gh-ost | GitHub 's Online Schema-migration Tool for MySQL | Data Migration library

by github Go Version: v1.1.5 License: MIT

X-Ray Key Features Code Snippets Community Discussions(3)Vulnerabilities Install Support

kandi X-RAY | gh-ost Summary

gh-ost is a Go library typically used in Migration, Data Migration, Bootstrap applications. gh-ost has no bugs, it has no vulnerabilities, it has a Permissive License and it has medium support. You can download it from GitHub.

GitHub's Online Schema Migrations for MySQL

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Quality

Security

License

Reuse

Support

gh-ost has a medium active ecosystem.

It has 11139 star(s) with 1277 fork(s). There are 538 watchers for this library.

It had no major release in the last 12 months.

There are 221 open issues and 352 have been closed. On average issues are closed in 439 days. There are 57 open pull requests and 0 closed requests.

It has a neutral sentiment in the developer community.

The latest version of gh-ost is v1.1.5

Quality

gh-ost has 0 bugs and 0 code smells.

Security

gh-ost has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.

gh-ost code analysis shows 0 unresolved vulnerabilities.

There are 0 security hotspots that need review.

License

gh-ost is licensed under the MIT License. This license is Permissive.

Permissive licenses have the least restrictions, and you can use them in most projects.

Reuse

gh-ost releases are available to install and integrate.

It has 7895 lines of code, 455 functions and 35 files.

It has high code complexity. Code complexity directly impacts maintainability of the code.

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gh-ost Key Features

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gh-ost Examples and Code Snippets

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Community Discussions

Trending Discussions on gh-ost

what happens to binlog when alter a table using pt-online-schema-change or gh-ost

How to simulate long running alter query on MySQL

Ghost/copy table is many times bigger than original table

QUESTION

what happens to binlog when alter a table using pt-online-schema-change or gh-ost

Asked 2022-Feb-21 at 22:53

I was wondering what happens to the binlog when run an alter using pt-online-schema-change or gh-ost?

for the pt-online-schema-change I have read that it copies the table and use some triggers to apply the changes. I don't know if it create a table from the beginning with the new schema or it just apply the alter after copying the table?

if it alters the table from the beginning, then what happens to binglog? is the positions different than the previous binglog?

...

ANSWER

Answered 2022-Feb-21 at 22:53

pt-online-schema change copies the table structure and applies the desired ALTER TABLE to the zero-row table. This is virtually instantaneous. Then it creates triggers to mirror changes against the original table. Then it starts copying old data from the original table to the new table.

What happens to the binlog? It gets quite huge. The CREATE TABLE and ALTER TABLE and CREATE TRIGGER are pretty small. DDL is always statement-based in the binlog. The DML changes created by the triggers and the process of copying old data become transactions in the binlog. We prefer row-based binlogs, so these end up being pretty bulky.

gh-ost is similar, but without the triggers. gh-ost reads the binlog to find events that applied to the old table, and it applies those to the new table. Meanwhile, it also copies old data. Together these actions result in a similar volume of extra events in the binlog as occur when using pt-online-schema-change.

So you should check the amount of free disk space before you begin either of these online schema change operations. It will expand the binlogs approximately in proportion to the amount of data to be copied. And of course you need to store two copies of the whole table — the original and the altered version — temporarily, until the original table can be dropped at the end of the process.

I have had to run pt-online-schema change on large tables (500GB+) when I had a disk that was close to being full. It causes some tense moments. I had to PURGE BINARY LOGS periodically to get some more free space, because the schema change would fill the disk to 100% if I didn't! This is not a situation I recommend.

Source https://stackoverflow.com/questions/71213673

QUESTION

How to simulate long running alter query on MySQL

Asked 2021-Jul-28 at 17:22

I have a system and I want to test it which executes Alter queries. I'm looking for a way to simulate a long-running Alter query that I can test "panic", "resource usage", "concurrency", ... when it's running.

Is there any way that exists I can simulate a long-running Alter query?

I'm using gh-ost for alter execution.

...

ANSWER

Answered 2021-Jul-28 at 17:22

Here's what I do when I want to test a long-running ALTER TABLE:

Create a table.
Fill it with a few million rows of random data, until it's large enough that ALTER TABLE takes a few minutes. How many rows are required depends on the speed of your computer.
Run ALTER TABLE on it.

I have not found a better solution, and I've been using MySQL since 2001.

Here's a trick for filling lots of rows without needing a client app or script:

Source https://stackoverflow.com/questions/68564128

QUESTION

Ghost/copy table is many times bigger than original table

Asked 2020-Dec-02 at 06:50

Info: I am using AWS RDS Mysql 5.6.34 (500GB) instance (Without replica, just the master)

Note: Binlog is enabled & set to Row

Target: Modify a column field_1 from enum to tinyint

Extra info: I am using Rails application. So everytime I wanted to add a value to the enum, I need to write a migration. So converting the enum field to tinyint so I can add or delete a enum value without writing a migration using Active Enum

Other info: I also tried LHM but the RDS instance went out of memory at 93%

Database info before running gh-ost:

...

ANSWER

Answered 2020-Dec-02 at 06:50

I created the mysql DB from a backup of production db.

Production had innodb_file_format parameter as Barracuda

The new environment had innodb_file_format parameter as Antelope

The ROW_FORMAT for the table in production was COMPRESSED

Unfortunately Antelope db doesn't support ROW_FORMAT as COMPRESSED

If I had looked more into the details of information_schema, I could have resolved it eatlier!

Source https://stackoverflow.com/questions/64630426

Community Discussions, Code Snippets contain sources that include Stack Exchange Network

Vulnerabilities

No vulnerabilities reported

Install gh-ost

You can download it from GitHub.

Support

gh-ost is released at a stable state, but with mileage to go. We are open to pull requests. Please first discuss your intentions via Issues. We develop gh-ost at GitHub and for the community. We may have different priorities than others. From time to time we may suggest a contribution that is not on our immediate roadmap but which may appeal to others. Please see Coding gh-ost for a guide to getting started developing with gh-ost.

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