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https://issues.apache.org/jira/browse/HBASE-9870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13811646#comment-13811646
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Jimmy Xiang edited comment on HBASE-9870 at 11/1/13 9:05 PM:
-------------------------------------------------------------

[~anoop.hbase], when we open a hfile, do we always use the encoding from the 
file?
{code}
    // Read data block encoding algorithm name from file info.
    dataBlockEncoder = HFileDataBlockEncoderImpl.createFromFileInfo(fileInfo,
        preferredEncodingInCache);
    fsBlockReaderV2.setDataBlockEncoder(dataBlockEncoder);
{code}


was (Author: jxiang):
[~anoop.hbase], when we open a hfile, do we also use the encoding from the file?
{code}
    // Read data block encoding algorithm name from file info.
    dataBlockEncoder = HFileDataBlockEncoderImpl.createFromFileInfo(fileInfo,
        preferredEncodingInCache);
    fsBlockReaderV2.setDataBlockEncoder(dataBlockEncoder);
{code}

> HFileDataBlockEncoderImpl#diskToCacheFormat uses wrong format
> -------------------------------------------------------------
>
>                 Key: HBASE-9870
>                 URL: https://issues.apache.org/jira/browse/HBASE-9870
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Jimmy Xiang
>
> In this method, we have
> {code}
>     if (block.getBlockType() == BlockType.ENCODED_DATA) {
>       if (block.getDataBlockEncodingId() == onDisk.getId()) {
>         // The block is already in the desired in-cache encoding.
>         return block;
>       }
> {code}
> This assumes onDisk encoding is the same as that of inCache.  This is not 
> true when we change the encoding of a CF.  This could be one of the reasons I 
> got data loss with online encoding change?
> If I make sure onDisk == inCache all the time, my ITBLL with online encoding 
> change worked once for me.



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