[GitHub] spark pull request: [SPARK-13871][SQL] Support for inferring filte...

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

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

    https://github.com/apache/spark/pull/11665#discussion_r56068722
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala ---
    @@ -598,50 +598,44 @@ object NullPropagation extends Rule[LogicalPlan] {
     }
     
     /**
    - * Attempts to eliminate reading (unnecessary) NULL values if they are not required for correctness
    - * by inserting isNotNull filters in the query plan. These filters are currently inserted beneath
    - * existing Filters and Join operators and are inferred based on their data constraints.
    + * Eliminate reading unnecessary values if they are not required for correctness (and can help in
    + * optimizing the query) by inserting relevant filters in the query plan based on an operator's
    + * data constraints. These filters are currently inserted to the existing conditions in the Filter
    + * operators and on either side of Join operators.
      *
      * Note: While this optimization is applicable to all types of join, it primarily benefits Inner and
      * LeftSemi joins.
      */
    -object NullFiltering extends Rule[LogicalPlan] with PredicateHelper {
    +object InferFiltersFromConstraints extends Rule[LogicalPlan] with PredicateHelper {
    +  // We generate a list of additional filters from the operator's existing constraint but remove
    +  // those that are either already part of the operator's condition or are part of the operator's
    +  // child constraints.
       def apply(plan: LogicalPlan): LogicalPlan = plan transform {
         case filter @ Filter(condition, child) =>
    -      // We generate a list of additional isNotNull filters from the operator's existing constraints
    -      // but remove those that are either already part of the filter condition or are part of the
    -      // operator's child constraints.
    -      val newIsNotNullConstraints = filter.constraints.filter(_.isInstanceOf[IsNotNull]) --
    +      // For the Filter operator, we try to generate additional filters by only inferring the
    +      // IsNotNull constraints. These IsNotNull filters are then used while generating the
    +      // physical plan to quickly short circuit the null checks in the generated code.
    +      val newFilters = filter.constraints.filter(_.isInstanceOf[IsNotNull]) --
    --- End diff --
    
    I think I see what you mean. Queries of the form: `x.join(y, Inner, Some(x.a === y.a)).where(x.a > 5)` can be optimized to `x.where('a > 5).join(y.where('a > 5), Inner, Some(x.a === y.a)`. Thanks, I'll add it back.


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