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adding documentation

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Shlomi Noach 2016-05-20 16:34:52 +02:00
parent 7463079e0d
commit a9d4c11aa1
1 changed files with 9 additions and 3 deletions
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doc/testing-on-replica.md
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@ -7,7 +7,10 @@ Test on replica if you:
- Just want to experiment with a real migration without affecting production (maybe measure migration time?)
- Wish to observe data change impact
### What testing on replica means
## What testing on replica means
`gh-ost` will make all changes
## Issuing a test drive
Apply `--test-on-replica --host=<a.replica>`.
- `gh-ost` would connect to the indicated server
@ -28,8 +31,11 @@ You are now left with the original table **and** the ghost table. They _should_
You now have the time to verify the tool works correctly. You may checksum the entire table data if you like.
- e.g.
`mysql -e 'select * from mydb.mytable' | md5sum`
`mysql -e 'select * from mydb._mytable_gst' | md5sum`
`mysql -e 'select * from mydb.mytable order by id' | md5sum`
`mysql -e 'select * from mydb._mytable_gst order by id' | md5sum`
- or of course only select the shared columns before/after the migration
- We use the trivial `engine=innodb` for `alter` when testing. This way the resulting ghost table is identical in structure to the original table (including indexes) and we expect data to be completely identical. We use `md5sum` on the entire dataset to confirm the test result.
### Cleanup