| 1 | /* Copyright (c) 2017, MariaDB |
| 2 | |
| 3 | This program is free software; you can redistribute it and/or modify |
| 4 | it under the terms of the GNU General Public License as published by |
| 5 | the Free Software Foundation; version 2 of the License. |
| 6 | |
| 7 | This program is distributed in the hope that it will be useful, |
| 8 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 9 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 10 | GNU General Public License for more details. |
| 11 | |
| 12 | You should have received a copy of the GNU General Public License |
| 13 | along with this program; if not, write to the Free Software |
| 14 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ |
| 15 | |
| 16 | #include "mariadb.h" |
| 17 | #include "sql_list.h" |
| 18 | #include "sql_tvc.h" |
| 19 | #include "sql_class.h" |
| 20 | #include "opt_range.h" |
| 21 | #include "sql_select.h" |
| 22 | #include "sql_explain.h" |
| 23 | #include "sql_parse.h" |
| 24 | #include "sql_cte.h" |
| 25 | |
| 26 | /** |
| 27 | @brief |
| 28 | Fix fields for TVC values |
| 29 | |
| 30 | @param |
| 31 | @param thd The context of the statement |
| 32 | @param li The iterator on the list of lists |
| 33 | |
| 34 | @details |
| 35 | Call fix_fields procedure for TVC values. |
| 36 | |
| 37 | @retval |
| 38 | true if an error was reported |
| 39 | false otherwise |
| 40 | */ |
| 41 | |
| 42 | bool fix_fields_for_tvc(THD *thd, List_iterator_fast<List_item> &li) |
| 43 | { |
| 44 | DBUG_ENTER("fix_fields_for_tvc" ); |
| 45 | List_item *lst; |
| 46 | li.rewind(); |
| 47 | |
| 48 | while ((lst= li++)) |
| 49 | { |
| 50 | List_iterator_fast<Item> it(*lst); |
| 51 | Item *item; |
| 52 | |
| 53 | while ((item= it++)) |
| 54 | { |
| 55 | if (item->fix_fields(thd, 0)) |
| 56 | DBUG_RETURN(true); |
| 57 | } |
| 58 | } |
| 59 | DBUG_RETURN(false); |
| 60 | } |
| 61 | |
| 62 | |
| 63 | /** |
| 64 | @brief |
| 65 | Defines types of matrix columns elements where matrix rows are defined by |
| 66 | some lists of values. |
| 67 | |
| 68 | @param |
| 69 | @param thd The context of the statement |
| 70 | @param li The iterator on the list of lists |
| 71 | @param holders The structure where types of matrix columns are stored |
| 72 | @param first_list_el_count Count of the list values. It should be the same |
| 73 | for each list of lists elements. It contains |
| 74 | number of elements of the first list from list of |
| 75 | lists. |
| 76 | |
| 77 | @details |
| 78 | For each list list_a from list of lists the procedure gets its elements |
| 79 | types and aggregates them with the previous ones stored in holders. If |
| 80 | list_a is the first one in the list of lists its elements types are put in |
| 81 | holders. The errors can be reported when count of list_a elements is |
| 82 | different from the first_list_el_count. Also error can be reported whe |
| 83 | n aggregation can't be made. |
| 84 | |
| 85 | @retval |
| 86 | true if an error was reported |
| 87 | false otherwise |
| 88 | */ |
| 89 | |
| 90 | bool join_type_handlers_for_tvc(THD *thd, List_iterator_fast<List_item> &li, |
| 91 | Type_holder *holders, uint first_list_el_count) |
| 92 | { |
| 93 | DBUG_ENTER("join_type_handlers_for_tvc" ); |
| 94 | List_item *lst; |
| 95 | li.rewind(); |
| 96 | bool first= true; |
| 97 | |
| 98 | while ((lst= li++)) |
| 99 | { |
| 100 | List_iterator_fast<Item> it(*lst); |
| 101 | Item *item; |
| 102 | |
| 103 | if (first_list_el_count != lst->elements) |
| 104 | { |
| 105 | my_message(ER_WRONG_NUMBER_OF_VALUES_IN_TVC, |
