Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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10.1.3, 10.2.0, 10.3.0
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10.3.6-1
Description
The CREATE TABLE attribute page_compressed that was introduced in MariaDB 10.1.3 has no effect when innodb_doublewrite=0. This is because the actual compression only takes place within the doublewrite buffer code path.
The purpose of the doublewrite buffer is to guarantee crash-safety in the event that InnoDB is killed in the middle of a page write. Because it could become a performance bottleneck for write-heavy workloads, some users may choose to set innodb_doublewrite=0 and take the risk that crash recovery may fail. (The page should be referred to by the redo log, and a log checkpoint should not be made while a page write is still in progress, so the page corruption should be detected at InnoDB startup.)
Attachments
Issue Links
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Activity
Commit a6ea7b353b5143f5a61fd37c246c49072ba8c421 has been pushed as a workaround of MDEV-15527.
commit e27535093d1670fde6034c92366e8128b683b903
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Author: Thirunarayanan Balathandayuthapani <thiru@mariadb.com>
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Date: Mon Mar 26 15:48:27 2018 +0530
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- Follow-up fix to MDEV-15229
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It only writes zero in remaining uncompressed size of the page with zero.
Commit a6ea7b353b5143f5a61fd37c246c49072ba8c421 looks OK to push (with minor changes), but I do not think that it qualifies as a full fix. We should punch holes to the page_compressed files even if the doublewrite buffer is disabled.
--source include/have_innodb.inc
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let $innodb_compression_algo = `SELECT @@innodb_compression_algorithm`;
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SET GLOBAL innodb_compression_algorithm = 1;
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--let $MYSQLD_DATADIR = `SELECT @@datadir`
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create table t1(c1 bigint not null, b char(200)) engine=innodb page_compressed=1;
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show create table t1;
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delimiter //;
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create procedure innodb_insert_proc (repeat_count int)
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begin
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declare current_num int;
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set current_num = 0;
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while current_num < repeat_count do
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insert into t1 values(current_num, repeat('maria', 30));
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set current_num = current_num + 1;
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end while;
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end//
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delimiter ;//
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commit;
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set autocommit=0;
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call innodb_insert_proc(2000);
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commit;
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set autocommit=1;
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SELECT COUNT(*) from t1;
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-- let SEARCH_PATTERN=maria
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-- let SEARCH_FILE=$MYSQLD_DATADIR/test/t1.ibd
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--source include/search_pattern_in_file.inc
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FLUSH TABLES t1 FOR EXPORT;
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let MYSQLD_DATADIR=`select @@datadir`;
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perl;
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do "$ENV{MTR_SUITE_DIR}/include/innodb-util.pl";
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ib_backup_tablespaces("test", "t1");
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EOF
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UNLOCK TABLES;
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SELECT SPACE FROM INFORMATION_SCHEMA.innodb_sys_tables where name = "test/t1";
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drop table t1;
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create table t1(c1 bigint not null, b char(200)) engine=innodb page_compressed=1;
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ALTER TABLE t1 DISCARD TABLESPACE;
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--list_files $MYSQLD_DATADIR/test
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perl;
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do "$ENV{MTR_SUITE_DIR}/include/innodb-util.pl";
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ib_discard_tablespaces("test", "t1");
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ib_restore_tablespaces("test", "t1");
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EOF
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--list_files $MYSQLD_DATADIR/test
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SELECT SPACE FROM INFORMATION_SCHEMA.innodb_sys_tables where name ="test/t1";
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ALTER TABLE t1 IMPORT TABLESPACE;
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SELECT COUNT(*) from t1;
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SHOW CREATE TABLE t1;
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-- let SEARCH_PATTERN=maria
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-- let SEARCH_FILE=$MYSQLD_DATADIR/test/t1.ibd
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--source include/search_pattern_in_file.inc
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drop procedure innodb_insert_proc;
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drop table t1;
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The above test case can able to repeat the scenario.
String value("maria") found only in root page of clustered index. (3rd page)
err = btr_root_adjust_on_import(index);
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The above function call is omitted then t1.ibd doesn't contain maria. Need to check.
To repeat this, run:
./mtr --mysqld=--skip-innodb-doublewrite encryption.innodb-discard-import
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And observe the test failure:
CURRENT_TEST: encryption.innodb-discard-import
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--- /mariadb/10.2/mysql-test/suite/encryption/r/innodb-discard-import.result 2017-05-10 14:14:26.228207275 +0300
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+++ /mariadb/10.2/mysql-test/suite/encryption/r/innodb-discard-import.reject 2018-03-09 14:32:57.500763121 +0200
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@@ -129,6 +129,6 @@
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# t3 yes on expecting NOT FOUND
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NOT FOUND /tmpres/ in t3.ibd
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# t4 yes on expecting NOT FOUND
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-NOT FOUND /mysql/ in t4.ibd
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+FOUND 484 /mysql/ in t4.ibd
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DROP PROCEDURE innodb_insert_proc;
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DROP TABLE t1,t2,t3,t4;
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mysqltest: Result content mismatch
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MDEV-15529 will disable this part of the test.
I posted some comments for the 10.2-based patch. I think that we will also need a 10.5-based version, because the I/O code is quite different there.