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From "ChiaPing Tsai (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-13492) The estimation of result size may be different between ClientScanner and RSRpcServices
Date Fri, 17 Apr 2015 11:08:59 GMT
ChiaPing Tsai created HBASE-13492:

             Summary: The estimation of result size may be different between ClientScanner
and RSRpcServices
                 Key: HBASE-13492
                 URL: https://issues.apache.org/jira/browse/HBASE-13492
             Project: HBase
          Issue Type: Bug
            Reporter: ChiaPing Tsai

The ClientScanner try to find next scanner if remainingResultSize and countdown are bigger
than zero. 
The remainingResultSize is calculated by CellUtil.estimatedHeapSizeOf(cell)
    public Result next() throws IOException {
        do {
          if (values != null && values.length > 0) {
            for (Result rs : values) {
              // We don't make Iterator here
              for (Cell cell : rs.rawCells()) {
                remainingResultSize -= CellUtil.estimatedHeapSizeOf(cell);
              this.lastResult = rs;
       }while (remainingResultSize > 0 && countdown > 0 &&
            possiblyNextScanner(countdown, values == null));
RSRpcServices also use CellUtil.estimatedHeapSizeOf(cell) to calculate the result size
  public ScanResponse scan(final RpcController controller, final ScanRequest request)
  throws ServiceException {
            if (!results.isEmpty()) {
              for (Result r : results) {
                for (Cell cell : r.rawCells()) {
                  currentScanResultSize += CellUtil.estimatedHeapSizeOf(cell);
                  totalCellSize += CellUtil.estimatedSerializedSizeOf(cell);

If we encode the data block, like FastDiff, the cell read from HFile is implemented by ClonedSeekerState.
And it's heap size is bigger than KeyValue. 

So the RSRpcServices return the results to client with insufficient caching due to result
size reaches the limit. ClientScanner consider that current region has no more data, and remainingResultSize
and countdown are both bigger than zero. In fact, the remainingResultSize should be smaller
than zero, and current region still have more data for reading.

Does result size calculated by RSRpcServices should be return to client for checking the remainingResultSize

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