/* 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 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; 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()) { if (owner->with_recursive) { 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); } else { st_unit_ctxt_elem ctxt= {NULL, spec}; check_dependencies_in_select(sl, &ctxt, 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 *found= 0; st_select_lex_unit *top_unit= 0; 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) { /* If the reference to tbl that has to be resolved belongs to the FROM clause of a descendant of top_unit->with_element and this with element belongs to with_clause then this element must be used as the barrier for the search in the the list of CTEs from with_clause unless the clause contains RECURSIVE. */ With_element *barrier= 0; if (top_unit && !with_clause->with_recursive && top_unit->with_element && top_unit->with_element->get_owner() == with_clause) barrier= top_unit->with_element; found= with_clause->find_table_def(tbl, barrier); if (found) break; } top_unit= unit; } return found; } /** @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) { bool is_spec_select= sl->get_with_element() == this; for (TABLE_LIST *tbl= sl->table_list.first; tbl; tbl= tbl->next_local) { if (tbl->with || tbl->derived || tbl->nested_join) continue; tbl->with_internal_reference_map= 0; /* Look first for the definition of tbl in the with clause to which this with element belongs. If such definition is not found there look in the with clauses of the upper levels via the context chain of embedding with elements. If the definition of tbl is found somewhere in with clauses then tbl->with is set to point to this definition. */ if (is_spec_select) { With_clause *with_clause= sl->master_unit()->with_clause; if (with_clause) tbl->with= with_clause->find_table_def(tbl, NULL); if (!tbl->with) tbl->with= owner->find_table_def(tbl, owner->with_recursive ? NULL : this); } 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()) { 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) { st_unit_ctxt_elem unit_ctxt_elem= {ctxt, unit}; if (unit->with_clause) { (void) unit->with_clause->check_dependencies(); check_dependencies_in_with_clause(unit->with_clause, &unit_ctxt_elem, in_subq, dep_map); } in_subq |= unit->item != NULL; 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(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; /* There's no need to add SPs/SFs referenced in the clone to the global list of the SPs/SFs used in the query as they were added when the first reference to the cloned CTE was parsed. Yet the recursive call of the parser must to know that they were already included into the list. */ lex->sroutines= old_lex->sroutines; lex->sroutines_list_own_last= old_lex->sroutines_list_own_last; lex->sroutines_list_own_elements= old_lex->sroutines_list_own_elements; /* 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 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; } /* 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; } } old_lex->sroutines_list_own_last= lex->sroutines_list_own_last; old_lex->sroutines_list_own_elements= lex->sroutines_list_own_elements; res= &lex->unit; res->with_element= this; 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 it(select->item_list); List_iterator_fast 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->base_flags|= item_base_t::IS_EXPLICIT_NAME; } if (arena) thd->restore_active_arena(arena, &backup); } else make_valid_column_names(thd, select->item_list); if (cycle_list) { List_iterator_fast it(select->item_list); List_iterator_fast nm(*cycle_list); List_iterator_fast 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->base_flags|= item_base_t::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 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 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(STRING_WITH_LEN(", ")); with_elem->print(thd, str, query_type); } } static void list_strlex_print(THD *thd, String *str, List *list) { List_iterator_fast 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 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 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 *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; } } }