit(unit); + derived->table= derived->derived_result->table; + if (derived->is_with_table_recursive_reference()) + { + /* Here 'derived" is a secondary recursive table reference */ + unit->with_element->rec_result->rec_table_refs.push_back(derived); + } + } + DBUG_ASSERT(derived->table || res); + goto exit; + } + + // Skip already prepared views/DT + if (unit->prepared || + (derived->merged_for_insert && + !(derived->is_multitable() && + (thd->lex->sql_command == SQLCOM_UPDATE_MULTI || + thd->lex->sql_command == SQLCOM_DELETE_MULTI)))) + { + /* + System versioned tables may still require to get versioning conditions + when modifying view (see vers_setup_conds()). Only UPDATE and DELETE are + affected because they use WHERE condition. + */ + if (!unit->prepared && + derived->table->versioned() && + derived->merge_underlying_list && + /* choose only those merged views that do not select from other views */ + !derived->merge_underlying_list->merge_underlying_list) + { + switch (thd->lex->sql_command) + { + case SQLCOM_DELETE: + case SQLCOM_DELETE_MULTI: + case SQLCOM_UPDATE: + case SQLCOM_UPDATE_MULTI: + if ((res= first_select->vers_setup_conds(thd, + derived->merge_underlying_list))) + goto exit; + if (derived->merge_underlying_list->where) + { + Query_arena_stmt on_stmt_arena(thd); + derived->where= and_items(thd, derived->where, + derived->merge_underlying_list->where); + } + default: + break; + } + } + DBUG_RETURN(FALSE); + } + + /* prevent name resolving out of derived table */ + for (SELECT_LEX *sl= first_select; sl; sl= sl->next_select()) + { + // Prevent it for the WHERE clause + sl->context.outer_context= 0; + + // And for ON clauses, if there are any + nullify_outer_context_for_on_clauses(*sl->join_list); + + if (!derived->is_with_table_recursive_reference() || + (!derived->with->with_anchor && + !derived->with->is_with_prepared_anchor())) + { + /* + Prepare underlying views/DT first unless 'derived' is a recursive + table reference and either the anchors from the specification of + 'derived' has been already prepared or there no anchor in this + specification + */ + if ((res= sl->handle_derived(lex, DT_PREPARE))) + goto exit; + } + if (derived->outer_join && sl->first_cond_optimization) + { + /* Mark that table is part of OUTER JOIN and fields may be NULL */ + for (TABLE_LIST *cursor= (TABLE_LIST*) sl->table_list.first; + cursor; + cursor= cursor->next_local) + cursor->outer_join|= JOIN_TYPE_OUTER; + } + } + + if (unlikely(thd->trace_started())) + { + /* + Add to optimizer trace whether a derived table/view + is merged into the parent select or not. + */ + OPT_TRACE_VIEWS_TRANSFORM(thd, trace_wrapper, trace_derived, + derived->is_derived() ? "derived" : "view", + derived->alias.str ? derived->alias.str : "<NULL>", + derived->get_unit()->first_select()->select_number, + derived->is_merged_derived() ? "merged" : "materialized"); + } + /* + Above cascade call of prepare is important for PS protocol, but after it + is called we can check if we really need prepare for this derived + */ + if (derived->merged) + { + DBUG_PRINT("info", ("Irreversibly merged: exit")); + DBUG_RETURN(FALSE); + } + + derived->fill_me= FALSE; + + if ((!derived->is_with_table_recursive_reference() || + !derived->derived_result) && + !