Schema-related functions¶
This topic describes the schema-related functions supported by NebulaGraph. There are two types of schema-related functions, one for native nGQL statements and the other for openCypher-compatible statements.
For nGQL statements¶
The following functions are available in YIELD and WHERE clauses of nGQL statements.
Note
Since vertex, edge, vertices, edges, and path are keywords, you need to use AS <alias> to set the alias, such as GO FROM "player100" OVER follow YIELD edge AS e;.
id(vertex)¶
id(vertex) returns the ID of a vertex.
Syntax: id(vertex)
- Result type: Same as the vertex ID.
Example:
nebula> LOOKUP ON player WHERE player.age > 45 YIELD id(vertex);
+-------------+
| id(VERTEX) |
+-------------+
| "player144" |
| "player140" |
+-------------+
properties(vertex)¶
properties(vertex) returns the properties of a vertex.
Syntax: properties(vertex)
- Result type: Map
Example:
nebula> LOOKUP ON player WHERE player.age > 45 \
YIELD properties(vertex);
+-------------------------------------+
| properties(VERTEX) |
+-------------------------------------+
| {age: 47, name: "Shaquille O'Neal"} |
| {age: 46, name: "Grant Hill"} |
+-------------------------------------+
properties(edge)¶
properties(edge) returns the properties of an edge.
Syntax: properties(edge)
- Result type: Map
Example:
nebula> GO FROM "player100" OVER follow \
YIELD properties(edge);
+------------------+
| properties(EDGE) |
+------------------+
| {degree: 95} |
| {degree: 95} |
+------------------+
type(edge)¶
type(edge) returns the edge type of an edge.
Syntax: type(edge)
- Result type: String
Example:
nebula> GO FROM "player100" OVER follow \
YIELD src(edge), dst(edge), type(edge), rank(edge);
+-------------+-------------+------------+------------+
| src(EDGE) | dst(EDGE) | type(EDGE) | rank(EDGE) |
+-------------+-------------+------------+------------+
| "player100" | "player101" | "follow" | 0 |
| "player100" | "player125" | "follow" | 0 |
+-------------+-------------+------------+------------+
src(edge)¶
src(edge) returns the source vertex ID of an edge.
Syntax: src(edge)
- Result type: Same as the vertex ID.
Example:
nebula> GO FROM "player100" OVER follow \
YIELD src(edge), dst(edge);
+-------------+-------------+
| src(EDGE) | dst(EDGE) |
+-------------+-------------+
| "player100" | "player101" |
| "player100" | "player125" |
+-------------+-------------+
Note
The semantics of the query for the starting vertex with src(edge) and properties($^) are different. src(edge) indicates the starting vertex ID of the edge in the graph database, while properties($^) indicates the data of the starting vertex where you start to expand the graph, such as the data of the starting vertex player100 in the above GO statement.
dst(edge)¶
dst(edge) returns the destination vertex ID of an edge.
Syntax: dst(edge)
- Result type: Same as the vertex ID.
Example:
nebula> GO FROM "player100" OVER follow \
YIELD src(edge), dst(edge);
+-------------+-------------+
| src(EDGE) | dst(EDGE) |
+-------------+-------------+
| "player100" | "player101" |
| "player100" | "player125" |
+-------------+-------------+
Note
dst(edge) indicates the destination vertex ID of the edge in the graph database.
rank(edge)¶
rank(edge) returns the rank value of an edge.
Syntax: rank(edge)
- Result type: Int
Example:
nebula> GO FROM "player100" OVER follow \
YIELD src(edge), dst(edge), rank(edge);
+-------------+-------------+------------+
| src(EDGE) | dst(EDGE) | rank(EDGE) |
+-------------+-------------+------------+
| "player100" | "player101" | 0 |
| "player100" | "player125" | 0 |
+-------------+-------------+------------+
vertex¶
vertex returns the information of vertices, including VIDs, tags, properties, and values. You need to use AS <alias> to set the alias.
Syntax: vertex
Example:
nebula> LOOKUP ON player WHERE player.age > 45 YIELD vertex AS v;
+----------------------------------------------------------+
| v |
+----------------------------------------------------------+
| ("player144" :player{age: 47, name: "Shaquille O'Neal"}) |
| ("player140" :player{age: 46, name: "Grant Hill"}) |
+----------------------------------------------------------+
edge¶
edge returns the information of edges, including edge types, source vertices, destination vertices, ranks, properties, and values. You need to use AS <alias> to set the alias.
