References:
> QSG code example provided with the installer
> RedisGraph native commands and documentation, Cypher query syntax
After installation, a group PyBridge will appear in the Tool Palette of Delphi, where you can find the new component TPBRedisGraph. PBClient for RedisGraph requires PBClient for Redis as the core component. It should be installed to provide a connection with the Redis server.
New component TPBRedisGraph can be found in the Tool Palette under PyBridge group
Place TPBRedisGraph onto the form and set up its main properties:
- AutoConnect – set to True for automatic connection to Redis
- RedisServer – host, password and port number to access Redis
The default Redis database ID that TPBRedisGraph is going to work with is 0, but you may specify a different database ID. To do so – create the OnConnect event handler procedure of the PBRedisClient object. Keep in mind that the trial version does not support the selection of databases.
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procedure TForm1.PBRedisClient1Connect;
begin
PBRedisClient1.Select(0); // PBRedisClient. Selecting a database number in redis.
end;
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Place TPBRedisGraph onto the form and set up its main properties:
- RedisClient – select the PBRedisClient object which should provide a connection with the Redis server
- GraphName – setup the default Graph name. You should set a new value of the parameter in your code every time when you intend to work with a different graph
Now PBClient for RedisGraph is ready to be used. PBClient for RedisGraph provides entire Redis GRAPH.QUERY syntax based on Cypher. In addition, PBClient for RedisGraph has special tools for the most used Cypher commands for nodes and edges, such as: CREATE, MATCH and DELETE. To demonstrate how PBClient for RedisGraph works, let’s create a simple application to manage the nodes and edges of the RedisGraph base. Add the corresponding Buttons, Edits and Memo to your form:
In ‘GRAPH_NODE_CREATE’ and ‘GRAPH_NODE_MATCH’ ButtonClick event handler procedures we are using following PBRedisGraph functions:
When providing a JSON string as function parameter, you can use single quotes instead of double quotes:
‘{“key_str”: “value_str”, …}’ – double quotes
‘{”key_str”: ”value_str”, …}’ – escaped single quotes
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30 | procedure TForm2.GRAPH_NODE_CREATEClick(Sender: TObject);
var
Rslt, jres: string;
begin
Rslt:= PBRedisGraph1.GRAPH_NODE_CREATE('Person', '{"name": "Alice", "age": 23, "hair": "blonde"}');
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBRedisGraph1.GRAPH_NODE_CREATE('Person', '{"name": "Alice", "age": 27, "hair": "brown"}');
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBRedisGraph1.GRAPH_NODE_CREATE('Person', '{"name": "Kurt", "age": 27}');
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBRedisGraph1.GRAPH_NODE_CREATE('Movie', '{"name": "Wall Street"}');
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
end
procedure TForm2.GRAPH_NODE_MATCHClick(Sender: TObject);
var
Rslt, jres: string;
begin
Rslt:= PBRedisGraph1.GRAPH_NODE_MATCH('Person', '{"name": "Alice", "hair": "blonde"}', ['name', 'age']);
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBRedisGraph1.GRAPH_NODE_MATCH('Person', '{"name": "Alice", "age": 23}', ['name', 'hair']);
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Memo1.Lines.Append('')
end;
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To delete a node we should provide its ID to the GRAPH_NODE_DELETE function.
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procedure TForm2.GRAPH_NODE_DELETEClick(Sender: TObject);
begin
if trim(EditDelNode.Text) = '' then
exit;
PBRedisGraph1.GRAPH_NODE_DELETE(StrToInt(EditDelNode.Text))
end;
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In ‘GRAPH_EDGE_CREATE’ and ‘GRAPH_EDGE_MATCH’ ButtonClick event handler procedures we are using following PBRedisGraph functions:
- GRAPH_EDGE_CREATE(source_int, destination_int, ‘label’, ‘{“key_str”: “value_str”, “key_int”: value_int, …, “key_n”:”value_n”}’) – based on native GRAPH.QUERY CREATE this function creates a new ‘label’ edge between source and destination nodes with corresponding ‘{“key”:”value”}’ pairs.
