First Row #
By specifying 'merge-engine' = 'first-row'
, users can keep the first row of the same primary key. It differs from the
deduplicate
merge engine that in the first-row
merge engine, it will generate insert only changelog.
- You can not specify sequence.field.
- Not accept
DELETE
andUPDATE_BEFORE
message. You can configignore-delete
to ignore these two kinds records.- Visibility guarantee: Tables with First Row engine, the files with level 0 will only be visible after compaction. So by default, compaction is synchronous, and if asynchronous is turned on, there may be delays in the data.
This is of great help in replacing log deduplication in streaming computation.