[GitHub] drill pull request #805: Drill-4139: Exception while trying to prune partiti...

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

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

    https://github.com/apache/drill/pull/805#discussion_r140055857
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/Metadata.java ---
    @@ -1054,8 +1057,36 @@ public void setMax(Object max) {
           return nulls;
         }
     
    -    @Override public boolean hasSingleValue() {
    -      return (max != null && min != null && max.equals(min));
    +    /**
    +     * Checks that the column chunk has a single value.
    +     * Returns {@code true} if {@code min} and {@code max} are the same but not null
    +     * and nulls count is 0 or equal to the rows count.
    +     * <p>
    +     * Returns {@code true} if {@code min} and {@code max} are null and the number of null values
    +     * in the column chunk is equal to the rows count.
    +     * <p>
    +     * Comparison of nulls and rows count is needed for the cases:
    +     * <ul>
    +     * <li>column with primitive type has single value and null values</li>
    +     *
    +     * <li>column <b>with primitive type</b> has only null values, min/max couldn't be null,
    +     * but column has single value</li>
    +     * </ul>
    +     *
    +     * @param rowCount rows count in column chunk
    +     * @return true if column has single value
    +     */
    +    @Override
    +    public boolean hasSingleValue(long rowCount) {
    +      if (nulls != null) {
    +        if (min != null) {
    +          // Objects.deepEquals() is used here, since min and max may be byte arrays
    +          return Objects.deepEquals(min, max) && (nulls == 0 || nulls == rowCount);
    --- End diff --
    
    - if (min != null), then nulls cannot be equal to rowCount
    - In this case, only nulls == 0 should be checked 


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