Basic Operations and Compatibility

Basic Operations

Operation	Cypher Statement
Querying vertices	match (n) return n
Querying edges	match (n)-[r]->(m) return n, r, m
Querying paths	match (n:user)-[r]->(m:movie)-->(s:series) return n,r,m,s
Querying information by specifying filtering criteria	match(n:user) where n.userid>=5 return n
Grouping and aggregating	match(n:movie) return n.genres, count(*)
Deduplicating	match(n:movie) return distinct n.genres
Sorting	match(n:movie) return n order by n.movieid
Creating a vertex	create (n:user{userid:1}) return n
Creating an edge	match (n:user{userid:15}),(m:movie{movieid:10}) create (n)-[r:rate]->(m)
Deleting a vertex	match (n:user{userid:1}) delete n
Modifying labels	match (n:user{userid:1}) set n:movie return n
Modifying properties	match (n:user{userid:1}) set n.userid=2 return n

Compatibility to Cypher

Cypher clauses

Cypher implements a couple of clauses. You can combine clauses to implement different query semantics, including vertex and edge filtering, multi-hop query, sorting and deduplication, and grouping and aggregation.

Currently, GES supports the Cypher clauses listed in the following table.

**Table 1** Supported Cypher clauses
Clause	Support	Example
match	Partially supported	match (n:movie) return n
optional match	Partially supported	optional match (n)-->(m) where id(n)='1' return m
return	Supported	return [1,2,3] as p
with	Supported	match (n) with labels(n) as label, count() as count where count > 10 return
where	Supported	match (n:movie) where n.movieid > 10 return n
order by	Supported	match (n:movie) return n order by n.genres
skip	Supported	match (n:movie) return n order by n.genres skip 5
limit	Supported	match (n:movie) return n order by n.genres skip 5 limit 10
create	Supported	create (n:user{_ID_: 'Jack' }) return n
delete	Supported	match (n:movie)<-[r]-(m:user) delete r
set	Supported	match (n:user{userid:0}) set n.gender='M' return n
call procedures	Supported	call db.schema()
unwind	Supported	unwind [1, 2, 3] as p return p
union	Supported	match (n:movie) return id(n) union match (n:user) return id(n) NOTE: Union is available for graphs smaller than 10 billion edges only.

Currently, merge and foreach operations are not supported. Cypher statements cannot add or delete indexes.
GES metadata is not schema-free, and the vertex and edge label properties are strictly restricted. Therefore, the remove operation is not supported.
The order by clause does not support sorting of the list type. When Cardinality of the property value is not single, the sorting result is unknown.

Available items for the match clause

Item	Description	Example Clauses	Earliest Version Required
Vertex pattern	Patterns for matching vertex with specified labels, properties, and IDs.	match (n:movie{title:'hello'}) match (n) where id(n)='xx'	2.2.16
Edge pattern	Patterns for matching directional and non-directional edges with specified labels and properties. Specified IDs of both start and end vertices are supported.	match (n)-[r] -> (m) match (n)-[r]- (m) match (n)-[r:rate{Rating:1}] - (m) match (n)-[r]- (m) where id(n)='x'and id(m)='y'	2.2.16
Path	Anonymous paths	match (n)-[r]->(m)-->(s)	2.2.16
Path	Named paths	match p=(n)-[r]->(m)-->(s)	2.2.19
Multiple patterns	You can enter multiple patterns after match and separate them with commas (,). match (n)-[r]->(m), (m)-->(s)		2.2.16
Multi-match	You can enter multiple match clauses. You can use with to connect multiple clauses. match (n)-[r]->(m) with m match (m)-->(s)		2.2.16
Variable-length path pattern	Patterns for matching variable-length paths starting with a specified vertex. match p=(n)-[r1..3]->(m) where id(n)='xx'return p match p=(n{title:'name'})-[r1..3]->(m) return p		2.2.19
	Traversal conditions for matching variable-length paths. match p=(n)-[r*1..3]->(m) where id(n)='xx'and all (x in nodes(p) where x.prop='value1') return p		2.2.28
	Both start vertex and end vertex of a variable-length path can be specified. match p=(n)-[r*1..3]->(m) where id(n)='xx' and id(m)='y' return p		2.3.9
	Deduplication by end vertex is not supported: match p=(n)-[r*1..3]->(m) where id(n)='xx' and id(m)='yy'return distinct m		None

Parameterized queries

Cypher supports parameterized queries. Numeric and string values in a query statement are extracted and converted to parameters for faster compilation, improving the query speed.

There are some examples of parameterized queries:

Example 1

POST http://{SERVER_URL}/ges/v1.0/{project_id}/graphs/{graph_name}/action?action_id=execute-cypher-query
{
         "statements": [{
                   "statement": " match (n:user) where n.occupation = $occupation return n",
                   "parameters": {
                         "occupation" : "artist"
                    },
                   "resultDataContents": ["row"]
         }]
}

Example 2

POST http://{SERVER_URL}/ges/v1.0/{project_id}/graphs/{graph_name}/action?action_id=execute-cypher-query
{
         "statements": [{
                   "statement": " match (n:user {`Zip-code`:'98133'}) set n = $props return n",
                   "parameters": {
                           "props": {
                           "gender": "M",
                           "age": "56+"
                        }
                    },
                   "resultDataContents": ["row"]
         }]
}

There are some scenarios where parameterized queries are not supported. The following syntax is not valid:

Using $param to search by property key and value. For example, match (n) where n.$param = 'something'
Using $code for vertex and edge labels. For example, match (n:user) set n:$code

Supported data types

Currently, GES supports 10 data types: char, char_array, float, double, Boolean, long, Integer, date, enum, and string. Both Boolean and numeric types are supported in the Cypher syntax. The following table lists the mapping between other types and Cypher data types.

**Table 2** Mapping between data types of GES and Cypher
GES	Cypher	Description
char	String	-
char_array	String	-
string	String	-
enum	String	The Cypher syntax does not provide enum-related syntax. During Cypher query, an enum is converted to a string. When Cypher is used to set properties, values that are not in the enumeration list fail to be set.
date	Temporal	Currently, Cypher dates can be converted into GES dates, but Cypher date functions cannot be used for inputting a date.

**Table 3** Special types supported by Cypher
Type	Supported	Example
Node	Yes	match (n) return n limit 10
Relationship	Yes	match (n)-[r]->(m) return r limit 10
List	Yes	return [1,2,3] as li
Map	Yes	match (n)-->(m) return {start:id(n), end:id(m)}
Path	Yes	match p=(n1)-[:friends*1..2]-(n2) return p limit 10
Point, Spatial	No	-

For the special types listed above, only the List type can be used to match multi-value properties in GES. Other types cannot be used in a set statement for setting the value of a property.

Vertex ID compatibility
- Cypher does not provide the syntax for setting the ID when a vertex is added. In GES, however, an ID of the string type is required to uniquely identify a vertex. To use the Cypher syntax in GES, add _ID_ to specify the ID of a vertex in the create statement. For example, the create(n{_ID_:'123456'}) statement creates a vertex whose ID is 123456.
- If the ID is not specified, a random ID is generated for the vertex.
  
  The _ID_ identifier is supported only in the create statement. The match and set clauses do not support the _ID_ identifier. In the match clause, you can use the id() function to obtain the vertex ID.