Neo4j

1[
2{"name": "a", "val": 120},
3{"name": "b", "val": 60}
4]
5MATCH (n)
6RETURN COALESCE(n.alias, n.name) AS name, sum(n.val) AS val
7

1org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [MyDTO] to type [org.neo4j.driver.Value]
2@Node
3data class MyEntity(
4    @Id
5    val attr1: String,
6    val attr2: String,
7    val attr3: String
8)
9data class MyDTO(
10    val field1: String,
11    val field2: String
12)
13@Repository
14interface MyRepository : PagingAndSortingRepository<MyEntity, String> {
15
16    // ConverterNotFoundException is thrown when this method is called
17    @Query("MATCH (e:MyEntity {attr1: {0}.field1}) " +
18           "CREATE (e)-[l:LINK]->(n:OtherEntity {attr2: {0}.field2))")
19    fun doSomethingWithDto(dto: MyDTO)
20}
21@Node
22data class MyDTO(
23    @Id
24    val field1: String,
25    val field2: String
26)
27@Repository
28interface MyRepository : PagingAndSortingRepository<MyEntity, String> {
29    
30    // ConverterNotFoundException is thrown when this method is called
31    @Query("MATCH (e:MyEntity {attr1: $0.field1}) " +
32           "CREATE (e)-[l:LINK]->(n:OtherEntity {attr2: $0.field2))")
33    fun doSomethingWithDto(dto: MyDTO)
34}
35import mypackage.model.*
36import com.fasterxml.jackson.core.type.TypeReference
37import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
38import org.neo4j.driver.Value
39import org.neo4j.driver.Values
40import org.springframework.core.convert.TypeDescriptor
41import org.springframework.core.convert.converter.GenericConverter
42import org.springframework.core.convert.converter.GenericConverter.ConvertiblePair
43import java.util.HashSet
44
45class DtoToNeo4jValueConverter : GenericConverter {
46    override fun getConvertibleTypes(): Set<ConvertiblePair>? {
47        val convertiblePairs: MutableSet<ConvertiblePair> = HashSet()
48        convertiblePairs.add(ConvertiblePair(MyDTO::class.java, Value::class.java))
49        return convertiblePairs
50    }
51
52    override fun convert(source: Any?, sourceType: TypeDescriptor, targetType: TypeDescriptor?): Any? {
53        return if (MyDTO::class.java.isAssignableFrom(sourceType.type)) {
54            // generic way of converting an object into a map
55            val dataclassAsMap = jacksonObjectMapper().convertValue(source as MyDTO, object :
56                    TypeReference<Map<String, Any>>() {})
57            Values.value(dataclassAsMap)
58        } else null
59    }
60}
61

1org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [MyDTO] to type [org.neo4j.driver.Value]
2@Node
3data class MyEntity(
4    @Id
5    val attr1: String,
6    val attr2: String,
7    val attr3: String
8)
9data class MyDTO(
10    val field1: String,
11    val field2: String
12)
13@Repository
14interface MyRepository : PagingAndSortingRepository<MyEntity, String> {
15
16    // ConverterNotFoundException is thrown when this method is called
17    @Query("MATCH (e:MyEntity {attr1: {0}.field1}) " +
18           "CREATE (e)-[l:LINK]->(n:OtherEntity {attr2: {0}.field2))")
19    fun doSomethingWithDto(dto: MyDTO)
20}
21@Node
22data class MyDTO(
23    @Id
24    val field1: String,
25    val field2: String
26)
27@Repository
28interface MyRepository : PagingAndSortingRepository<MyEntity, String> {
29    
30    // ConverterNotFoundException is thrown when this method is called
31    @Query("MATCH (e:MyEntity {attr1: $0.field1}) " +
32           "CREATE (e)-[l:LINK]->(n:OtherEntity {attr2: $0.field2))")
33    fun doSomethingWithDto(dto: MyDTO)
34}
35import mypackage.model.*
36import com.fasterxml.jackson.core.type.TypeReference
37import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
38import org.neo4j.driver.Value
39import org.neo4j.driver.Values
40import org.springframework.core.convert.TypeDescriptor
41import org.springframework.core.convert.converter.GenericConverter
42import org.springframework.core.convert.converter.GenericConverter.ConvertiblePair
43import java.util.HashSet
44
45class DtoToNeo4jValueConverter : GenericConverter {
46    override fun getConvertibleTypes(): Set<ConvertiblePair>? {
47        val convertiblePairs: MutableSet<ConvertiblePair> = HashSet()
48        convertiblePairs.add(ConvertiblePair(MyDTO::class.java, Value::class.java))
49        return convertiblePairs
50    }
51
52    override fun convert(source: Any?, sourceType: TypeDescriptor, targetType: TypeDescriptor?): Any? {
53        return if (MyDTO::class.java.isAssignableFrom(sourceType.type)) {
54            // generic way of converting an object into a map
55            val dataclassAsMap = jacksonObjectMapper().convertValue(source as MyDTO, object :
56                    TypeReference<Map<String, Any>>() {})
57            Values.value(dataclassAsMap)
58        } else null
59    }
60}
61import org.springframework.context.annotation.Bean
62import org.springframework.context.annotation.Configuration
63import org.springframework.data.neo4j.core.convert.Neo4jConversions
64import org.springframework.core.convert.converter.GenericConverter
65import java.util.*
66
67
68@Configuration
69class MyNeo4jConfig {
70    @Bean
71    override fun neo4jConversions(): Neo4jConversions? {
72        val additionalConverters: Set<GenericConverter?> = Collections.singleton(DtoToNeo4jValueConverter())
73        return Neo4jConversions(additionalConverters)
74    }
75}
76

