[HBASE-14397] PrefixFilter doesn't filter all remaining rows if the prefix is longer than rowkey being compared

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.0.0
• Fix Version/s: 1.3.0, 2.0.0
• Component/s: Filters
• Hadoop Flags: Reviewed
• Assignee: Jianwei Cui
• Reporter: Jianwei Cui
• Created: 10/Sep/15 13:01
• Updated: 01/Jul/22 21:23
• Resolved: 20/Jun/16 19:30

Description

The PrefixFilter will filter rowkey as:

  public boolean filterRowKey(Cell firstRowCell) {
    ...
    int length = firstRowCell.getRowLength();
    if (length < prefix.length) return true; // ===> return directly if the prefix is longer
    ....
    if ((!isReversed() && cmp > 0) || (isReversed() && cmp < 0)) {
      passedPrefix = true;
    }
    filterRow = (cmp != 0);
    return filterRow;
  }

If the prefix is longer than the current rowkey, PrefixFilter#filterRowKey will filter the rowkey directly without comparing, so that won't set 'passedPrefix' flag even the current row is larger than the prefix.
For example, if there are three rows 'a', 'b' and 'c' in the table, and we issue a scan request as:

hbase(main):001:0> scan 'test_table', {STARTROW => 'a', FILTER => "(PrefixFilter ('aa'))"}

The region server will check the three rows before returning. In our production, the user issue a scan with a PrefixFilter. The prefix is longer than the rowkeys of following millions of rows, so the region server will continue to check rows until hit a rowkey longer than the prefix. This make the client easily timeout. To fix this case, it seems we need to compare the prefix with the rowkey every serveral rows even when the prefix is longer.