Scan protection handle could be cached in BasePage
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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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