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https://issues.apache.org/jira/browse/HBASE-7279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13510322#comment-13510322
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Matt Corgan commented on HBASE-7279:
------------------------------------
on a related note - one of the benefits of the mutable Cell implementations is
that the first time a cell gets parsed out of the data block, we can store all
the offset/length variables in nice fast int primitives. I'm trying to convert
the existing SeekerState to this right now.
When the cells are travelling through all the scanners/heaps/filters, the
methods like getQualifierLength() will simply return the already-calculated
primitive int. With plain KeyValue as it is now, each time
getQualifierLength() is called you have to do all of the following, and it may
get called many times on the way from disk to client:
{code}
@Override
public short getRowLength() {
return Bytes.toShort(this.bytes, getKeyOffset());
}
public int getFamilyOffset(int rlength) {
return this.offset + ROW_OFFSET + Bytes.SIZEOF_SHORT + rlength +
Bytes.SIZEOF_BYTE;
}
@Override
public byte getFamilyLength() {
return getFamilyLength(getFamilyOffset());
}
@Override
public int getQualifierLength() {
return getQualifierLength(getRowLength(),getFamilyLength());
}
public int getQualifierLength(int rlength, int flength) {
return getKeyLength() - (int) getKeyDataStructureSize(rlength, flength, 0);
}
public static long getKeyDataStructureSize(int rlength, int flength, int
qlength) {
return KeyValue.KEY_INFRASTRUCTURE_SIZE + rlength + flength + qlength;
}
{code}
> Avoid copying the rowkey in RegionScanner, StoreScanner, and ScanQueryMatcher
> -----------------------------------------------------------------------------
>
> Key: HBASE-7279
> URL: https://issues.apache.org/jira/browse/HBASE-7279
> Project: HBase
> Issue Type: Bug
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Fix For: 0.96.0, 0.94.4
>
> Attachments: 7279-0.94.txt, 7279-0.94-v2.txt
>
>
> Did some profiling again.
> I we can gain some performance [1] when passing buffer, rowoffset, and
> rowlength instead of making a copy of the row key.
> That way we can also remove the row key caching (and this patch also removes
> the timestamps caching). Considering the sheer number in which we create KVs,
> every byte save is good.
> [1] (15-20% when data is in the block cache we setup a Filter such that only
> a single row is returned to the client).
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