Syntax: edge
Example:
nebula> GO FROM "player100" OVER follow YIELD edge AS e;
+----------------------------------------------------+
| e |
+----------------------------------------------------+
| [:follow "player100"->"player101" @0 {degree: 95}] |
| [:follow "player100"->"player125" @0 {degree: 95}] |
+----------------------------------------------------+
vertices¶
vertices returns the information of vertices in a subgraph. For more information, see GET SUBGRAPH.
edges¶
edges returns the information of edges in a subgraph. For more information, see GET SUBGRAPH.
path¶
path returns the information of a path. For more information, see FIND PATH.
For statements compatible with openCypher¶
The following functions are available in RETURN and WHERE clauses of openCypher-compatible statements.
id()¶
id() returns the ID of a vertex.
Syntax: id(<vertex>)
- Result type: Same as the vertex ID.
Example:
nebula> MATCH (v:player) RETURN id(v);
+-------------+
| id(v) |
+-------------+
| "player129" |
| "player115" |
| "player106" |
| "player102" |
...
tags() and labels()¶
tags() and labels() return the Tag of a vertex.
Syntax: tags(<vertex>), labels(<vertex>)
- Result type: List
Example:
nebula> MATCH (v) WHERE id(v) == "player100" \
RETURN tags(v);
+------------+
| tags(v) |
+------------+
| ["player"] |
+------------+
properties()¶
properties() returns the properties of a vertex or an edge.
Syntax: properties(<vertex_or_edge>)
- Result type: Map
Example:
nebula> MATCH (v:player)-[e:follow]-() RETURN properties(v),properties(e);
+---------------------------------------+---------------+
| properties(v) | properties(e) |
+---------------------------------------+---------------+
| {age: 31, name: "Stephen Curry"} | {degree: 90} |
| {age: 47, name: "Shaquille O'Neal"} | {degree: 100} |
| {age: 34, name: "LeBron James"} | {degree: 13} |
...
type()¶
type() returns the edge type of an edge.
Syntax: type(<edge>)
- Result type: String
Example:
nebula> MATCH (v:player{name:"Tim Duncan"})-[e]->() \
RETURN type(e);
+----------+
| type(e) |
+----------+
| "serve" |
| "follow" |
| "follow" |
+----------+
src()¶
src() returns the source vertex ID of an edge.
Syntax: src(<edge>)
- Result type: Same as the vertex ID.
Example:
nebula> MATCH ()-[e]->(v:player{name:"Tim Duncan"}) \
RETURN src(e);
+-------------+
| src(e) |
+-------------+
| "player125" |
| "player113" |
| "player102" |
...
dst()¶
dst() returns the destination vertex ID of an edge.
Syntax: dst(<edge>)
- Result type: Same as the vertex ID.
Example:
nebula> MATCH (v:player{name:"Tim Duncan"})-[e]->() \
RETURN dst(e);
+-------------+
| dst(e) |
+-------------+
| "team204" |
| "player101" |
| "player125" |
+-------------+
startNode()¶
startNode() visits a path and returns its information of source vertex ID, including VIDs, tags, properties, and values.
Syntax: startNode(<path>)
Example:
nebula> MATCH p = (a :player {name : "Tim Duncan"})-[r:serve]-(t) \
RETURN startNode(p);
+----------------------------------------------------+
| startNode(p) |
+----------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) |
+----------------------------------------------------+
endNode()¶
endNode() visits a path and returns its information of destination vertex ID, including VIDs, tags, properties, and values.
Syntax: endNode(<path>)
Example:
nebula> MATCH p = (a :player {name : "Tim Duncan"})-[r:serve]-(t) \
RETURN endNode(p);
+----------------------------------+
| endNode(p) |
+----------------------------------+
| ("team204" :team{name: "Spurs"}) |
+----------------------------------+
rank()¶
rank() returns the rank value of an edge.
Syntax: rank(<edge>)
- Result type: Int
Example:
nebula> MATCH (v:player{name:"Tim Duncan"})-[e]->() \
RETURN rank(e);
+---------+
| rank(e) |
+---------+
| 0 |
| 0 |
| 0 |
+---------+