| 106 | ER_THD(thd, ER_WRONG_NUMBER_OF_VALUES_IN_TVC), |
| 107 | MYF(0)); |
| 108 | DBUG_RETURN(true); |
| 109 | } |
| 110 | for (uint pos= 0; (item=it++); pos++) |
| 111 | { |
| 112 | const Type_handler *item_type_handler= item->real_type_handler(); |
| 113 | if (first) |
| 114 | holders[pos].set_handler(item_type_handler); |
| 115 | else if (holders[pos].aggregate_for_result(item_type_handler)) |
| 116 | { |
| 117 | my_error(ER_ILLEGAL_PARAMETER_DATA_TYPES2_FOR_OPERATION, MYF(0), |
| 118 | holders[pos].type_handler()->name().ptr(), |
| 119 | item_type_handler->name().ptr(), |
| 120 | "TABLE VALUE CONSTRUCTOR" ); |
| 121 | DBUG_RETURN(true); |
| 122 | } |
| 123 | } |
| 124 | first= false; |
| 125 | } |
| 126 | DBUG_RETURN(false); |
| 127 | } |
| 128 | |
| 129 | |
| 130 | /** |
| 131 | @brief |
| 132 | Define attributes of matrix columns elements where matrix rows are defined |
| 133 | by some lists of values. |
| 134 | |
| 135 | @param |
| 136 | @param thd The context of the statement |
| 137 | @param li The iterator on the list of lists |
| 138 | @param holders The structure where names of matrix columns are stored |
| 139 | @param count_of_lists Count of list of lists elements |
| 140 | @param first_list_el_count Count of the list values. It should be the same |
| 141 | for each list of lists elements. It contains |
| 142 | number of elements of the first list from list |
| 143 | of lists. |
| 144 | |
| 145 | @details |
| 146 | For each list list_a from list of lists the procedure gets its elements |
| 147 | attributes and aggregates them with the previous ones stored in holders. |
| 148 | The errors can be reported when aggregation can't be made. |
| 149 | |
| 150 | @retval |
| 151 | true if an error was reported |
| 152 | false otherwise |
| 153 | */ |
| 154 | |
| 155 | bool get_type_attributes_for_tvc(THD *thd, |
| 156 | List_iterator_fast<List_item> &li, |
| 157 | Type_holder *holders, uint count_of_lists, |
| 158 | uint first_list_el_count) |
| 159 | { |
| 160 | DBUG_ENTER("get_type_attributes_for_tvc" ); |
| 161 | List_item *lst; |
| 162 | li.rewind(); |
| 163 | |
| 164 | for (uint pos= 0; pos < first_list_el_count; pos++) |
| 165 | { |
| 166 | if (holders[pos].alloc_arguments(thd, count_of_lists)) |
| 167 | DBUG_RETURN(true); |
| 168 | } |
| 169 | |
| 170 | while ((lst= li++)) |
| 171 | { |
| 172 | List_iterator_fast<Item> it(*lst); |
| 173 | Item *item; |
| 174 | for (uint holder_pos= 0 ; (item= it++); holder_pos++) |
| 175 | { |
| 176 | DBUG_ASSERT(item->fixed); |
| 177 | holders[holder_pos].add_argument(item); |
| 178 | } |
| 179 | } |
| 180 | |
| 181 | for (uint pos= 0; pos < first_list_el_count; pos++) |
| 182 | { |
| 183 | if (holders[pos].aggregate_attributes(thd)) |
| 184 | DBUG_RETURN(true); |
| 185 | } |
| 186 | DBUG_RETURN(false); |
| 187 | } |
| 188 | |
| 189 | |
| 190 | /** |
| 191 | @brief |
| 192 | Prepare of TVC |
| 193 | |
| 194 | @param |
| 195 | @param thd The context of the statement |
| 196 | @param sl The select where this TVC is defined |
| 197 | @param tmp_result Structure that contains the information |
| 198 | about where to send the result of the query |
| 199 | @param unit_arg The union where sl is defined |
| 200 | |
| 201 | @details |
| 202 | Gets types and attributes of values of this TVC that will be used |
| 203 | for temporary table creation for this TVC. It creates Item_type_holders |
| 204 | for each element of the first list from list of lists (VALUES from tvc), |
| 205 | using its elements name, defined type and attribute. |
| 206 | |
| 207 | @retval |
| 208 | true if an error was reported |
