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Improve fetch of pending segments from metadata store #13310

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Merged
gianm merged 5 commits into from
Nov 8, 2022
Merged

Improve fetch of pending segments from metadata store #13310

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247c4eb
Deserialize only when needed
kfaraz Nov 4, 2022
7356862
Merge branch 'master' of github.com:apache/druid into get_pending_seg…
kfaraz Nov 5, 2022
3713725
Update query to fetch pending segments
kfaraz Nov 5, 2022
e7edd5c
Revert unneeded changes
kfaraz Nov 7, 2022
ac9f11d
Fix query
kfaraz Nov 7, 2022
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14 changes: 9 additions & 5 deletions server/src/main/java/org/apache/druid/metadata/IndexerSQLMetadataStorageCoordinator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -232,7 +232,10 @@ private Set<SegmentIdWithShardSpec> getPendingSegmentsForIntervalWithHandle(
final ResultIterator<byte[]> dbSegments =
handle.createQuery(
StringUtils.format(
"SELECT payload FROM %1$s WHERE dataSource = :dataSource AND start <= :end and %2$send%2$s >= :start",
// This query might fail if the year has a different number of digits
// See https://github.com/apache/druid/pull/11582 for a similar issue
// Using long for these timestamps instead of varchar would give correct time comparisons
"SELECT payload FROM %1$s WHERE dataSource = :dataSource AND start < :end and %2$send%2$s > :start",
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@gianm gianm Nov 7, 2022

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This looks like the only material change in the patch: what's the idea behind changing <= to < and what's the expected benefit?

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@kfaraz kfaraz Nov 7, 2022 •
edited
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We are trying to avoid selecting segments with intervals that only abut the search interval and don't have an actual overlap. Such intervals eventually get filtered out via the check on interval.overlaps(identifier.getInterval()) but only after the costly deserialization.

I have updated the description, which gives an example of such an interval.
This is still not a complete fix as the query can return incorrect results in cases where a string comparison of the two intervals is not feasible.

dbTables.getPendingSegmentsTable(), connector.getQuoteString()
)
)
Expand Down Expand Up @@ -584,7 +587,7 @@ private SegmentIdWithShardSpec allocatePendingSegmentWithSegmentLineageCheck(
.asBytes()
);

insertToMetastore(
insertPendingSegmentIntoMetastore(
handle,
newIdentifier,
dataSource,
Expand Down Expand Up @@ -662,7 +665,7 @@ private SegmentIdWithShardSpec allocatePendingSegment(
);

// always insert empty previous sequence id
insertToMetastore(handle, newIdentifier, dataSource, interval, "", sequenceName, sequenceNamePrevIdSha1);
insertPendingSegmentIntoMetastore(handle, newIdentifier, dataSource, interval, "", sequenceName, sequenceNamePrevIdSha1);

log.info("Allocated pending segment [%s] for sequence[%s] in DB", newIdentifier, sequenceName);

Expand Down Expand Up @@ -742,7 +745,7 @@ private static class CheckExistingSegmentIdResult
}
}

private void insertToMetastore(
private void insertPendingSegmentIntoMetastore(
Handle handle,
SegmentIdWithShardSpec newIdentifier,
String dataSource,
Expand Down Expand Up @@ -943,7 +946,7 @@ private SegmentIdWithShardSpec createNewSegment(

return new SegmentIdWithShardSpec(
dataSource,
overallMaxId.getInterval(),
interval,
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@kfaraz kfaraz Nov 4, 2022

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Changed to emphasize that the interval used in the SegmentIdWithShardSpec is always the same as the one passed to the method createNewSegment.

Preconditions.checkNotNull(newSegmentVersion, "newSegmentVersion"),
partialShardSpec.complete(
jsonMapper,
Expand Down Expand Up @@ -1468,4 +1471,5 @@ public int removeDataSourceMetadataOlderThan(long timestamp, @NotNull Set<String
}
);
}

}