[jira] [Commented] (HBASE-10531) Revisit how the key byte[] is passed to HFileScanner.seekTo and reseekTo

[ramkrishna.s.vasudevan (JIRA)]

    [ 
https://issues.apache.org/jira/browse/HBASE-10531?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13919313#comment-13919313
 ] 

ramkrishna.s.vasudevan commented on HBASE-10531:
------------------------------------------------

bq.otherwise we'll add yet another copy to an already expensive part of the 
scanning.
I have a way to work around this.  Now as we are creating a cell here for 
comparision, I will create a new KV here and that will not do any copy.
{code}
 public static class DerivedKeyValue extends KeyValue {

    private int length = 0;
    private int offset = 0;
    private byte[] b;

    public DerivedKeyValue(byte[] b, int offset, int length) {
      super(b,offset,length);
      this.b = b;
      setKeyOffset(offset);
      setKeyLength(length);
      this.length = length;
      this.offset = offset;
    }

    public void setKeyLength(int kLength) {
      this.length = kLength;
    }

    public void setKeyOffset(int kOffset) {
      this.offset = kOffset;
    }

    @Override
    public int getKeyOffset() {
        return this.offset;
    }
    
    @Override
    public byte[] getRowArray() {
      // TODO Auto-generated method stub
      return b;
    }
    
    @Override
    public int getRowOffset() {
      // TODO Auto-generated method stub
      return getKeyOffset() + Bytes.SIZEOF_SHORT;
    }
    
    @Override
    public byte[] getFamilyArray() {
      // TODO Auto-generated method stub
      return b;
    }
    
    @Override
    public byte getFamilyLength() {
      // TODO Auto-generated method stub
      return this.b[getFamilyOffset() - 1];
    }
    
    @Override
    public int getFamilyOffset() {
      // TODO Auto-generated method stub
      return this.offset  + Bytes.SIZEOF_SHORT + getRowLength() + 
Bytes.SIZEOF_BYTE;
    }
    
    @Override
    public byte[] getQualifierArray() {
      // TODO Auto-generated method stub
      return b;
    }
    
    @Override
    public int getQualifierLength() {
      // TODO Auto-generated method stub
      return getQualifierLength(getRowLength(),getFamilyLength());
    }
    
    @Override
    public int getQualifierOffset() {
      // TODO Auto-generated method stub
      return super.getQualifierOffset();
    }
    @Override
    public int getKeyLength() {
      // TODO Auto-generated method stub
      return length;
    }
    @Override
    public short getRowLength() {
      return Bytes.toShort(this.b, getKeyOffset());
    }
    
    private int getQualifierLength(int rlength, int flength) {
      return getKeyLength() - (int) getKeyDataStructureSize(rlength, flength, 
0);
    }
}
{code}
Now here if you see the only difference between a normal Kv and the one craeted 
by KeyValue.createKeyValueFromKeyValue, we actually don't need the first 8 
bytes(ROW_OFFSET).  so by avoiding those bytes if we are able to implement our 
own getKeyLength, getRowOffset, etc we will be able to a proper comparison. Now 
we can compare the individual rows, families, qualifiers individually.  What 
you think?  so we avoid byte copy but we will create a new object.  But I think 
that is going to be cheaper.


> Revisit how the key byte[] is passed to HFileScanner.seekTo and reseekTo
> ------------------------------------------------------------------------
>
>                 Key: HBASE-10531
>                 URL: https://issues.apache.org/jira/browse/HBASE-10531
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 0.99.0
>
>         Attachments: HBASE-10531.patch, HBASE-10531_1.patch
>
>
> Currently the byte[] key passed to HFileScanner.seekTo and 
> HFileScanner.reseekTo, is a combination of row, cf, qual, type and ts.  And 
> the caller forms this by using kv.getBuffer, which is actually deprecated.  
> So see how this can be achieved considering kv.getBuffer is removed.



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