# What are "Explicit LOCK TABLES" and "Fast Hash UDFs"?

**URL:** <https://forums.percona.com/t/what-are-explicit-lock-tables-and-fast-hash-udfs/22493>\
**Category:** Percona Server for MySQL 5.7\
**Created:** [June 1, 2023, 8:33pm UTC](https://forums.percona.com/t/what-are-explicit-lock-tables-and-fast-hash-udfs/22493 "2023-06-01T20:33:09Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jshirley](https://avatars.discourse-cdn.com/v4/letter/j/c89c15/32.png) [@jshirley](https://forums.percona.com/u/jshirley)\
**Post date:** [June 1, 2023, 8:33pm UTC](https://forums.percona.com/t/what-are-explicit-lock-tables-and-fast-hash-udfs/22493/1 "2023-06-01T20:33:09Z")

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Hello,

I am trying to compare the differences between 2 mysql percona instances and noticed 2 differences being reported by **pt-mysql-summary** :

- Explicit LOCK TABLES
- Fast Hash UDFs

What I would like to understand is what configuration determines whether these are enabled or not? Also, are there any resources that I’m missing for better understanding the output from pt-mysql-summary? I did come across: [pt-mysql-summary — Percona Toolkit Documentation](https://docs.percona.com/percona-toolkit/pt-mysql-summary.html) but that doesn’t really go into detail for each line item.

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**Author:** ![matthewb](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/matthewb/32/34_2.png) [@matthewb](https://forums.percona.com/u/matthewb)\
**Post date:** [June 1, 2023, 8:59pm UTC](https://forums.percona.com/t/what-are-explicit-lock-tables-and-fast-hash-udfs/22493/2 "2023-06-01T20:59:16Z")

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All Percona software is completely open source, so if you want to know why something is doing something, just go look at the source code 🙂

> [@jshirley](#):
>
> Explicit LOCK TABLES

[https://github.com/percona/percona-toolkit/blob/3.x/bin/pt-mysql-summary#L2479](https://github.com/percona/percona-toolkit/blob/3.x/bin/pt-mysql-summary#L2479)  
This is checking a system counter that says at some point someone executed an explicit LOCK TABLES DML. `SHOW GLOBAL STATUS LIKE "Com_Lock%";`

> [@jshirley](#):
>
> Fast Hash UDFs

[https://github.com/percona/percona-toolkit/blob/3.x/bin/pt-mysql-summary#L2005](https://github.com/percona/percona-toolkit/blob/3.x/bin/pt-mysql-summary#L2005)  
This is checking if you have the Percona UDFs installed  
[https://docs.percona.com/percona-server/8.0/management/udf\_percona\_toolkit.html](https://docs.percona.com/percona-server/8.0/management/udf_percona_toolkit.html)