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| -rw-r--r-- | sql/sql_cte.cc | 1746 |
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diff --git a/sql/sql_cte.cc b/sql/sql_cte.cc new file mode 100644 index 00000000..c53ae300 --- /dev/null +++ b/sql/sql_cte.cc @@ -0,0 +1,1746 @@ +/* + Copyright (c) 2016, 2017 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_class.h" +#include "sql_lex.h" +#include "sql_cte.h" +#include "sql_view.h" // for make_valid_column_names +#include "sql_parse.h" +#include "sql_select.h" +#include "sql_show.h" // append_definer, append_identifier + + +/** + @brief + Add a new element to this with clause + + @param elem The with element to add to this with clause + + @details + The method adds the with element 'elem' to the elements + in this with clause. The method reports an error if + the number of the added element exceeds the value + of the constant max_number_of_elements_in_with_clause. + + @retval + true if an error is reported + false otherwise +*/ + +bool With_clause::add_with_element(With_element *elem) +{ + if (with_list.elements == max_number_of_elements_in_with_clause) + { + my_error(ER_TOO_MANY_DEFINITIONS_IN_WITH_CLAUSE, MYF(0)); + return true; + } + elem->owner= this; + elem->number= with_list.elements; + elem->spec->with_element= elem; + with_list.link_in_list(elem, &elem->next); + return false; +} + + +void st_select_lex_unit::set_with_clause(With_clause *with_cl) +{ + with_clause= with_cl; + if (with_clause) + with_clause->set_owner(this); +} + + +/** + @brief + Check dependencies between tables defined in a list of with clauses + + @param + with_clauses_list Pointer to the first clause in the list + + @details + For each with clause from the given list the procedure finds all + dependencies between tables defined in the clause by calling the + method With_clause::checked_dependencies. + Additionally, based on the info collected by this method the procedure + finds anchors for each recursive definition and moves them at the head + of the definition. + + @retval + false on success + true on failure +*/ + +bool LEX::check_dependencies_in_with_clauses() +{ + for (With_clause *with_clause= with_clauses_list; + with_clause; + with_clause= with_clause->next_with_clause) + { + if (with_clause->check_dependencies()) + return true; + if (with_clause->check_anchors()) + return true; + with_clause->move_anchors_ahead(); + } + return false; +} + + +/** + @brief + Resolve references to CTE in specification of hanging CTE + + @details + A CTE to which there are no references in the query is called hanging CTE. + Although such CTE is not used for execution its specification must be + subject to context analysis. All errors concerning references to + non-existing tables or fields occurred in the specification must be + reported as well as all other errors caught at the prepare stage. + The specification of a hanging CTE might contain references to other + CTE outside of the specification and within it if the specification + contains a with clause. This function resolves all such references for + all hanging CTEs encountered in the processed query. + + @retval + false on success + true on failure +*/ + +bool +LEX::resolve_references_to_cte_in_hanging_cte() +{ + for (With_clause *with_clause= with_clauses_list; + with_clause; with_clause= with_clause->next_with_clause) + { + for (With_element *with_elem= with_clause->with_list.first; + with_elem; with_elem= with_elem->next) + { + if (!with_elem->is_referenced()) + { + TABLE_LIST *first_tbl= + with_elem->spec->first_select()->table_list.first; + TABLE_LIST **with_elem_end_pos= with_elem->head->tables_pos.end_pos; + if (first_tbl && resolve_references_to_cte(first_tbl, with_elem_end_pos)) + return true; + } + } + } + return false; +} + + +/** + @brief + Resolve table references to CTE from a sub-chain of table references + + @param tables Points to the beginning of the sub-chain + @param tables_last Points to the address with the sub-chain barrier + + @details + The method resolves tables references to CTE from the chain of + table references specified by the parameters 'tables' and 'tables_last'. + It resolves the references against the CTE definition occurred in a query + or the specification of a CTE whose parsing tree is represented by + this LEX structure. The method is always called right after the process + of parsing the query or of the specification of a CTE has been finished, + thus the chain of table references used in the parsed fragment has been + already built. It is assumed that parameters of the method specify a + a sub-chain of this chain. + If a table reference can be potentially a table reference to a CTE and it + has not been resolved yet then the method tries to find the definition + of the CTE against which the reference can be resolved. If it succeeds + it sets the field TABLE_LIST::with to point to the found definition. + It also sets the field TABLE_LIST::derived to point to the specification + of the found CTE and sets TABLE::db.str to empty_c_string. This will + allow to handle this table reference like a reference to a derived handle. + If another table reference has been already resolved against this CTE + and this CTE is not recursive then a clone of the CTE specification is + constructed using the function With_element::clone_parsed_spec() and + TABLE_LIST::derived is set to point to this clone rather than to the + original specification. + If the method does not find a matched CTE definition in the parsed fragment + then in the case when the flag this->only_cte_resolution is set to true + it just moves to the resolution of the next table reference from the + specified sub-chain while in the case when this->only_cte_resolution is set + to false the method additionally sets an mdl request for this table + reference. + + @notes + The flag this->only_cte_resolution is set to true in the cases when + the failure to resolve a table reference as a CTE reference within + the fragment associated with this LEX structure does not imply that + this table reference cannot be resolved as such at all. + + @retval false On success: no errors reported, no memory allocations failed + @retval true Otherwise +*/ + +bool LEX::resolve_references_to_cte(TABLE_LIST *tables, + TABLE_LIST **tables_last) +{ + With_element *with_elem= 0; + + for (TABLE_LIST *tbl= tables; tbl != *tables_last; tbl= tbl->next_global) + { + if (tbl->derived) + continue; + if (!tbl->db.str && !tbl->with) + tbl->with= tbl->select_lex->find_table_def_in_with_clauses(tbl); + if (!tbl->with) // no CTE matches table reference tbl + { + if (only_cte_resolution) + continue; + if (!tbl->db.str) // no database specified in table reference tbl + { + if (!thd->db.str) // no default database is set + { + my_message(ER_NO_DB_ERROR, ER(ER_NO_DB_ERROR), MYF(0)); + return true; + } + if (copy_db_to(&tbl->db)) + return true; + if (!