| 209 | false otherwise |
| 210 | */ |
| 211 | |
| 212 | bool table_value_constr::prepare(THD *thd, SELECT_LEX *sl, |
| 213 | select_result *tmp_result, |
| 214 | st_select_lex_unit *unit_arg) |
| 215 | { |
| 216 | DBUG_ENTER("table_value_constr::prepare" ); |
| 217 | select_lex->in_tvc= true; |
| 218 | List_iterator_fast<List_item> li(lists_of_values); |
| 219 | |
| 220 | List_item *first_elem= li++; |
| 221 | uint cnt= first_elem->elements; |
| 222 | Type_holder *holders; |
| 223 | |
| 224 | if (cnt == 0) |
| 225 | { |
| 226 | my_error(ER_EMPTY_ROW_IN_TVC, MYF(0)); |
| 227 | DBUG_RETURN(true); |
| 228 | } |
| 229 | |
| 230 | if (fix_fields_for_tvc(thd, li)) |
| 231 | DBUG_RETURN(true); |
| 232 | |
| 233 | if (!(holders= new (thd->mem_root) |
| 234 | Type_holder[cnt]) || |
| 235 | join_type_handlers_for_tvc(thd, li, holders, |
| 236 | cnt) || |
| 237 | get_type_attributes_for_tvc(thd, li, holders, |
| 238 | lists_of_values.elements, cnt)) |
| 239 | DBUG_RETURN(true); |
| 240 | |
| 241 | List_iterator_fast<Item> it(*first_elem); |
| 242 | Item *item; |
| 243 | |
| 244 | sl->item_list.empty(); |
| 245 | for (uint pos= 0; (item= it++); pos++) |
| 246 | { |
| 247 | /* Error's in 'new' will be detected after loop */ |
| 248 | Item_type_holder *new_holder= new (thd->mem_root) |
| 249 | Item_type_holder(thd, |
| 250 | item, |
| 251 | holders[pos].type_handler(), |
| 252 | &holders[pos]/*Type_all_attributes*/, |
| 253 | holders[pos].get_maybe_null()); |
| 254 | new_holder->fix_fields(thd, 0); |
| 255 | sl->item_list.push_back(new_holder); |
| 256 | } |
| 257 | |
| 258 | if (unlikely(thd->is_fatal_error)) |
| 259 | DBUG_RETURN(true); // out of memory |
| 260 | |
| 261 | result= tmp_result; |
| 262 | |
| 263 | if (result && result->prepare(sl->item_list, unit_arg)) |
| 264 | DBUG_RETURN(true); |
| 265 | |
| 266 | select_lex->in_tvc= false; |
| 267 | DBUG_RETURN(false); |
| 268 | } |
| 269 | |
| 270 | |
| 271 | /** |
| 272 | Save Query Plan Footprint |
| 273 | */ |
| 274 | |
| 275 | int table_value_constr::save_explain_data_intern(THD *thd, |
| 276 | Explain_query *output) |
| 277 | { |
| 278 | const char *message= "No tables used" ; |
| 279 | DBUG_ENTER("table_value_constr::save_explain_data_intern" ); |
| 280 | DBUG_PRINT("info" , ("Select %p, type %s, message %s" , |
| 281 | select_lex, select_lex->type, |
| 282 | message)); |
| 283 | DBUG_ASSERT(have_query_plan == QEP_AVAILABLE); |
| 284 | |
| 285 | /* There should be no attempts to save query plans for merged selects */ |
| 286 | DBUG_ASSERT(!select_lex->master_unit()->derived || |
| 287 | select_lex->master_unit()->derived->is_materialized_derived() || |
| 288 | select_lex->master_unit()->derived->is_with_table()); |
| 289 | |
| 290 | explain= new (output->mem_root) Explain_select(output->mem_root, |
| 291 | thd->lex->analyze_stmt); |
| 292 | if (!explain) |
| 293 | DBUG_RETURN(1); |
| 294 | |
| 295 | select_lex->set_explain_type(true); |
| 296 | |
| 297 | explain->select_id= select_lex->select_number; |
| 298 | explain->select_type= select_lex->type; |
| 299 | explain->linkage= select_lex->linkage; |
| 300 | explain->using_temporary= false; |
| 301 | explain->using_filesort= false; |
| 302 | /* Setting explain->message means that all other members are invalid */ |
| 303 | explain->message= message; |
| 304 | |
| 305 | if (select_lex->master_unit()->derived) |
| 306 | explain->connection_type= Explain_node::EXPLAIN_NODE_DERIVED; |
| 307 | |
| 308 | output->add_node(explain); |
| 309 | |
| 310 | if (select_lex->is_top_level_node()) |
| 311 | output->query_plan_ready(); |
