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https://issues.apache.org/jira/browse/SPARK-7727?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14558697#comment-14558697
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Cheng Hao commented on SPARK-7727:
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As we probably don't want to change the `SQLContext.optimizer`, which supposed
to be an `Optimizer`, how about making the `DefaultOptimizer` from `object` to
`class`? So people could extend it very easily? And as well as the `Analyzer`
etc.
> Avoid inner classes in RuleExecutor
> -----------------------------------
>
> Key: SPARK-7727
> URL: https://issues.apache.org/jira/browse/SPARK-7727
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 1.3.1
> Reporter: Santiago M. Mola
> Labels: easyfix, starter
>
> In RuleExecutor, the following classes and objects are defined as inner
> classes or objects: Strategy, Once, FixedPoint, Batch.
> This does not seem to accomplish anything in this case, but makes
> extensibility harder. For example, if I want to define a new Optimizer that
> uses all batches from the DefaultOptimizer plus some more, I would do
> something like:
> {code}
> new Optimizer {
> override protected val batches: Seq[Batch] =
> DefaultOptimizer.batches ++ myBatches
> }
> {code}
> But this will give a typing error because batches in DefaultOptimizer are of
> type DefaultOptimizer#Batch while myBatches are this#Batch.
> Workarounds include either copying the list of batches from DefaultOptimizer
> or using a method like this:
> {code}
> private def transformBatchType(b: DefaultOptimizer.Batch): Batch = {
> val strategy = b.strategy.maxIterations match {
> case 1 => Once
> case n => FixedPoint(n)
> }
> Batch(b.name, strategy, b.rules)
> }
> {code}
> However, making these classes outer would solve the problem.
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