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7259b299a5
A query in form SELECT DISTINCT expr_that_is_inferred_to_be_const LIMIT 0 OFFSET n produces one row when it should produce none. The issue was in JOIN_TAB::remove_duplicates() in the piece of logic that tried to avoid duplicate removal for such cases but didn't account for possible "LIMIT 0". Fixed by making Select_limit_counters::set_limit() change OFFSET to 0 when LIMIT is 0.
74 lines
2.1 KiB
C++
74 lines
2.1 KiB
C++
/* Copyright (c) 2019, MariaDB Corporation.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
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#ifndef INCLUDES_MARIADB_SQL_LIMIT_H
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#define INCLUDES_MARIADB_SQL_LIMIT_H
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/**
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LIMIT/OFFSET parameters for execution.
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*/
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class Select_limit_counters
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{
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ha_rows select_limit_cnt, offset_limit_cnt;
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public:
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Select_limit_counters():
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select_limit_cnt(0), offset_limit_cnt(0)
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{};
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Select_limit_counters(Select_limit_counters &orig):
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select_limit_cnt(orig.select_limit_cnt),
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offset_limit_cnt(orig.offset_limit_cnt)
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{};
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void set_limit(ha_rows limit, ha_rows offset)
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{
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if (limit == 0)
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offset= 0;
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offset_limit_cnt= offset;
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select_limit_cnt= limit;
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if (select_limit_cnt + offset_limit_cnt >=
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select_limit_cnt)
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select_limit_cnt+= offset_limit_cnt;
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else
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select_limit_cnt= HA_POS_ERROR;
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}
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void set_single_row()
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{
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offset_limit_cnt= 0;
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select_limit_cnt= 1;
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}
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bool is_unlimited()
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{ return select_limit_cnt == HA_POS_ERROR; }
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bool is_unrestricted()
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{ return select_limit_cnt == HA_POS_ERROR && offset_limit_cnt == 0; }
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void set_unlimited()
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{ select_limit_cnt= HA_POS_ERROR; offset_limit_cnt= 0; }
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bool check_offset(ha_rows sent)
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{
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return sent < offset_limit_cnt;
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}
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void remove_offset() { offset_limit_cnt= 0; }
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ha_rows get_select_limit()
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{ return select_limit_cnt; }
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ha_rows get_offset_limit()
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{ return offset_limit_cnt; }
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};
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#endif // INCLUDES_MARIADB_SQL_LIMIT_H
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