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When there is a huge transaction in the undo log, the purge subsystem may get stuck and fail to shut down. This was reproduced with the following on MariaDB 10.4:
diff --git a/mysql-test/suite/innodb/include/innodb-page-compression.inc b/mysql-test/suite/innodb/include/innodb-page-compression.inc
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index 0e7ae8cf029..83e5387cdf4 100644
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--- a/mysql-test/suite/innodb/include/innodb-page-compression.inc
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+++ b/mysql-test/suite/innodb/include/innodb-page-compression.inc
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@@ -11,7 +11,7 @@ create table innodb_page_compressed9 (c1 int not null auto_increment primary key
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--disable_query_log
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begin;
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-let $i = 2000;
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+let $i = 5000;
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while ($i)
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{
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insert into innodb_normal(b) values(REPEAT('Aa',50));
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With this change, the attempt to restart the server would actually time out in the shutdown, like this:
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10.4
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innodb.innodb-page_compression_snappy 'innodb' [ fail ] Found warnings/errors in server log file!
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Test ended at 2019-03-15 11:15:05
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line
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2019-03-15 11:14:48 0 [Warning] /dev/shm/10.4/sql/mysqld: Thread 5 (user : '') did not exit
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2019-03-15 11:14:48 0 [Warning] /dev/shm/10.4/sql/mysqld: Thread 4 (user : '') did not exit
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2019-03-15 11:14:48 0 [Warning] /dev/shm/10.4/sql/mysqld: Thread 3 (user : '') did not exit
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2019-03-15 11:14:48 0 [Warning] /dev/shm/10.4/sql/mysqld: Thread 2 (user : '') did not exit
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2019-03-15 11:14:48 0 [Warning] /dev/shm/10.4/sql/mysqld: Thread 1 (user : '') did not exit
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^ Found warnings in /dev/shm/10.4/mysql-test/var/log/mysqld.1.err
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ok
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The cause is that a purge thread would remain stuck in trx_purge_attach_undo_recs(). Apparently the innodb_purge_batch_size does not work correctly, or the n_pages_handled is not being incremented correctly. In any case, we should exit the loop on non-slow shutdown even before reaching the batch size.
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