Current File : //usr/include/mysql/server/private/sql_limit.h
/* Copyright (c) 2019, MariaDB Corporation.
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 02110-1335 USA */
#ifndef INCLUDES_MARIADB_SQL_LIMIT_H
#define INCLUDES_MARIADB_SQL_LIMIT_H
/**
LIMIT/OFFSET parameters for execution.
*/
class Select_limit_counters
{
ha_rows select_limit_cnt, offset_limit_cnt;
bool with_ties;
public:
Select_limit_counters():
select_limit_cnt(0), offset_limit_cnt(0), with_ties(false)
{};
Select_limit_counters(const Select_limit_counters &orig):
select_limit_cnt(orig.select_limit_cnt),
offset_limit_cnt(orig.offset_limit_cnt),
with_ties(orig.with_ties)
{};
void set_limit(ha_rows limit, ha_rows offset, bool with_ties_arg)
{
if (limit == 0)
offset= 0;
offset_limit_cnt= offset;
select_limit_cnt= limit;
with_ties= with_ties_arg;
/*
Guard against an overflow condition, where limit + offset exceede
ha_rows value range. This case covers unreasonably large parameter
values that do not have any practical use so assuming in this case
that the query does not have a limit is fine.
*/
if (select_limit_cnt + offset_limit_cnt >= select_limit_cnt)
select_limit_cnt+= offset_limit_cnt;
else
select_limit_cnt= HA_POS_ERROR;
}
void set_single_row()
{
offset_limit_cnt= 0;
select_limit_cnt= 1;
with_ties= false;
}
/* Send the first row, still honoring offset_limit_cnt */
void send_first_row()
{
/* Guard against overflow */
if ((select_limit_cnt= offset_limit_cnt +1 ) == 0)
select_limit_cnt= offset_limit_cnt;
// with_ties= false; Remove // on merge to 10.6
}
bool is_unlimited() const
{ return select_limit_cnt == HA_POS_ERROR; }
/*
Set the limit to allow returning an unlimited number of rows. Useful
for cases when we want to continue execution indefinitely after the limit
is reached (for example for SQL_CALC_ROWS extension).
*/
void set_unlimited()
{ select_limit_cnt= HA_POS_ERROR; }
/* Reset the limit entirely. */
void clear()
{ select_limit_cnt= HA_POS_ERROR; offset_limit_cnt= 0; with_ties= false;}
bool check_offset(ha_rows sent) const
{
return sent < offset_limit_cnt;
}
void remove_offset() { offset_limit_cnt= 0; }
ha_rows get_select_limit() const
{ return select_limit_cnt; }
ha_rows get_offset_limit() const
{ return offset_limit_cnt; }
bool is_with_ties() const
{ return with_ties; }
};
#endif // INCLUDES_MARIADB_SQL_LIMIT_H
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