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Persistence API: add CurrentLastSequenceNumberByPersistenceIdQuery #1773

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Persistence API: add CurrentLastSequenceNumberByPersistenceIdQuery #1773

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636a803
new CurrentLastKnownSequenceNumberByPersistenceIdQuery
pjfanning Feb 14, 2025
d19d5e2
java Long
pjfanning Feb 16, 2025
879b86c
Update CurrentLastKnownSequenceNumberByPersistenceIdQuery.scala
pjfanning Feb 16, 2025
33ba6a7
rename traits and functions
pjfanning Feb 20, 2025
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36 changes: 36 additions & 0 deletions .../pekko/persistence/query/javadsl/CurrentLastKnownSequenceNumberByPersistenceIdQuery.scala
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package org.apache.pekko.persistence.query.javadsl

import java.util.Optional
import java.util.concurrent.CompletionStage

/**
* A trait that enables querying the current last known sequence number for a given `persistenceId`.
* @since 1.2.0
*/
trait CurrentLastKnownSequenceNumberByPersistenceIdQuery extends ReadJournal {

/**
* Returns the last known sequence number for the given `persistenceId`. Empty if the `persistenceId` is unknown.
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Optional should use the value is absent instead of Empty?

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I think 'empty' makes since this is the terminology used by scala.Option and java Optional.

*
* @param persistenceId The `persistenceId` for which the last known sequence number should be returned.
* @return Some sequence number or None if the `persistenceId` is unknown.
*/
def currentLastKnownSequenceNumberByPersistenceId(persistenceId: String): CompletionStage[Optional[java.lang.Long]]
}
35 changes: 35 additions & 0 deletions ...pekko/persistence/query/scaladsl/CurrentLastKnownSequenceNumberByPersistenceIdQuery.scala
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package org.apache.pekko.persistence.query.scaladsl

import scala.concurrent.Future

/**
* A trait that enables querying the current last known sequence number for a given `persistenceId`.
* @since 1.2.0
*/
trait CurrentLastKnownSequenceNumberByPersistenceIdQuery extends ReadJournal {
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@He-Pin He-Pin Feb 19, 2025 •
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LastKnownSequenceNumberQuery ?

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Just to highlight the intent behind the Current in name: It seemed to me that "final" queries like CurrentEventsByPersistenceIdQuery are prefixed with 'Current', while continuous corresponding queries like EventsByPersistenceIdQuery drop this prefix. The ByPersistenceId clarifies the scope of query. Even though a LastKnownSequenceNumberByPersistenceIdQuery doesn't exist yet, one could imagine a query that continuously emits the last known sequence number for persistence id in future and thus I had preferred to 1. not block the name already 2. align to existing naming schema.

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@He-Pin He-Pin Feb 19, 2025 •
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I just think the name is too long, maybe CurrentLastKnownSequenceNumberQuery, otherwise , if we need add more methods to this trait, then we need another trait.

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@ptrdom ptrdom Feb 19, 2025 •
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How about dropping the Known from the name? Current already implies it in a way. EventSourcedBehavior.lastSequenceNumber already exist, so naming would align.

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Would CurrentLastSequenceNumberQuery work?

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I think CurrentLastSequenceNumberByPersistenceIdQuery is good if we are sticking to the style of having a trait per least amount of methods, which does make sense - for example each journal might want to implement CurrentLastSequenceNumberByPersistenceIdQuery, but not necessarily CurrentLastSequenceNumberBySliceQuery or CurrentLastSequenceNumberByTagQuery if we ever implement them.


/**
* Returns the last known sequence number for the given `persistenceId`. Empty if the `persistenceId` is unknown.
*
* @param persistenceId The `persistenceId` for which the last known sequence number should be returned.
* @return Some sequence number or None if the `persistenceId` is unknown.
*/
def currentLastKnownSequenceNumberByPersistenceId(persistenceId: String): Future[Option[Long]]
}