ListAgg

A ListAgg aggregator value variable (ListAgg<T>) aggregates all inputs into a list in insertion order, where T represents the data type of the input values. To aggregate a set of unique input values, see SetAgg.

Declaration syntax

diagramsource

list_agg_declaration

list_agg_declaration ::=
'NODE'? 'VALUE' aggregator_value_variable 'ListAgg' '<' ('INT8'|'INT16'|'INT32'|'INT64'|'FLOAT'|'DOUBLE'|'STRING'|'LIST' '<' data_type '>' |( 'RECORD' )? '{' ( (field_name data_type) ( ',' (field_name data_type) )* )? '}') '>'

Parameters

The following are the specific parameters for ListAgg aggregator value variables. For information about other parameters in the declaration syntax, see Parameters.

data_type

The data type of the value that the field holds. Supported data types include numeric, string, boolean, temporal, vector, list, record, and spatial. For more information, see Data types.

field_name

The name of a field in a record. field_name must be an identifier. For more information about identifiers, see Rules for naming identifiers.

Initial value

As indicated in the declaration syntax, an initial value must not be specified during declaration.

Input type and supported operations

The input type must be T, which is specified during declaration.

Both assignment and aggregation operations are supported.

Return type

ListAgg<T> -> LIST<T>

The return type is LIST<T>, with elements of the same type as the type T specified during declaration.

Member functions

This section introduces the member functions supported by ListAgg aggregator value variables.

size()

Returns the number of elements in the list held by a ListAgg aggregator value variable.

Function signature

size() -> UINT64

clear()

Removes all elements from the list held by a ListAgg aggregator value variable.

Function signature

clear() -> VOID

Examples

The following examples are based on the temporary graph #movie_temporary_graph created in CREATE TEMPORARY GRAPH.

Global ListAgg aggregator value variables

'''
USE #movie_temporary_graph {
  VALUE global_list_1 ListAgg<INT>
  VALUE global_list_2 ListAgg<INT>
  SET @global_list_1 += 3     // list: [3]
  SET @global_list_1 += 7     // list: [3, 7]  
  SET @global_list_1 += 5     // list: [3, 7, 5]
  LOG_INFO("@global_list_1: ", @global_list_1)

  // Assignment from empty LIST
  SET @global_list_1 = []   // Clear the list
  LOG_INFO("List from empty LIST:", @global_list_1)   // output: []

  // Assignment from a LIST 
  SET @global_list_1 = [1, 2, 2, 3, 1, 4]   // list: [1, 2, 2, 3, 1, 4]
  LOG_INFO("List from LIST assignment: ", @global_list_1)

  SET @global_list_2 += 3   // global_list_2: [3]
  SET @global_list_2 += 4   // global_list_2: [3, 4]
  LOG_INFO("@global_list_2: ", @global_list_2)

  // Assignment from another ListAgg
  SET @global_list_1 = @global_list_2         // global_list_1: [3, 4]
  LOG_INFO("After assignment from list_2: ", @global_list_1)

  // Aggregation from another ListAgg
  SET @global_list_1 += @global_list_2        // global_list_1: [3, 4, 3, 4]
  LOG_INFO("After aggregation from list_2: ", @global_list_1)

  // Member functions
  SET @global_list_2.clear()   // Clear the list 
  LOG_INFO("Clear the list: ", @global_list_2)       // Output: []
  LOG_INFO("Size: ", @global_list_1.size())       // Output: 4
}
'''

Return:

Log:
2025-08-21T02:18:53.175811 INFO  - @global_list_1: [3,7,5]
2025-08-21T02:18:53.176426 INFO  - List from empty LIST:[]
2025-08-21T02:18:53.176812 INFO  - List from LIST assignment: [1,2,2,3,1,4]
2025-08-21T02:18:53.177273 INFO  - @global_list_2: [3,4]
2025-08-21T02:18:53.177556 INFO  - After assignment from list_2: [3,4]
2025-08-21T02:18:53.177808 INFO  - After aggregation from list_2: [3,4,3,4]
2025-08-21T02:18:53.178056 INFO  - Clear the list: []
2025-08-21T02:18:53.178199 INFO  - Size: 4

Node-attached ListAgg aggregator value variables

'''
USE #movie_temporary_graph {
  NODE VALUE node_list ListAgg<DOUBLE>
  MATCH (a@User WHERE a.id IN [1,3,4])-[w@Watch]->(b@Movie)
  PER PATH {
    // For each matched path, add the movie ID to the corresponding user's list
    SET a.@node_list += b.id
  }
  PER NODE (a) {
    LOG_INFO("a.id: ", a.id, " a.@node_list: ", a.@node_list)
  }
}
'''

In the preceding example, a node-attached ListAgg aggregator value variable node_list of type ListAgg<DOUBLE> is declared to hold a list of movie IDs for each user.

Return:

Log:
2025-08-21T06:25:50.230307 INFO  - a.id: 3 a.@node_list: [473,152]
2025-08-21T06:25:50.230307 INFO  - a.id: 1 a.@node_list: [11,651,10,104,601,100,497,252,473]
2025-08-21T06:25:50.230307 INFO  - a.id: 4 a.@node_list: [99,648,671,144,146,346,637,11,10,104,252,473]