thevar1able/ClickHouse
1
0
Fork 0
mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-11-26 09:32:01 +00:00
Code Issues Packages Projects Releases Wiki Activity

Add warning about easily breaking replication

Browse Source
This commit is contained in:
Stig Bakken 2021-12-13 11:35:41 +01:00
parent 215865930f
commit ada16f6ebe
1 changed files with 8 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
docs/en/engines/database-engines/materialized-mysql.md
View File

@ -194,6 +194,14 @@ when the `CREATE DATABASE` query executes, so extra care needs to be taken.
You may specify overrides for tables that do not exist yet. You may specify overrides for tables that do not exist yet.
!!! note "Warning"
It is easy to break replication with TABLE OVERRIDEs if not used with care. For example:
* If a column is added with a table override, but then later added to the source MySQL table, the converted ALTER TABLE
query in ClickHouse will fail because the column already exists.
* It is currently possible to add overrides that reference nullable columns where not-nullable are required, such as in
`ORDER BY` or `PARTITION BY`.
## Examples of Use {#examples-of-use} ## Examples of Use {#examples-of-use}
Queries in MySQL: Queries in MySQL: