[jira] [Commented] (SPARK-26841) Timestamp pushdown on Kafka table

["Richard Yu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-26841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16843509#comment-16843509 ] 

Richard Yu commented on SPARK-26841:
------------------------------------

[~Bartalos] Could you expain what use cases there are for supporting these queries? It would be helpful if you could provide an example where a "historic snapshot" might be necessary.

> Timestamp pushdown on Kafka table
> ---------------------------------
>
>                 Key: SPARK-26841
>                 URL: https://issues.apache.org/jira/browse/SPARK-26841
>             Project: Spark
>          Issue Type: Improvement
>          Components: Input/Output
>    Affects Versions: 2.4.0
>            Reporter: Tomas Bartalos
>            Priority: Major
>              Labels: Kafka, pushdown, timestamp
>
> As a Spark user I'd like to have fast queries on Kafka table restricted by timestamp.
> I'd like to have quick answers on questions like:
>  * What was inserted to Kafka in past x minutes
>  * What was inserted to Kafka in specified time range
> Example:
> {quote}select * from kafka_table where timestamp > from_unixtime(unix_timestamp() - 5 * 60, "YYYY-MM-dd HH:mm:ss")
> select * from kafka_table where timestamp > $from_time and timestamp < $end_time
> {quote}
> Currently timestamp restrictions are not pushdown to KafkaRelation and querying by timestamp on a large Kafka topic takes forever to complete.
> *Technical solution*
> Technically its possible to retrieve Kafka's offsets by provided timestamp with org.apache.kafka.clients.consumer.Consumer#offsetsForTimes(..) method. Afterwards we can query Kafka topic by retrieved timestamp ranges.
> Querying by timestamp range is already implemented so this change should have minor impact.



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