(tbl->table_options & TL_OPTION_ALIAS)) + MDL_REQUEST_INIT(&tbl->mdl_request, MDL_key::TABLE, + tbl->db.str, tbl->table_name.str, + tbl->mdl_type, MDL_TRANSACTION); + tbl->mdl_request.set_type((tbl->lock_type >= TL_WRITE_ALLOW_WRITE) ? + MDL_SHARED_WRITE : MDL_SHARED_READ); + } + continue; + } + with_elem= tbl->with; + if (tbl->is_recursive_with_table() && + !tbl->is_with_table_recursive_reference()) + { + tbl->with->rec_outer_references++; + while ((with_elem= with_elem->get_next_mutually_recursive()) != + tbl->with) + with_elem->rec_outer_references++; + } + if (!with_elem->is_used_in_query || with_elem->is_recursive) + { + tbl->derived= with_elem->spec; + if (tbl->derived != tbl->select_lex->master_unit() && + !with_elem->is_recursive && + !tbl->is_with_table_recursive_reference()) + { + tbl->derived->move_as_slave(tbl->select_lex); + } + with_elem->is_used_in_query= true; + } + else + { + if (!(tbl->derived= tbl->with->clone_parsed_spec(thd->lex, tbl))) + return true; + } + tbl->db.str= empty_c_string; + tbl->db.length= 0; + tbl->schema_table= 0; + if (tbl->derived) + { + tbl->derived->first_select()->set_linkage(DERIVED_TABLE_TYPE); + tbl->select_lex->add_statistics(tbl->derived); + } + if (tbl->with->is_recursive && tbl->is_with_table_recursive_reference()) + continue; + with_elem->inc_references(); + } + return false; +} + + +/** + @brief + Find out dependencies between CTEs, resolve references to them + + @details + The function can be called in two modes. With this->with_cte_resolution + set to false the function only finds out all dependencies between CTEs + used in a query expression with a WITH clause whose parsing has been + just finished. Based on these dependencies recursive CTEs are detected. + If this->with_cte_resolution is set to true the function additionally + resolves all references to CTE occurred in this query expression. + + @retval + true on failure + false on success +*/ + +bool +LEX::check_cte_dependencies_and_resolve_references() +{ + if (check_dependencies_in_with_clauses()) + return true; + if (!with_cte_resolution) + return false; + if (resolve_references_to_cte(query_tables, query_tables_last)) + return true; + if (resolve_references_to_cte_in_hanging_cte()) + return true; + return false; +} + + +/** + @brief + Check dependencies between tables defined in this with clause + + @details + The method performs the following for this with clause: + - checks that there are no definitions of the tables with the same name + - for each table T defined in this with clause looks for the tables + from the same with clause that are used in the query that specifies T + and set the dependencies of T on these tables in a bitmap. + - builds the transitive closure of the above direct dependencies + to find out all recursive definitions. + + @retval + true if an error is reported + false otherwise +*/ + +bool With_clause::check_dependencies() +{ + if (dependencies_are_checked) + return false; + /* + Look for for definitions with the same query name. + When found report an error and return true immediately. + For each table T defined in this with clause look for all other tables + from the same with clause that are used in the specification of T. + For each such table set the dependency bit in the dependency map of + the with element for T. + */ + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + { + for (With_element *elem= with_list.first; + elem != with_elem; + elem= elem->next) + { + if (lex_string_cmp(system_charset_info, with_elem->get_name(), + elem->get_name()) == 0) + { + my_error(ER_DUP_QUERY_NAME, MYF(0), + with_elem->get_name_str()); + return true; + } + } + if (with_elem->check_dependencies_in_spec()) + return true; + } + /* Build the transitive closure of the direct dependencies found above */ + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + with_elem->derived_dep_map= with_elem->base_dep_map; + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + { + table_map with_elem_map= with_elem->get_elem_map(); + for (With_element *elem= with_list.first; elem; elem= elem->next) + { + if (elem->derived_dep_map & with_elem_map) + elem->derived_dep_map |= with_elem->derived_dep_map; + } + } + + /* + Mark those elements where tables are defined with direct or indirect + recursion. + */ + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + { + if (with_elem->derived_dep_map & with_elem->get_elem_map()) + with_elem->is_recursive= true; + } + + dependencies_are_checked= true; + return false; +} + + +/* + This structure describes an element of the stack of embedded units. + The stack is used when looking for a definition of a table in + with clauses. The definition can be found only in the scopes + of the with clauses attached to the units from the stack. + The with clauses are looked through from starting from the top + element of the stack. +*/ + +struct st_unit_ctxt_elem +{ + st_unit_ctxt_elem *prev; // the previous element of the stack + st_select_lex_unit *unit; +}; + + +/** + @brief + Find the dependencies of this element on its siblings in its specification + + @details + For each table reference ref(T) from the FROM list of every select sl + immediately contained in the specification query of this element this + method searches for the definition of T in the the with clause which + this element belongs to. If such definition is found then the dependency + on it is set in sl->with_dep and in this->base_dep_map. +*/ + +bool With_element::check_dependencies_in_spec() +{ + for (st_select_lex *sl= spec->first_select(); sl; sl= sl->next_select()) + { + st_unit_ctxt_elem ctxt0= {NULL, owner->owner}; + st_unit_ctxt_elem ctxt1= {&ctxt0, spec}; + check_dependencies_in_select(sl, &ctxt1, false, &sl->with_dep); + base_dep_map|= sl->with_dep; + } + return false; +} + + +/** + @brief + Search for the definition of a table among the elements of this with clause + + @param table The reference