[GitHub] [druid] clintropolis commented on a change in pull request #10366: Add caching support to join queries

[GitBox <gi...@apache.org>]

clintropolis commented on a change in pull request #10366:
URL: https://github.com/apache/druid/pull/10366#discussion_r493188636



##########
File path: processing/src/main/java/org/apache/druid/segment/join/JoinableFactory.java
##########
@@ -43,8 +43,18 @@
    *
    * @param dataSource the datasource to join on
    * @param condition  the condition to join on
-   *
    * @return a Joinable if this datasource + condition combo is joinable; empty if not
    */
   Optional<Joinable> build(DataSource dataSource, JoinConditionAnalysis condition);
+
+  /**
+   * Compute the cache key for a data source participating in join operation. This is done separately from {{@link #build(DataSource, JoinConditionAnalysis)}}
+   * which can be an expensive operation and can potentially be avoided if cached results can be used.
+   *
+   * @param dataSource the datasource to join on
+   */
+  default Optional<byte[]> computeJoinCacheKey(DataSource dataSource)

Review comment:
       +1 for having a consistent interface with `build` since they need to make the same decisions. I'm not sure this PR is the correct venue to refactor `build` so I would be in favor of adding `JoinConditionAnalysis` argument




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