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From "Daniel John Debrunner (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-2912) Reduce checkpoint cost in truncateEnd phase of SYSCS_INPLACE_COMPRESS_TABLE
Date Fri, 06 Jul 2007 15:04:04 GMT
Reduce checkpoint cost in truncateEnd phase of SYSCS_INPLACE_COMPRESS_TABLE
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                 Key: DERBY-2912
                 URL: https://issues.apache.org/jira/browse/DERBY-2912
             Project: Derby
          Issue Type: Improvement
          Components: Performance, Store
            Reporter: Daniel John Debrunner
            Priority: Minor


The truncate phase of SYSCS_INPLACE_COMPRESS_TABLE always performs a checkpoint per container.
For any table this is likely to mean a number of checkpoints (one per index and one for the
base table).

Potential improvements are:

   1) Only perform the checkpoint (and the clean of the allocation cache) if the truncate
will actually free some space up.

   2) Perform the checkpoint once for a table, not once per container.

   3) Don;t perform a complete checkpoint, just flush the pages for the table/container being
truncated.

1) Seems fairly possible, I have no idea if the others are.

This affects the JUnit tests which perform a inplace compress on SYSDEPENDS, even with no
space to free up the inplace compress takes about 0.5 seconds and upto two seconds with changes
(even on a fairly small table).

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