to the table that is looked for + @param barrier The barrier with element for the search + + @details + The function looks through the elements of this with clause trying to find + the definition of the given table. When it encounters the element with + the same query name as the table's name it returns this element. If no + such definitions are found the function returns NULL. + + @retval + found with element if the search succeeded + NULL - otherwise +*/ + +With_element *With_clause::find_table_def(TABLE_LIST *table, + With_element *barrier) +{ + for (With_element *with_elem= with_list.first; + with_elem != barrier; + with_elem= with_elem->next) + { + if (my_strcasecmp(system_charset_info, with_elem->get_name_str(), + table->table_name.str) == 0 && + !table->is_fqtn) + { + table->set_derived(); + with_elem->referenced= true; + return with_elem; + } + } + return NULL; +} + + +/** + @brief + Search for the definition of a table in with clauses + + @param tbl The reference to the table that is looked for + @param ctxt The context describing in what with clauses of the upper + levels the table has to be searched for. + + @details + The function looks for the definition of the table tbl in the definitions + of the with clauses from the upper levels specified by the parameter ctxt. + When it encounters the element with the same query name as the table's name + it returns this element. If no such definitions are found the function + returns NULL. + + @retval + found with element if the search succeeded + NULL - otherwise +*/ + +With_element *find_table_def_in_with_clauses(TABLE_LIST *tbl, + st_unit_ctxt_elem *ctxt) +{ + With_element *barrier= NULL; + for (st_unit_ctxt_elem *unit_ctxt_elem= ctxt; + unit_ctxt_elem; + unit_ctxt_elem= unit_ctxt_elem->prev) + { + st_select_lex_unit *unit= unit_ctxt_elem->unit; + With_clause *with_clause= unit->with_clause; + if (with_clause && + (tbl->with= with_clause->find_table_def(tbl, barrier))) + return tbl->with; + barrier= NULL; + if (unit->with_element && !unit->with_element->get_owner()->with_recursive) + { + /* + This unit is the specification if the with element unit->with_element. + The with element belongs to a with clause without the specifier RECURSIVE. + So when searching for the matching definition of tbl this with clause must + be looked up to this with element + */ + barrier= unit->with_element; + } + } + return NULL; +} + + +/** + @brief + Find the dependencies of this element on its siblings in a select + + @param sl The select where to look for the dependencies + @param ctxt The structure specifying the scope of the definitions + of the with elements of the upper levels + @param in_sbq if true mark dependencies found in subqueries in + this->sq_dep_map + @param dep_map IN/OUT The bit where to mark the found dependencies + + @details + For each table reference ref(T) from the FROM list of the select sl + the method searches in with clauses for the definition of the table T. + If the found definition belongs to the same with clause as this with + element then the method set dependency on T in the in/out parameter + dep_map, add if required - in this->sq_dep_map. + The parameter ctxt describes the proper context for the search + of the definition of T. +*/ + +void With_element::check_dependencies_in_select(st_select_lex *sl, + st_unit_ctxt_elem *ctxt, + bool in_subq, + table_map *dep_map) +{ + With_clause *with_clause= sl->get_with_clause(); + for (TABLE_LIST *tbl= sl->table_list.first; tbl; tbl= tbl->next_local) + { + if (tbl->derived || tbl->nested_join) + continue; + tbl->with_internal_reference_map= 0; + /* + If there is a with clause attached to the unit containing sl + look first for the definition of tbl in this with clause. + If such definition is not found there look in the with + clauses of the upper levels. + If the definition of tbl is found somewhere in with clauses + then tbl->with is set to point to this definition + */ + if (with_clause && !tbl->with) + tbl->with= with_clause->find_table_def(tbl, NULL); + if (!tbl->with) + tbl->with= find_table_def_in_with_clauses(tbl, ctxt); + + if (tbl->with && tbl->with->owner== this->owner) + { + /* + The found definition T of tbl belongs to the same + with clause as this with element. In this case: + - set the dependence on T in the bitmap dep_map + - set tbl->with_internal_reference_map with + the bitmap for this definition + - set the dependence on T in the bitmap this->sq_dep_map + if needed + */ + *dep_map|= tbl->with->get_elem_map(); + tbl->with_internal_reference_map= get_elem_map(); + if (in_subq) + sq_dep_map|= tbl->with->get_elem_map(); + else + top_level_dep_map|= tbl->with->get_elem_map(); + } + } + /* Now look for the dependencies in the subqueries of sl */ + st_select_lex_unit *inner_unit= sl->first_inner_unit(); + for (; inner_unit; inner_unit= inner_unit->next_unit()) + { + if (!inner_unit->with_element) + check_dependencies_in_unit(inner_unit, ctxt, in_subq, dep_map); + } +} + + +/** + @brief + Find a recursive reference to this with element in subqueries of a select + + @param sel The select in whose subqueries the reference + to be looked for + + @details + The function looks for a recursive reference to this with element in + subqueries of select sl. When the first such reference is found + it is returned as the result. + The function assumes that the identification of all CTE references + has been performed earlier. + + @retval + Pointer to the found recursive reference if the search succeeded + NULL - otherwise +*/ + +TABLE_LIST *With_element::find_first_sq_rec_ref_in_select(st_select_lex *sel) +{ + TABLE_LIST *rec_ref= NULL; + st_select_lex_unit *inner_unit= sel->first_inner_unit(); + for (; inner_unit; inner_unit= inner_unit->next_unit()) + { + st_select_lex *sl= inner_unit->first_select(); + for (; sl; sl= sl->next_select()) + { + for (TABLE_LIST *tbl= sl->table_list.first; tbl; tbl= tbl->next_local) + { + if (tbl->derived || tbl->nested_join) + continue; + if (tbl->with && tbl->with->owner== this->owner && + (tbl->with_internal_reference_map & mutually_recursive)) + { + rec_ref= tbl; + return rec_ref; + } + } + if ((rec_ref= find_first_sq_rec_ref_in_select(sl))) + return rec_ref; + } + } + return 0; +} + + +/** + @brief + Find the dependencies of this element on its siblings in a unit + + @param unit The unit where to look for the dependencies + @param ctxt The structure