satishkotha commented on a change in pull request #1396: [HUDI-687] Stop
incremental reader on RO table before a pending compaction
URL: https://github.com/apache/incubator-hudi/pull/1396#discussion_r403836768
##########
File path:
hudi-hadoop-mr/src/main/java/org/apache/hudi/hadoop/HoodieParquetInputFormat.java
##########
@@ -118,6 +119,34 @@
return returns.toArray(new FileStatus[returns.size()]);
}
+ /**
+ * Filter any specific instants that we do not want to process.
+ * example timeline:
+ *
+ * t0 -> create bucket1.parquet
+ * t1 -> create and append updates bucket1.log
+ * t2 -> request compaction
+ * t3 -> create bucket2.parquet
+ *
+ * if compaction at t2 takes a long time, incremental readers on RO tables
can move to t3 and would skip updates in t1
+ *
+ * To workaround this problem, we want to stop returning data belonging to
commits > t2.
+ * After compaction is complete, incremental reader would see updates in t2,
t3, so on.
+ */
+ protected HoodieDefaultTimeline filterInstantsTimeline(HoodieDefaultTimeline
timeline) {
+ Option<HoodieInstant> pendingCompactionInstant =
timeline.filterPendingCompactionTimeline().firstInstant();
+ if (pendingCompactionInstant.isPresent()) {
Review comment:
Yes, this is the crux of the change. My understanding is this bug caused
data loss on derived ETL tables multiple times. These ETL tables are generated
using incremental reads on "RO"views. As you suggested, that is core issue and
switching to RT views is likely going to get rid of the problem.
Also given "getting started" and other demo examples include incremental
reads on RO views, I think this new safeguard is useful to have, especially
given that finding root cause for this took a while. I am fine with
abandoning this change if we can remove incremental read examples on RO views
in documentation.
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