Add Ahead of Time Repository support

[mp911de]

We now provide AOT support to generate repository implementations during build-time for Cassandra repository query methods.

Supported Features

• Derived query methods, @Query and named query methods.
• Window, Slice, Stream, and Optional return types
• Sort query rewriting
• Interface and DTO Projections
• Value Expressions (Those require a bit of reflective information.
  Mind that using Value Expressions requires expression parsing and contextual information to evaluate the expression)

Limitation

• Vector Search not yet supported

Excluded methods

• CrudRepository and other base interface methods as their implementation is provided by the base class respective fragments
• Vector Search Methods

Example repository:

interface PersonRepository extends CrudRepository<Person, String> {

	@Query(idempotent = Query.Idempotency.IDEMPOTENT)
	Person findByFirstname(String firstname);

	Stream<PersonDto> streamDtoProjectionByFirstname(String firstname);

	@Query("select numberOfChildren from person where firstname = :firstname")
	int findDeclaredNumberOfChildrenByFirstname(String firstname);

	Window<Person> findWindowByLastname(String lastname, ScrollPosition scrollPosition, Limit limit);
}

Generated fragment:

/**
 * AOT generated Cassandra repository implementation for {@link PersonRepository}.
 */
public class PersonRepositoryImpl__AotRepository extends AotRepositoryFragmentSupport {
  private final CassandraOperations operations;

  public PersonRepositoryImpl__AotRepository(CassandraOperations operations,
      RepositoryFactoryBeanSupport.FragmentCreationContext context) {
    super(operations, context);
    this.operations = operations;
  }

  /**
   * AOT generated implementation of {@link PersonRepository#findByFirstname(java.lang.String)}.
   */
  public Person findByFirstname(String firstname) {
    Query query = Query.query(Criteria.where("firstname").is(firstname));

    ExecutableSelectOperation.TerminatingSelect<Person> select = operations.query(Person.class).matching(query);
    return select.oneValue();
  }

  /**
   * AOT generated implementation of {@link PersonRepository#streamDtoProjectionByFirstname(java.lang.String)}.
   */
  public Stream<PersonRepository.PersonDto> streamDtoProjectionByFirstname(String firstname) {
    Query query = Query.query(Criteria.where("firstname").is(firstname));

    ExecutableSelectOperation.TerminatingSelect<PersonRepository.PersonDto> select = operations.query(Person.class).as(PersonRepository.PersonDto.class).matching(query);
    return select.stream();
  }

  /**
   * AOT generated implementation of {@link PersonRepository#findDeclaredNumberOfChildrenByFirstname(java.lang.String)}.
   */
  public int findDeclaredNumberOfChildrenByFirstname(String firstname) {
    Object[] args = new Object[1];
    args[0] = potentiallyConvertBindingValue(firstname);
    SimpleStatement query = SimpleStatement.newInstance("select numberOfChildren from person where firstname = ?", args);

    ExecutableSelectOperation.TerminatingResults<Integer> select = operations.query(query).as(Integer.class);
    return select.oneValue();
  }

  /**
   * AOT generated implementation of {@link PersonRepository#findWindowByLastname(java.lang.String, org.springframework.data.domain.ScrollPosition, org.springframework.data.domain.Limit)}.
   */
  public Window<Person> findWindowByLastname(String lastname, ScrollPosition scrollPosition,
      Limit limit) {
    Query query = Query.query(Criteria.where("lastname").is(lastname));
    if (limit.isLimited()) {
      query = query.limit(limit.max() + 1);
    }
    if (!scrollPosition.isInitial()) {
      query = query.pagingState((CassandraScrollPosition) scrollPosition);
    }
    QueryOptions.QueryOptionsBuilder optionsBuilder = QueryOptions.builder();
    if (limit.isLimited()) {
      optionsBuilder.pageSize(limit.max());
    }
    query = query.queryOptions(optionsBuilder.build());

    ExecutableSelectOperation.TerminatingSelect<Person> select = operations.query(Person.class).matching(query);
    return WindowUtil.of(select.slice());
  }
  
}

Metadata (truncated):

{
  "name": "org.springframework.data.cassandra.repository.aot.PersonRepository",
  "module": "Cassandra",
  "type": "IMPERATIVE",
  "methods": [
    {
      "name": "findByFirstname",
      "signature": "public abstract org.springframework.data.cassandra.domain.Person org.springframework.data.cassandra.repository.aot.PersonRepository.findByFirstname(java.lang.String)",
      "query": {
        "query": "SELECT * FROM person WHERE firstname=?"
      }
    },
    {
      "name": "streamDtoProjectionByFirstname",
      "signature": "public abstract java.util.stream.Stream<org.springframework.data.cassandra.repository.aot.PersonRepository$PersonDto> org.springframework.data.cassandra.repository.aot.PersonRepository.streamDtoProjectionByFirstname(java.lang.String)",
      "query": {
        "query": "SELECT * FROM person WHERE firstname=?"
      }
    },
    {
      "name": "findDeclaredNumberOfChildrenByFirstname",
      "signature": "public abstract int org.springframework.data.cassandra.repository.aot.PersonRepository.findDeclaredNumberOfChildrenByFirstname(java.lang.String)",
      "query": {
        "query": "select numberOfChildren from person where firstname = ?"
      }
    },
    {
      "name": "findWindowByLastname",
      "signature": "public abstract org.springframework.data.domain.Window<org.springframework.data.cassandra.domain.Person> org.springframework.data.cassandra.repository.aot.PersonRepository.findWindowByLastname(java.lang.String,org.springframework.data.domain.ScrollPosition,org.springframework.data.domain.Limit)",
      "query": {
        "query": "SELECT * FROM person WHERE lastname=?"
      }
    }
  ]
}

[christophstrobl]

is there a need to escape the value of the parameter?

[mp911de]

😫 https://issues.apache.org/jira/browse/CASSANDRA-12675

[christophstrobl]

Having a CodeBlock that concats $S with $L given the provided arguments makes me think parameterNames should maybe be represented differently. Right now it seems to render a magic switch that separates arguments used to call a specific variant of the evaluateExpressionMethod making this piece pretty hard to understand.

[christophstrobl]

no need to use index numbers when there're no repeating arguments. doesn't harm having them.

[christophstrobl]

does a limited query only return the first available result? Not too familiar with the cassandra domain, but shouldn't this be like a limit to a certain number of results at most (aka TopN results)?

[mp911de]

isLimited is a fallback. TopN for collection queries is handled through .isCollectionQuery() a few lines above. This instance here is for User findFirst(…) while User findTop10(…) could work as well.

[christophstrobl]

addAll seems to be a nice shortcut for appending multiple parts at once.
I wonder if readability suffers a bit from it, like having the closing bracket being added in a nested builder is confusing.

[christophstrobl]

would it make sense to split the argument from the rendering? thinking of invocation.addArgument(sort).as((argument) -> ... return ) where we do not pass in the builder but have a function that returns a new code block.

as might event be optional if the argument can be rendered as is using $L.