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Re: MySQL gets long semaphore locks on dict0dict.cc - but on DML operations
Posted by: Nikhil Nair
Date: August 16, 2016 08:31AM

CREATE TABLE `mytable` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`json` longtext,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

There are ~17k rows, with an auto increment value of 5.3Million. Data size is 135.8GB, with free data size 99.8GB. Index size is 0.

The insert queries are typically:
Insert into `mytable` (`json`) values (...);

The select queries are:
Select `json` from `mytable` where id = ...;

The delete queries are:
Delete from `mytable` where id = ...;

Once a row is inserted, it is selected by the ID, and once the json data is read, it is deleted. Ideally there should be 0 rows in the table, but sometimes with certain failures, the delete does not complete. These failures are on the application level not the DB level.

Let me know if there is more info i can provide to clarify.

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Re: MySQL gets long semaphore locks on dict0dict.cc - but on DML operations
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August 16, 2016 08:31AM


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