specifying the scope of the definitions + of the with elements of the upper levels + @param in_sbq if true mark dependencies found in subqueries in + this->sq_dep_map + @param dep_map IN/OUT The bit where to mark the found dependencies + + @details + This method searches in the unit 'unit' for the the references in FROM + lists of all selects contained in this unit and in the with clause + attached to this unit that refer to definitions of tables from the + same with clause as this element. + If such definitions are found then the dependencies on them are + set in the in/out parameter dep_map and optionally in this->sq_dep_map. + The parameter ctxt describes the proper context for the search. +*/ + +void With_element::check_dependencies_in_unit(st_select_lex_unit *unit, + st_unit_ctxt_elem *ctxt, + bool in_subq, + table_map *dep_map) +{ + if (unit->with_clause) + check_dependencies_in_with_clause(unit->with_clause, ctxt, in_subq, dep_map); + in_subq |= unit->item != NULL; + st_unit_ctxt_elem unit_ctxt_elem= {ctxt, unit}; + st_select_lex *sl= unit->first_select(); + for (; sl; sl= sl->next_select()) + { + check_dependencies_in_select(sl, &unit_ctxt_elem, in_subq, dep_map); + } +} + + +/** + @brief + Find the dependencies of this element on its siblings in a with clause + + @param witt_clause The with clause where to look for the dependencies + @param ctxt The structure specifying the scope of the definitions + of the with elements of the upper levels + @param in_sbq if true mark dependencies found in subqueries in + this->sq_dep_map + @param dep_map IN/OUT The bit where to mark the found dependencies + + @details + This method searches in the with_clause for the the references in FROM + lists of all selects contained in the specifications of the with elements + from this with_clause that refer to definitions of tables from the + same with clause as this element. + If such definitions are found then the dependencies on them are + set in the in/out parameter dep_map and optionally in this->sq_dep_map. + The parameter ctxt describes the proper context for the search. +*/ + +void +With_element::check_dependencies_in_with_clause(With_clause *with_clause, + st_unit_ctxt_elem *ctxt, + bool in_subq, + table_map *dep_map) +{ + for (With_element *with_elem= with_clause->with_list.first; + with_elem; + with_elem= with_elem->next) + { + check_dependencies_in_unit(with_elem->spec, ctxt, in_subq, dep_map); + } +} + + +/** + @brief + Find mutually recursive with elements and check that they have ancors + + @details + This method performs the following: + - for each recursive with element finds all mutually recursive with it + - links each group of mutually recursive with elements into a ring chain + - checks that every group of mutually recursive with elements contains + at least one anchor + - checks that after removing any with element with anchor the remaining + with elements mutually recursive with the removed one are not recursive + anymore + + @retval + true if an error is reported + false otherwise +*/ + +bool With_clause::check_anchors() +{ + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + { + if (!with_elem->is_recursive) + continue; + + /* + It with_elem is recursive with element find all elements mutually recursive + with it (any recursive element is mutually recursive with itself). Mark all + these elements in the bitmap->mutually_recursive. Also link all these + elements into a ring chain. + */ + if (!with_elem->next_mutually_recursive) + { + With_element *last_mutually_recursive= with_elem; + table_map with_elem_dep= with_elem->derived_dep_map; + table_map with_elem_map= with_elem->get_elem_map(); + for (With_element *elem= with_elem; elem; elem= elem->next) + { + if (!elem->is_recursive) + continue; + + if (elem == with_elem || + ((elem->derived_dep_map & with_elem_map) && + (with_elem_dep & elem->get_elem_map()))) + { + elem->next_mutually_recursive= with_elem; + last_mutually_recursive->next_mutually_recursive= elem; + last_mutually_recursive= elem; + with_elem->mutually_recursive|= elem->get_elem_map(); + } + } + for (With_element *elem= with_elem->next_mutually_recursive; + elem != with_elem; + elem= elem->next_mutually_recursive) + elem->mutually_recursive= with_elem->mutually_recursive; + } + + /* + For each select from the specification of 'with_elem' check whether + it is an anchor i.e. does not depend on any with elements mutually + recursive with 'with_elem". + */ + for (st_select_lex *sl= with_elem->spec->first_select(); + sl; + sl= sl->next_select()) + { + if (with_elem->is_anchor(sl)) + { + with_elem->with_anchor= true; + break; + } + } + } + + /* + Check that for any group of mutually recursive with elements + - there is at least one anchor + - after removing any with element with anchor the remaining with elements + mutually recursive with the removed one are not recursive anymore + */ + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + { + if (!with_elem->is_recursive) + continue; + + if (!with_elem->with_anchor) + { + /* + Check that the other with elements mutually recursive with 'with_elem' + contain at least one anchor. + */ + With_element *elem= with_elem; + while ((elem= elem->get_next_mutually_recursive()) != with_elem) + { + if (elem->with_anchor) + break; + } + if (elem == with_elem) + { + my_error(ER_RECURSIVE_WITHOUT_ANCHORS, MYF(0), + with_elem->get_name_str()); + return true; + } + } + else + { + /* 'with_elem' is a with element with an anchor */ + With_element *elem= with_elem; + /* + For the other with elements mutually recursive with 'with_elem' + set dependency bits between those elements in the field work_dep_map + and build transitive closure of these dependencies + */ + while ((elem= elem->get_next_mutually_recursive()) != with_elem) + elem->work_dep_map= elem->base_dep_map & elem->mutually_recursive; + elem= with_elem; + while ((elem= elem->get_next_mutually_recursive()) != with_elem) + { + table_map elem_map= elem->get_elem_map(); + With_element *el= with_elem; + while ((el= el->get_next_mutually_recursive()) != with_elem) + { + if (el->work_dep_map & elem_map) + el->work_dep_map|= elem->work_dep_map; + } + } + /* If the transitive closure displays any cycle report an arror */ + elem= with_elem; + while ((elem= elem->get_next_mutually_recursive()) != with_elem) + { + if (elem->work_dep_map & elem->get_elem_map()) + { + my_error(ER_UNACCEPTABLE_MUTUAL_RECURSION, MYF(0), + with_elem->get_name_str()); + return