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Update count vs. estimatedCount documentation.

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Closes #3055
Original pull request: #3541.
This commit is contained in:
Christoph Strobl
2021-01-21 11:11:02 +01:00
committed by Mark Paluch
parent e644692a8a
commit 076d334b3c
5 changed files with 60 additions and 0 deletions
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5
spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ExecutableFindOperation.java
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@@ -125,6 +125,11 @@ public interface ExecutableFindOperation {
/** /**
* Get the number of matching elements. * Get the number of matching elements.
* <p />
* This method uses an {@link com.mongodb.client.MongoCollection#countDocuments(org.bson.conversions.Bson, com.mongodb.client.model.CountOptions) aggregation
* execution} even for empty {@link Query queries} which may have an impact on performance, but guarantees shard,
* session and transaction compliance. In case an inaccurate count satisfies the applications needs use
* {@link MongoOperations#estimatedCount(String)} for empty queries instead.
* *
* @return total number of matching elements. * @return total number of matching elements.
*/ */

24
spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoOperations.java
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@@ -1160,6 +1160,12 @@ public interface MongoOperations extends FluentMongoOperations {
* influence on the resulting number of documents found as those values are passed on to the server and potentially * influence on the resulting number of documents found as those values are passed on to the server and potentially
* limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to * limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to
* count all matches. * count all matches.
* <p />
* This method uses an
* {@link com.mongodb.client.MongoCollection#countDocuments(org.bson.conversions.Bson, com.mongodb.client.model.CountOptions)
* aggregation execution} even for empty {@link Query queries} which may have an impact on performance, but guarantees
* shard, session and transaction compliance. In case an inaccurate count satisfies the applications needs use
* {@link #estimatedCount(Class)} for empty queries instead.
* *
* @param query the {@link Query} class that specifies the criteria used to find documents. Must not be * @param query the {@link Query} class that specifies the criteria used to find documents. Must not be
* {@literal null}. * {@literal null}.
@@ -1176,6 +1182,12 @@ public interface MongoOperations extends FluentMongoOperations {
* influence on the resulting number of documents found as those values are passed on to the server and potentially * influence on the resulting number of documents found as those values are passed on to the server and potentially
* limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to * limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to
* count all matches. * count all matches.
* <p />
* This method uses an
* {@link com.mongodb.client.MongoCollection#countDocuments(org.bson.conversions.Bson, com.mongodb.client.model.CountOptions)
* aggregation execution} even for empty {@link Query queries} which may have an impact on performance, but guarantees
* shard, session and transaction compliance. In case an inaccurate count satisfies the applications needs use
* {@link #estimatedCount(String)} for empty queries instead.
* *
* @param query the {@link Query} class that specifies the criteria used to find documents. * @param query the {@link Query} class that specifies the criteria used to find documents.
* @param collectionName must not be {@literal null} or empty. * @param collectionName must not be {@literal null} or empty.
@@ -1187,6 +1199,9 @@ public interface MongoOperations extends FluentMongoOperations {
/** /**
* Estimate the number of documents, in the collection {@link #getCollectionName(Class) identified by the given type}, * Estimate the number of documents, in the collection {@link #getCollectionName(Class) identified by the given type},
* based on collection statistics. * based on collection statistics.
* <p />
* Please make sure to read the MongoDB reference documentation about limitations on eg. sharded cluster or inside
* transactions.
* *
* @param entityClass must not be {@literal null}. * @param entityClass must not be {@literal null}.
* @return the estimated number of documents. * @return the estimated number of documents.
@@ -1200,6 +1215,9 @@ public interface MongoOperations extends FluentMongoOperations {
/** /**
* Estimate the number of documents in the given collection based on collection statistics. * Estimate the number of documents in the given collection based on collection statistics.
* <p />
* Please make sure to read the MongoDB reference documentation about limitations on eg. sharded cluster or inside
* transactions.
* *
* @param collectionName must not be {@literal null}. * @param collectionName must not be {@literal null}.
* @return the estimated number of documents. * @return the estimated number of documents.
@@ -1214,6 +1232,12 @@ public interface MongoOperations extends FluentMongoOperations {
* influence on the resulting number of documents found as those values are passed on to the server and potentially * influence on the resulting number of documents found as those values are passed on to the server and potentially
* limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to * limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to
* count all matches. * count all matches.
* <p />
* This method uses an
* {@link com.mongodb.client.MongoCollection#countDocuments(org.bson.conversions.Bson, com.mongodb.client.model.CountOptions)
* aggregation execution} even for empty {@link Query queries} which may have an impact on performance, but guarantees
* shard, session and transaction compliance. In case an inaccurate count satisfies the applications needs use
* {@link #estimatedCount(String)} for empty queries instead.
* *
* @param query the {@link Query} class that specifies the criteria used to find documents. Must not be * @param query the {@link Query} class that specifies the criteria used to find documents. Must not be
* {@literal null}. * {@literal null}.

