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Key: CORE-4353
Type: Bug Bug
Status: Closed Closed
Resolution: Fixed
Priority: Minor Minor
Assignee: Dmitry Yemanov
Reporter: Pavel Zotov
Votes: 0
Watchers: 0

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Firebird Core

Sorting records are larger than really necessary

Created: 25/Feb/14 08:58 AM   Updated: 22/Sep/15 09:41 AM
Component/s: Engine
Affects Version/s: 2.1.0, 2.1.1, 2.1.2, 2.1.3, 2.5.0, 2.1.4, 2.5.1, 2.1.5, 2.5.2, 2.1.5 Update 1, 2.5.2 Update 1, 3.0 Alpha 1, 3.0 Alpha 2
Fix Version/s: 2.5.3, 3.0 Beta 1

QA Status: Deferred
Test Details: TODO // compare output of mon$memory_usage ?

 Description  « Hide
In external sorting (SORT plan), every record being sorted is stored as the sort key plus all the referenced fields plus stream-level information plus padding/alignment. However, the sorting record length is calculated inaccurately, causing redundant bytes to be allocated but never used. This causes the sort blocks to grow more than necessary thus slowing down the operation, especially when number of records being sorted is huge and sort blocks are swapped to disk. In most practical cases, this overhead is relatively small and is unlikely to be more than 5-10%, but in some artificial cases it could be up to 50%.

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