| 312 | |
| 313 | DBUG_RETURN(0); |
| 314 | } |
| 315 | |
| 316 | |
| 317 | /** |
| 318 | Optimization of TVC |
| 319 | */ |
| 320 | |
| 321 | bool table_value_constr::optimize(THD *thd) |
| 322 | { |
| 323 | create_explain_query_if_not_exists(thd->lex, thd->mem_root); |
| 324 | have_query_plan= QEP_AVAILABLE; |
| 325 | |
| 326 | if (select_lex->select_number != UINT_MAX && |
| 327 | select_lex->select_number != INT_MAX /* this is not a UNION's "fake select */ && |
| 328 | have_query_plan != QEP_NOT_PRESENT_YET && |
| 329 | thd->lex->explain && // for "SET" command in SPs. |
| 330 | (!thd->lex->explain->get_select(select_lex->select_number))) |
| 331 | { |
| 332 | return save_explain_data_intern(thd, thd->lex->explain); |
| 333 | } |
| 334 | return 0; |
| 335 | } |
| 336 | |
| 337 | |
| 338 | /** |
| 339 | Execute of TVC |
| 340 | */ |
| 341 | |
| 342 | bool table_value_constr::exec(SELECT_LEX *sl) |
| 343 | { |
| 344 | DBUG_ENTER("table_value_constr::exec" ); |
| 345 | List_iterator_fast<List_item> li(lists_of_values); |
| 346 | List_item *elem; |
| 347 | |
| 348 | if (select_options & SELECT_DESCRIBE) |
| 349 | DBUG_RETURN(false); |
| 350 | |
| 351 | if (result->send_result_set_metadata(sl->item_list, |
| 352 | Protocol::SEND_NUM_ROWS | |
| 353 | Protocol::SEND_EOF)) |
| 354 | { |
| 355 | DBUG_RETURN(true); |
| 356 | } |
| 357 | |
| 358 | while ((elem= li++)) |
| 359 | { |
| 360 | result->send_data(*elem); |
| 361 | } |
| 362 | |
| 363 | if (result->send_eof()) |
| 364 | DBUG_RETURN(true); |
| 365 | |
| 366 | DBUG_RETURN(false); |
| 367 | } |
| 368 | |
| 369 | |
| 370 | /** |
| 371 | @brief |
| 372 | Print list |
| 373 | |
| 374 | @param str The reference on the string representation of the list |
| 375 | @param list The list that needed to be print |
| 376 | @param query_type The mode of printing |
| 377 | |
| 378 | @details |
| 379 | The method saves a string representation of list in the |
| 380 | string str. |
| 381 | */ |
| 382 | |
| 383 | void print_list_item(String *str, List_item *list, |
| 384 | enum_query_type query_type) |
| 385 | { |
| 386 | bool is_first_elem= true; |
| 387 | List_iterator_fast<Item> it(*list); |
| 388 | Item *item; |
| 389 | |
| 390 | str->append('('); |
| 391 | |
| 392 | while ((item= it++)) |
| 393 | { |
| 394 | if (is_first_elem) |
| 395 | is_first_elem= false; |
| 396 | else |
| 397 | str->append(','); |
| 398 | |
| 399 | item->print(str, query_type); |
| 400 | } |
| 401 | |
| 402 | str->append(')'); |
| 403 | } |
| 404 | |
| 405 | |
| 406 | /** |
| 407 | @brief |
| 408 | Print this TVC |
| 409 | |
| 410 | @param thd The context of the statement |
| 411 | @param str The reference on the string representation of this TVC |
| 412 | @param query_type The mode of printing |
| 413 | |
| 414 | @details |
| 415 | The method saves a string representation of this TVC in the |
| 416 | string str. |
| 417 | */ |
| 418 | |
| 419 | void table_value_constr::print(THD *thd, String *str, |
| 420 | enum_query_type query_type) |
| 421 | { |
| 422 | DBUG_ASSERT(thd); |
| 423 | |
| 424 | str->append(STRING_WITH_LEN("values " )); |
| 425 | |
| 426 | bool is_first_elem= true; |
| 427 | List_iterator_fast<List_item> li(lists_of_values); |
| 428 | List_item *list; |
| 429 | |
| 430 | while ((list= li++)) |
| 431 | { |
| 432 | if (is_first_elem) |
| 433 | is_first_elem= false; |
| 434 | else |
| 435 | str->append(','); |
| 436 | |
| 437 | print_list_item(str, list, query_type); |
| 438 | } |
| 439 | } |
| 440 | |
| 441 | |
| 442 | /** |
| 443 | @brief |
| 444 | Create list of lists for TVC from the list of this IN predicate |
