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https://issues.apache.org/jira/browse/PHOENIX-5577?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lars Hofhansl updated PHOENIX-5577:
-----------------------------------
Description:
See RegionScannerFactory.getWrappedScanner(...) -> new
RegionScanner(...).nextRaw(...) -> IndexUtil.wrapResultUsingOffset(...)
For index scans this issues a Get back to the same region for each single
scanned row. While the Get is local, it still needs to setup a scanner and seek
to the right key each time. This is pretty inefficient. Local indexes could be
much, much faster at read time for larger scans.
(This is mitigated some by setting the block encoding to ROW_INDEX_V1, but
still less than ideal.)
was:
See RegionScannerFactory.getWrappedScanner(...) -> new
RegionScanner(...).nextRaw(...) -> IndexUtil.wrapResultUsingOffset(...)
For a batched get this issues a Get back to the same region. While the Get is
local, it still needs to setup a scanner and seek to the right key each time.
This is pretty inefficient. Local indexes could be much, much faster at read
time for larger scans.
> Uncovered columns are retrieved one-by-one in local index scans.
> ----------------------------------------------------------------
>
> Key: PHOENIX-5577
> URL: https://issues.apache.org/jira/browse/PHOENIX-5577
> Project: Phoenix
> Issue Type: Improvement
> Reporter: Lars Hofhansl
> Priority: Major
> Labels: performance
>
> See RegionScannerFactory.getWrappedScanner(...) -> new
> RegionScanner(...).nextRaw(...) -> IndexUtil.wrapResultUsingOffset(...)
> For index scans this issues a Get back to the same region for each single
> scanned row. While the Get is local, it still needs to setup a scanner and
> seek to the right key each time. This is pretty inefficient. Local indexes
> could be much, much faster at read time for larger scans.
> (This is mitigated some by setting the block encoding to ROW_INDEX_V1, but
> still less than ideal.)
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