tibrewalpratik17 commented on code in PR #13285:
URL: https://github.com/apache/pinot/pull/13285#discussion_r1631700908
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pinot-core/src/main/java/org/apache/pinot/core/data/manager/realtime/RealtimeSegmentDataManager.java:
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@@ -703,9 +703,20 @@ public void run() {
// persisted.
// Take upsert snapshot before starting consuming events
if (_partitionUpsertMetadataManager != null) {
- _partitionUpsertMetadataManager.takeSnapshot();
- // If upsertTTL is enabled, we will remove expired primary keys from
upsertMetadata after taking snapshot.
- _partitionUpsertMetadataManager.removeExpiredPrimaryKeys();
+ if (_tableConfig.getUpsertMetadataTTL() > 0) {
+ // If upsertMetadataTTL is enabled, we will remove expired primary
keys from upsertMetadata
+ // AFTER taking a snapshot. Taking the snapshot first is crucial
to ensure we capture the final
+ // state of a particular key before it exits the TTL window.
Review Comment:
> curious why it is critical to take snapshot first? The states of those
particular keys will be gone in the next snapshot, and would that cause issue?
I don't see this as a very strict requirement, but let's consider the
scenario where we reverse the order and the _metadataTTL logic removes keys
older than the TTL window. If a server restart occurs before snapshotting, the
addSegment flow will not find a snapshot for an out-of-TTL segment and will
consider all records as valid for querying. However, some records may have had
updates and should not be served from this out-of-TTL segment. The snapshot
logic helps prevent this issue. This is my understanding from the code, but
@deemoliu can confirm.
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