true; + } + } + } + } + + return false; +} + + +/** + @brief + Move anchors at the beginning of the specifications for with elements + + @details + This method moves anchors at the beginning of the specifications for + all recursive with elements. +*/ + +void With_clause::move_anchors_ahead() +{ + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + { + if (with_elem->is_recursive) + with_elem->move_anchors_ahead(); + } +} + + +/** + @brief + Move anchors at the beginning of the specification of this with element + + @details + If the specification of this with element contains anchors the method + moves them at the very beginning of the specification. + Additionally for the other selects of the specification if none of them + contains a recursive reference to this with element or a mutually recursive + one the method looks for the first such reference in the first recursive + select and set a pointer to it in this->sq_rec_ref. +*/ + +void With_element::move_anchors_ahead() +{ + st_select_lex *next_sl; + st_select_lex *new_pos= spec->first_select(); + new_pos->set_linkage(UNION_TYPE); + for (st_select_lex *sl= new_pos; sl; sl= next_sl) + { + next_sl= sl->next_select(); + if (is_anchor(sl)) + { + sl->move_node(new_pos); + if (new_pos == spec->first_select()) + { + enum sub_select_type type= new_pos->get_linkage(); + new_pos->set_linkage(sl->get_linkage()); + sl->set_linkage(type); + new_pos->with_all_modifier= sl->with_all_modifier; + sl->with_all_modifier= false; + } + new_pos= sl->next_select(); + } + else if (!sq_rec_ref && no_rec_ref_on_top_level()) + { + sq_rec_ref= find_first_sq_rec_ref_in_select(sl); + DBUG_ASSERT(sq_rec_ref != NULL); + } + } + first_recursive= new_pos; + spec->first_select()->set_linkage(DERIVED_TABLE_TYPE); +} + + +/** + @brief + Perform context analysis for all unreferenced tables defined in with clause + + @param thd The context of the statement containing this with clause + + @details + For each unreferenced table T defined in this with clause the method + calls the method With_element::prepare_unreferenced that performs + context analysis of the element with the definition of T. + + @retval + false If context analysis does not report any error + true Otherwise +*/ + +bool With_clause::prepare_unreferenced_elements(THD *thd) +{ + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + { + if ((with_elem->is_hanging_recursive() || !with_elem->is_referenced()) && + with_elem->prepare_unreferenced(thd)) + return true; + } + + return false; +} + + +/** + @brief + Save the specification of the given with table as a string + + @param thd The context of the statement containing this with element + @param spec_start The beginning of the specification in the input string + @param spec_end The end of the specification in the input string + @param spec_offset The offset of the specification in the input string + + @details + The method creates for a string copy of the specification used in this + element. The method is called when the element is parsed. The copy may be + used to create clones of the specification whenever they are needed. + + @retval + false on success + true on failure +*/ + +bool With_element::set_unparsed_spec(THD *thd, + const char *spec_start, + const char *spec_end, + my_ptrdiff_t spec_offset) +{ + stmt_prepare_mode= thd->m_parser_state->m_lip.stmt_prepare_mode; + unparsed_spec.length= spec_end - spec_start; + + if (stmt_prepare_mode || !thd->lex->sphead) + unparsed_spec.str= spec_start; + else + unparsed_spec.str= thd->strmake(spec_start, unparsed_spec.length); + unparsed_spec_offset= spec_offset; + + if (!unparsed_spec.str) + { + my_error(ER_OUTOFMEMORY, MYF(ME_FATAL), + static_cast<int>(unparsed_spec.length)); + return true; + } + return false; +} + + +/** + @brief + Create a clone of the specification for the given with table + + @param old_lex The LEX structure created for the query or CTE specification + where this With_element is defined + @param with_table The reference to the table defined in this element for which + the clone is created. + + @details + The method creates a clone of the specification used in this element. + The clone is created for the given reference to the table defined by + this element. + The clone is created when the string with the specification saved in + unparsed_spec is fed into the parser as an input string. The parsing + this string a unit object representing the specification is built. + A chain of all table references occurred in the specification is also + formed. + The method includes the new unit and its sub-unit into hierarchy of + the units of the main query. I also insert the constructed chain of the + table references into the chain of all table references of the main query. + The method resolves all references to CTE in the clone. + + @note + Clones is created only for not first references to tables defined in + the with clause. They are necessary for merged specifications because + the optimizer handles any such specification as independent on the others. + When a table defined in the with clause is materialized in a temporary table + one could do without specification clones. However in this case they + are created as well, because currently different table references to a + the same temporary table cannot share the same definition structure. + + @retval + pointer to the built clone if succeeds + NULL - otherwise +*/ + +st_select_lex_unit *With_element::clone_parsed_spec(LEX *old_lex, + TABLE_LIST *with_table) +{ + THD *thd= old_lex->thd; + LEX *lex; + st_select_lex_unit *res= NULL; + + if (!