[GitHub] drill pull request #840: DRILL-5517: Size-aware set methods in value vectors

[bitblender <gi...@git.apache.org>]

Github user bitblender commented on a diff in the pull request:

    https://github.com/apache/drill/pull/840#discussion_r122526465
  
    --- Diff: exec/vector/src/main/codegen/templates/FixedValueVectors.java ---
    @@ -806,10 +998,32 @@ public void generateTestDataAlt(int size) {
         }
     
       </#if> <#-- type.width -->
    +    /**
    +     * Backfill missing offsets from the given last written position to the
    +     * given current write position. Used by the "new" size-safe column
    +     * writers to allow skipping values. The <tt>set()</tt> and <tt>setSafe()</tt>
    +     * <b>do not</b> fill empties. See DRILL-5529 and DRILL-xxxx.
    +     * @param lastWrite the position of the last valid write: the offset
    +     * to be copied forward
    +     * @param index the current write position filling occurs up to,
    +     * but not including, this position
    +     */
    +
    +    public void fillEmptiesBounded(int lastWrite, int index)
    +            throws VectorOverflowException {
    +      for (int i = lastWrite; i < index; i++) {
    +    <#if type.width <= 8>
    --- End diff --
    
    You can avoid an extra op in the loop by adjusting the bounds of the induction variable. The compiler's  induction variable analysis might automatically figure this one out.
    
    public void fillEmptiesBounded(int lastWrite, int index)
                throws VectorOverflowException {
          for (int i = lastWrite + 1; i <= index; i++) {
            setSafe(i, (int) 0);                                            <-- one less addition in the loop and less register pressure
          }
        }


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