6
spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveFindOperation.java
View File

@@ -106,6 +106,12 @@ public interface ReactiveFindOperation {
/** /**
* Get the number of matching elements. * Get the number of matching elements.
* <p />
* This method uses an
* {@link com.mongodb.reactivestreams.client.MongoCollection#countDocuments(org.bson.conversions.Bson, com.mongodb.client.model.CountOptions)
* aggregation execution} even for empty {@link Query queries} which may have an impact on performance, but
* guarantees shard, session and transaction compliance. In case an inaccurate count satisfies the applications
* needs use {@link ReactiveMongoOperations#estimatedCount(String)} for empty queries instead.
* *
* @return {@link Mono} emitting total number of matching elements. Never {@literal null}. * @return {@link Mono} emitting total number of matching elements. Never {@literal null}.
*/ */

24
spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveMongoOperations.java
View File

@@ -940,6 +940,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
* influence on the resulting number of documents found as those values are passed on to the server and potentially * influence on the resulting number of documents found as those values are passed on to the server and potentially
* limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to * limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to
* count all matches. * count all matches.
* <p />
* This method uses an
* {@link com.mongodb.reactivestreams.client.MongoCollection#countDocuments(org.bson.conversions.Bson, com.mongodb.client.model.CountOptions)
* aggregation execution} even for empty {@link Query queries} which may have an impact on performance, but guarantees
* shard, session and transaction compliance. In case an inaccurate count satisfies the applications needs use
* {@link #estimatedCount(Class)} for empty queries instead.
* *
* @param query the {@link Query} class that specifies the criteria used to find documents. Must not be * @param query the {@link Query} class that specifies the criteria used to find documents. Must not be
* {@literal null}. * {@literal null}.
@@ -956,6 +962,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
* influence on the resulting number of documents found as those values are passed on to the server and potentially * influence on the resulting number of documents found as those values are passed on to the server and potentially
* limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to * limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to
* count all matches. * count all matches.
* <p />
* This method uses an
* {@link com.mongodb.reactivestreams.client.MongoCollection#countDocuments(org.bson.conversions.Bson, com.mongodb.client.model.CountOptions)
* aggregation execution} even for empty {@link Query queries} which may have an impact on performance, but guarantees
* shard, session and transaction compliance. In case an inaccurate count satisfies the applications needs use
* {@link #estimatedCount(String)} for empty queries instead.
* *
* @param query the {@link Query} class that specifies the criteria used to find documents. * @param query the {@link Query} class that specifies the criteria used to find documents.
* @param collectionName must not be {@literal null} or empty. * @param collectionName must not be {@literal null} or empty.
@@ -971,6 +983,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
* influence on the resulting number of documents found as those values are passed on to the server and potentially * influence on the resulting number of documents found as those values are passed on to the server and potentially
* limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to * limit the range and order within which the server performs the count operation. Use an {@literal unpaged} query to
* count all matches. * count all matches.
* <p />
* This method uses an
* {@link com.mongodb.reactivestreams.client.MongoCollection#countDocuments(org.bson.conversions.Bson, com.mongodb.client.model.CountOptions)
* aggregation execution} even for empty {@link Query queries} which may have an impact on performance, but guarantees
* shard, session and transaction compliance. In case an inaccurate count satisfies the applications needs use
* {@link #estimatedCount(String)} for empty queries instead.
* *
* @param query the {@link Query} class that specifies the criteria used to find documents. Must not be * @param query the {@link Query} class that specifies the criteria used to find documents. Must not be
* {@literal null}. * {@literal null}.
@@ -983,6 +1001,9 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
/** /**
* Estimate the number of documents, in the collection {@link #getCollectionName(Class) identified by the given type}, * Estimate the number of documents, in the collection {@link #getCollectionName(Class) identified by the given type},
* based on collection statistics. * based on collection statistics.
* <p />
* Please make sure to read the MongoDB reference documentation about limitations on eg. sharded cluster or inside
* transactions.
* *
* @param entityClass must not be {@literal null}. * @param entityClass must not be {@literal null}.
* @return a {@link Mono} emitting the estimated number of documents. * @return a {@link Mono} emitting the estimated number of documents.
@@ -996,6 +1017,9 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
/** /**
* Estimate the number of documents in the given collection based on collection statistics. * Estimate the number of documents in the given collection based on collection statistics.
* <p />
* Please make sure to read the MongoDB reference documentation about limitations on eg. sharded cluster or inside
* transactions.
* *
* @param collectionName must not be {@literal null}. * @param collectionName must not be {@literal null}.
* @return a {@link Mono} emitting the estimated number of documents. * @return a {@link Mono} emitting the estimated number of documents.

1
src/main/asciidoc/reference/mongodb.adoc
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@@ -2221,6 +2221,7 @@ With the introduction of <<mongo.transactions>> this was no longer possible beca
So in version 2.x `MongoOperations.count()` would use the collection statistics if no transaction was in progress, and the aggregation variant if so. So in version 2.x `MongoOperations.count()` would use the collection statistics if no transaction was in progress, and the aggregation variant if so.
As of Spring Data MongoDB 3.x any `count` operation uses regardless the existence of filter criteria the aggregation-based count approach via MongoDBs `countDocuments`. As of Spring Data MongoDB 3.x any `count` operation uses regardless the existence of filter criteria the aggregation-based count approach via MongoDBs `countDocuments`.
If the application is fine with the limitations of working upon collection statistics `MongoOperations.estimatedCount()` offers an alternative.
[NOTE] [NOTE]
==== ====