Cypher: Test whether endpoints exist before running inserts

Author: szarnyasg

cypher/queries/interactive-update-1.cypher

@@ -1,3 +1,5 @@
+OPTIONAL MATCH (c:City {id: $cityId})
+WITH 1/count(c) AS testWhetherCityFound
 MATCH (c:City {id: $cityId})
 CREATE (p:Person {
     id: $personId,

cypher/queries/interactive-update-2.cypher

@@ -1,2 +1,4 @@
+OPTIONAL MATCH (person:Person {id: $personId}), (post:Post {id: $postId})
+WITH 1/count(person) AS testWhetherPersonFound, 1/count(post) AS testWhetherPostFound
 MATCH (person:Person {id: $personId}), (post:Post {id: $postId})
 CREATE (person)-[:LIKES {creationDate: $creationDate}]->(post)

cypher/queries/interactive-update-3.cypher

@@ -1,2 +1,4 @@
+OPTIONAL MATCH (person:Person {id: $personId}), (comment:Comment {id: $commentId})
+WITH 1/count(person) AS testWhetherPersonFound, 1/count(comment) AS testWhetherCommentFound
 MATCH (person:Person {id: $personId}), (comment:Comment {id: $commentId})
 CREATE (person)-[:LIKES {creationDate: $creationDate}]->(comment)

cypher/queries/interactive-update-4.cypher

@@ -1,3 +1,5 @@
+OPTIONAL MATCH (p:Person {id: $moderatorPersonId})
+WITH 1/count(p) AS testWhetherPersonFound
 MATCH (p:Person {id: $moderatorPersonId})
 CREATE (f:Forum {id: $forumId, title: $forumTitle, creationDate: $creationDate})-[:HAS_MODERATOR]->(p)
 WITH f

cypher/queries/interactive-update-5.cypher

@@ -1,2 +1,4 @@
+OPTIONAL MATCH (f:Forum {id: $forumId}), (p:Person {id: $personId})
+WITH 1/count(f) AS testWhetherForumFound, 1/count(p) AS testWhetherPersonFound
 MATCH (f:Forum {id: $forumId}), (p:Person {id: $personId})
 CREATE (f)-[:HAS_MEMBER {creationDate: $creationDate}]->(p)

cypher/queries/interactive-update-6.cypher

@@ -1,4 +1,15 @@
-MATCH (author:Person {id: $authorPersonId}), (country:Country {id: $countryId}), (forum:Forum {id: $forumId})
+OPTIONAL MATCH
+  (author:Person {id: $authorPersonId}),
+  (country:Country {id: $countryId}),
+  (forum:Forum {id: $forumId})
+WITH
+  1/count(author) AS testWhetherAuthorFound,
+  1/count(country) AS testWhetherCountryFound,
+  1/count(forum) AS testWhetherForumFound
+MATCH
+  (author:Person {id: $authorPersonId}),
+  (country:Country {id: $countryId}),
+  (forum:Forum {id: $forumId})
 CREATE (author)<-[:HAS_CREATOR]-(p:Post:Message {
     id: $postId,
     creationDate: $creationDate,

cypher/queries/interactive-update-7.cypher

@@ -1,3 +1,11 @@
+OPTIONAL MATCH
+  (author:Person {id: $authorPersonId}),
+  (country:Country {id: $countryId}),
+  (message:Message {id: $replyToPostId + $replyToCommentId})
+WITH
+  1/count(author) AS testWhetherAuthorFound,
+  1/count(country) AS testWhetherCountryFound,
+  1/count(message) AS testWhetherMessageFound
 MATCH
   (author:Person {id: $authorPersonId}),
   (country:Country {id: $countryId}),

cypher/queries/interactive-update-8.cypher

@@ -1,2 +1,4 @@
+OPTIONAL MATCH (p1:Person {id: $person1Id}), (p2:Person {id: $person2Id})
+WITH 1/count(p1) AS testWhetherP1Found, 1/count(p2) AS testWhetherP2Found
 MATCH (p1:Person {id: $person1Id}), (p2:Person {id: $person2Id})
 CREATE (p1)-[:KNOWS {creationDate: $creationDate}]->(p2)