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unnestOptional.scala
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unnestOptional.scala
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/*
* Copyright (c) 2002-2017 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.cypher.internal.compiler.v3_4.planner.logical.plans.rewriter
import org.neo4j.cypher.internal.util.v3_4.{Rewriter, bottomUp}
import org.neo4j.cypher.internal.v3_4.expressions.Expression
import org.neo4j.cypher.internal.ir.v3_4.{CardinalityEstimation, PlannerQuery}
import org.neo4j.cypher.internal.v3_4.logical.plans._
case object unnestOptional extends Rewriter {
override def apply(input: AnyRef) = if (isSafe(input)) instance.apply(input) else input
import org.neo4j.cypher.internal.util.v3_4.Foldable._
/*
* It is not safe to unnest an optional expand with when we have
* a merge relationship, since it must be able to read its own
* writes
*/
private def isSafe(input: AnyRef) = !input.treeExists {
case _:MergeCreateRelationship => true
}
private val instance: Rewriter = bottomUp(Rewriter.lift {
case apply:AntiConditionalApply => apply
case apply@Apply(lhs,
Optional(
e@Expand(_: Argument, _, _, _, _, _, _), _)) =>
optionalExpand(e, lhs)(Seq.empty)(apply.solved)
case apply@Apply(lhs,
Optional(
Selection(predicates,
e@Expand(_: Argument, _, _, _, _, _, _)), _)) =>
optionalExpand(e, lhs)(predicates)(apply.solved)
})
private def optionalExpand(e: Expand, lhs: LogicalPlan): (Seq[Expression] => PlannerQuery with CardinalityEstimation => OptionalExpand) =
predicates => OptionalExpand(lhs, e.from, e.dir, e.types, e.to, e.relName, e.mode, predicates)
}