(derived->derived_result= new (thd->mem_root) select_unit(thd))) + DBUG_RETURN(TRUE); // out of memory + + // st_select_lex_unit::prepare correctly work for single select + if ((res= unit->prepare(derived, derived->derived_result, 0))) + goto exit; + if (derived->with && + (res= derived->with->process_columns_of_derived_unit(thd, unit))) + goto exit; + if ((res= check_duplicate_names(thd, unit->types, 0))) + goto exit; + + /* + Check whether we can merge this derived table into main select. + Depending on the result field translation will or will not + be created. + */ + if (!derived->is_with_table_recursive_reference() && + derived->init_derived(thd, FALSE)) + goto exit; + + /* + Temp table is created so that it hounours if UNION without ALL is to be + processed + + As 'distinct' parameter we always pass FALSE (0), because underlying + query will control distinct condition by itself. Correct test of + distinct underlying query will be is_unit_op && + !unit->union_distinct->next_select() (i.e. it is union and last distinct + SELECT is last SELECT of UNION). + */ + thd->create_tmp_table_for_derived= TRUE; + if (!(derived->table) && + derived->derived_result->create_result_table(thd, &unit->types, FALSE, + (first_select->options | + thd->variables.option_bits | + TMP_TABLE_ALL_COLUMNS), + &derived->alias, + FALSE, FALSE, FALSE, + 0)) + { + thd->create_tmp_table_for_derived= FALSE; + goto exit; + } + thd->create_tmp_table_for_derived= FALSE; + + if (!derived->table) + derived->table= derived->derived_result->table; + DBUG_ASSERT(derived->table); + if (derived->is_derived() && derived->is_merged_derived()) + first_select->mark_as_belong_to_derived(derived); + + derived->dt_handler= derived->find_derived_handler(thd); + if (derived->dt_handler) + { + char query_buff[4096]; + String derived_query(query_buff, sizeof(query_buff), thd->charset()); + derived_query.length(0); + derived->derived->print(&derived_query, + enum_query_type(QT_VIEW_INTERNAL | + QT_ITEM_ORIGINAL_FUNC_NULLIF | + QT_PARSABLE)); + if (!thd->make_lex_string(&derived->derived_spec, + derived_query.ptr(), derived_query.length())) + { + delete derived->dt_handler; + derived->dt_handler= NULL; + } + } + +exit: + /* Hide "Unknown column" or "Unknown function" error */ + if (derived->view) + { + if (thd->is_error() && + (thd->get_stmt_da()->sql_errno() == ER_BAD_FIELD_ERROR || + thd->get_stmt_da()->sql_errno() == ER_FUNC_INEXISTENT_NAME_COLLISION || + thd->get_stmt_da()->sql_errno() == ER_SP_DOES_NOT_EXIST)) + { + thd->clear_error(); + my_error(ER_VIEW_INVALID, MYF(0), derived->db.str, + derived->table_name.str); + } + } + + /* + if it is preparation PS only or commands that need only VIEW structure + then we do not need real data and we can skip execution (and parameters + is not defined, too) + */ + if (res) + { + if (!derived->is_with_table_recursive_reference()) + { + if (derived->table && derived->table->s->tmp_table) + free_tmp_table(thd, derived->table); + delete derived->derived_result; + } + } + else + { + TABLE *table= derived->table; + table->derived_select_number= first_select->select_number; + table->s->tmp_table= INTERNAL_TMP_TABLE; +#ifndef NO_EMBEDDED_ACCESS_CHECKS + if (derived->is_view()) + table->grant= derived->grant; + else + { + DBUG_ASSERT(derived->is_derived()); + DBUG_ASSERT(derived->is_anonymous_derived_table()); + table->grant.privilege= SELECT_ACL; + derived->grant.privilege= SELECT_ACL; + } +#endif + /* Add new temporary table to list of open derived tables */ + if (!derived->is_with_table_recursive_reference()) + { + table->next= thd->derived_tables; + thd->derived_tables= table; + } + + /* If table is used by a left join, mark that any column may be null */ + if (derived->outer_join) + table->maybe_null= 1; + } + DBUG_RETURN(res); +} + + +/** + Runs optimize phase for a derived table/view. + + @param thd thread handle + @param lex LEX of the embedding query. + @param derived reference to the derived table. + + @details + Runs optimize phase for given 'derived' derived table/view. + If optimizer finds out that it's of the type "SELECT a_constant" then this + functions also materializes it. + + @return FALSE ok. + @return