[jira] [Created] (IMPALA-11293) Add COMPACT command for Iceberg tables

["Zoltán Borók-Nagy (Jira)" <ji...@apache.org>]

Zoltán Borók-Nagy created IMPALA-11293:
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             Summary: Add COMPACT command for Iceberg tables
                 Key: IMPALA-11293
                 URL: https://issues.apache.org/jira/browse/IMPALA-11293
             Project: IMPALA
          Issue Type: Improvement
          Components: Frontend
            Reporter: Zoltán Borók-Nagy


Currently Impala cannot convert Iceberg tables.

The following INSERT OVERWRITE statement could be used in the simple cases, i.e. when the following conditions met:
 * all data files use the same partition spec (i.e. no partition evolution)
 * no bucket partitioning (we currently forbid INSERT OVERWRITE for bucket partitioning)

{noformat}
INSERT OVERWRITE t SELECT * FROM T;{noformat}
We could have a command that compacts the Iceberg table (syntax needs to be the same with Hive), e.g.:
{noformat}
ALTER TABLE t EXECUTE compaction();{noformat}
At first, the compact command could be just rewritten to the INSERT OVERWRITE command, but it would also check that there's no partition evolution.

The "no bucket" partitioning condition could be relaxed in this case, because the result would be deterministic. I.e. the only condition we need to check is that there was no partition evolution.

Later, we could do compaction by
{noformat}
TRUNCATE TABLE t;
INSERT INTO t SELECT * FROM t FOR SYSTEM_TIME AS OF ...;{noformat}
Currently time-travel queries are not optimized, but we could workaround it by doing planning at first of:
{noformat}
Create the plan for:
TRUNCATE TABLE t;
INSERT INTO t SELECT * FROM t;{noformat}
Then execute them:
{noformat}
Actually execute:
TRUNCATE TABLE t;
INSERT INTO t SELECT * FROM t; (no need for time-travel, plan created before TRUNCATE){noformat}
This could workaround the planning overhead of time-travel queries.

Also, we might add some locking for the table if possible.



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