Peter Varga created HIVE-24403:
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Summary: change min_history_level schema change to be compatible
with previous version
Key: HIVE-24403
URL: https://issues.apache.org/jira/browse/HIVE-24403
Project: Hive
Issue Type: Improvement
Components: Metastore
Reporter: Peter Varga
Assignee: Peter Varga
In some configurations the HMS backend DB is used by HMS services with
different versions.
HIVE-23107 dropped the min_history_level table from the backend DB making the
new schema version incompatible with the older HMS services.
It is possible to modify that change to keep the compatibility
* Keep the min_history_level table
* Add the new fields for the compaction_queue the same way
* Create a feature flag for min_history_level and if it is on
* Keep the logic inserting to the table during openTxn
* Change the logic in the cleaner, to get the highwatermark the old way
* But still change it to not start the cleaning before that
* Keep the min_history level delete after cleaner
* Change the logic in AcidHouseKeeper to clean the txn_to_write_id the old way
* This feature flag can be automatically setup based on the existence of the
min_history level table, this way if the table will be dropped all HMS-s can
switch to the new functionality without restart
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