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MDEV-20301 InnoDB's MVCC has O(N^2) behaviors
If there're multiple row versions in InnoDB, reading one row from PK may have O(N) complexity and reading from secondary keys may have O(N^2) complexity. The problem occurs when there are many pending versions of the same row, meaning that the primary key is the same, but a secondary key is different. The slowdown occurs when the secondary index is traversed. This patch creates a helper class for the function row_sel_get_clust_rec_for_mysql() which can remember and re-use cached_clust_rec & cached_old_vers so that rec_get_offsets() does not need to be called over and over for the clustered record. Corrections by Kevin Lewis <kevin.lewis@oracle.com> MDEV-20341 Unstable innodb.innodb_bug14704286 Removed test that tested the ability of interrupting long query which is not long anymore.
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parent
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commit
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5 changed files with 213 additions and 169 deletions
mysql-test/suite/innodb
storage/innobase/row
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@ -1,65 +0,0 @@
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use test;
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drop table if exists t1;
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create table t1 (id int primary key, value int, value2 int,
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value3 int, index(value,value2)) engine=innodb;
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insert into t1 values
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(10,10,10,10),(11,11,11,11),(12,12,12,12),(13,13,13,13),(14,14,14,14),
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(15,15,15,15),(16,16,16,16),(17,17,17,17),(18,18,18,18),(19,19,19,19),
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(20,20,20,20);
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connect conn1, localhost, root,,;
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connect conn2, localhost, root,,;
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connect conn3, localhost, root,,;
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connection conn1;
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use test;
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start transaction with consistent snapshot;
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connection conn2;
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use test;
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CREATE PROCEDURE update_t1()
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BEGIN
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DECLARE i INT DEFAULT 1;
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while (i <= 5000) DO
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update test.t1 set value2=value2+1, value3=value3+1 where id=12;
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SET i = i + 1;
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END WHILE;
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END|
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set autocommit=0;
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CALL update_t1();
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select * from t1;
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id value value2 value3
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10 10 10 10
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11 11 11 11
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12 12 5012 5012
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13 13 13 13
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14 14 14 14
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15 15 15 15
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16 16 16 16
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17 17 17 17
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18 18 18 18
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19 19 19 19
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20 20 20 20
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set autocommit=1;
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select * from t1;
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id value value2 value3
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10 10 10 10
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11 11 11 11
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12 12 5012 5012
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13 13 13 13
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14 14 14 14
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15 15 15 15
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16 16 16 16
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17 17 17 17
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18 18 18 18
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19 19 19 19
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20 20 20 20
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connection conn1;
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select * from t1 force index(value) where value=12;
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connection conn3;
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kill query @id;
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connection conn1;
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ERROR 70100: Query execution was interrupted
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connection default;
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disconnect conn1;
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disconnect conn2;
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disconnect conn3;
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drop procedure if exists update_t1;
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drop table if exists t1;
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81
mysql-test/suite/innodb/r/innodb_bug84958.result
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81
mysql-test/suite/innodb/r/innodb_bug84958.result
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@ -0,0 +1,81 @@
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#
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# Bug #84958 InnoDB's MVCC has O(N^2) behaviors
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# https://bugs.mysql.com/bug.php?id=84958
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#
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# Set up the test with a procedure and a function.
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#
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CREATE PROCEDURE insert_n(start int, end int)
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BEGIN
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DECLARE i INT DEFAULT start;
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WHILE i <= end do
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INSERT INTO t1 VALUES (1, 2, 3) ON DUPLICATE KEY UPDATE c = i;
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SET i = i + 1;
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END WHILE;
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END~~
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CREATE FUNCTION num_pages_get()
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RETURNS INT
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BEGIN
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DECLARE ret INT;
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SELECT variable_value INTO ret
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FROM information_schema.global_status
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WHERE variable_name = 'innodb_buffer_pool_read_requests';
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RETURN ret;
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END~~
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#
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# Create a table with one record in it and start an RR transaction
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#
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CREATE TABLE t1 (a INT, b INT, c INT, PRIMARY KEY(a,b), KEY (b,c))
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ENGINE=InnoDB;
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BEGIN;
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SELECT * FROM t1;
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a b c
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#
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# Create 100 newer record versions in con2 and con3
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#
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connect con2, localhost, root,,;
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connection con2;
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INSERT INTO t1 VALUES (1, 2, 3) ON DUPLICATE KEY UPDATE c = NULL;
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CALL insert_n(1, 50);;
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connect con3, localhost, root,,;
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connection con3;
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CALL insert_n(51, 100);;
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connection con2;
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connection con3;
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INSERT INTO t1 VALUES (1, 2, 1) ON DUPLICATE KEY UPDATE c = NULL;
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connection default;
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#
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# Connect to default and record how many pages were accessed
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# when selecting the record using the secondary key.