(lex= (LEX*) new(thd->mem_root) st_lex_local)) + return res; + thd->lex= lex; + + bool parse_status= false; + st_select_lex *with_select; + st_select_lex *last_clone_select; + + char save_end= unparsed_spec.str[unparsed_spec.length]; + ((char*) &unparsed_spec.str[unparsed_spec.length])[0]= '\0'; + + lex_start(thd); + lex->clone_spec_offset= unparsed_spec_offset; + lex->with_cte_resolution= true; + + /* + The specification of a CTE is to be parsed as a regular query. + At the very end of the parsing query the function + check_cte_dependencies_and_resolve_references() will be called. + It will check the dependencies between CTEs that are defined + within the query and will resolve CTE references in this query. + If a table reference is not resolved as a CTE reference within + this query it still can be resolved as a reference to a CTE defined + in the same clause as the CTE whose specification is to be parsed + or defined in an embedding CTE definition. + + Example: + with + cte1 as ( ... ), + cte2 as ([WITH ...] select ... from cte1 ...) + select ... from cte2 as r, ..., cte2 as s ... + + Here the specification of cte2 has be cloned for table reference + with alias s1. The specification contains a reference to cte1 + that is defined outside this specification. If the reference to + cte1 cannot be resolved within the specification of cte2 it's + not necessarily has to be a reference to a non-CTE table. That's + why the flag lex->only_cte_resolution has to be set to true + before parsing of the specification of cte2 invoked by this + function starts. Otherwise an mdl_lock would be requested for s + and this would not be correct. + */ + + lex->only_cte_resolution= true; + + lex->stmt_lex= old_lex->stmt_lex ? old_lex->stmt_lex : old_lex; + + parse_status= thd->sql_parser(old_lex, lex, + (char*) unparsed_spec.str, + (unsigned int)unparsed_spec.length, + stmt_prepare_mode); + + ((char*) &unparsed_spec.str[unparsed_spec.length])[0]= save_end; + with_select= lex->unit.first_select(); + + if (parse_status) + goto err; + + /* + The global chain of TABLE_LIST objects created for the specification that + just has been parsed is added to such chain that contains the reference + to the CTE whose specification is parsed right after the TABLE_LIST object + created for the reference. + */ + if (lex->query_tables) + { + head->tables_pos.set_start_pos(&with_table->next_global); + head->tables_pos.set_end_pos(lex->query_tables_last); + TABLE_LIST *next_tbl= with_table->next_global; + if (next_tbl) + { + *(lex->query_tables->prev_global= next_tbl->prev_global)= + lex->query_tables; + *(next_tbl->prev_global= lex->query_tables_last)= next_tbl; + } + else + { + *(lex->query_tables->prev_global= old_lex->query_tables_last)= + lex->query_tables; + old_lex->query_tables_last= lex->query_tables_last; + } + } + res= &lex->unit; + res->with_element= this; + + /* + The unit of the specification that just has been parsed is included + as a slave of the select that contained in its from list the table + reference for which the unit has been created. + */ + lex->unit.include_down(with_table->select_lex); + lex->unit.set_slave(with_select); + lex->unit.cloned_from= spec; + + /* + Now all references to the CTE defined outside of the cloned specification + has to be resolved. Additionally if old_lex->only_cte_resolution == false + for the table references that has not been resolved requests for mdl_locks + has to be set. + */ + lex->only_cte_resolution= old_lex->only_cte_resolution; + if (lex->resolve_references_to_cte(lex->query_tables, + lex->query_tables_last)) + { + res= NULL; + goto err; + } + + last_clone_select= lex->all_selects_list; + while (last_clone_select->next_select_in_list()) + last_clone_select= last_clone_select->next_select_in_list(); + old_lex->all_selects_list= + (st_select_lex*) (lex->all_selects_list-> + insert_chain_before( + (st_select_lex_node **) &(old_lex->all_selects_list), + last_clone_select)); + + lex->sphead= NULL; // in order not to delete lex->sphead + lex_end(lex); +err: + thd->lex= old_lex; + return res; +} + + +/** + @brief + Rename columns of the unit derived from the spec of this with element + @param thd The context of the statement containing the with element + @param unit The specification of the with element or its clone + + @details + The method assumes that the parameter unit is either specification itself + of this with element or a clone of this specification. The looks through + the column list in this with element. It reports an error if the cardinality + of this list differs from the cardinality of select lists in 'unit'. + Otherwise it renames the columns of the first select list and sets the flag + unit->column_list_is_processed to true preventing renaming columns for the + second time. + + @retval + true if an error was reported + false otherwise +*/ + +bool +With_element::process_columns_of_derived_unit(THD *thd, + st_select_lex_unit *unit) +{ + if (unit->columns_are_renamed) + return false; + + st_select_lex *select= unit->first_select(); + + if (column_list.elements) // The column list is optional + { + List_iterator_fast<Item> it(select->item_list); + List_iterator_fast<Lex_ident_sys> nm(column_list); + Item *item; + LEX_CSTRING *name; + + if (column_list.elements != select->item_list.elements) + { + my_error(ER_WITH_COL_WRONG_LIST, MYF(0)); + return true; + } + + Query_arena *arena, backup; + arena= thd->activate_stmt_arena_if_needed(&backup); + + /* Rename the columns of the first select in the unit */ + while ((item= it++, name= nm++)) + { + item->set_name(thd, *name); + item->common_flags&= ~IS_AUTO_GENERATED_NAME; + } + + if (arena) + thd->restore_active_arena(arena, &backup); + } + else + make_valid_column_names(thd, select->item_list); + + if (cycle_list) + { + List_iterator_fast<Item> it(select->item_list); + List_iterator_fast<Lex_ident_sys> nm(*cycle_list); + List_iterator_fast<Lex_ident_sys> nm_check(*cycle_list); + DBUG_ASSERT(cycle_list->elements != 0); + while (LEX_CSTRING *name= nm++) + { + Item *item; + /* + Check for uniqueness of each element in the cycle list: + It's sufficient to check that there is no duplicate of 'name' + among the elements that precede it. + */ + LEX_CSTRING *check; + nm_check.rewind(); + while ((check= nm_check++) && check != name) + { + if (check->length == name->length && + strncmp(check->str, name->str, name->length) == 0) + { + my_error(ER_DUP_FIELDNAME, MYF(0), check->str); + return true; + } + } + /* Check that 'name' is the name of a column of the processed CTE */ + while ((item= it++) && + (item->name.length != name->length || + strncmp(item->name.str, name->str, name->length) != 0)); + if (item == NULL) + { + my_error(ER_BAD_FIELD_ERROR, MYF(0), name->str, "CYCLE clause"); + return true; + } + item->common_flags|= IS_IN_WITH_CYCLE; + } + } + unit->columns_are_renamed= true; + + return false; +} + + +/** + @brief + Perform context analysis the definition of an unreferenced table + + @param thd The context of the statement containing this with element + + @details + The method assumes that this with element contains the definition + of a table that is not used anywhere. In this case one has to check + that context conditions are met. + + @retval + true if an error was reported + false otherwise +*/ + +bool With_element::prepare_unreferenced(THD *thd) +{ + bool rc= false; + st_select_lex *first_sl= spec->first_select(); + + /* Prevent name resolution for field references out of with elements */ + for (st_select_lex *sl= first_sl; + sl; + sl= sl->next_select()) + sl->context.outer_context= 0; + + thd->lex->context_analysis_only|= CONTEXT_ANALYSIS_ONLY_DERIVED; + if (!spec->prepared && + (spec->prepare(spec->derived, 0, 0) || + process_columns_of_derived_unit(thd, spec) || + check_duplicate_names(thd, first_sl->item_list, 1))) + rc= true; + + thd->lex->context_analysis_only&= ~CONTEXT_ANALYSIS_ONLY_DERIVED; + return rc; +} + + +bool With_element::is_anchor(st_select_lex *sel) +{ + return !