GQL functions

All GoogleSQL functions are supported, including the following GQL-specific functions:

Function list

Name	Summary
`DESTINATION_NODE_ID`	Gets a unique identifier of a graph edge's destination node.
`EDGES`	Gets the edges in a graph path. The resulting array retains the original order in the graph path.
`ELEMENT_ID`	Gets a graph element's unique identifier.
`LABELS`	Gets the labels associated with a graph element.
`NODES`	Gets the nodes in a graph path. The resulting array retains the original order in the graph path.
`PATH_FIRST`	Gets the first node in a graph path.
`PATH_LAST`	Gets the last node in a graph path.
`PATH_LENGTH`	Gets the number of edges in a graph path.
`SOURCE_NODE_ID`	Gets a unique identifier of a graph edge's source node.

`DESTINATION_NODE_ID`

DESTINATION_NODE_ID(edge_element)

Description

Gets a unique identifier of a graph edge's destination node. The unique identifier is only valid for the scope of the query where it's obtained.

Definitions

edge_element: A GRAPH_ELEMENT value that represents an edge.

Details

Returns NULL if edge_element is NULL.

Return type

STRING

Examples

GRAPH graph_db.FinGraph
MATCH (:Person)-[o:Owns]->(a:Account)
RETURN a.id AS account_id, DESTINATION_NODE_ID(o) AS destination_node_id

/*------------------------------------------+
 |account_id | destination_node_id          |
 +-----------|------------------------------+
 | 7         | mUZpbkdyYXBoLkFjY291bnQAeJEO |
 | 16        | mUZpbkdyYXBoLkFjY291bnQAeJEg |
 | 20        | mUZpbkdyYXBoLkFjY291bnQAeJEo |
 +------------------------------------------*/

Note that the actual identifiers obtained may be different from what's shown above.

`EDGES`

EDGES(graph_path)

Description

Gets the edges in a graph path. The resulting array retains the original order in the graph path.

Definitions

graph_path: A GRAPH_PATH value that represents a graph path.

Details

If graph_path is NULL, returns NULL.

Return type

ARRAY<GRAPH_ELEMENT>

Examples

GRAPH graph_db.FinGraph
MATCH p=(src:Account)-[t1:Transfers]->(mid:Account)-[t2:Transfers]->(dst:Account)
LET es = EDGES(p)
RETURN TO_JSON(es) AS edges

`ELEMENT_ID`

ELEMENT_ID(element)

Description

Gets a graph element's unique identifier. The unique identifier is only valid for the scope of the query where it's obtained.

Definitions

element: A GRAPH_ELEMENT value.

Details

Returns NULL if element is NULL.

Return type

STRING

Examples

GRAPH graph_db.FinGraph
MATCH (p:Person)-[o:Owns]->(:Account)
RETURN p.name AS name, ELEMENT_ID(p) AS node_element_id, ELEMENT_ID(o) AS edge_element_id

/*--------------------------------------------------------------------------------------------------------------------------------------------+
 | name | node_element_id              | edge_element_id                                                                                      |
 +------|------------------------------|------------------------------------------------------------------------------------------------------+
 | Alex | mUZpbkdyYXBoLlBlcnNvbgB4kQI= | mUZpbkdyYXBoLlBlcnNvbk93bkFjY291bnQAeJECkQ6ZRmluR3JhcGguUGVyc29uAHiRAplGaW5HcmFwaC5BY2NvdW50AHiRDg== |
 | Dana | mUZpbkdyYXBoLlBlcnNvbgB4kQQ= | mUZpbkdyYXBoLlBlcnNvbk93bkFjY291bnQAeJEGkSCZRmluR3JhcGguUGVyc29uAHiRBplGaW5HcmFwaC5BY2NvdW50AHiRIA== |
 | Lee  | mUZpbkdyYXBoLlBlcnNvbgB4kQY= | mUZpbkdyYXBoLlBlcnNvbk93bkFjY291bnQAeJEEkSiZRmluR3JhcGguUGVyc29uAHiRBJlGaW5HcmFwaC5BY2NvdW50AHiRKA== |
 +--------------------------------------------------------------------------------------------------------------------------------------------*/

Note that the actual identifiers obtained may be different from what's shown above.

