[jira] [Commented] (HBASE-17623) Reuse the bytes array when building the hfile block

["Ted Yu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-17623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15860763#comment-15860763 ] 

Ted Yu commented on HBASE-17623:
--------------------------------

Have you measured the memory savings through the change ?

Thanks

> Reuse the bytes array when building the hfile block
> ---------------------------------------------------
>
>                 Key: HBASE-17623
>                 URL: https://issues.apache.org/jira/browse/HBASE-17623
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: ChiaPing Tsai
>            Assignee: ChiaPing Tsai
>            Priority: Minor
>             Fix For: 2.0.0
>
>         Attachments: HBASE-17623.v0.patch
>
>
> There are two improvements.
> # The uncompressedBlockBytesWithHeader and onDiskBlockBytesWithHeader should maintain a bytes array which can be reused when building the hfile.
> # The uncompressedBlockBytesWithHeader/onDiskBlockBytesWithHeader is copied to an new bytes array only when we need to cache the block.
> {code:title=HFileBlock.java|borderStyle=solid}
>     private void finishBlock() throws IOException {
>       if (blockType == BlockType.DATA) {
>         this.dataBlockEncoder.endBlockEncoding(dataBlockEncodingCtx, userDataStream,
>             baosInMemory.getBuffer(), blockType);
>         blockType = dataBlockEncodingCtx.getBlockType();
>       }
>       userDataStream.flush();
>       // This does an array copy, so it is safe to cache this byte array when cache-on-write.
>       // Header is still the empty, 'dummy' header that is yet to be filled out.
>       uncompressedBlockBytesWithHeader = baosInMemory.toByteArray();
>       prevOffset = prevOffsetByType[blockType.getId()];
>       // We need to set state before we can package the block up for cache-on-write. In a way, the
>       // block is ready, but not yet encoded or compressed.
>       state = State.BLOCK_READY;
>       if (blockType == BlockType.DATA || blockType == BlockType.ENCODED_DATA) {
>         onDiskBlockBytesWithHeader = dataBlockEncodingCtx.
>             compressAndEncrypt(uncompressedBlockBytesWithHeader);
>       } else {
>         onDiskBlockBytesWithHeader = defaultBlockEncodingCtx.
>             compressAndEncrypt(uncompressedBlockBytesWithHeader);
>       }
>       // Calculate how many bytes we need for checksum on the tail of the block.
>       int numBytes = (int) ChecksumUtil.numBytes(
>           onDiskBlockBytesWithHeader.length,
>           fileContext.getBytesPerChecksum());
>       // Put the header for the on disk bytes; header currently is unfilled-out
>       putHeader(onDiskBlockBytesWithHeader, 0,
>           onDiskBlockBytesWithHeader.length + numBytes,
>           uncompressedBlockBytesWithHeader.length, onDiskBlockBytesWithHeader.length);
>       // Set the header for the uncompressed bytes (for cache-on-write) -- IFF different from
>       // onDiskBlockBytesWithHeader array.
>       if (onDiskBlockBytesWithHeader != uncompressedBlockBytesWithHeader) {
>         putHeader(uncompressedBlockBytesWithHeader, 0,
>           onDiskBlockBytesWithHeader.length + numBytes,
>           uncompressedBlockBytesWithHeader.length, onDiskBlockBytesWithHeader.length);
>       }
>       if (onDiskChecksum.length != numBytes) {
>         onDiskChecksum = new byte[numBytes];
>       }
>       ChecksumUtil.generateChecksums(
>           onDiskBlockBytesWithHeader, 0, onDiskBlockBytesWithHeader.length,
>           onDiskChecksum, 0, fileContext.getChecksumType(), fileContext.getBytesPerChecksum());
>     }{code}



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