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#
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SET @num_pages_1 = num_pages_get();
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SELECT * FROM t1 force index (b);
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a b c
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SET @num_pages_2= num_pages_get();
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SELECT @num_pages_2 - @num_pages_1 < 500;
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@num_pages_2 - @num_pages_1 < 500
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1
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#
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# Commit and show the final record.
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#
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SELECT * FROM t1;
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a b c
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SELECT * FROM t1 force index (b);
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a b c
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COMMIT;
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SELECT * FROM t1 force index (b);
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a b c
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1 2 NULL
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SELECT * FROM t1;
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a b c
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1 2 NULL
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CHECK TABLE t1;
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Table Op Msg_type Msg_text
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test.t1 check status OK
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#
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# Cleanup
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#
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disconnect con2;
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disconnect con3;
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DROP TABLE t1;
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DROP PROCEDURE insert_n;
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DROP FUNCTION num_pages_get;
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@ -1,95 +0,0 @@
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--source include/have_innodb.inc
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#
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# create test-bed to run test
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#
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use test;
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--disable_warnings
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drop table if exists t1;
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--enable_warnings
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create table t1 (id int primary key, value int, value2 int,
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value3 int, index(value,value2)) engine=innodb;
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insert into t1 values
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(10,10,10,10),(11,11,11,11),(12,12,12,12),(13,13,13,13),(14,14,14,14),
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(15,15,15,15),(16,16,16,16),(17,17,17,17),(18,18,18,18),(19,19,19,19),
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(20,20,20,20);
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let $ID= `SELECT @id := CONNECTION_ID()`;
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#
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# we need multiple connections as we need to keep one connection
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# active with trx requesting consistent read.
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#
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connect (conn1, localhost, root,,);
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connect (conn2, localhost, root,,);
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connect (conn3, localhost, root,,);
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#
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# start trx with consistent read
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#
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connection conn1;
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use test;
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start transaction with consistent snapshot;
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#
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# update table such that secondary index is updated.
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#
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connection conn2;
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use test;
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delimiter |;
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CREATE PROCEDURE update_t1()
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BEGIN
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DECLARE i INT DEFAULT 1;
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while (i <= 5000) DO
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update test.t1 set value2=value2+1, value3=value3+1 where id=12;
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SET i = i + 1;
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END WHILE;
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END|
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delimiter ;|
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set autocommit=0;
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CALL update_t1();
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select * from t1;
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set autocommit=1;
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select * from t1;
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#
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# Now try to fire select query from connection-1 enforcing
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# use of secondary index.
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#
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connection conn1;
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let $ID= `SELECT @id := CONNECTION_ID()`;
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#--error ER_QUERY_INTERRUPTED
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--send
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select * from t1 force index(value) where value=12;
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#
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# select is going to take good time so let's kill query.
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#
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connection conn3;
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let $wait_condition=
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select * from information_schema.processlist where state = 'Sending data' and
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info = 'select * from t1 force index(value) where value=12';
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--source include/wait_condition.inc
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let $ignore= `SELECT @id := $ID`;
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kill query @id;
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#
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# reap the value of connection-1
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#
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connection conn1;
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--error ER_QUERY_INTERRUPTED
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reap;
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#
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# clean test-bed.
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#
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connection default;
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disconnect conn1;
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disconnect conn2;
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disconnect conn3;
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drop procedure if exists update_t1;
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drop table if exists t1;
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86
mysql-test/suite/innodb/t/innodb_bug84958.test
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86
mysql-test/suite/innodb/t/innodb_bug84958.test
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--echo #
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--echo # Bug #84958 InnoDB's MVCC has O(N^2) behaviors
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--echo # https://bugs.mysql.com/bug.php?id=84958
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--echo #
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--echo # Set up the test with a procedure and a function.
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--echo #
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--source include/have_innodb.inc
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DELIMITER ~~;
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CREATE PROCEDURE insert_n(start int, end int)
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BEGIN
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DECLARE i INT DEFAULT start;
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WHILE i <= end do
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INSERT INTO t1 VALUES (1, 2, 3) ON DUPLICATE KEY UPDATE c = i;
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SET i = i + 1;
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END WHILE;
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END~~
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CREATE FUNCTION num_pages_get()
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RETURNS INT
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BEGIN
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DECLARE ret INT;
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SELECT variable_value INTO ret
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FROM information_schema.global_status
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WHERE variable_name = 'innodb_buffer_pool_read_requests';
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RETURN ret;
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END~~
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DELIMITER ;~~
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--echo #
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--echo # Create a table with one record in it and start an RR transaction
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--echo #
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CREATE TABLE t1 (a INT, b INT, c INT, PRIMARY KEY(a,b), KEY (b,c))
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ENGINE=InnoDB;
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BEGIN;
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SELECT * FROM t1;
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--echo #
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--echo # Create 100 newer record versions in con2 and con3
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--echo #
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connect (con2, localhost, root,,);
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connection con2;
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INSERT INTO t1 VALUES (1, 2, 3) ON DUPLICATE KEY UPDATE c = NULL;
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--send CALL insert_n(1, 50);
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connect (con3, localhost, root,,);
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connection con3;
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--send CALL insert_n(51, 100);
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connection con2;
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reap;
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connection con3;
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reap;
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INSERT INTO t1 VALUES (1, 2, 1) ON DUPLICATE KEY UPDATE c = NULL;
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connection default;
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--echo #
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--echo # Connect to default and record how many pages were accessed
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--echo # when selecting the record using the secondary key.
