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https://issues.apache.org/jira/browse/DERBY-3130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12534918
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Knut Anders Hatlen commented on DERBY-3130:
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A StoredRecordHeader object is created the first time its corresponding record
is accessed after a page has been fetched into the page cache. When a page is
evicted from the cache, all its StoredRecordHeader objects can be gc'ed. The
number 136814 means that there are 1000 pages, on each of which 136.8 records
have been accessed.
> Reduce memory footprint of StoredRecordHeader
> ---------------------------------------------
>
> Key: DERBY-3130
> URL: https://issues.apache.org/jira/browse/DERBY-3130
> Project: Derby
> Issue Type: Improvement
> Components: Store
> Affects Versions: 10.4.0.0
> Reporter: Knut Anders Hatlen
> Priority: Minor
> Attachments: SmallRecordsTest.java, srh.diff
>
>
> Derby's page cache often has a memory footprint that is much larger than
> pageSize*pageCacheSize. One large contributor to the footprint is the array
> of StoredPageHeader objects in BasePage. The memory consumed by these objects
> can be as large as, and sometimes even larger than, the byte arrays
> containing the raw page data. (See for instance
> http://www.nabble.com/How-much-derby-need-memory--tf3307655.html.) Reducing
> the size of the StoredPageHeader objects could therefore reduce Derby's
> memory footprint significantly, especially if the page cache is large and
> contains many pages from tables with small records or from indices.
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