TRUE if an error occur. +*/ + +static +bool mysql_derived_optimize(THD *thd, LEX *lex, TABLE_LIST *derived) +{ + SELECT_LEX_UNIT *unit= derived->get_unit(); + SELECT_LEX *first_select= unit->first_select(); + SELECT_LEX *save_current_select= lex->current_select; + bool res= FALSE; + DBUG_ENTER("mysql_derived_optimize"); + DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", + (derived->alias.str ? derived->alias.str : "<NULL>"), + derived->get_unit())); + if (derived->merged) + { + DBUG_PRINT("info", ("Irreversibly merged: exit")); + DBUG_RETURN(FALSE); + } + + if (derived->is_materialized_derived() && derived->dt_handler) + { + /* Create an object for execution of the query specifying the table */ + if (!(derived->pushdown_derived= + new (thd->mem_root) Pushdown_derived(derived, derived->dt_handler))) + { + delete derived->dt_handler; + derived->dt_handler= NULL; + DBUG_RETURN(TRUE); + } + } + + lex->current_select= first_select; + + if (unit->is_unit_op()) + { + if (unit->optimized) + DBUG_RETURN(FALSE); + // optimize union without execution + res= unit->optimize(); + } + else if (unit->derived) + { + if (!derived->is_merged_derived()) + { + JOIN *join= first_select->join; + unit->set_limit(unit->global_parameters()); + if (join && + join->optimization_state == JOIN::OPTIMIZATION_PHASE_1_DONE && + join->with_two_phase_optimization) + { + if (unit->optimized_2) + DBUG_RETURN(FALSE); + unit->optimized_2= TRUE; + } + else + { + if (unit->optimized) + DBUG_RETURN(FALSE); + unit->optimized= TRUE; + if (!join) + { + /* + This happens when derived is used in SELECT for which + zer_result_cause != 0. + In this case join is already destroyed. + */ + DBUG_RETURN(FALSE); + } + } + if ((res= join->optimize())) + goto err; + if (join->table_count == join->const_tables) + derived->fill_me= TRUE; + } + } + /* + Materialize derived tables/views of the "SELECT a_constant" type. + Such tables should be materialized at the optimization phase for + correct constant evaluation. + */ + if (!res && derived->fill_me && !derived->merged_for_insert) + { + if (derived->is_merged_derived()) + { + derived->change_refs_to_fields(); + derived->set_materialized_derived(); + } + if ((res= mysql_derived_create(thd, lex, derived))) + goto err; + if ((res= mysql_derived_fill(thd, lex, derived))) + goto err; + } +err: + lex->current_select= save_current_select; + DBUG_RETURN(res); +} + + +/** + Actually create result table for a materialized derived table/view. + + @param thd thread handle + @param lex LEX of the embedding query. + @param derived reference to the derived table. + + @details + This function actually creates the result table for given 'derived' + table/view, but it doesn't fill it. + 'thd' and 'lex' parameters are not used by this function. + + @return FALSE ok. + @return TRUE if an error occur. +*/ + +static +bool mysql_derived_create(THD *thd, LEX *lex, TABLE_LIST *derived) +{ + DBUG_ENTER("mysql_derived_create"); + DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", + (derived->alias.str ? derived->alias.str : "<NULL>"), + derived->get_unit())); + TABLE *table= derived->table; + SELECT_LEX_UNIT *unit= derived->get_unit(); + + if (table->is_created()) + DBUG_RETURN(FALSE); + select_unit *result= derived->derived_result; + if (table->s->db_type() == TMP_ENGINE_HTON) + { + result->tmp_table_param.keyinfo= table->s->key_info; + if (create_internal_tmp_table(table, result->tmp_table_param.keyinfo, + result->tmp_table_param.start_recinfo, + &result->tmp_table_param.recinfo, + (unit->first_select()->options | + thd->variables.option_bits | TMP_TABLE_ALL_COLUMNS))) + DBUG_RETURN(TRUE); + } + if (open_tmp_table(table)) + DBUG_RETURN(TRUE); + table->file->extra(HA_EXTRA_WRITE_CACHE); + table->file->extra(HA_EXTRA_IGNORE_DUP_KEY); + DBUG_RETURN(FALSE); +} + + +void TABLE_LIST::register_as_derived_with_rec_ref(With_element *rec_elem) +{ + rec_elem->derived_with_rec_ref.link_in_list(this, &this->next_with_rec_ref); + is_derived_with_recursive_reference= true; + get_unit()->uncacheable|= UNCACHEABLE_DEPENDENT; +} + + +bool TABLE_LIST::is_nonrecursive_derived_with_rec_ref() +{ + return is_derived_with_recursive_reference; +} + + +/** + @brief + Fill the recursive with table + + @param thd The thread handle + + @details + The method is called only for recursive with tables. + The method executes the recursive part of the specification + of this with table until no more rows are added to the table + or the number of the performed iteration reaches the allowed + maximum. + + @retval + false on success + true on failure +*/ + +bool TABLE_LIST::fill_recursive(THD *thd) +{ + bool rc= false; + st_select_lex_unit *unit= get_unit(); + rc= with->instantiate_tmp_tables(); + while (!rc && !with->all_are_stabilized()) + { + if (with->level > thd->variables.max_recursive_iterations) + break; + with->prepare_for_next_iteration(); + rc= unit->exec_recursive(); + } + if (!rc) + { + TABLE *src= with->rec_result->table; + rc =src->insert_all_rows_into_tmp_table(thd, + table, + &with->rec_result->tmp_table_param, + true); + } + return rc; +} + + +/* + Execute subquery of a materialized derived table/view and fill the result + table. + + @param thd Thread handle + @param lex LEX for this thread + @param derived reference to the derived table. + + @details + Execute subquery of given 'derived' table/view and fill the result + table. After result table is filled, if this is not the EXPLAIN statement + and the table is not specified with a recursion the entire unit / node + is deleted. unit is deleted if UNION is used for derived table and node + is deleted is it is a simple SELECT. + 'lex' is unused and 'thd' is passed as an argument to an underlying function. + + @note + If you use this function, make sure it's not called at prepare. + Due to evaluation of LIMIT clause it can not be used at prepared stage. + + @return FALSE OK + @return TRUE Error +*/ + +static +bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived) +{ + Field_iterator_table field_iterator; + SELECT_LEX_UNIT *unit= derived->get_unit(); + bool derived_is_recursive= derived->is_recursive_with_table(); + bool res= FALSE; + DBUG_ENTER("mysql_derived_fill"); + DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", + (derived->alias.str ? derived->alias.str : "<NULL>"), + derived->get_unit())); + + if (unit->executed && !unit->uncacheable && !unit->describe && + !derived_is_recursive) + DBUG_RETURN(FALSE); + /*check that table creation passed without problems. */ + DBUG_ASSERT(derived->table && derived->table->is_created()); + select_unit *derived_result= derived->derived_result; + SELECT_LEX *save_current_select= lex->current_select; + + if (derived->pushdown_derived) + { + int res; + if (unit->executed) + DBUG_RETURN(FALSE); + /* Execute the query that specifies the derived table by a foreign engine */ + res= derived->pushdown_derived->execute(); + unit->executed= true; + delete derived->pushdown_derived; + DBUG_RETURN(res); + } + + if (unit->executed && !derived_is_recursive && + (unit->uncacheable & UNCACHEABLE_DEPENDENT)) + { + if ((res= derived->table->file->ha_delete_all_rows())) + goto err; + JOIN *join= unit->first_select()->join; + join->first_record= false; + for (uint i= join->top_join_tab_count; + i < join->top_join_tab_count + join->aggr_tables; + i++) + { + if ((res= join->join_tab[i].table->file->ha_delete_all_rows())) + goto err; + } + } + + if (derived_is_recursive) + { + if (derived->is_with_table_recursive_reference()) + { + /* Here only one iteration step is performed */ + res= unit->exec_recursive(); + } + else + { + /* In this case all iteration are performed */ + res= derived->fill_recursive(thd); + } + } + else if (unit->is_unit_op()) + { + // execute union without clean up + res= unit->exec(); + } + else + { + SELECT_LEX *first_select= unit->first_select(); + unit->set_limit(unit->global_parameters()); + if (unit->lim.is_unlimited()) + first_select->options&= ~OPTION_FOUND_ROWS; + + lex->current_select= first_select; + res= mysql_select(thd, + first_select->table_list.first, + first_select->item_list, first_select->where, + (first_select->order_list.elements+ + first_select->group_list.elements), + first_select->order_list.first, + first_select->group_list.first, + first_select->having, (ORDER*) NULL, + (first_select->options |thd->variables.option_bits | + SELECT_NO_UNLOCK), + derived_result, unit, first_select); + } + + if (!res && !derived_is_recursive) + { + if (derived_result->flush()) + res= TRUE; + unit->executed= TRUE; + + if (derived->field_translation) + { + /* reset translation table to materialized table */ + field_iterator.set_table(derived->table); + for (uint i= 0; + !field_iterator.end_of_fields(); + field_iterator.next(), i= i + 1) + { + Item *item; + + if (!(item= field_iterator.create_item(thd))) + { + res= TRUE; + break; + } + thd->change_item_tree(&derived->field_translation[i].item, item); + } + } + } +err: + if (res || (!derived_is_recursive && !lex->describe && !unit->uncacheable)) + unit->cleanup(); + lex->current_select= save_current_select; + + DBUG_RETURN(res); +} + + +/** + Re-initialize given derived table/view for the next execution. + + @param thd thread handle + @param lex LEX for this thread + @param derived reference to the derived table. + + @details + Re-initialize given 'derived' table/view for the next execution. + All underlying views/derived tables are recursively reinitialized prior + to re-initialization of given derived table. + 'thd' and 'lex' are passed as arguments to called functions. + + @return FALSE OK + @return TRUE Error +*/ + +static +bool mysql_derived_reinit(THD *thd, LEX *lex, TABLE_LIST *derived) +{ + DBUG_ENTER("mysql_derived_reinit"); + DBUG_PRINT("enter", ("Alias: '%s' Unit: %p", + (derived->alias.str ? derived->alias.str : "<NULL>"), + derived->get_unit())); + st_select_lex_unit *unit= derived->get_unit(); + + derived->merged_for_insert= FALSE; + unit->unclean(); + unit->types.empty(); + /* for derived tables & PS (which can't be reset by Item_subselect) */ + unit->reinit_exec_mechanism(); + unit->set_thd(thd); + DBUG_RETURN(FALSE); +} + + +/* + @brief + Given condition cond and transformer+argument, try transforming as many + conjuncts as possible. + + @detail + The motivation of this function is to convert the condition that's being + pushed into a WHERE clause with derived_field_transformer_for_where or + with derived_grouping_field_transformer_for_where. + The transformer may fail for some sub-condition, in this case we want to + convert the most restrictive part of the condition that can be pushed. + + This function only does it for top-level AND: conjuncts that could not be + converted are dropped. + + @return + Converted condition, or NULL if nothing could be converted +*/ + +Item *transform_condition_or_part(THD *thd, + Item *cond, + Item_transformer transformer, + uchar *arg) +{ + if (cond->type() != Item::COND_ITEM || + ((Item_cond*) cond)->functype() != Item_func::COND_AND_FUNC) + { + Item *new_item= cond->transform(thd, transformer, arg); + // Indicate that the condition is not pushable + if (!new_item) + cond->clear_extraction_flag(); + return