| 445 | |
| 446 | @param thd The context of the statement |
| 447 | @param values TVC list of values |
| 448 | |
| 449 | @details |
| 450 | The method uses the list of values of this IN predicate to build |
| 451 | an equivalent list of values that can be used in TVC. |
| 452 | |
| 453 | E.g.: |
| 454 | |
| 455 | <value_list> = 5,2,7 |
| 456 | <transformed_value_list> = (5),(2),(7) |
| 457 | |
| 458 | <value_list> = (5,2),(7,1) |
| 459 | <transformed_value_list> = (5,2),(7,1) |
| 460 | |
| 461 | @retval |
| 462 | false if the method succeeds |
| 463 | true otherwise |
| 464 | */ |
| 465 | |
| 466 | bool Item_func_in::create_value_list_for_tvc(THD *thd, |
| 467 | List< List<Item> > *values) |
| 468 | { |
| 469 | bool is_list_of_rows= args[1]->type() == Item::ROW_ITEM; |
| 470 | |
| 471 | for (uint i=1; i < arg_count; i++) |
| 472 | { |
| 473 | List<Item> *tvc_value; |
| 474 | if (!(tvc_value= new (thd->mem_root) List<Item>())) |
| 475 | return true; |
| 476 | |
| 477 | if (is_list_of_rows) |
| 478 | { |
| 479 | Item_row *row_list= (Item_row *)(args[i]); |
| 480 | |
| 481 | for (uint j=0; j < row_list->cols(); j++) |
| 482 | { |
| 483 | if (tvc_value->push_back(row_list->element_index(j), |
| 484 | thd->mem_root)) |
| 485 | return true; |
| 486 | } |
| 487 | } |
| 488 | else if (tvc_value->push_back(args[i]->real_item())) |
| 489 | return true; |
| 490 | |
| 491 | if (values->push_back(tvc_value, thd->mem_root)) |
| 492 | return true; |
| 493 | } |
| 494 | return false; |
| 495 | } |
| 496 | |
| 497 | |
| 498 | /** |
| 499 | @brief |
| 500 | Create name for the derived table defined by TVC |
| 501 | |
| 502 | @param thd The context of the statement |
| 503 | @param parent_select The SELECT where derived table is used |
| 504 | @param alias The returned created name |
| 505 | |
| 506 | @details |
| 507 | Create name for the derived table using current TVC number |
| 508 | for this parent_select stored in parent_select |
| 509 | |
| 510 | @retval |
| 511 | true if creation fails |
| 512 | false otherwise |
| 513 | */ |
| 514 | |
| 515 | static bool create_tvc_name(THD *thd, st_select_lex *parent_select, |
| 516 | LEX_CSTRING *alias) |
| 517 | { |
| 518 | char buff[6]; |
| 519 | |
| 520 | alias->length= my_snprintf(buff, sizeof(buff), |
| 521 | "tvc_%u" , parent_select->curr_tvc_name); |
| 522 | alias->str= thd->strmake(buff, alias->length); |
| 523 | if (!alias->str) |
| 524 | return true; |
| 525 | |
| 526 | return false; |
| 527 | } |
| 528 | |
| 529 | |
| 530 | bool Item_subselect::wrap_tvc_in_derived_table(THD *thd, |
| 531 | st_select_lex *tvc_sl) |
| 532 | { |
| 533 | LEX *lex= thd->lex; |
| 534 | /* SELECT_LEX object where the transformation is performed */ |
| 535 | SELECT_LEX *parent_select= lex->current_select; |
| 536 | uint8 save_derived_tables= lex->derived_tables; |
| 537 | |
| 538 | Query_arena backup; |
| 539 | Query_arena *arena= thd->activate_stmt_arena_if_needed(&backup); |
| 540 | |
| 541 | /* |
| 542 | Create SELECT_LEX of the subquery SQ used in the result of transformation |
| 543 | */ |
| 544 | lex->current_select= tvc_sl; |
| 545 | if (mysql_new_select(lex, 0, NULL)) |
| 546 | goto err; |
| 547 | mysql_init_select(lex); |
| 548 | /* Create item list as '*' for the subquery SQ */ |
| 549 | Item *item; |
| 550 | SELECT_LEX *sq_select; // select for IN subquery; |
| 551 | sq_select= lex->current_select; |
| 552 | sq_select->linkage= tvc_sl->linkage; |
| 553 | sq_select->parsing_place= SELECT_LIST; |
| 554 | item= new (thd->mem_root) Item_field(thd, &sq_select->context, |