- GRAPH_EDGE_MATCH(‘label’, ‘{“key_1”: “value_1”, …, “key_n”: “value_n”}’, [‘key_1’, …, ‘key_n’]) – based on native GRAPH.QUERY MATCH this function searches for all the ‘label’ edges with matching ‘{“key”:”value”}’ pairs, and returns values of selected [‘keys’].
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29 | procedure TForm2.GRAPH_NODE_CREATEClick(Sender: TObject);
var
Rslt, jres: string;
begin
Rslt:= PBRedisGraph1.GRAPH_NODE_CREATE('Person', '{"name": "Alice", "age": 23, "hair": "blonde"}');
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBRedisGraph1.GRAPH_NODE_CREATE('Person', '{"name": "Alice", "age": 27, "hair": "brown"}');
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBRedisGraph1.GRAPH_NODE_CREATE('Person', '{"name": "Kurt", "age": 27}');
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBRedisGraph1.GRAPH_NODE_CREATE('Movie', '{"name": "Wall Street"}');
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
end
procedure TForm2.GRAPH_NODE_MATCHClick(Sender: TObject);
var
Rslt, jres: string;
begin
Rslt:= PBRedisGraph1.GRAPH_NODE_MATCH('Person', '{"name": "Alice", "hair": "blonde"}', ['name', 'age']);
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Rslt:= PBRedisGraph1.GRAPH_NODE_MATCH('Person', '{"name": "Alice", "age": 23}', ['name', 'hair']);
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append(jres);
Memo1.Lines.Append('')
end;
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To delete an edge we should provide its ID to the GRAPH_EDGE_DELETE function.
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procedure TForm2.GRAPH_EDGE_DELETEClick(Sender: TObject);
begin
if trim(EditDelEdge.Text) = '' then
exit;
PBRedisGraph1.GRAPH_EDGE_DELETE(StrToInt(EditDelEdge.Text))
end;
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The most powerful function of PBRedisGraph is GRAPH_QUERY. Based on native GRAPH.QUERY this function can execute any Cypher query that is supported by RedisGraph.
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procedure TForm2.ButtonQueryClick(Sender: TObject);
var
Rslt, jres: string;
begin
if trim(EditQuery.Text) = '' then
exit;
Rslt := PBRedisGraph1.GRAPH_QUERY(trim(EditQuery.Text));
jres := PBRedisGraph1.res2dic(Rslt);
Memo1.Lines.Append((jres.Replace('},{', '},' + #13#10 + '{').Replace('rslt":[', 'Result":[' + #13#10)));
Memo1.Lines.Append('')
end;
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Below are some sample commands for you to try. Feel free to experiment with your own requests.
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MATCH (n) RETURN *
MATCH (n)-[r]-() RETURN r
MATCH (a:Person) WHERE a.name = 'Kurt' CREATE (a)-[:MEMBER]->(:Band {name:'Nirvana'})
CREATE (jim:Person{name:'Jim', age:29})-[:FRIENDS]->(pam:Person {name:'Pam', age:27})-[:WORKS]->(:Employer {name:'Dunder Mifflin'})
MATCH (:Person {name:'Jim'})-[r:FRIENDS]->() DELETE r
MATCH (n) DELETE n
MATCH (n:Person{name: 'Alice', hair: 'blonde'}) RETURN n.name, n.age
MATCH (n:Person{name: 'Alice', age: 23}) RETURN n.name, n.hair
MATCH ()-[r:FRIENDS]->() WHERE r.duration=3 RETURN r.duration
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This example demonstrates how easy it is to develop Delphi applications relying on RedisGraph with a help of PBClient for RedisGraph. Now you can also enjoy the full power of RedisGraph in your applications!
