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Add builders for pick-accumulators / window functions (#954)
JAVA-4094
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8 files changed

+1195
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‎driver-core/src/main/com/mongodb/client/model/Accumulators.java

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@@ -20,10 +20,13 @@
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import org.bson.BsonArray;
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import org.bson.BsonDocument;
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import org.bson.BsonString;
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import org.bson.Document;
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import org.bson.conversions.Bson;
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import java.util.List;
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import static java.util.stream.Collectors.toList;
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import static org.bson.assertions.Assertions.notNull;
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/**
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* Builders for accumulators used in the group pipeline stage of an aggregation pipeline.
@@ -78,6 +81,69 @@ public static <TExpression> BsonField first(final String fieldName, final TExpre
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return accumulatorOperator("$first", fieldName, expression);
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}
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/**
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* Returns a combination of a computed field and an accumulator that produces a BSON {@link org.bson.BsonType#ARRAY Array}
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* of values of the given {@code inExpression} computed for the first {@code N} elements within a presorted group,
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* where {@code N} is the positive integral value of the {@code nExpression}.
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*
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* @param fieldName The field computed by the accumulator.
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* @param inExpression The input expression.
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* @param nExpression The expression limiting the number of produced values.
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* @param <InExpression> The type of the input expression.
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* @param <NExpression> The type of the limiting expression.
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* @return The requested {@link BsonField}.
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* @mongodb.driver.manual reference/operator/aggregation/firstN/ $firstN
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* @since 4.7
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* @mongodb.server.release 5.2
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*/
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public static <InExpression, NExpression> BsonField firstN(
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final String fieldName, final InExpression inExpression, final NExpression nExpression) {
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return pickNAccumulator(notNull("fieldName", fieldName), "$firstN",
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notNull("inExpression", inExpression), notNull("nExpression", nExpression));
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}
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/**
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* Returns a combination of a computed field and an accumulator that produces
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* a value of the given {@code outExpression} computed for the top element within a group
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* sorted according to the provided {@code sortBy} specification.
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*
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* @param fieldName The field computed by the accumulator.
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* @param sortBy The {@linkplain Sorts sort specification}. The syntax is identical to the one expected by {@link Aggregates#sort(Bson)}.
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* @param outExpression The output expression.
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* @param <OutExpression> The type of the output expression.
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* @return The requested {@link BsonField}.
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* @mongodb.driver.manual reference/operator/aggregation/top/ $top
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* @since 4.7
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* @mongodb.server.release 5.2
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*/
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public static <OutExpression> BsonField top(final String fieldName, final Bson sortBy, final OutExpression outExpression) {
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return sortingPickAccumulator(notNull("fieldName", fieldName), "$top",
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notNull("sortBy", sortBy), notNull("outExpression", outExpression));
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}
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/**
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* Returns a combination of a computed field and an accumulator that produces a BSON {@link org.bson.BsonType#ARRAY Array}
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* of values of the given {@code outExpression} computed for the top {@code N} elements within a group
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* sorted according to the provided {@code sortBy} specification,
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* where {@code N} is the positive integral value of the {@code nExpression}.
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*
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* @param fieldName The field computed by the accumulator.
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* @param sortBy The {@linkplain Sorts sort specification}. The syntax is identical to the one expected by {@link Aggregates#sort(Bson)}.
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* @param outExpression The output expression.
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* @param nExpression The expression limiting the number of produced values.
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* @param <OutExpression> The type of the output expression.
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* @param <NExpression> The type of the limiting expression.
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* @return The requested {@link BsonField}.
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* @mongodb.driver.manual reference/operator/aggregation/topN/ $topN
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* @since 4.7
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* @mongodb.server.release 5.2
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*/
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public static <OutExpression, NExpression> BsonField topN(
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final String fieldName, final Bson sortBy, final OutExpression outExpression, final NExpression nExpression) {
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return sortingPickNAccumulator(notNull("fieldName", fieldName), "$topN",
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notNull("sortBy", sortBy), notNull("outExpression", outExpression), notNull("nExpression", nExpression));
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}
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/**
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* Gets a field name for a $group operation representing the value of the given expression when applied to the last member of
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* the group.
@@ -92,6 +158,69 @@ public static <TExpression> BsonField last(final String fieldName, final TExpres
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return accumulatorOperator("$last", fieldName, expression);
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}
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/**
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* Returns a combination of a computed field and an accumulator that produces a BSON {@link org.bson.BsonType#ARRAY Array}
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* of values of the given {@code inExpression} computed for the last {@code N} elements within a presorted group,
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* where {@code N} is the positive integral value of the {@code nExpression}.
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*
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* @param fieldName The field computed by the accumulator.
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* @param inExpression The input expression.
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* @param nExpression The expression limiting the number of produced values.
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* @param <InExpression> The type of the input expression.
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* @param <NExpression> The type of the limiting expression.
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* @return The requested {@link BsonField}.
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* @mongodb.driver.manual reference/operator/aggregation/lastN/ $lastN
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* @since 4.7
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* @mongodb.server.release 5.2
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*/
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public static <InExpression, NExpression> BsonField lastN(
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final String fieldName, final InExpression inExpression, final NExpression nExpression) {
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return pickNAccumulator(notNull("fieldName", fieldName), "$lastN",
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notNull("inExpression", inExpression), notNull("nExpression", nExpression));
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}
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/**
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* Returns a combination of a computed field and an accumulator that produces
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* a value of the given {@code outExpression} computed for the bottom element within a group
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* sorted according to the provided {@code sortBy} specification.
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*
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* @param fieldName The field computed by the accumulator.
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* @param sortBy The {@linkplain Sorts sort specification}. The syntax is identical to the one expected by {@link Aggregates#sort(Bson)}.