(mutually_recursive & sel->with_dep); +} + + +/** + @brief + Search for the definition of the given table referred in this select node + + @param table reference to the table whose definition is searched for + + @details + The method looks for the definition of the table whose reference is occurred + in the FROM list of this select node. First it searches for it in the + with clause attached to the unit this select node belongs to. If such a + definition is not found then the embedding units are looked through. + + @retval + pointer to the found definition if the search has been successful + NULL - otherwise +*/ + +With_element *st_select_lex::find_table_def_in_with_clauses(TABLE_LIST *table) +{ + With_element *found= NULL; + With_clause *containing_with_clause= NULL; + st_select_lex_unit *master_unit; + st_select_lex *outer_sl; + for (st_select_lex *sl= this; sl; sl= outer_sl) + { + /* + If sl->master_unit() is the spec of a with element then the search for + a definition was already done by With_element::check_dependencies_in_spec + and it was unsuccesful. Yet for units cloned from the spec it has not + been done yet. + */ + With_clause *attached_with_clause= sl->get_with_clause(); + if (attached_with_clause && + attached_with_clause != containing_with_clause && + (found= attached_with_clause->find_table_def(table, NULL))) + break; + master_unit= sl->master_unit(); + outer_sl= master_unit->outer_select(); + With_element *with_elem= sl->get_with_element(); + if (with_elem) + { + containing_with_clause= with_elem->get_owner(); + With_element *barrier= containing_with_clause->with_recursive ? + NULL : with_elem; + if ((found= containing_with_clause->find_table_def(table, barrier))) + break; + if (outer_sl && !outer_sl->get_with_element()) + break; + } + /* Do not look for the table's definition beyond the scope of the view */ + if (master_unit->is_view) + break; + } + return found; +} + + +bool TABLE_LIST::is_recursive_with_table() +{ + return with && with->is_recursive; +} + + +/* + A reference to a with table T is recursive if it occurs somewhere + in the query specifying T or in the query specifying one of the tables + mutually recursive with T. +*/ + +bool TABLE_LIST::is_with_table_recursive_reference() +{ + return (with_internal_reference_map && + (with->get_mutually_recursive() & with_internal_reference_map)); +} + + +/* + Specifications of with tables with recursive table references + in non-mergeable derived tables are not allowed in this + implementation. +*/ + + +/* + We say that the specification of a with table T is restricted + if all below is true. + 1. Any immediate select of the specification contains at most one + recursive table reference taking into account table references + from mergeable derived tables. + 2. Any recursive table reference is not an inner operand of an + outer join operation used in an immediate select of the + specification. + 3. Any immediate select from the specification of T does not + contain aggregate functions. + 4. The specification of T does not contain recursive table references. + + If the specification of T is not restricted we call the corresponding + with element unrestricted. + + The SQL standards allows only with elements with restricted specification. + By default we comply with the standards here. + + Yet we allow unrestricted specification if the status variable + 'standards_compliant_cte' set to 'off'(0). +*/ + + +/** + @brief + Check if this select makes the including specification unrestricted + + @param + only_standards_compliant true if the system variable + 'standards_compliant_cte' is set to 'on' + @details + This method checks whether the conditions 1-4 (see the comment above) + are satisfied for this select. If not then mark this element as + unrestricted and report an error if 'only_standards_compliant' is true. + + @retval + true if an error is reported + false otherwise +*/ + +bool st_select_lex::check_unrestricted_recursive(bool only_standard_compliant) +{ + With_element *with_elem= get_with_element(); + if (!with_elem ||!with_elem->is_recursive) + { + /* + If this select is not from the specifiocation of a with elememt or + if this not a recursive with element then there is nothing to check. + */ + return false; + } + + /* Check conditions 1-2 for restricted specification*/ + table_map unrestricted= 0; + table_map encountered= 0; + if (with_elem->check_unrestricted_recursive(this, + unrestricted, + encountered)) + return true; + with_elem->get_owner()->add_unrestricted(unrestricted); + + + /* Check conditions 3-4 for restricted specification*/ + if ((with_sum_func && !with_elem->is_anchor(this)) || + (with_elem->contains_sq_with_recursive_reference())) + with_elem->get_owner()->add_unrestricted( + with_elem->get_mutually_recursive()); + + /* Report an error on unrestricted specification if this is required */ + if (only_standard_compliant && with_elem->is_unrestricted()) + { + my_error(ER_NOT_STANDARD_COMPLIANT_RECURSIVE, + MYF(0), with_elem->get_name_str()); + return true; + } + + return false; +} + + +/** + @brief + Check if a select from the spec of this with element is partially restricted + + @param + sel select from the specification of this element where to check + whether conditions 1-2 are satisfied + unrestricted IN/OUT bitmap where to mark unrestricted specs + encountered IN/OUT bitmap where to mark encountered recursive references + @details + This method checks whether the conditions 1-2 (see the comment above) + are satisfied for the select sel. + This method is called recursively for derived tables. + + @retval + true if an error is reported + false otherwise +*/ + +bool With_element::check_unrestricted_recursive(st_select_lex *sel, + table_map &unrestricted, + table_map &encountered) +{ + /* Check conditions 1 for restricted specification*/ + List_iterator<TABLE_LIST> ti(sel->leaf_tables); + TABLE_LIST *tbl; + while ((tbl= ti++)) + { + st_select_lex_unit *unit= tbl->get_unit(); + if (unit) + { + if(!tbl->is_with_table()) + { + if (check_unrestricted_recursive(unit->first_select(), + unrestricted, + encountered)) + return true; + } + if (!