spark-reviews mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From hvanhovell <...@git.apache.org>
Subject [GitHub] spark pull request #13155: [SPARK-15370] [SQL] Update RewriteCorrelatedScala...
Date Fri, 10 Jun 2016 21:04:31 GMT
Github user hvanhovell commented on a diff in the pull request:

    https://github.com/apache/spark/pull/13155#discussion_r66680828
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
    @@ -1695,16 +1696,205 @@ object RewriteCorrelatedScalarSubquery extends Rule[LogicalPlan]
{
       }
     
       /**
    +   * Statically evaluate an expression containing zero or more placeholders, given a
set
    +   * of bindings for placeholder values.
    +   */
    +  private def evalExpr(expr: Expression, bindings: Map[ExprId, Option[Any]]) : Option[Any]
= {
    +    val rewrittenExpr = expr transform {
    +      case r @ AttributeReference(_, dataType, _, _) =>
    +        bindings(r.exprId) match {
    +          case Some(v) => Literal.create(v, dataType)
    +          case None => Literal.default(NullType)
    +        }
    +    }
    +    Option(rewrittenExpr.eval())
    +  }
    +
    +  /**
    +   * Statically evaluate an expression containing one or more aggregates on an empty
input.
    +   */
    +  private def evalAggOnZeroTups(expr: Expression) : Option[Any] = {
    +    // AggregateExpressions are Unevaluable, so we need to replace all aggregates
    +    // in the expression with the value they would return for zero input tuples.
    +    // Also replace attribute refs (for example, for grouping columns) with NULL.
    +    val rewrittenExpr = expr transform {
    +      case a @ AggregateExpression(aggFunc, _, _, resultId) =>
    +        aggFunc.defaultResult.getOrElse(Literal.default(NullType))
    +
    +      case AttributeReference(_, _, _, _) => Literal.default(NullType)
    +    }
    +    Option(rewrittenExpr.eval())
    +  }
    +
    +  /**
    +   * Statically evaluate a scalar subquery on an empty input.
    +   *
    +   * <b>WARNING:</b> This method only covers subqueries that pass the checks
under
    +   * [[org.apache.spark.sql.catalyst.analysis.CheckAnalysis]]. If the checks in
    +   * CheckAnalysis become less restrictive, this method will need to change.
    +   */
    +  private def evalSubqueryOnZeroTups(plan: LogicalPlan) : Option[Any] = {
    +    // Inputs to this method will start with a chain of zero or more SubqueryAlias
    +    // and Project operators, followed by an optional Filter, followed by an
    +    // Aggregate. Traverse the operators recursively.
    +    def evalPlan(lp : LogicalPlan) : Map[ExprId, Option[Any]] = {
    +      lp match {
    +        case SubqueryAlias(_, child) => evalPlan(child)
    +        case Filter(condition, child) =>
    +          val bindings = evalPlan(child)
    +          if (bindings.isEmpty) bindings
    +          else {
    +            val exprResult = evalExpr(condition, bindings).getOrElse(false)
    +              .asInstanceOf[Boolean]
    +            if (exprResult) bindings else Map.empty
    +          }
    +
    +        case Project(projectList, child) =>
    +          val bindings = evalPlan(child)
    +          if (bindings.isEmpty) {
    +            bindings
    +          } else {
    +            projectList.map(ne => (ne.exprId, evalExpr(ne, bindings))).toMap
    +          }
    +
    +        case Aggregate(_, aggExprs, _) =>
    +          // Some of the expressions under the Aggregate node are the join columns
    +          // for joining with the outer query block. Fill those expressions in with
    +          // nulls and statically evaluate the remainder.
    +          aggExprs.map(ne => ne match {
    --- End diff --
    
    style: do the pattern match directly, i.e.:
    ```scala
    aggExpr.map {
      case _: AttributeReference =>
      case ...
    }
    ```


---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastructure@apache.org or file a JIRA ticket
with INFRA.
---

---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org


Mime
View raw message