[jira] [Created] (ARROW-13847) Avoid unnecessary copies of collection

["Laurent Goujon (Jira)" <ji...@apache.org>]

Laurent Goujon created ARROW-13847:
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             Summary: Avoid unnecessary copies of collection
                 Key: ARROW-13847
                 URL: https://issues.apache.org/jira/browse/ARROW-13847
             Project: Apache Arrow
          Issue Type: Improvement
          Components: Java
            Reporter: Laurent Goujon
            Assignee: Laurent Goujon


There are several occurences of unnecessary copies of collections in Arrow Java code.

One typical example is for a constructor to copy a collection provided as an argument, and then invoking {{Collections2}} method to create a immutable copy of it, like for {{Schema}} ([https://github.com/apache/arrow/blob/247a7a9bf1b7090b1bffc14bec84d188dccb52dc/java/vector/src/main/java/org/apache/arrow/vector/types/pojo/Schema.java#L113)]
{code:java}

  /**
   * Constructor with metadata.
   */
  public Schema(Iterable<Field> fields,
                Map<String, String> metadata) {
    List<Field> fieldList = new ArrayList<>();
    for (Field field : fields) {
      fieldList.add(field);
    }
    this.fields = Collections2.immutableListCopy(fieldList);
    this.metadata = metadata == null ? Collections.emptyMap() : Collections2.immutableMapCopy(metadata);
  } {code}



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