`LABELS`

LABELS(element)

Description

Gets the labels associated with a graph element and preserves the original case of each label.

Definitions

element: A GRAPH_ELEMENT value that represents the graph element to extract labels from.

Details

Returns NULL if element is NULL.

Return type

ARRAY<STRING>

Examples

GRAPH graph_db.FinGraph
MATCH (n:Person|Account)
RETURN LABELS(n) AS label, n.id

/*----------------+
 | label     | id |
 +----------------+
 | [Account] | 7  |
 | [Account] | 16 |
 | [Account] | 20 |
 | [Person]  | 1  |
 | [Person]  | 2  |
 | [Person]  | 3  |
 +----------------*/

`NODES`

NODES(graph_path)

Description

Gets the nodes in a graph path. The resulting array retains the original order in the graph path.

Definitions

graph_path: A GRAPH_PATH value that represents a graph path.

Details

Returns NULL if graph_path is NULL.

Return type

ARRAY<GRAPH_ELEMENT>

Examples

GRAPH graph_db.FinGraph
MATCH p=(src:Account)-[t1:Transfers]->(mid:Account)-[t2:Transfers]->(dst:Account)
LET ns = NODES(p)
RETURN
  JSON_QUERY(TO_JSON(ns)[0], '$.labels') AS labels,
  JSON_QUERY(TO_JSON(ns)[0], '$.properties.nick_name') AS nick_name;

/*--------------------------------+
 | labels      | nick_name        |
 +--------------------------------+
 | ["Account"] | "Vacation Fund"  |
 | ["Account"] | "Rainy Day Fund" |
 | ["Account"] | "Rainy Day Fund" |
 | ["Account"] | "Rainy Day Fund" |
 | ["Account"] | "Vacation Fund"  |
 | ["Account"] | "Vacation Fund"  |
 | ["Account"] | "Vacation Fund"  |
 | ["Account"] | "Rainy Day Fund" |
 +--------------------------------*/

`PATH_FIRST`

PATH_FIRST(graph_path)

Description

Gets the first node in a graph path.

Definitions

graph_path: A GRAPH_PATH value that represents the graph path to extract the first node from.

Details

Returns NULL if graph_path is NULL.

Return type

GRAPH_ELEMENT

Examples

GRAPH graph_db.FinGraph
MATCH p=(src:Account)-[t1:Transfers]->(mid:Account)-[t2:Transfers]->(dst:Account)
LET f = PATH_FIRST(p)
RETURN
  LABELS(f) AS labels,
  f.nick_name AS nick_name;

/*--------------------------+
 | labels  | nick_name      |
 +--------------------------+
 | Account | Vacation Fund  |
 | Account | Rainy Day Fund |
 | Account | Rainy Day Fund |
 | Account | Vacation Fund  |
 | Account | Vacation Fund  |
 | Account | Vacation Fund  |
 | Account | Rainy Day Fund |
 +--------------------------*/

`PATH_LAST`

PATH_LAST(graph_path)

Description

Gets the last node in a graph path.

Definitions

graph_path: A GRAPH_PATH value that represents the graph path to extract the last node from.

Details

Returns NULL if graph_path is NULL.

Return type

GRAPH_ELEMENT

Examples

GRAPH graph_db.FinGraph
MATCH p=(src:Account)-[t1:Transfers]->(mid:Account)-[t2:Transfers]->(dst:Account)
LET f = PATH_LAST(p)
RETURN
  LABELS(f) AS labels,
  f.nick_name AS nick_name;

/*--------------------------+
 | labels  | nick_name      |
 +--------------------------+
 | Account | Vacation Fund  |
 | Account | Vacation Fund  |
 | Account | Vacation Fund  |
 | Account | Vacation Fund  |
 | Account | Rainy Day Fund |
 | Account | Rainy Day Fund |
 | Account | Rainy Day Fund |
 +--------------------------*/

`PATH_LENGTH`

PATH_LENGTH(graph_path)

Description

Gets the number of edges in a graph path.

