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PathExpression.scala
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PathExpression.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.compatibility.v3_3.runtime.commands
import org.neo4j.cypher.internal.compatibility.v3_3.runtime.ExecutionContext
import org.neo4j.cypher.internal.compatibility.v3_3.runtime.commands.expressions.Expression
import org.neo4j.cypher.internal.compatibility.v3_3.runtime.commands.predicates.Predicate
import org.neo4j.cypher.internal.compatibility.v3_3.runtime.executionplan.builders.PatternGraphBuilder
import org.neo4j.cypher.internal.compatibility.v3_3.runtime.pipes.QueryState
import org.neo4j.cypher.internal.compatibility.v3_3.runtime.pipes.matching.MatchingContext
import org.neo4j.cypher.internal.compatibility.v3_3.runtime.symbols.SymbolTable
import org.neo4j.cypher.internal.frontend.v3_3.helpers.UnNamedNameGenerator.isNamed
import org.neo4j.cypher.internal.frontend.v3_3.symbols._
import org.neo4j.values.AnyValue
import org.neo4j.values.storable.Values
import org.neo4j.values.virtual.VirtualValues
/*
This class does pattern matching inside an Expression. It's used as a fallback when the
expression cannot be unnested from inside an expression. It is used for pattern expressions
and pattern comprehension
*/
case class PathExpression(pathPattern: Seq[Pattern], predicate: Predicate,
projection: Expression, allowIntroducingNewIdentifiers: Boolean = false)
extends Expression with PatternGraphBuilder {
private val variables: Seq[(String, CypherType)] =
pathPattern.flatMap(pattern => pattern.possibleStartPoints.filter(p => isNamed(p._1)))
private val symbols2 = SymbolTable(variables.toMap)
private val variablesInClause = Pattern.variables(pathPattern)
private val matchingContext = new MatchingContext(symbols2, predicate.atoms, buildPatternGraph(symbols2, pathPattern), variablesInClause)
private val interestingPoints: Seq[String] = pathPattern.
flatMap(_.possibleStartPoints.map(_._1)).
filter(isNamed).
distinct
override def apply(ctx: ExecutionContext)(implicit state: QueryState): AnyValue = {
// If any of the points we need is null, the whole expression will return null
val returnNull = interestingPoints.exists(key => ctx.get(key) match {
case Some(Values.NO_VALUE) => true
case None if !allowIntroducingNewIdentifiers =>
throw new AssertionError("This execution plan should not exist.")
case _ => false
})
if (returnNull) {
Values.NO_VALUE
} else {
VirtualValues.list(matchingContext.
getMatches(ctx, state). // find matching subgraphs
filter(predicate.isTrue(_)(state)). // filter out graphs not matching the predicate
map(projection.apply(_)(state)).toArray:_*) // project from found subgraphs
}
}
override def children = pathPattern :+ predicate
override def arguments = Seq.empty
override def rewrite(f: (Expression) => Expression) =
f(PathExpression(pathPattern.map(_.rewrite(f)), predicate.rewriteAsPredicate(f), projection, allowIntroducingNewIdentifiers))
override def symbolTableDependencies = {
val patternDependencies = pathPattern.flatMap(_.symbolTableDependencies).toSet
val startPointDependencies = pathPattern.flatMap(_.possibleStartPoints).map(_._1).filter(isNamed).toSet
patternDependencies ++ startPointDependencies
}
override def toString() = s"PathExpression(${pathPattern.mkString(",")}, $predicate, $projection)"
}