Davis-Zhang-Onehouse commented on code in PR #12646:
URL: https://github.com/apache/hudi/pull/12646#discussion_r1927817254
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hudi-common/src/main/java/org/apache/hudi/common/table/TableSchemaResolver.java:
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@@ -514,4 +580,56 @@ public static Schema appendPartitionColumns(Schema
dataSchema, Option<String[]>
private Supplier<Exception> schemaNotFoundError() {
return () -> new HoodieSchemaNotFoundException("No schema found for table
at " + metaClient.getBasePath());
}
+
+ /**
+ * WARNING: This method should be only used as part of HUDI-8438 before the
jira owner fully accommodate all existing use
+ * cases.
+ *
+ * Get timeline in REVERSE order that only contains completed instants which
POTENTIALLY evolve the table schema.
+ * For types of instants that are included and not reflecting table schema
at their instant completion time please refer
+ * comments inside the code.
+ * */
+ HoodieTimeline getSchemaEvolutionTimelineInReverseOrder() {
+ HoodieActiveTimeline timeline = metaClient.getActiveTimeline();
+ Stream<HoodieInstant> timelineStream = timeline.getInstantsAsStream();
+ final Set<String> actions;
+ switch (metaClient.getTableType()) {
+ case COPY_ON_WRITE: {
+ actions = new HashSet<>(Arrays.asList(COMMIT_ACTION,
REPLACE_COMMIT_ACTION));
+ break;
+ }
+ case MERGE_ON_READ: {
+ actions = new HashSet<>(Arrays.asList(DELTA_COMMIT_ACTION,
REPLACE_COMMIT_ACTION));
+ break;
+ }
+ default:
+ throw new HoodieException("Unsupported table type :" +
metaClient.getTableType());
+ }
+
+ // We only care committed instant when it comes to table schema.
+ TimelineLayout timelineLayout = metaClient.getTimelineLayout();
+ Comparator<HoodieInstant> reversedComparator =
timelineLayout.getInstantComparator().requestedTimeOrderedComparator().reversed();
+
+ // The timeline still contains DELTA_COMMIT_ACTION/COMMIT_ACTION which
might not contain a valid schema
+ // field in their commit metadata.
+ // Since the operations of filtering them out are expensive, we should do
on-demand stream based
+ // filtering when we actually need the table schema.
+ Stream<HoodieInstant> reversedTimelineWithTableSchema = timelineStream
+ // Only focuses on those who could potentially evolve the table schema.
+ .filter(s -> actions.contains(s.getAction()))
+ // Further filtering out clustering operations as it does not evolve
table schema.
+ .filter(s -> isaBoolean(s, timeline))
+ .filter(HoodieInstant::isCompleted)
+ // We reverse the order as the operation against this timeline would
be very efficient if
+ // we always start from the tail.
+ .sorted(reversedComparator);
+ return timelineLayout.getTimelineFactory().createDefaultTimeline(
+ reversedTimelineWithTableSchema,
+ metaClient.getActiveTimeline()::getInstantDetails);
+ }
+
+ private boolean isaBoolean(HoodieInstant s, HoodieActiveTimeline timeline) {
Review Comment:
done
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