Zoltán Borók-Nagy created IMPALA-9859:
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Summary: Milestone 4: Read updated tables
Key: IMPALA-9859
URL: https://issues.apache.org/jira/browse/IMPALA-9859
Project: IMPALA
Issue Type: Sub-task
Reporter: Zoltán Borók-Nagy
Hive ACID supports row-level DELETE and UPDATE operatations on a table. It
achieves it via assigning a unique row-id for each row, and maintinaining two
sets of files in a table. The first set is in the delta directories, they
contain the INSERTed rows. The second set of files are in the delete-delta
directories, they contain the DELETEd rows.
_Note: UPDATE operations are implemented via DELETE+INSERT._
In the filesystem it looks like e.g.:
{noformat}
full_acid/delta_0000001_0000001_0000/0000_0
full_acid/delete_delta_0000002_0000002_0000/0000_0
{noformat}
During scanning we need to return INSERTed rows minus DELETEd rows. One way of
doing that is to create an ANTI JOIN between INSERT and DELETE events.
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