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--echo #
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SET @num_pages_1 = num_pages_get();
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SELECT * FROM t1 force index (b);
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SET @num_pages_2= num_pages_get();
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SELECT @num_pages_2 - @num_pages_1 < 500;
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--echo #
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--echo # Commit and show the final record.
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--echo #
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SELECT * FROM t1;
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SELECT * FROM t1 force index (b);
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COMMIT;
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SELECT * FROM t1 force index (b);
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SELECT * FROM t1;
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CHECK TABLE t1;
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--echo #
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--echo # Cleanup
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--echo #
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disconnect con2;
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disconnect con3;
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DROP TABLE t1;
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DROP PROCEDURE insert_n;
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DROP FUNCTION num_pages_get;
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@ -3309,14 +3309,29 @@ row_sel_build_prev_vers_for_mysql(
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return(err);
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}
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/** Helper class to cache clust_rec and old_ver */
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class Row_sel_get_clust_rec_for_mysql
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{
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const rec_t *cached_clust_rec;
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rec_t *cached_old_vers;
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public:
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Row_sel_get_clust_rec_for_mysql() :
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cached_clust_rec(NULL), cached_old_vers(NULL) {}
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dberr_t operator()(row_prebuilt_t *prebuilt, dict_index_t *sec_index,
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const rec_t *rec, que_thr_t *thr, const rec_t **out_rec,
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ulint **offsets, mem_heap_t **offset_heap,
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dtuple_t **vrow, mtr_t *mtr);
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};
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/*********************************************************************//**
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Retrieves the clustered index record corresponding to a record in a
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non-clustered index. Does the necessary locking. Used in the MySQL
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interface.
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@return DB_SUCCESS, DB_SUCCESS_LOCKED_REC, or error code */
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static MY_ATTRIBUTE((warn_unused_result))
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dberr_t
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row_sel_get_clust_rec_for_mysql(
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Row_sel_get_clust_rec_for_mysql::operator()(
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/*============================*/
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row_prebuilt_t* prebuilt,/*!< in: prebuilt struct in the handle */
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dict_index_t* sec_index,/*!< in: secondary index where rec resides */
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clust_rec, clust_index, *offsets,
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trx_get_read_view(trx))) {
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/* The following call returns 'offsets' associated with
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'old_vers' */
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err = row_sel_build_prev_vers_for_mysql(
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trx->read_view, clust_index, prebuilt,
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clust_rec, offsets, offset_heap, &old_vers,
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vrow, mtr);
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if (clust_rec != cached_clust_rec) {
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/* The following call returns 'offsets' associated with
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'old_vers' */
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err = row_sel_build_prev_vers_for_mysql(
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trx->read_view, clust_index, prebuilt,
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clust_rec, offsets, offset_heap, &old_vers,
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vrow, mtr);
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if (err != DB_SUCCESS || old_vers == NULL) {
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if (err != DB_SUCCESS) {
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goto err_exit;
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}
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cached_clust_rec = clust_rec;
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cached_old_vers = old_vers;
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} else {
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err = DB_SUCCESS;
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old_vers = cached_old_vers;
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/* The offsets need not be same for the latest
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version of clust_rec and its old version
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old_vers. Re-calculate the offsets for old_vers. */
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if (old_vers != NULL) {
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*offsets = rec_get_offsets(
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old_vers, clust_index, *offsets,
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true, ULINT_UNDEFINED, offset_heap);
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}
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}
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if (old_vers == NULL) {
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goto err_exit;
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}
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@ -4233,6 +4269,7 @@ row_search_mvcc(
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dtuple_t* vrow = NULL;
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const rec_t* result_rec = NULL;
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const rec_t* clust_rec;
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Row_sel_get_clust_rec_for_mysql row_sel_get_clust_rec_for_mysql;
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dberr_t err = DB_SUCCESS;
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ibool unique_search = FALSE;
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ibool mtr_has_extra_clust_latch = FALSE;
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