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Diffstat (limited to 'sql/select_handler.cc')
| -rw-r--r-- | sql/select_handler.cc | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/sql/select_handler.cc b/sql/select_handler.cc new file mode 100644 index 00000000000..f020d2f6b80 --- /dev/null +++ b/sql/select_handler.cc @@ -0,0 +1,188 @@ +/* + Copyright (c) 2018, 2019 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 Pushdown_select class. + + The objects of this class are used for pushdown of the select queries + into engines. The main method of the class is Pushdown_select::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. +*/ + + +Pushdown_select::Pushdown_select(SELECT_LEX *sel, select_handler *h) + : select(sel), handler(h) +{ + is_analyze= handler->thd->lex->analyze_stmt; +} + + +Pushdown_select::~Pushdown_select() +{ + delete handler; + select->select_h= NULL; +} + + +bool Pushdown_select::init() +{ + List<Item> types; + TMP_TABLE_PARAM tmp_table_param; + THD *thd= handler->thd; + DBUG_ENTER("Pushdown_select::init"); + if (select->master_unit()->join_union_item_types(thd, types, 1)) + DBUG_RETURN(true); + tmp_table_param.init(); + tmp_table_param.field_count= types.elements; + + handler->table= create_tmp_table(thd, &tmp_table_param, types, + (ORDER *) 0, false, 0, + TMP_TABLE_ALL_COLUMNS, 1, + &empty_clex_str, true, false); + if (!handler->table) + DBUG_RETURN(true); + if (handler->table->fill_item_list(&result_columns)) + DBUG_RETURN(true); + DBUG_RETURN(false); +} + + +bool Pushdown_select::send_result_set_metadata() +{ + THD *thd= handler->thd; + Protocol *protocol= thd->protocol; + DBUG_ENTER("Pushdown_select::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 (protocol->send_result_set_metadata(&result_columns, + Protocol::SEND_NUM_ROWS | + Protocol::SEND_EOF)) + DBUG_RETURN(true); + + DBUG_RETURN(false); +} + + +bool Pushdown_select::send_data() +{ + THD *thd= handler->thd; + Protocol *protocol= thd->protocol; + DBUG_ENTER("Pushdown_select::send_data"); + + if (thd->killed == ABORT_QUERY) + DBUG_RETURN(false); + + protocol->prepare_for_resend(); + if (protocol->send_result_set_row(&result_columns)) + { + protocol->remove_last_row(); + DBUG_RETURN(true); + } + + thd->inc_sent_row_count(1); + + if (thd->vio_ok()) + DBUG_RETURN(protocol->write()); + + DBUG_RETURN(false); +} + + +bool Pushdown_select::send_eof() +{ + THD *thd= handler->thd; + DBUG_ENTER("Pushdown_select::send_eof"); + + /* + Don't send EOF if we're in error condition (which implies we've already + sent or are sending an error) + */ + if (thd->is_error()) + DBUG_RETURN(true); + ::my_eof(thd); + DBUG_RETURN(false); +} + + +int Pushdown_select::execute() +{ + int err; + THD *thd= handler->thd; + + DBUG_ENTER("Pushdown_select::execute"); + + if ((err= handler->init_scan())) + goto error; + + if (is_analyze) + { + handler->end_scan(); + DBUG_RETURN(0); + } + + if (send_result_set_metadata()) + DBUG_RETURN(-1); + + while (!(err= handler->next_row())) + { + if (thd->check_killed() || send_data()) + { + handler->end_scan(); + DBUG_RETURN(-1); + } + } + + if (err != 0 && err != HA_ERR_END_OF_FILE) + goto error; + + if ((err= handler->end_scan())) + goto error_2; + + if (send_eof()) + DBUG_RETURN(-1); + + DBUG_RETURN(0); + +error: + handler->end_scan(); +error_2: + handler->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); +} |