Merge pull request #5603 from Mats-SX/2.2-selectivity-precision

Add LDBC test to cover precision loss

community/cypher/cypher/src/test/scala/org/neo4j/cypher/LdbcAcceptanceTest.scala

@@ -19,6 +19,9 @@
  */
 package org.neo4j.cypher
 
+import org.neo4j.cypher.internal.compiler.v2_2.pipes.RonjaPipe
+import org.neo4j.cypher.internal.compiler.v2_2.planDescription._
+
 /**
  * Runs the 14 LDBC queries and checks so that the result is what is expected.
  */
@@ -38,4 +41,32 @@ class LdbcAcceptanceTest extends ExecutionEngineFunSuite with NewPlannerTestSupp
       result should equal(ldbcQuery.expectedResult)
     }
   }
+
+  test("LDBC query 12 should not get a bad plan because of lost precision in selectivity calculation") {
+    executeWithRulePlannerOnly(LdbcQueries.Query12.createQuery, LdbcQueries.Query12.createParams.toSeq: _*)
+    LdbcQueries.Query12.constraintQueries.foreach(executeWithRulePlannerOnly(_))
+
+    val updatedLdbc12 =
+      """MATCH (:Person {id:{1}})-[:KNOWS]-(friend:Person)
+        |MATCH (friend)<-[:COMMENT_HAS_CREATOR]-(comment:Comment)-[:REPLY_OF_POST]->(:Post)-[:POST_HAS_TAG]->(tag:Tag)-[:HAS_TYPE]->(tagClass:TagClass)-[:IS_SUBCLASS_OF*0..]->(baseTagClass:TagClass)
+        |WHERE tagClass.name = {2} OR baseTagClass.name = {2}
+        |RETURN friend.id AS friendId, friend.firstName AS friendFirstName, friend.lastName AS friendLastName, collect(DISTINCT tag.name) AS tagNames, count(DISTINCT comment) AS count
+        |ORDER BY count DESC, friendId ASC
+        |LIMIT {3}
+      """.stripMargin
+
+    val params: Map[String, Any] = Map("1" -> 0, "2" -> 1, "3" -> 10)
+
+    val result = executeWithAllPlanners(s"PROFILE $updatedLdbc12", params.toSeq:_*)
+
+    // no precision loss resulting in insane numbers
+    all (collectEstimations(result.executionPlanDescription())) should be > 0.0
+    all (collectEstimations(result.executionPlanDescription())) should be < 10.0
+  }
+
+  private def collectEstimations(plan: InternalPlanDescription): Seq[Double] = {
+    (plan.pipe match {
+      case r: RonjaPipe => r.estimatedCardinality.get
+    }) +: plan.children.toSeq.flatMap(collectEstimations)
+  }
 }