ERROR 2013 (HY000): Lost connection to MySQL server during query.
Posted by: Sharath Chandra Karnati
Date: October 18, 2018 12:09AM

I tried a query to alter a table which contains 2,00,000 records and has 14 columns and its size is 4.38 GB. The alter query creates a temp table every time it is executed.

The query is

ALTER TABLE table_name ADD COLUMN column_name varchar(255) NOT NULL COMMENT " ";

The available space in the server is 12GB and available RAM is 7GB.

The query always takes more than 15 min and then stops and leaves behind a #sql- file.
even though the table is 4.38GB the temp file it leaves behind is 4.7GB.
The MySQL memory allocation is as follows

key_buffer_size = 1G
connect_timeout = 10
delayed_insert_timeout = 300
innodb_flush_log_at_timeout = 1
innodb_lock_wait_timeout = 50
innodb_rollback_on_timeout = OFF
interactive_timeout = 60
lock_wait_timeout = 31536000
net_read_timeout = 30
net_write_timeout = 60
rpl_stop_slave_timeout = 31536000
slave_net_timeout = 3600
wait_timeout= 30

Of these net_read_timeout and net_write_timeout are not mentioned in my.cnf

This issue has been going on for 3 days and only on this table it is happening.
I have other servers that have larger tables and they do not show any of these problems and their cinfigurations are almost same.

I would be vary happy if anyone would come up with a solution.

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ERROR 2013 (HY000): Lost connection to MySQL server during query.
October 18, 2018 12:09AM

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