Updating data in Clickhouse

Question

I went over the documentation for Clickhouse and I did not see the option to UPDATE nor DELETE. It seems to me its an append only system. Is there a possibility to update existing records or is there some workaround like truncating a partition that has records in it that have changed and then re-insering the entire data for that partition?

Answer 1

Through Alter query in clickhouse we can able to delete/update the rows in a table.

For delete: Query should be constructed as

ALTER TABLE testing.Employee DELETE  WHERE  Emp_Name='user4';

For Update: Query should be constructed as

ALTER TABLE testing.employee UPDATE AssignedUser='sunil' where AssignedUser='sunny';

Answer 2

It's an old question, but updates are now supported in Clickhouse. Note it's not recommended to do many small changes for performance reasons. But it is possible.

Syntax:

ALTER TABLE [db.]table UPDATE column1 = expr1 [, ...] WHERE filter_expr

Clickhouse UPDATE documentation