This page introduces statements for managing graphs in a database.

Showing Graphs

The SHOW GRAPH statement retrieves information about all graphs in the database.

SHOW GRAPH

The information about graphs is organized into tables _graph, _graph_shard_1, _graph_shard_2, and so on:

• The _graph table contains all graphs in the database.
• Each _graph_shard_<N> table contains the graphs that have data stored in the shard with id <N>.

Each table includes fields that provide essential details about each graph:

Creating Graphs

The CREATE GRAPH statement creates new graphs in the database.

<create graph statement> ::= 
  "CREATE GRAPH" <graph name> <graph structure> <graph sharding> <graph description>

<graph structure> ::= 
  "{" [ <element schemas> ] "}"

<element schemas> ::=
  <element schema> [ { "," <element schema> }... ]
  
<element schema> ::=
  <node schema> | <edge schema>
    
<node schema> ::=
  "NODE" [ "TYPE" ] <node schema name> "(" <property types> ")"

<edge schema> ::=
  "EDGE" [ "TYPE" ] <edge schema name> "()-[" <property types> "]->()"
  
<property types> ::= 
  "{" <property type> [ { "," <property type> }... ] "}"

<property type> ::= 
  <property name> <property value type>
  
<graph sharding> ::= 
  "PARTITION BY" <hash function> "SHARDS" <shard id list> 
    
<graph description> ::=
  "COMMENTS" <description string>

When creating a graph, you can specify four components:

To create a graph g1 with the following specifications:

• Node schemas: User and Club
• Edge schemas: Follows and Joins
• Sharding: Data distributed across shards 1, 2, and 3 using the Crc32 hash function

CREATE GRAPH g1 { 
  NODE User ({name string, gender string}),
  NODE Club ({name string, since uint32}),
  EDGE Follows ()-[{createdOn datetime}]->(),
  EDGE Joins ()-[{memberNo uint64}]->()
} PARTITION BY HASH(Crc32) SHARDS [1,2,3] COMMENT 'My first graph'

To create a graph g2 with node and edge schemas only:

CREATE GRAPH g2 { 
  NODE User (),
  NODE Club (),
  EDGE Joins ()-[{}]->()
} PARTITION BY HASH(Crc32) SHARDS [1,2]

To create a graph g3 with an empty structure, and distribute its data only to shard 1 using the CityHash64 hash function:

CREATE GRAPH g3 {} PARTITION BY HASH(CityHash64) SHARDS [1]

To create two graphs:

CREATE GRAPH g1 { 
  NODE User ({name string, gender string}),
  NODE Club ({name string, since uint32}),
  EDGE Follows ({createdOn datetime}),
  EDGE Joins ({memberNo uint64})
} PARTITION BY HASH(Crc32) SHARDS [1,2,3] COMMENT 'My first graph'
CREATE GRAPH g2 {} PARTITION BY HASH(CityHash64) SHARDS [1]

Dropping Graphs

The DROP GRAPH statement drops graphs from the database.

<drop graph statement> ::= 
  "DROP GRAPH" <graph name> 

To drop the graph g1:

DROP GRAPH g1

To drop two graphs:

DROP GRAPH g1
DROP GRAPH g2

Adding Schemas to Graph

The ALTER GRAPH statement allows you to add node and edge schemas to a graph.

<alter graph statement> ::= 
  "ALTER GRAPH" <graph name> <add element schemas>

<add element schemas> ::=
  <add node schemas> | <add edge schemas>

<add node schemas> ::=
  "ADD NODE" "{" <add node schema> [ { "," <add node schema> }... ] "}"

<add node schema> ::=
  <node schema name> "(" <property types> ")"

<add edge schemas> ::=
  "ADD EDGE" "{" <add edge schema> [ { "," <add edge schema> }... ] "}"

<add edge schema> ::=
  <edge schema name> "(" <property types> ")"

Details

• See naming conventions of node and edge schemas.

To add node schemas Book and Company to the graph g1:

ALTER GRAPH g1 ADD NODE {Book ({title string, rating float}), Company ({name string})}

To add an edge schema Rates to the graph g1:

ALTER GRAPH g1 ADD EDGE {Rates ({value float})}

Dropping Schemas from Graph

The ALTER GRAPH statement allows you to drop node and edge schemas from a graph. Dropping a node or edge schema deletes the schema along with the nodes or edges belonging to it from the database. Note that the deletion of a node leads to the removal of all edges that are connected to it. The two default schemas cannot be dropped.

The schema dropping operation runs as a job, you may run SHOW JOB afterward to verify its completion.

<alter graph statement> ::= 
  "ALTER GRAPH" <graph name> <drop element schemas>
  
<drop element schemas> ::=
  <drop node schemas> | <drop edge schemas>

<drop node schemas> ::=
  "DROP NODE" <node schema name> [ { "," <node schema name> }... ]

<drop edge schemas> ::=
  "DROP EDGE" <edge schema name> [ { "," <edge schema name> }... ]

To drop a node schema User from the graph g1:

ALTER GRAPH g1 DROP NODE User 

To drop edge schemas Follows and Joins from the graph g1:

ALTER GRAPH g1 DROP EDGE Follows, Joins