| 555 | NULL, NULL, &star_clex_str); |
| 556 | if (item == NULL || add_item_to_list(thd, item)) |
| 557 | goto err; |
| 558 | (sq_select->with_wild)++; |
| 559 | |
| 560 | /* Exclude SELECT with TVC */ |
| 561 | tvc_sl->exclude(); |
| 562 | /* |
| 563 | Create derived table DT that will wrap TVC in the result of transformation |
| 564 | */ |
| 565 | SELECT_LEX *tvc_select; // select for tvc |
| 566 | SELECT_LEX_UNIT *derived_unit; // unit for tvc_select |
| 567 | if (mysql_new_select(lex, 1, tvc_sl)) |
| 568 | goto err; |
| 569 | tvc_select= lex->current_select; |
| 570 | derived_unit= tvc_select->master_unit(); |
| 571 | tvc_select->linkage= DERIVED_TABLE_TYPE; |
| 572 | |
| 573 | lex->current_select= sq_select; |
| 574 | |
| 575 | /* |
| 576 | Create the name of the wrapping derived table and |
| 577 | add it to the FROM list of the subquery SQ |
| 578 | */ |
| 579 | Table_ident *ti; |
| 580 | LEX_CSTRING alias; |
| 581 | TABLE_LIST *derived_tab; |
| 582 | if (!(ti= new (thd->mem_root) Table_ident(derived_unit)) || |
| 583 | create_tvc_name(thd, parent_select, &alias)) |
| 584 | goto err; |
| 585 | if (!(derived_tab= |
| 586 | sq_select->add_table_to_list(thd, |
| 587 | ti, &alias, 0, |
| 588 | TL_READ, MDL_SHARED_READ))) |
| 589 | goto err; |
| 590 | sq_select->add_joined_table(derived_tab); |
| 591 | sq_select->add_where_field(derived_unit->first_select()); |
| 592 | sq_select->context.table_list= sq_select->table_list.first; |
| 593 | sq_select->context.first_name_resolution_table= sq_select->table_list.first; |
| 594 | sq_select->table_list.first->derived_type= DTYPE_TABLE | DTYPE_MATERIALIZE; |
| 595 | lex->derived_tables|= DERIVED_SUBQUERY; |
| 596 | |
| 597 | sq_select->where= 0; |
| 598 | sq_select->set_braces(false); |
| 599 | derived_unit->set_with_clause(0); |
| 600 | |
| 601 | if (engine->engine_type() == subselect_engine::SINGLE_SELECT_ENGINE) |
| 602 | ((subselect_single_select_engine *) engine)->change_select(sq_select); |
| 603 | |
| 604 | if (arena) |
| 605 | thd->restore_active_arena(arena, &backup); |
| 606 | lex->current_select= sq_select; |
| 607 | return false; |
| 608 | |
| 609 | err: |
| 610 | if (arena) |
| 611 | thd->restore_active_arena(arena, &backup); |
| 612 | lex->derived_tables= save_derived_tables; |
| 613 | lex->current_select= parent_select; |
| 614 | return true; |
| 615 | } |
| 616 | |
| 617 | |
| 618 | /** |
| 619 | @brief |
| 620 | Transform IN predicate into IN subquery |
| 621 | |
| 622 | @param thd The context of the statement |
| 623 | @param arg Not used |
| 624 | |
| 625 | @details |
| 626 | The method transforms this IN predicate into in equivalent IN subquery: |
| 627 | |
| 628 | <left_expr> IN (<value_list>) |
| 629 | => |
| 630 | <left_expr> IN (SELECT * FROM (VALUES <transformed_value_list>) AS tvc_#) |
| 631 | |
| 632 | E.g.: |
| 633 | |
| 634 | <value_list> = 5,2,7 |
| 635 | <transformed_value_list> = (5),(2),(7) |
| 636 | |
| 637 | <value_list> = (5,2),(7,1) |
| 638 | <transformed_value_list> = (5,2),(7,1) |
| 639 | |
| 640 | If the transformation succeeds the method returns the result IN subquery, |
| 641 | otherwise this IN predicate is returned. |
| 642 | |
| 643 | @retval |
| 644 | pointer to the result of transformation if succeeded |
| 645 | pointer to this IN predicate otherwise |
| 646 | */ |
| 647 | |
| 648 | Item *Item_func_in::in_predicate_to_in_subs_transformer(THD *thd, |
| 649 | uchar *arg) |
| 650 | { |
| 651 | if (!transform_into_subq) |
| 652 | return this; |
| 653 | |
| 654 | transform_into_subq= false; |
| 655 | |
| 656 | List<List_item> values; |