1| Type                    | Name           | Status   |
2| --------                | -------------- | -------- |
3| ["Thriller" , "Horror"] | Conjuring      | Released | 
4| ["Action" , "Thriller"] | Evil Dead      | Released |
5| ["Drama" , "Thriller"]  |   XYZ          | Released |
6| Type     | Name           | 
7| -------- | -------------- |
8| "Horror" | Conjuring      |     
9| "Action" | Evil Dead      |      
10| "Drama"  |   XYZ          |
11[x in type WHERE x <> "Thriller" | x]
12

1LOAD CSV FROM "https://drive.google.com/file/d/12DiEwM8XatMZBXA6TdekxWl8qrsgVj3l/view?usp=sharing" AS requests RETURN requests
2At https://drive.google.com/file/d/12DiEwM8XatMZBXA6TdekxWl8qrsgVj3l/view?usp=sharing @ position 1691 -  there's a field starting with a quote and whereas it ends that quote there seems to be characters in that field after that ending quote. That isn't supported. This is what I read: 'docs-fwds":'
3LOAD CSV WITH HEADERS FROM "https://drive.google.com/u/0/uc?id=12DiEwM8XatMZBXA6TdekxWl8qrsgVj3l&export=download" as row
4RETURN row LIMIT 5
5

1from neomodel import config
2
3user = 'neo4j'
4psw = 'awesome_password'
5uri = 'awesome.databases.neo4j.io'
6    
7config.DATABASE_URL = 'neo4j+s://{}:{}@{}'.format(user, psw, uri)
8print(config.DATABASE_URL)
9
10Result: 
11
12   neo4j+s://neo4j:awesome_password@awesome.databases.neo4j.io
13

1// order Schema
2
3export const order = gql`
4  type Order {
5    id: ID! @id
6    state: OrderState!
7    user: User! @relationship(type: "MADE", direction: IN)
8    createdAt: DateTime! @timestamp(operations: [CREATE])
9    products: [Product!] @relationship(type: "INCLUDE", direction: OUT)
10  }
11
12  enum OrderState {
13    UNAPPROVED
14    APPROVED
15    CANCELLED
16    FULFILLED
17  }
18`;
19
20export const extendOrder = gql`
21  extend input OrderCreateInput {
22    state: OrderState!
23  }
24`;
25Middleware
26
27import { ValidationError } from "apollo-server-micro";
28import { IMiddleware } from "graphql-middleware";
29import { Order } from "pages/api/graphql";
30
31export const checkStateMiddleware: IMiddleware = {
32  Mutation: {
33    updateOrders: async (resolve, parent, args, ctx, info) => {
34      const { where, update } = args;
35
36      const [existing] = await Order.find({
37        ...where,
38      });
39
40      const states = ["UNAPPROVED", "APPROVED", "CANCELLED", "FULLFIELD"];
41
42      const currentState = states.indexOf(existing.state);
43      const toBeUpdatedState = states.indexOf(update.state);
44
45      if (toBeUpdatedState < currentState) {
46        throw new ValidationError("Can't update value with previous state.");
47      }
48
49      return resolve(parent, args);
50    },
51  },
52};
53

1// order Schema
2
3export const order = gql`
4  type Order {
5    id: ID! @id
6    state: OrderState!
7    user: User! @relationship(type: "MADE", direction: IN)
8    createdAt: DateTime! @timestamp(operations: [CREATE])
9    products: [Product!] @relationship(type: "INCLUDE", direction: OUT)
10  }
11
12  enum OrderState {
13    UNAPPROVED
14    APPROVED
15    CANCELLED
16    FULFILLED
17  }
18`;
19
20export const extendOrder = gql`
21  extend input OrderCreateInput {
22    state: OrderState!
23  }
24`;
25Middleware
26
27import { ValidationError } from "apollo-server-micro";
28import { IMiddleware } from "graphql-middleware";
29import { Order } from "pages/api/graphql";
30
31export const checkStateMiddleware: IMiddleware = {
32  Mutation: {
33    updateOrders: async (resolve, parent, args, ctx, info) => {
34      const { where, update } = args;
35
36      const [existing] = await Order.find({
37        ...where,
38      });
39
40      const states = ["UNAPPROVED", "APPROVED", "CANCELLED", "FULLFIELD"];
41
42      const currentState = states.indexOf(existing.state);
43      const toBeUpdatedState = states.indexOf(update.state);
44
45      if (toBeUpdatedState < currentState) {
46        throw new ValidationError("Can't update value with previous state.");
47      }
48
49      return resolve(parent, args);
50    },
51  },
52};
53//...
54import { applyMiddleware } from "graphql-middleware";
55//...
56const schemaWithMiddleware = applyMiddleware(schema, checkStateMiddleware);
57
58const apolloServer = new ApolloServer({ schema: schemaWithMiddleware });
59//...
60

1WITH ['pepper', 'salt'] as ingredients
2MATCH (i:Ingredient)-[:INGREDIENT_OF]->(r:Recipe)
3WHERE i.name in ingredients
4WITH r, size(ingredients) as inputCnt, count(DISTINCT i) as cnt
5WHERE cnt = inputCnt
6RETURN r;
7SELECT recipe_id FROM used_in WHERE ingredient_id = ingedient1
8     AND  ingredient_id = ingedient2;
9