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* @param outExpression The output expression.
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* @param <OutExpression> The type of the output expression.
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* @return The requested {@link BsonField}.
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* @mongodb.driver.manual reference/operator/aggregation/bottom/ $bottom
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* @since 4.7
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* @mongodb.server.release 5.2
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*/
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public static <OutExpression> BsonField bottom(final String fieldName, final Bson sortBy, final OutExpression outExpression) {
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return sortingPickAccumulator(notNull("fieldName", fieldName), "$bottom",
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notNull("sortBy", sortBy), notNull("outExpression", outExpression));
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}
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/**
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* Returns a combination of a computed field and an accumulator that produces a BSON {@link org.bson.BsonType#ARRAY Array}
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* of values of the given {@code outExpression} computed for the bottom {@code N} elements within a group
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* sorted according to the provided {@code sortBy} specification,
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* where {@code N} is the positive integral value of the {@code nExpression}.
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*
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* @param fieldName The field computed by the accumulator.
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* @param sortBy The {@linkplain Sorts sort specification}. The syntax is identical to the one expected by {@link Aggregates#sort(Bson)}.
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* @param outExpression The output expression.
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* @param nExpression The expression limiting the number of produced values.
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* @param <OutExpression> The type of the output expression.
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* @param <NExpression> The type of the limiting expression.
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* @return The requested {@link BsonField}.
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* @mongodb.driver.manual reference/operator/aggregation/bottomN/ $bottomN
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* @since 4.7
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* @mongodb.server.release 5.2
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*/
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public static <OutExpression, NExpression> BsonField bottomN(
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final String fieldName, final Bson sortBy, final OutExpression outExpression, final NExpression nExpression) {
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return sortingPickNAccumulator(notNull("fieldName", fieldName), "$bottomN",
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notNull("sortBy", sortBy), notNull("outExpression", outExpression), notNull("nExpression", nExpression));
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}
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/**
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* Gets a field name for a $group operation representing the maximum of the values of the given expression when applied to all
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* members of the group.
@@ -106,6 +235,27 @@ public static <TExpression> BsonField max(final String fieldName, final TExpress
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return accumulatorOperator("$max", fieldName, expression);
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}
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/**
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* Returns a combination of a computed field and an accumulator that produces a BSON {@link org.bson.BsonType#ARRAY Array}
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* of {@code N} largest values of the given {@code inExpression},
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* where {@code N} is the positive integral value of the {@code nExpression}.
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*
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* @param fieldName The field computed by the accumulator.
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* @param inExpression The input expression.
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* @param nExpression The expression limiting the number of produced values.
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* @param <InExpression> The type of the input expression.
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* @param <NExpression> The type of the limiting expression.
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* @return The requested {@link BsonField}.
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* @mongodb.driver.manual reference/operator/aggregation/maxN/ $maxN
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* @since 4.7
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* @mongodb.server.release 5.2
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*/
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public static <InExpression, NExpression> BsonField maxN(
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final String fieldName, final InExpression inExpression, final NExpression nExpression) {
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return pickNAccumulator(notNull("fieldName", fieldName), "$maxN",
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notNull("inExpression", inExpression), notNull("nExpression", nExpression));
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}
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/**
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* Gets a field name for a $group operation representing the minimum of the values of the given expression when applied to all
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* members of the group.
@@ -120,6 +270,27 @@ public static <TExpression> BsonField min(final String fieldName, final TExpress
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return accumulatorOperator("$min", fieldName, expression);
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}
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/**
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* Returns a combination of a computed field and an accumulator that produces a BSON {@link org.bson.BsonType#ARRAY Array}
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* of {@code N} smallest values of the given {@code inExpression},
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* where {@code N} is the positive integral value of the {@code nExpression}.
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*
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* @param fieldName The field computed by the accumulator.
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* @param inExpression The input expression.
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* @param nExpression The expression limiting the number of produced values.
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* @param <InExpression> The type of the input expression.
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* @param <NExpression> The type of the limiting expression.
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* @return The requested {@link BsonField}.
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* @mongodb.driver.manual reference/operator/aggregation/minN/ $minN
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* @since 4.7
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* @mongodb.server.release 5.2
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*/
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public static <InExpression, NExpression> BsonField minN(
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final String fieldName, final InExpression inExpression, final NExpression nExpression) {
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return pickNAccumulator(notNull("fieldName", fieldName), "$minN",
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notNull("inExpression", inExpression), notNull("nExpression", nExpression));
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}
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/**
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* Gets a field name for a $group operation representing an array of all values that results from applying an expression to each
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* document in a group of documents that share the same group by key.
@@ -321,6 +492,24 @@ private static <TExpression> BsonField accumulatorOperator(final String name, fi
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return new BsonField(fieldName, new SimpleExpression<TExpression>(name, expression));
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}
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private static <InExpression, NExpression> BsonField pickNAccumulator(
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final String fieldName, final String accumulatorName, final InExpression inExpression, final NExpression nExpression) {
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return new BsonField(fieldName, new Document(accumulatorName, new Document("input", inExpression).append("n", nExpression)));
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}
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private static <OutExpression> BsonField sortingPickAccumulator(
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final String fieldName, final String accumulatorName, final Bson sort, final OutExpression outExpression) {
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return new BsonField(fieldName, new Document(accumulatorName, new Document("sortBy", sort).append("output", outExpression)));
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}
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private static <OutExpression, NExpression> BsonField sortingPickNAccumulator(
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final String fieldName, final String accumulatorName,
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final Bson sort, final OutExpression outExpression, final NExpression nExpression) {
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return new BsonField(fieldName, new Document(accumulatorName, new Document("sortBy", sort)
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.append("output", outExpression)
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.append("n", nExpression)));
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}
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private Accumulators() {
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}
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}

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