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/*
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)
{
List<Item> types;
TMP_TABLE_PARAM tmp_table_param;
TABLE *table;
DBUG_ENTER("select_handler::create_tmp_table");
if (select->master_unit()->join_union_item_types(thd, types, 1))
DBUG_RETURN(NULL);
tmp_table_param.init();
tmp_table_param.field_count= tmp_table_param.func_count= types.elements;
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);
}
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