[jira] [Created] (SPARK-15742) Reduce collections allocations in Catalyst tree transformation methods

["Josh Rosen (JIRA)" <ji...@apache.org>]

Josh Rosen created SPARK-15742:
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             Summary: Reduce collections allocations in Catalyst tree transformation methods
                 Key: SPARK-15742
                 URL: https://issues.apache.org/jira/browse/SPARK-15742
             Project: Spark
          Issue Type: Improvement
          Components: SQL
            Reporter: Josh Rosen
            Assignee: Josh Rosen


In Catalyst's TreeNode {{transform}} methods we end up calling {{productIterator.map(...).toArray()}} in a number of places, which is slightly inefficient because it needs to allocate and grow ArrayBuilders. Since we already know the size of the final output ({{productArity}}), we can simply allocate an array up-front and use a while loop to consume the iterator and populate the array.

For most workloads, this performance difference is negligible but it does make a measurable difference in optimizer performance for queries that operate over very wide schemas (thousands of columns).



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