[GitHub] drill pull request #837: DRILL-5514: Enhance VectorContainer to merge two ro...

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

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

    https://github.com/apache/drill/pull/837#discussion_r120198724
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/record/BatchSchema.java ---
    @@ -157,4 +158,26 @@ private boolean majorTypeEqual(MajorType t1, MajorType t2) {
         return true;
       }
     
    +  /**
    +   * Merge two schema to produce a new, merged schema. The caller is responsible
    +   * for ensuring that column names are unique. The order of the fields in the
    +   * new schema is the same as that of this schema, with the other schema's fields
    +   * appended in the order defined in the other schema. The resulting selection
    +   * vector mode is the same as this schema. (That is, this schema is assumed to
    +   * be the main part of the batch, possibly with a selection vector, with the
    +   * other schema representing additional, new columns.)
    +   * @param otherSchema the schema to merge with this one
    +   * @return the new, merged, schema
    +   */
    +
    +  public BatchSchema merge(BatchSchema otherSchema) {
    +    if (otherSchema.selectionVectorMode != SelectionVectorMode.NONE &&
    +        selectionVectorMode != otherSchema.selectionVectorMode) {
    +      throw new IllegalArgumentException("Left schema must carry the selection vector mode");
    +    }
    +    List<MaterializedField> mergedFields = new ArrayList<>();
    --- End diff --
    
    List<MaterializedField> mergedFields = new ArrayList(this.fields.size() +  otherSchema.fields.size()) would avoid having to potentially grow the ArrayList twice.


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