Duo Zhang created HBASE-17910:
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Summary: Use separated StoreFileReader for streaming read
Key: HBASE-17910
URL: https://issues.apache.org/jira/browse/HBASE-17910
Project: HBase
Issue Type: Bug
Reporter: Duo Zhang
For now we have already supportted using private readers for compaction, by
creating a new StoreFile copy. I think a better way is to allow creating
multiple readers from a single StoreFile instance, thus we can avoid the ugly
cloning, and the reader can also be used for streaming scan, not only for
compaction.
The reason we want to do this is that, we found a read amplification when using
short circult read. {{BlockReaderLocal}} will use an internal buffer to read
data first, the buffer size is based on the configured buffer size and the
readahead option in CachingStrategy. For normal pread request, we should just
bypass the buffer, this can be achieved by setting readahead to 0. But for
streaming read I think the buffer is somehow still useful? So we need to use
different FSDataInputStream for pread and streaming read.
And one more thing is that, we can also remove the streamLock if streaming read
always use its own reader.
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