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From arina-ielchiieva <...@git.apache.org>
Subject [GitHub] drill pull request #819: DRILL-5419: Calculate return string length for lite...
Date Fri, 05 May 2017 12:30:53 GMT
Github user arina-ielchiieva commented on a diff in the pull request:

    https://github.com/apache/drill/pull/819#discussion_r113908201
  
    --- Diff: common/src/main/java/org/apache/drill/common/types/Types.java ---
    @@ -636,43 +658,63 @@ public static String toString(final MajorType type) {
     
       /**
        * Get the <code>precision</code> of given type.
    -   * @param majorType
    -   * @return
    +   *
    +   * @param majorType major type
    +   * @return precision value
        */
       public static int getPrecision(MajorType majorType) {
    -    MinorType type = majorType.getMinorType();
    -
    -    if (type == MinorType.VARBINARY || type == MinorType.VARCHAR) {
    -      return 65536;
    -    }
    -
         if (majorType.hasPrecision()) {
           return majorType.getPrecision();
         }
     
    -    return 0;
    +    return isScalarStringType(majorType) ? MAX_VARCHAR_LENGTH : UNDEFINED;
    --- End diff --
    
    Currently Drill does not consider length change in varchar as schema change.
    Regarding sampling data, since Drill is schema-less, I think it's OK to return unknown
or max length, sampling won't give exact result any way and will complicate query process.
This PR will help users who want to have length to be specified (ex: by means of cast function
usage).


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