GQL Syntax

Supported GQL Clauses

GES supports the following GQL clauses:

1. Currently, multi-graph joint query and the USE GRAPH semantics are not supported.
2. The SELECT... FROM... GROUP BY... HAVING clause is not supported.
3. The at schema operation is not supported.
4. Currently, only the union operation is supported for the result set. The set operation semantics such as except, intersect, and otherwise are not supported.
5. The keyword call can only be followed by a procedure name. Subqueries of the call style are not supported.

Pattern Matching

In GQL, pattern matching generally refers to Cypher. Patterns described in the following table that do not include the match keyword are graph patterns within the match clause.

1. The optional keyword cannot be followed by a subquery enclosed in curly braces.
2. The SHORTEST and GROUP keywords cannot follow the match keyword.
3. The keep keyword is not currently supported.

Path Mode

In the match statement, you can input several graph patterns representing multiple paths, with each path separated by commas. GQL supports the following four path modes, which are configured as optional keywords before the graph pattern. If no keyword is configured, the default value walk is used.

Supported Types

1. The mapping between basic data types in GQL and GES types is as follows:

   Table 4 GQL basic types

   GQL Type	GES Type	Remarks
   bool	Boolean	-
   string	string, char array, and enum	-
   int32	Integer	-
   int64	long	-
   float	float	-
   double	double	-
   datetime	date	The smallest time unit supported in GES is second.

2. Additionally, there are some complex types in GQL, with their construction methods and GES support detailed as follows:

   Table 5 GQL complex types

   GQL Type	Support	Example
   vertex/node	Supported	match (n) return n
   edge/ relationship	Supported	match (n)-[r]->(m) return r
   array/list	Supported	return [1,2,3] as li
   record	Supported	match (n)-->(m) return {start:id(n), end:id(m)}
   path	Supported	match p=(n1)-[:friends]-{1,2}(n2) return p limit 10

   

   1. Among the complex types mentioned in GQL complex types, only List can be used to correspond to multi-valued properties in GES. Other types cannot be assigned as values to properties on vertices or edges using the SET statement.
   2. Currently, the path type can be created using the match statement, but connecting multiple paths or constructing a path from vertices and edges is not yet supported.
   3. Display construction and assignment for graph and table objects are currently unsupported.
   4. Support for the Duration type compliant with the GQL standard is also unavailable.

Supported Expressions and Functions

1. GQL supports the expressions and functions in Supported Expressions, Functions, and Procedures. GQL also supports the following functions.

   Table 6 Functions supported by GQL

   Function	Corresponding Cypher Function	Description	Example
   collect_list	collect	Aggregate function, which collects results into a list.	match (n:movie) return n.genres, collect_list(n) as movieList
   element_id	id	Obtains the vertex or edge ID.	match (n) where element_id(n)= '0' return n
   character_length	size	Obtains the length of a string.	return character_length('abc')
   path_length	length	Obtains the path length.	match p=TRAIL (n)--{1,2}(m) where id(n)='0' return path_length(p)

2. The following expressions are supported:

   Table 7 Expressions supported by GQL

   Expression	Description	Example
   ||	Supports concatenation between lists and between strings.	return 'abc'||'de', [1,2]||[3,4]

3. Supports GQL-style value type predicate expressions.

   Table 8 Judgment expressions supported by GQL

   Category	Type Keyword	Example
   Basic type determination	Boolean, string, int, long, float,double, datetime,node,edge,path,list,record	let a=1 return a is ::int
   Nested type determination	list	let a=[1,2] return a is ::list<int>
   Union type	any Note: any<int|string|long> indicates that a type is one of int, string, and long.	for a in [1,2,'a1'] return a is ::any<int|string|long>

   

   Currently, mod and trigonometric functions are not supported.

Index Support

Currently, GQL supports vertex indexes with hasLabel set to true and supports single-value matching and multi-value matching. For details about how to create and edit indexes, refer to Index Operation APIs.

Example:

The indexes in the above table serve as an example. The following queries can utilize the indexes:

When performing EXPLAIN or PROFILE on a query statement that utilizes an index, the NodeIndexSeek operator is printed, indicating that the index was used for the query.