linkOn Create Set / On Match Set

QueryBuilderParameters['OnCreateSetI'] / QueryBuilderParameters['OnMatchSetI']

The ON CREATE SET and ON MATCH SET clauses are used with MERGE to specify different actions depending on whether the pattern was created or matched.

linkOn Create Set

Sets properties when a new node is created by a MERGE statement.

linkOn Create Set by using a literal string

A literal string will be used as is.

1linkconst queryBuilder = new QueryBuilder()

2link    .merge({

3link        identifier: 'n',

4link        label: 'Person',

5link        properties: { name: 'John' }

6link    })

7link    .onCreateSet('n.created = timestamp()') /* --> literal string to use */

8link    .return('n.name, n.created');

9link

10linkconsole.log(queryBuilder.getStatement());

11link// MERGE (n:Person { name: $name }) ON CREATE SET n.created = timestamp() RETURN n.name, n.created

12link

13linkconsole.log(queryBuilder.getBindParam().get());

14link// { name: 'John' }

linkOn Create Set by using an object

An ON CREATE SET statement can be generated using an object with an identifier and properties.

1linkconst queryBuilder = new QueryBuilder()

2link    .merge({

3link        identifier: 'n',

4link        label: 'User',

5link        properties: { email: 'test@example.com' }

6link    })

7link    .onCreateSet({

8link        /* --> identifier whose properties will be set */

9link        identifier: 'n',

10link        /* --> properties to set when created */

11link        properties: {

12link            createdAt: '2024-01-01',

13link            status: 'pending',

14link        },

15link    })

16link    .return('n');

17link

18linkconsole.log(queryBuilder.getStatement());

19link// MERGE (n:User { email: $email }) ON CREATE SET n.createdAt = $createdAt, n.status = $status RETURN n

20link

21linkconsole.log(queryBuilder.getBindParam().get());

22link// { email: 'test@example.com', createdAt: '2024-01-01', status: 'pending' }

linkOn Create Set with Literal for Cypher functions

You can use the Literal class to include Cypher functions that should not be parameterized.

1linkconst queryBuilder = new QueryBuilder()

2link    .merge({

3link        identifier: 'n',

4link        label: 'Person',

5link        properties: { name: 'John' }

6link    })

7link    .onCreateSet({

8link        identifier: 'n',

9link        properties: {

10link            created: new Literal('timestamp()'),

11link            version: 1,

12link        },

13link    })

14link    .return('n');

15link

16linkconsole.log(queryBuilder.getStatement());

17link// MERGE (n:Person { name: $name }) ON CREATE SET n.created = timestamp(), n.version = $version RETURN n

18link

19linkconsole.log(queryBuilder.getBindParam().get());

20link// { name: 'John', version: 1 }

linkOn Match Set

Sets properties when an existing node is matched by a MERGE statement.

linkOn Match Set by using a literal string

A literal string will be used as is.

1linkconst queryBuilder = new QueryBuilder()

2link    .merge({

3link        identifier: 'n',

4link        label: 'Counter',

5link        properties: { name: 'pageViews' }

6link    })

7link    .onMatchSet('n.count = n.count + 1') /* --> literal string to use */

8link    .return('n');

9link

10linkconsole.log(queryBuilder.getStatement());

11link// MERGE (n:Counter { name: $name }) ON MATCH SET n.count = n.count + 1 RETURN n

12link

13linkconsole.log(queryBuilder.getBindParam().get());

14link// { name: 'pageViews' }

linkOn Match Set by using an object

An ON MATCH SET statement can be generated using an object with an identifier and properties.

1linkconst queryBuilder = new QueryBuilder()

2link    .merge({

3link        identifier: 'n',

4link        label: 'User',

5link        properties: { email: 'test@example.com' }

6link    })

7link    .onMatchSet({

8link        /* --> identifier whose properties will be set */

9link        identifier: 'n',

10link        /* --> properties to set when matched */

11link        properties: {

12link            lastLogin: '2024-01-01',

13link            loginCount: 5,

14link        },

15link    })

16link    .return('n');

17link

18linkconsole.log(queryBuilder.getStatement());

19link// MERGE (n:User { email: $email }) ON MATCH SET n.lastLogin = $lastLogin, n.loginCount = $loginCount RETURN n

20link

21linkconsole.log(queryBuilder.getBindParam().get());

22link// { email: 'test@example.com', lastLogin: '2024-01-01', loginCount: 5 }

linkOn Match Set with Literal for increment expressions

You can use the Literal class to include expressions like incrementing a counter.

1linkconst queryBuilder = new QueryBuilder()

2link    .merge({

3link        identifier: 'n',

4link        label: 'Counter',

5link        properties: { name: 'pageViews' }

6link    })

7link    .onMatchSet({

8link        identifier: 'n',

9link        properties: {

10link            count: new Literal('n.count + 1'),

11link            lastUpdated: new Literal('timestamp()'),

12link        },

13link    })

14link    .return('n');

15link

16linkconsole.log(queryBuilder.getStatement());

17link// MERGE (n:Counter { name: $name }) ON MATCH SET n.count = n.count + 1, n.lastUpdated = timestamp() RETURN n

18link

19linkconsole.log(queryBuilder.getBindParam().get());

20link// { name: 'pageViews' }

linkUsing On Create Set and On Match Set together

You can combine both clauses to handle creation and matching differently.

1linkconst queryBuilder = new QueryBuilder()

2link    .merge({

3link        identifier: 'n',

4link        label: 'Counter',

5link        properties: { name: 'pageViews' }

6link    })

7link    .onCreateSet({

8link        identifier: 'n',

9link        properties: {

10link            count: 1,

11link            created: new Literal('timestamp()'),

12link        },

13link    })

14link    .onMatchSet({

15link        identifier: 'n',

16link        properties: {

17link            count: new Literal('n.count + 1'),

18link            lastUpdated: new Literal('timestamp()'),

19link        },

20link    })

21link    .return('n');

22link

23linkconsole.log(queryBuilder.getStatement());

24link// MERGE (n:Counter { name: $name }) ON CREATE SET n.count = $count, n.created = timestamp() ON MATCH SET n.count = n.count + 1, n.lastUpdated = timestamp() RETURN n

25link

26linkconsole.log(queryBuilder.getBindParam().get());

27link// { name: 'pageViews', count: 1 }

This pattern is commonly used for:

• Counters: Initialize to 1 on create, increment on match
• Timestamps: Set created on create, set lastUpdated on match
• Status tracking: Set initial status on create, update status on match