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https://issues.apache.org/jira/browse/TRAFODION-1420?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14643467#comment-14643467
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Eric Owhadi commented on TRAFODION-1420:
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Qifan, your recall that small scan was enabled by default: REading the code, I
don't see how, BUT:
I do see that there is a JIRA on HBase (HBAse 12411 Optionally enable p-reads
and private readers for compaction) that is about changing the behavior of the
scanner globally to always use pread instead of seek/read (so behave like small
scanner except for the RPC count optimization), and it comes hand in hand with
compaction that can optionally use private readers (so you can still use
seek/read for compaction).
On paper, that looks like the way to go for trafodion high concurrency
workload, since pread is stateless and no locking happen.
configuration: hbase.storescanner.use.pread on and
hbase.regionserver.compaction.private.readers on. Is that what you recall as
"small scanner being already on in Trafodion"?
> Use ClientSmallScanner for small scans to improve performance
> -------------------------------------------------------------
>
> Key: TRAFODION-1420
> URL: https://issues.apache.org/jira/browse/TRAFODION-1420
> Project: Apache Trafodion
> Issue Type: Improvement
> Components: sql-cmp, sql-exe
> Reporter: Eric Owhadi
> Labels: performance
> Fix For: 2.0-incubating
>
>
> Hbase implements an optimization for small scan (defined as scanning less
> than a data block ie 64Kb) resulting in 3X performance improvement. The
> underlying trick is about cutting down RPC calls from 3 (OpenScan/Next/Close)
> to 1, and use pread stateless instead of seek/read state-full and locking
> method to read data. This JIRA is about improving the compiler who can be
> aware if a scan will be acting on single data block (small) or not, and pass
> this data to executor so that it can use the right parameter for scan.
> (scan.setSmall(boolean)).
> reference:
> https://issues.apache.org/jira/browse/HBASE-9488
> https://issues.apache.org/jira/browse/HBASE-7266
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