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Diffstat (limited to '')
| -rw-r--r-- | sql/select_handler.cc | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/sql/select_handler.cc b/sql/select_handler.cc new file mode 100644 index 00000000..795ed8eb --- /dev/null +++ b/sql/select_handler.cc @@ -0,0 +1,172 @@ +/* + Copyright (c) 2018, 2020, MariaDB + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; version 2 of the License. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1301 USA */ + +#include "mariadb.h" +#include "sql_priv.h" +#include "sql_select.h" +#include "select_handler.h" + + +/** + The methods of the select_handler class. + + The objects of this class are used for pushdown of the select queries + into engines. The main method of the class is select_handler::execute() + that initiates execution of a select query by a foreign engine, receives the + rows of the result set, put it in a buffer of a temporary table and send + them from the buffer directly into output. + + The method uses the functions of the select_handle interface to do this. + It also employes plus some helper functions to create the needed temporary + table and to send rows from the temporary table into output. + The constructor of the class gets the select_handler interface as a parameter. +*/ + + +select_handler::select_handler(THD *thd_arg, handlerton *ht_arg) + : thd(thd_arg), ht(ht_arg), table(NULL), + is_analyze(thd_arg->lex->analyze_stmt) +{} + + +select_handler::~select_handler() +{ + if (table) + free_tmp_table(thd, table); +} + + +TABLE *select_handler::create_tmp_table(THD *thd, SELECT_LEX *select) +{ + DBUG_ENTER("select_handler::create_tmp_table"); + List<Item> types; + TMP_TABLE_PARAM tmp_table_param; + if (select->master_unit()->join_union_item_types(thd, types, 1)) + DBUG_RETURN(NULL); + tmp_table_param.init(); + tmp_table_param.field_count= types.elements; + + TABLE *table= ::create_tmp_table(thd, &tmp_table_param, types, + (ORDER *) 0, false, 0, + TMP_TABLE_ALL_COLUMNS, 1, + &empty_clex_str, true, false); + DBUG_RETURN(table); +} + + +bool select_handler::prepare() +{ + DBUG_ENTER("select_handler::prepare"); + /* + Some engines (e.g. XPand) initialize "table" on their own. + So we need to create a temporary table only if "table" is NULL. + */ + if (!table && !(table= create_tmp_table(thd, select))) + DBUG_RETURN(true); + DBUG_RETURN(table->fill_item_list(&result_columns)); +} + + +bool select_handler::send_result_set_metadata() +{ + DBUG_ENTER("select_handler::send_result_set_metadata"); + +#ifdef WITH_WSREP + if (WSREP(thd) && thd->wsrep_retry_query) + { + WSREP_DEBUG("skipping select metadata"); + DBUG_RETURN(false); + } + #endif /* WITH_WSREP */ + if (select->join->result->send_result_set_metadata(result_columns, + Protocol::SEND_NUM_ROWS | + Protocol::SEND_EOF)) + DBUG_RETURN(true); + + DBUG_RETURN(false); +} + + +bool select_handler::send_data() +{ + DBUG_ENTER("Pushdown_select::send_data"); + + if (select->join->result->send_data(result_columns)) + DBUG_RETURN(true); + + DBUG_RETURN(false); +} + + +bool select_handler::send_eof() +{ + DBUG_ENTER("select_handler::send_eof"); + + if (select->join->result->send_eof()) + DBUG_RETURN(true); + DBUG_RETURN(false); +} + + +int select_handler::execute() +{ + int err; + + DBUG_ENTER("select_handler::execute"); + + if ((err= init_scan())) + goto error; + + if (is_analyze) + { + end_scan(); + DBUG_RETURN(0); + } + + if (send_result_set_metadata()) + DBUG_RETURN(-1); + + while (!(err= next_row())) + { + if (thd->check_killed() || send_data()) + { + end_scan(); + DBUG_RETURN(-1); + } + } + + if (err != 0 && err != HA_ERR_END_OF_FILE) + goto error; + + if ((err= end_scan())) + goto error_2; + + if (send_eof()) + DBUG_RETURN(-1); + + DBUG_RETURN(0); + +error: + end_scan(); +error_2: + print_error(err, MYF(0)); + DBUG_RETURN(-1); // Error not sent to client +} + +void select_handler::print_error(int error, myf errflag) +{ + my_error(ER_GET_ERRNO, MYF(0), error, hton_name(ht)->str); +} |