Definitions

graph_path: A GRAPH_PATH value that represents the graph path with the edges to count.

Details

Returns NULL if graph_path is NULL.

Return type

INT64

Examples

GRAPH graph_db.FinGraph
MATCH p=(src:Account)-[t1:Transfers]->(mid:Account)-[t2:Transfers]->(dst:Account)
RETURN PATH_LENGTH(p) AS results

/*---------+
 | results |
 +---------+
 | 2       |
 | 2       |
 | 2       |
 | 2       |
 | 2       |
 | 2       |
 | 2       |
 +---------*/

`SOURCE_NODE_ID`

SOURCE_NODE_ID(edge_element)

Description

Gets a unique identifier of a graph edge's source node. The unique identifier is only valid for the scope of the query where it's obtained.

Definitions

edge_element: A GRAPH_ELEMENT value that represents an edge.

Details

Returns NULL if edge_element is NULL.

Return type

STRING

Examples

GRAPH graph_db.FinGraph
MATCH (p:Person)-[o:Owns]->(:Account)
RETURN p.name AS name, SOURCE_NODE_ID(o) AS source_node_id

/*-------------------------------------+
 | name | source_node_id               |
 +------|------------------------------+
 | Alex | mUZpbkdyYXBoLlBlcnNvbgB4kQI= |
 | Dana | mUZpbkdyYXBoLlBlcnNvbgB4kQQ= |
 | Lee  | mUZpbkdyYXBoLlBlcnNvbgB4kQY= |
 +-------------------------------------*/

Note that the actual identifiers obtained may be different from what's shown above.

Supplemental materials

Horizontal aggregate function calls in GQL

In GQL, a horizontal aggregate function is an aggregate function that summarizes the contents of exactly one array-typed value. Because a horizontal aggregate function doesn't need to aggregate vertically across rows like a traditional aggregate function, you can use it like a normal function expression. Horizontal aggregates are only allowed in certain syntactic contexts: LET, FILTER statements or WHERE clauses.

Horizontal aggregation is especially useful when paired with a group variable. You can create a group variable inside a quantified path pattern in a linear graph query.

Some aggregates use an ORDER BY clause, such as the ARRAY_AGG, STRING_AGG, and ARRAY_CONCAT_AGG functions. For these aggregates the system orders inputs by their position in the array if you don't provide an ORDER BY clause.

Syntactic restrictions

The argument to the aggregate function must reference exactly one array-typed value.
Can be used in LET, FILTER statements, or WHERE clauses only.
Nesting horizontal aggregates isn't allowed.

Examples

In the following query, the SUM function horizontally aggregates over an array (arr), and then produces the sum of the values in arr:

GRAPH graph_db.FinGraph
LET arr = [1, 2, 3]
LET total = SUM(arr)
RETURN total

/*-------+
 | total |
 +-------+
 | 6     |
 +-------*/

In the following query, the SUM function horizontally aggregates over an array of structs (arr), and then produces the sum of the x fields in the array:

GRAPH graph_db.FinGraph
LET arr = [STRUCT(1 as x, 10 as y), STRUCT(2, 9), STRUCT(3, 8)]
LET total = SUM(arr.x)
RETURN total

/*-------+
 | total |
 +-------+
 | 6     |
 +-------*/

In the following query, the AVG function horizontally aggregates over an array of structs (arr), and then produces the average of the x and y fields in the array:

GRAPH graph_db.FinGraph
LET arr = [STRUCT(1 as x, 10 as y), STRUCT(2, 9), STRUCT(3, 8)]
LET avg_sum = AVG(arr.x + arr.y)
RETURN avg_sum

/*---------+
 | avg_sum |
 +---------+
 | 11      |
 +---------*/

The ARRAY_AGG function can be used as a projection when horizontally aggregating. The resulting array is in the same order as the array that's horizontally aggregated over.

