Blake Eggleston created CASSANDRA-14861:
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Summary: Inaccurate sstable min/max metadata can cause data loss
Key: CASSANDRA-14861
URL: https://issues.apache.org/jira/browse/CASSANDRA-14861
Project: Cassandra
Issue Type: Bug
Reporter: Blake Eggleston
Assignee: Blake Eggleston
Fix For: 3.0.18, 3.11.4, 4.0
There’s a bug in the way we filter sstables in the read path that can cause
sstables containing relevant range tombstones to be excluded from reads. This
can cause data resurrection for an individual read, and if compaction timing is
right, permanent resurrection via read repair.
We track the min and max clustering values when writing an sstable so we can
avoid reading from sstables that don’t contain the clustering values we’re
looking for in a given read. The min max for each clustering column are updated
for each row / RT marker we write. In the case of range tombstones markers
though, we only update the min max for the clustering values they contain,
which is almost never the full set of clustering values. This leaves a min/max
that are above/below (respectively) the real ranges covered by the range
tombstone contained in the sstable.
For instance, assume we’re writing an sstable for a table with 3 clustering
values. The current min clustering is 5:6:7. We write an RT marker for a range
tombstone that deletes any row with the value 4 in the first clustering value
so the open marker is [4:]. This would make the new min clustering 4:6:7 when
it should really be 4:. If we do a read for clustering values of 4:5 and lower,
we’ll exclude this sstable and it’s range tombstone, resurrecting any data
there that this tombstone would have deleted.
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