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Fix interface projections for string based aggregations.

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Closes #4839
Original pull request: #4841
This commit is contained in:
Christoph Strobl
2024-11-25 14:17:38 +01:00
committed by Mark Paluch
parent 2580af2935
commit f2a9d1f1b3
4 changed files with 45 additions and 25 deletions
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36
src/main/antora/modules/ROOT/pages/mongodb/repositories/query-methods.adoc
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@@ -571,23 +571,29 @@ public interface PersonRepository extends CrudRepository<Person, String> {
@Aggregation("{ $group: { _id : $lastname, names : { $addToSet : $firstname } } }")
Stream<PersonAggregate> groupByLastnameAndFirstnamesAsStream(); <5>
@Aggregation("{ $group : { _id : null, total : { $sum : $age } } }")
SumValue sumAgeUsingValueWrapper(); <6>
@Aggregation(pipeline = {
"{ '$match' : { 'lastname' : '?0'} }",
"{ '$project': { _id : 0, firstname : 1, lastname : 1 } }"
})
Stream<PersonAggregate> groupByLastnameAndFirstnamesAsStream(); <6>
@Aggregation("{ $group : { _id : null, total : { $sum : $age } } }")
Long sumAge(); <7>
SumValue sumAgeUsingValueWrapper(); <7>
@Aggregation("{ $group : { _id : null, total : { $sum : $age } } }")
AggregationResults<SumValue> sumAgeRaw(); <8>
Long sumAge(); <8>
@Aggregation("{ $group : { _id : null, total : { $sum : $age } } }")
AggregationResults<SumValue> sumAgeRaw(); <9>
@Aggregation("{ '$project': { '_id' : '$lastname' } }")
List<String> findAllLastnames(); <9>
List<String> findAllLastnames(); <10>
@Aggregation(pipeline = {
"{ $group : { _id : '$author', books: { $push: '$title' } } }",
"{ $out : 'authors' }"
})
void groupAndOutSkippingOutput(); <10>
void groupAndOutSkippingOutput(); <11>
}
----
[source,java]
@@ -614,19 +620,25 @@ public class SumValue {
// Getter omitted
}
interface PersonProjection {
String getFirstname();
String getLastname();
}
----
<1> Aggregation pipeline to group first names by `lastname` in the `Person` collection returning these as `PersonAggregate`.
<2> If `Sort` argument is present, `$sort` is appended after the declared pipeline stages so that it only affects the order of the final results after having passed all other aggregation stages.
Therefore, the `Sort` properties are mapped against the methods return type `PersonAggregate` which turns `Sort.by("lastname")` into `{ $sort : { '_id', 1 } }` because `PersonAggregate.lastname` is annotated with `@Id`.
<3> Replaces `?0` with the given value for `property` for a dynamic aggregation pipeline.
<4> `$skip`, `$limit` and `$sort` can be passed on via a `Pageable` argument. Same as in <2>, the operators are appended to the pipeline definition. Methods accepting `Pageable` can return `Slice` for easier pagination.
<5> Aggregation methods can return `Stream` to consume results directly from an underlying cursor. Make sure to close the stream after consuming it to release the server-side cursor by either calling `close()` or through `try-with-resources`.
<6> Map the result of an aggregation returning a single `Document` to an instance of a desired `SumValue` target type.
<7> Aggregations resulting in single document holding just an accumulation result like e.g. `$sum` can be extracted directly from the result `Document`.
<5> Aggregation methods can return interface based projections wrapping the resulting `org.bson.Document` behind a proxy, exposing getters delegating to fields within the document.
<6> Aggregation methods can return `Stream` to consume results directly from an underlying cursor. Make sure to close the stream after consuming it to release the server-side cursor by either calling `close()` or through `try-with-resources`.
<7> Map the result of an aggregation returning a single `Document` to an instance of a desired `SumValue` target type.
<8> Aggregations resulting in single document holding just an accumulation result like e.g. `$sum` can be extracted directly from the result `Document`.
To gain more control, you might consider `AggregationResult` as method return type as shown in <7>.
<8> Obtain the raw `AggregationResults` mapped to the generic target wrapper type `SumValue` or `org.bson.Document`.
<9> Like in <6>, a single value can be directly obtained from multiple result ``Document``s.
<10> Skips the output of the `$out` stage when return type is `void`.
<9> Obtain the raw `AggregationResults` mapped to the generic target wrapper type `SumValue` or `org.bson.Document`.
<10> Like in <6>, a single value can be directly obtained from multiple result ``Document``s.
<11> Skips the output of the `$out` stage when return type is `void`.
====
In some scenarios, aggregations might require additional options, such as a maximum run time, additional log comments, or the permission to temporarily write data to disk.