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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-2878) Scan protection handle could be cached in BasePage
Date Wed, 27 Jun 2007 14:05:26 GMT
Scan protection handle could be cached in BasePage
--------------------------------------------------

                 Key: DERBY-2878
                 URL: https://issues.apache.org/jira/browse/DERBY-2878
             Project: Derby
          Issue Type: Improvement
          Components: Performance, Store
    Affects Versions: 10.4.0.0
            Reporter: Knut Anders Hatlen
            Priority: Minor


Each time a leaf node in a B-tree is visited in an index scan, a scan protection row is locked
and unlocked. Both the lock operation and the unlock operation will allocate a new RecordId
object representing the scan protection row (the unlock operation additionally allocates a
PageKey object for the RecordId). Since the scan protection handle created will be identical
(seen from equals()) each time it is created for a page, it would make sense to cache it in
BasePage. Then we only need to allocate the protection handle for a page once for as long
as it stays in the page cache. This would save three object allocations per single-record
lookup via index.

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