| 657 | |
| 658 | LEX *lex= thd->lex; |
| 659 | /* SELECT_LEX object where the transformation is performed */ |
| 660 | SELECT_LEX *parent_select= lex->current_select; |
| 661 | uint8 save_derived_tables= lex->derived_tables; |
| 662 | |
| 663 | for (uint i=1; i < arg_count; i++) |
| 664 | { |
| 665 | if (!args[i]->const_item()) |
| 666 | return this; |
| 667 | } |
| 668 | |
| 669 | Query_arena backup; |
| 670 | Query_arena *arena= thd->activate_stmt_arena_if_needed(&backup); |
| 671 | |
| 672 | /* |
| 673 | Create SELECT_LEX of the subquery SQ used in the result of transformation |
| 674 | */ |
| 675 | if (mysql_new_select(lex, 1, NULL)) |
| 676 | goto err; |
| 677 | mysql_init_select(lex); |
| 678 | /* Create item list as '*' for the subquery SQ */ |
| 679 | Item *item; |
| 680 | SELECT_LEX *sq_select; // select for IN subquery; |
| 681 | sq_select= lex->current_select; |
| 682 | sq_select->parsing_place= SELECT_LIST; |
| 683 | item= new (thd->mem_root) Item_field(thd, &sq_select->context, |
| 684 | NULL, NULL, &star_clex_str); |
| 685 | if (item == NULL || add_item_to_list(thd, item)) |
| 686 | goto err; |
| 687 | (sq_select->with_wild)++; |
| 688 | /* |
| 689 | Create derived table DT that will wrap TVC in the result of transformation |
| 690 | */ |
| 691 | SELECT_LEX *tvc_select; // select for tvc |
| 692 | SELECT_LEX_UNIT *derived_unit; // unit for tvc_select |
| 693 | if (mysql_new_select(lex, 1, NULL)) |
| 694 | goto err; |
| 695 | mysql_init_select(lex); |
| 696 | tvc_select= lex->current_select; |
| 697 | derived_unit= tvc_select->master_unit(); |
| 698 | tvc_select->linkage= DERIVED_TABLE_TYPE; |
| 699 | |
| 700 | /* Create TVC used in the transformation */ |
| 701 | if (create_value_list_for_tvc(thd, &values)) |
| 702 | goto err; |
| 703 | if (!(tvc_select->tvc= |
| 704 | new (thd->mem_root) |
| 705 | table_value_constr(values, |
| 706 | tvc_select, |
| 707 | tvc_select->options))) |
| 708 | goto err; |
| 709 | |
| 710 | lex->current_select= sq_select; |
| 711 | |
| 712 | /* |
| 713 | Create the name of the wrapping derived table and |
| 714 | add it to the FROM list of the subquery SQ |
| 715 | */ |
| 716 | Table_ident *ti; |
| 717 | LEX_CSTRING alias; |
| 718 | TABLE_LIST *derived_tab; |
| 719 | if (!(ti= new (thd->mem_root) Table_ident(derived_unit)) || |
| 720 | create_tvc_name(thd, parent_select, &alias)) |
| 721 | goto err; |
| 722 | if (!(derived_tab= |
| 723 | sq_select->add_table_to_list(thd, |
| 724 | ti, &alias, 0, |
| 725 | TL_READ, MDL_SHARED_READ))) |
| 726 | goto err; |
| 727 | sq_select->add_joined_table(derived_tab); |
| 728 | sq_select->add_where_field(derived_unit->first_select()); |
| 729 | sq_select->context.table_list= sq_select->table_list.first; |
| 730 | sq_select->context.first_name_resolution_table= sq_select->table_list.first; |
| 731 | sq_select->table_list.first->derived_type= DTYPE_TABLE | DTYPE_MATERIALIZE; |
| 732 | lex->derived_tables|= DERIVED_SUBQUERY; |
| 733 | |
| 734 | sq_select->where= 0; |
| 735 | sq_select->set_braces(false); |
| 736 | derived_unit->set_with_clause(0); |
| 737 | |
| 738 | /* Create IN subquery predicate */ |
| 739 | sq_select->parsing_place= parent_select->parsing_place; |
| 740 | Item_in_subselect *in_subs; |
| 741 | Item *sq; |
| 742 | if (!(in_subs= |
| 743 | new (thd->mem_root) Item_in_subselect(thd, args[0], sq_select))) |
| 744 | goto err; |
| 745 | sq= in_subs; |
| 746 | if (negated) |
| 747 | sq= negate_expression(thd, in_subs); |
| 748 | else |
| 749 | in_subs->emb_on_expr_nest= emb_on_expr_nest; |
| 750 | |
| 751 | if (arena) |