new_item; + } + + List_iterator<Item> li(*((Item_cond*) cond)->argument_list()); + Item *item; + while ((item=li++)) + { + Item *new_item= item->transform(thd, transformer, arg); + if (!new_item) + { + // Indicate that the condition is not pushable + item->clear_extraction_flag(); + li.remove(); + } + else + li.replace(new_item); + } + + switch (((Item_cond*) cond)->argument_list()->elements) + { + case 0: + return NULL; + case 1: + return ((Item_cond*) cond)->argument_list()->head(); + default: + return cond; + } +} + + +/** + @brief + Extract condition that can be pushed into a derived table/view + + @param thd the thread handle + @param cond current condition + @param derived the reference to the derived table/view + + @details + This function builds the most restrictive condition depending only on + the derived table/view (directly or indirectly through equality) that + can be extracted from the given condition cond and pushes it into the + derived table/view. + + Example of the transformation: + + SELECT * + FROM t1, + ( + SELECT x,MAX(y) AS max_y + FROM t2 + GROUP BY x + ) AS d_tab + WHERE d_tab.x>1 AND d_tab.max_y<30; + + => + + SELECT * + FROM t1, + ( + SELECT x,z,MAX(y) AS max_y + FROM t2 + WHERE x>1 + HAVING max_y<30 + GROUP BY x + ) AS d_tab + WHERE d_tab.x>1 AND d_tab.max_y<30; + + In details: + 1. Check what pushable formula can be extracted from cond + 2. Build a clone PC of the formula that can be extracted + (the clone is built only if the extracted formula is a AND subformula + of cond or conjunction of such subformulas) + Do for every select specifying derived table/view: + 3. If there is no HAVING clause prepare PC to be conjuncted with + WHERE clause of the select. Otherwise do 4-7. + 4. Check what formula PC_where can be extracted from PC to be pushed + into the WHERE clause of the select + 5. Build PC_where and if PC_where is a conjunct(s) of PC remove it from PC + getting PC_having + 6. Prepare PC_where to be conjuncted with the WHERE clause of the select + 7. Prepare PC_having to be conjuncted with the HAVING clause of the select + @note + This method is similar to pushdown_cond_for_in_subquery() + + @retval TRUE if an error occurs + @retval FALSE otherwise +*/ + +bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived) +{ + DBUG_ENTER("pushdown_cond_for_derived"); + if (!cond) + DBUG_RETURN(false); + + st_select_lex_unit *unit= derived->get_unit(); + st_select_lex *first_sl= unit->first_select(); + st_select_lex *sl= first_sl; + + if (derived->prohibit_cond_pushdown) + DBUG_RETURN(false); + + /* Do not push conditions into constant derived */ + if (unit->executed) + DBUG_RETURN(false); + + /* Do not push conditions into recursive with tables */ + if (derived->is_recursive_with_table()) + DBUG_RETURN(false); + + /* Do not push conditions into unit with global ORDER BY ... LIMIT */ + if (unit->fake_select_lex && unit->fake_select_lex->explicit_limit) + DBUG_RETURN(false); + + /* Check whether any select of 'unit' allows condition pushdown */ + bool some_select_allows_cond_pushdown= false; + for (; sl; sl= sl->next_select()) + { + if (sl->cond_pushdown_is_allowed()) + { + some_select_allows_cond_pushdown= true; + break; + } + } + if (!some_select_allows_cond_pushdown) + DBUG_RETURN(false); + + /* 1. Check what pushable formula can be extracted from cond */ + Item *extracted_cond; + cond->check_pushable_cond(&Item::pushable_cond_checker_for_derived, + (uchar *)(&derived->table->map)); + /* 2. Build a clone PC of the formula that can be extracted */ + extracted_cond= + cond->build_pushable_cond(thd, + &Item::pushable_equality_checker_for_derived, + ((uchar *)&derived->table->map)); + if (!extracted_cond) + { + /* Nothing