(tbl->is_recursive_with_table() && unit->with_element->owner == owner)) + continue; + With_element *with_elem= unit->with_element; + if (encountered & with_elem->get_elem_map()) + unrestricted|= with_elem->mutually_recursive; + else if (with_elem ==this) + encountered|= with_elem->get_elem_map(); + } + } + for (With_element *with_elem= owner->with_list.first; + with_elem; + with_elem= with_elem->next) + { + if (!with_elem->is_recursive && (unrestricted & with_elem->get_elem_map())) + continue; + if (encountered & with_elem->get_elem_map()) + { + uint cnt= 0; + table_map encountered_mr= encountered & with_elem->mutually_recursive; + for (table_map map= encountered_mr >> with_elem->number; + map != 0; + map>>= 1) + { + if (map & 1) + { + if (cnt) + { + unrestricted|= with_elem->mutually_recursive; + break; + } + else + cnt++; + } + } + } + } + + + /* Check conditions 2 for restricted specification*/ + ti.rewind(); + while ((tbl= ti++)) + { + if (!tbl->is_with_table_recursive_reference()) + continue; + for (TABLE_LIST *tab= tbl; tab; tab= tab->embedding) + { + if (tab->outer_join & (JOIN_TYPE_LEFT | JOIN_TYPE_RIGHT)) + { + unrestricted|= mutually_recursive; + break; + } + } + } + return false; +} + + +/** + @brief + Check subqueries with recursive table references from FROM list of this select + + @details + For each recursive table reference from the FROM list of this select + this method checks: + - whether this reference is within a materialized derived table and + if so it report an error + - whether this reference is within a subquery and if so it set a flag + in this subquery that disallows some optimization strategies for + this subquery. + + @retval + true if an error is reported + false otherwise +*/ + +bool st_select_lex::check_subqueries_with_recursive_references() +{ + List_iterator<TABLE_LIST> ti(leaf_tables); + TABLE_LIST *tbl; + while ((tbl= ti++)) + { + if (!(tbl->is_with_table_recursive_reference())) + continue; + With_element *rec_elem= tbl->with; + st_select_lex_unit *sl_master; + for (st_select_lex *sl= this; sl; sl= sl_master->outer_select()) + { + sl_master= sl->master_unit(); + if (sl_master->with_element && + sl_master->with_element->get_owner() == rec_elem->get_owner()) + break; + sl->uncacheable|= UNCACHEABLE_DEPENDENT; + sl_master->uncacheable|= UNCACHEABLE_DEPENDENT; + if (sl_master->derived) + sl_master->derived->register_as_derived_with_rec_ref(rec_elem); + if (sl_master->item) + { + Item_subselect *subq= (Item_subselect *) (sl_master->item); + subq->register_as_with_rec_ref(rec_elem); + } + } + } + return false; +} + + +/** + @brief + Print this with clause + + @param thd Thread handle + @param str Where to print to + @param query_type The mode of printing + + @details + The method prints a string representation of this clause in the + string str. The parameter query_type specifies the mode of printing. +*/ + +void With_clause::print(THD *thd, String *str, enum_query_type query_type) +{ + /* + Any with clause contains just definitions of CTE tables. + No data expansion is applied to these definitions. + */ + query_type= (enum_query_type) (query_type | QT_NO_DATA_EXPANSION); + + str->append(STRING_WITH_LEN("with ")); + if (with_recursive) + str->append(STRING_WITH_LEN("recursive ")); + for (With_element *with_elem= with_list.first; + with_elem; + with_elem= with_elem->next) + { + if (with_elem != with_list.first) + str->append(", "); + with_elem->print(thd, str, query_type); + } +} + + +static void list_strlex_print(THD *thd, String *str, List<Lex_ident_sys> *list) +{ + List_iterator_fast<Lex_ident_sys> li(*list); + bool first= TRUE; + while(Lex_ident_sys *col_name= li++) + { + if (first) + first= FALSE; + else + str->append(','); + append_identifier(thd, str, col_name); + } +} + + +/** + @brief + Print this with element + + @param thd Thread handle + @param str Where to print to + @param query_type The mode of printing + + @details + The method prints a string representation of this with element in the + string str. The parameter query_type specifies the mode of printing. +*/ + +void With_element::print(THD *thd, String *str, enum_query_type query_type) +{ + str->append(get_name()); + if (column_list.elements) + { + List_iterator_fast<Lex_ident_sys> li(column_list); + str->append('('); + list_strlex_print(thd, str, &column_list); + str->append(')'); + } + str->append(STRING_WITH_LEN(" as (")); + spec->print(str, query_type); + str->append(')'); + + if (cycle_list) + { + DBUG_ASSERT(cycle_list->elements != 0); + str->append(STRING_WITH_LEN(" CYCLE ")); + list_strlex_print(thd, str, cycle_list); + str->append(STRING_WITH_LEN(" RESTRICT ")); + } +} + + +bool With_element::instantiate_tmp_tables() +{ + List_iterator_fast<TABLE_LIST> li(rec_result->rec_table_refs); + TABLE_LIST *rec_tbl; + while ((rec_tbl= li++)) + { + TABLE *rec_table= rec_tbl->table; + if (!rec_table->is_created() && + instantiate_tmp_table(rec_table, + rec_table->s->key_info, + rec_result->tmp_table_param.start_recinfo, + &rec_result->tmp_table_param.recinfo, + 0)) + return true; + + rec_table->file->extra(HA_EXTRA_WRITE_CACHE); + rec_table->file->extra(HA_EXTRA_IGNORE_DUP_KEY); + } + return false; +} + +void With_element::set_cycle_list(List<Lex_ident_sys> *cycle_list_arg) +{ + cycle_list= cycle_list_arg; + + /* + If a CTE table with columns c1,...,cn is defined with a cycle + clause CYCLE(ci1,...,cik) then no two rows r1 and r2 from the + table shall have r1.ci1=r2.ci1 && ... && r1.cik=r2.cik. + + If a cycle clause is used in the specification of a CTE then + each UNION ALL at the top level of the specification is interpreted + as a UNION DISTINCT over the cycle columns. + */ + for (st_select_lex *sl= spec->first_select(); sl; sl= sl->next_select()) + { + spec->union_distinct= sl; + if (sl != spec->first_select()) + { + sl->distinct= TRUE; + sl->with_all_modifier= FALSE; + } + } +} |