flink-libraries/flink-table/src/main/scala/org/apache/flink/table/sources/FilterableTableSource.scala

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 * to you under the Apache License, Version 2.0 (the
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package org.apache.flink.table.sources

import java.util.{List => JList}

import org.apache.calcite.tools.RelBuilder
import org.apache.flink.table.expressions.Expression
/**
  * Adds support for filtering push-down to a [[TableSource]].
  * A [[TableSource]] extending this interface is able to filter records before returning.
  */
trait FilterableTableSource {

  /**
    * Check and pick all predicates this table source can support. The passed in predicates
    * have been translated in conjunctive form, and table source can only pick those predicates
    * that it supports.
    * <p>
    * After trying to push predicates down, we should return a new [[TableSource]]
    * instance which holds all pushed down predicates. Even if we actually pushed nothing down,
    * it is recommended that we still return a new [[TableSource]] instance since we will
    * mark the returned instance as filter push down has been tried.
    * <p>
    * We also should note to not changing the form of the predicates passed in. It has been
    * organized in CNF conjunctive form, and we should only take or leave each element from the
    * list. Don't try to reorganize the predicates if you are absolutely confident with that.
    *
    * @param predicates A list contains conjunctive predicates, you should pick and remove all
    *                   expressions that can be pushed down. The remaining elements of this list
    *                   will further evaluated by framework.
    * @return A new cloned instance of [[TableSource]]
    */
  def applyPredicate(predicates: JList[Expression]): TableSource

  /**
    * Return the flag to indicate whether filter push down has been tried. Must return true on
    * the returned instance of [[applyPredicate]].
    */
  def isFilterPushedDown: Boolean

  /**
    * @param relBuilder Builder for relational expressions.
    */
  def setRelBuilder(relBuilder: RelBuilder): Unit

}