can be pushed into the derived table */ + DBUG_RETURN(false); + } + + st_select_lex *save_curr_select= thd->lex->current_select; + for (; sl; sl= sl->next_select()) + { + Item *extracted_cond_copy; + if (!sl->cond_pushdown_is_allowed()) + continue; + /* + For each select of the unit except the last one + create a clone of extracted_cond + */ + extracted_cond_copy= !sl->next_select() ? + extracted_cond : + extracted_cond->build_clone(thd); + if (!extracted_cond_copy) + continue; + + /* + Rename the columns of all non-first selects of a union to be compatible + by names with the columns of the first select. It will allow to use copies + of the same expression pushed into having clauses of different selects. + */ + if (sl != first_sl) + { + DBUG_ASSERT(sl->item_list.elements == first_sl->item_list.elements); + List_iterator_fast<Item> it(sl->item_list); + List_iterator_fast<Item> nm_it(unit->types); + while (Item *item= it++) + item->share_name_with(nm_it++); + } + + /* Collect fields that are used in the GROUP BY of sl */ + if (sl->have_window_funcs()) + { + if (sl->group_list.first || sl->join->implicit_grouping) + continue; + ORDER *common_partition_fields= + sl->find_common_window_func_partition_fields(thd); + if (!common_partition_fields) + continue; + sl->collect_grouping_fields_for_derived(thd, common_partition_fields); + } + else + sl->collect_grouping_fields_for_derived(thd, sl->group_list.first); + + Item *remaining_cond= NULL; + /* Do 4-6 */ + sl->pushdown_cond_into_where_clause(thd, extracted_cond_copy, + &remaining_cond, + &Item::derived_field_transformer_for_where, + (uchar *) sl); + + if (!remaining_cond) + continue; + /* + 7. Prepare PC_having to be conjuncted with the HAVING clause of + the select + */ + remaining_cond= + remaining_cond->transform(thd, + &Item::derived_field_transformer_for_having, + (uchar *) sl); + if (!remaining_cond) + continue; + + if (remaining_cond->walk(&Item::cleanup_excluding_const_fields_processor, + 0, 0)) + continue; + + mark_or_conds_to_avoid_pushdown(remaining_cond); + + sl->cond_pushed_into_having= remaining_cond; + } + thd->lex->current_select= save_curr_select; + DBUG_RETURN(false); +} + + +/** + @brief + Look for provision of the derived_handler interface by a foreign engine + + @param thd The thread handler + + @details + The function looks through its tables of the query that specifies this + derived table searching for a table whose handlerton owns a + create_derived call-back function. If the call of this function returns + a derived_handler interface object then the server will push the query + specifying the derived table into this engine. + This is a responsibility of the create_derived call-back function to + check whether the engine can execute the query. + + @retval the found derived_handler if the search is successful + 0 otherwise +*/ + +derived_handler *TABLE_LIST::find_derived_handler(THD *thd) +{ + if (!derived || is_recursive_with_table()) + return 0; + for (SELECT_LEX *sl= derived->first_select(); sl; sl= sl->next_select()) + { + if (!(sl->join)) + continue; + for (TABLE_LIST *tbl= sl->join->tables_list; tbl; tbl= tbl->next_local) + { + if (!tbl->table) + continue; + handlerton *ht= tbl->table->file->partition_ht(); + if (!ht->create_derived) + continue; + derived_handler *dh= ht->create_derived(thd, this); + if (dh) + { + dh->set_derived(this); + return dh; + } + } + } + return 0; +} + + +TABLE_LIST *TABLE_LIST::get_first_table() +{ + for (SELECT_LEX *sl= derived->first_select(); sl; sl= sl->next_select()) + { + if (!(sl->join)) + continue; + for (TABLE_LIST *tbl= sl->join->tables_list; tbl; tbl= tbl->next_local) + { + if (!tbl->table) + continue; + return tbl; + } + } + return 0; +} |