| 752 | thd->restore_active_arena(arena, &backup); |
| 753 | thd->lex->current_select= parent_select; |
| 754 | |
| 755 | if (sq->fix_fields(thd, (Item **)&sq)) |
| 756 | goto err; |
| 757 | |
| 758 | parent_select->curr_tvc_name++; |
| 759 | return sq; |
| 760 | |
| 761 | err: |
| 762 | if (arena) |
| 763 | thd->restore_active_arena(arena, &backup); |
| 764 | lex->derived_tables= save_derived_tables; |
| 765 | thd->lex->current_select= parent_select; |
| 766 | return NULL; |
| 767 | } |
| 768 | |
| 769 | |
| 770 | /** |
| 771 | @brief |
| 772 | Check if this IN-predicate can be transformed in IN-subquery |
| 773 | with TVC |
| 774 | |
| 775 | @param thd The context of the statement |
| 776 | |
| 777 | @details |
| 778 | Compare the number of elements in the list of |
| 779 | values in this IN-predicate with the |
| 780 | in_subquery_conversion_threshold special variable |
| 781 | |
| 782 | @retval |
| 783 | true if transformation can be made |
| 784 | false otherwise |
| 785 | */ |
| 786 | |
| 787 | bool Item_func_in::to_be_transformed_into_in_subq(THD *thd) |
| 788 | { |
| 789 | uint values_count= arg_count-1; |
| 790 | |
| 791 | if (args[1]->type() == Item::ROW_ITEM) |
| 792 | values_count*= ((Item_row *)(args[1]))->cols(); |
| 793 | |
| 794 | if (values_count < thd->variables.in_subquery_conversion_threshold) |
| 795 | return false; |
| 796 | |
| 797 | return true; |
| 798 | } |
| 799 | |
| 800 | |
| 801 | /** |
| 802 | @brief |
| 803 | Transform IN predicates into IN subqueries in WHERE and ON expressions |
| 804 | |
| 805 | @param thd The context of the statement |
| 806 | |
| 807 | @details |
| 808 | For each IN predicate from AND parts of the WHERE condition and/or |
| 809 | ON expressions of the SELECT for this join the method performs |
| 810 | the intransformation into an equivalent IN sunquery if it's needed. |
| 811 | |
| 812 | @retval |
| 813 | false always |
| 814 | */ |
| 815 | |
| 816 | bool JOIN::transform_in_predicates_into_in_subq(THD *thd) |
| 817 | { |
| 818 | DBUG_ENTER("JOIN::transform_in_predicates_into_in_subq" ); |
| 819 | if (!select_lex->in_funcs.elements) |
| 820 | DBUG_RETURN(false); |
| 821 | |
| 822 | SELECT_LEX *save_current_select= thd->lex->current_select; |
| 823 | enum_parsing_place save_parsing_place= select_lex->parsing_place; |
| 824 | thd->lex->current_select= select_lex; |
| 825 | if (conds) |
| 826 | { |
| 827 | select_lex->parsing_place= IN_WHERE; |
| 828 | conds= |
| 829 | conds->transform(thd, |
| 830 | &Item::in_predicate_to_in_subs_transformer, |
| 831 | (uchar*) 0); |
| 832 | if (!conds) |
| 833 | DBUG_RETURN(true); |
| 834 | select_lex->prep_where= conds ? conds->copy_andor_structure(thd) : 0; |
| 835 | select_lex->where= conds; |
| 836 | } |
| 837 | |
| 838 | if (join_list) |
| 839 | { |
| 840 | TABLE_LIST *table; |
| 841 | List_iterator<TABLE_LIST> li(*join_list); |
| 842 | select_lex->parsing_place= IN_ON; |
| 843 | |
| 844 | while ((table= li++)) |
| 845 | { |
| 846 | if (table->on_expr) |
| 847 | { |
| 848 | table->on_expr= |
| 849 | table->on_expr->transform(thd, |
| 850 | &Item::in_predicate_to_in_subs_transformer, |
| 851 | (uchar*) 0); |
| 852 | if (!table->on_expr) |
| 853 | DBUG_RETURN(true); |
| 854 | table->prep_on_expr= table->on_expr ? |
| 855 | table->on_expr->copy_andor_structure(thd) : 0; |
| 856 | } |
| 857 | } |
| 858 | } |
| 859 | |
| 860 | select_lex->in_funcs.empty(); |
| 861 | select_lex->parsing_place= save_parsing_place; |
| 862 | thd->lex->current_select= save_current_select; |
| 863 | DBUG_RETURN(false); |
| 864 | } |
| 865 | |
| 866 | |