Throughout this course, we will use the Asynchronous API to retrieve and process results from Neo4j.
To use the you will need to to define async methods and use the await keyword to await the results.
Results can also be retrieved synchronously by omitting the Async suffix.
Result Cursors
The IResultCursor implementation returned by calls to session.RunAsync() or tx.RunAsync() provides access to the result as an asynchronous stream of IRecord s along with additional metadata about the query and result.
The records in the result is lazily retrieved and could only be visited once in a sequential order.
A Record refers to the keyed set of values specified in the RETURN portion of the statement.
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/app-python/main/Examples/Neo4jExamples/Program.cs[tag=session.readTransaction]In the previous code block, the ToListAsync() method is called on the cursor implementation to convert all results returned by the Neo4j DBMS as a list.
The Select() method is then called to retrieve the name value returned in each Record.
Records can be consumed in order using a while loop, or more the commonly used approach is to use the ToListAsync() function as above, which will consume the results in order and return a set.
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/app-python/main/Examples/Neo4jExamples/Results.cs[tag=records]Where a singe result is expected, you can call the SingleAsync() function to retrieve the first record.
If zero, or more than one record are retrieve an error will be thrown.
Records
The IRecord interface provides access to an individual record returned by Neo4j.
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/app-python/main/Examples/Neo4jExamples/Results.cs[tag=record]The .Keys property provides the available keys for the record.
These relate to the aliases referenced in the RETURN clause of the Cypher statement.
You can use the square-bracket syntax to access a value, for example row["movie"].As<INode>() will access the movie item defined in the, cast as an implementation of the INode interface.
Result Summary
The meta data IResultCursor accessed by calling .Consume() include:
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statistics on how many nodes and relationships were created, updated, or deleted as a result of the query,
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the query type
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database and server info
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query plan with and without profile
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notifications
You can find more detail in the API docs for IResultSummary
For example, to get information about how long the query took to complete, you can use the following property:
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/app-python/main/Examples/Neo4jExamples/Results.cs[tag=summary]Another interesting part of the summary is the SummaryCounters available via the Counters property, which has update counts about a write-statement’s execution.
You can check via counters.ContainsUpdates if there were any updates.
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/app-python/main/Examples/Neo4jExamples/Results.cs[tag=summary:counters]Check Your Understanding
1. What implementation is returned by the .RunAsync() method?
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❏
IResult -
✓
IResultCursor -
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List<IRecord> -
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List<IResult>
Hint
Results returned by the driver are held in an implementation of result cursor.
Solution
The answer is IResultCursor.
Lesson Summary
You now have all the information required to send Cypher queries to Neo4j and consume the results.
Next, we will look at the Cypher Type System and some of the considerations that you need to make when working with values coming from Neo4j in your Java application.