GRAPH graph_db.FinGraph
LET arr = [STRUCT(1 as x, 9 as y), STRUCT(2, 9), STRUCT(4, 8)]
LET result = ARRAY_AGG(arr.x + arr.y)
RETURN result

/*--------------+
 | result       |
 +--------------+
 | [10, 11, 12] |
 +--------------*/

The following query produces an error because two arrays were passed into the AVG aggregate function:

-- ERROR: Horizontal aggregation on more than one array-typed variable
-- isn't allowed
GRAPH graph_db.FinGraph
LET arr1 = [1, 2, 3]
LET arr2 = [5, 4, 3]
LET avg_val = AVG(arr1 + arr2)
RETURN avg_val

The following query demonstrates a common pitfall. All instances of the array that is horizontally aggregated over are treated as a single element from that array in the aggregate.

To resolve this error, move expressions that use the entire array outside of the horizontal aggregation.

-- ERROR: No matching signature for function ARRAY_LENGTH for argument types: INT64
GRAPH graph_db.FinGraph
LET arr1 = [1, 2, 3]
LET bad_avg_val = SUM(arr1 / ARRAY_LENGTH(arr1))
RETURN bad_avg_val

The fix:

GRAPH graph_db.FinGraph
LET arr1 = [1, 2, 3]
LET len = ARRAY_LENGTH(arr1)
LET avg_val = SUM(arr1 / len)
RETURN avg_val

In the following query, the COUNT function counts the unique amount transfers with one to three hops between a source account (src) and a destination account (dst):

GRAPH graph_db.FinGraph
MATCH (src:Account)-[e:Transfers]->{1, 3}(dst:Account)
WHERE src != dst
LET num_transfers = COUNT(e)
LET unique_amount_transfers = COUNT(DISTINCT e.amount)
FILTER unique_amount_transfers != num_transfers
RETURN src.id as src_id, num_transfers, unique_amount_transfers, dst.id AS destination_account_id

/*---------------------------------------------------------------------------+
 | src_id | num_transfers | unique_transfers_amount | destination_account_id |
 +---------------------------------------------------------------------------+
 | 7      | 3             | 2                       | 16                     |
 | 20     | 3             | 2                       | 16                     |
 | 7      | 2             | 1                       | 20                     |
 | 16     | 3             | 2                       | 20                     |
 +---------------------------------------------------------------------------*/

In the following query, the SUM function takes a group variable called e that represents an array of transfers, and then sums the amount for each transfer. Horizontal aggregation isn't allowed in the RETURN statement. ARRAY_AGG is a vertical aggregate over the result set, which is grouped implicitly by the non-aggregated columns (source_account_id, destination_account_id). ARRAY_AGG produces one row for each distinct destination account.

GRAPH graph_db.FinGraph
MATCH (src:Account {id: 7})-[e:Transfers]->{1,2}(dst:Account)
LET total_amount = SUM(e.amount)
RETURN
  src.id AS source_account_id, dst.id AS destination_account_id,
  ARRAY_AGG(total_amount) as total_amounts_per_path

/*---------------------------------------------------------------------+
 | source_account_id | destination_account_id | total_amounts_per_path |
 +---------------------------------------------------------------------+
 | 7                 | 16                     | [300, 100]             |
 | 7                 | 20                     | [600, 400]             |
 +---------------------------------------------------------------------*/

GQL functions Stay organized with collections Save and categorize content based on your preferences.

Function list

DESTINATION_NODE_ID

EDGES

ELEMENT_ID

LABELS

NODES

PATH_FIRST

PATH_LAST

PATH_LENGTH

SOURCE_NODE_ID

Supplemental materials

Horizontal aggregate function calls in GQL

Syntactic restrictions

Examples

GQL functions

`DESTINATION_NODE_ID`

`EDGES`

`ELEMENT_ID`

`LABELS`

`NODES`

`PATH_FIRST`

`PATH_LAST`

`PATH_LENGTH`

`SOURCE_NODE_ID`