Yukei7 commented on code in PR #3754:
URL: https://github.com/apache/cassandra/pull/3754#discussion_r1984281912
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src/java/org/apache/cassandra/db/lifecycle/View.java:
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@@ -353,4 +361,40 @@ public boolean apply(T t)
}
};
}
+
+ // Match the SSTableReaders from the existing ones to the new one to be
added (with same ranges)
+ // Returns the map of toRemove <-> toAdd. Return empty map if such 1-1
replacement doesn't exist
+ private static Map<SSTableReader, SSTableReader> getReplacementMap(final
Set<SSTableReader> remove, final Iterable<SSTableReader> add)
+ {
+ List<SSTableReader> toAdds = new ArrayList<>();
+ for (SSTableReader s : add)
+ toAdds.add(s);
+
+ if (remove.size() != toAdds.size())
+ return Collections.emptyMap();
+
+ List<SSTableReader> toRemoves = new ArrayList<>(remove);
+ // sort the SSTableReader list by (first, last, descriptor.id). The
view is per cfs so id will be unique
+ Comparator<SSTableReader> comp = Comparator.comparing((SSTableReader
s) -> s.first)
+ .thenComparing(s -> s.last)
+
.thenComparing(SSTableReader.idComparator);
+ toRemoves.sort(comp);
+ toAdds.sort(comp);
+
+ Map<SSTableReader, SSTableReader> replacementMap = new HashMap<>();
+ // toAdd and toRemove have the same size
+ for (int i = 0; i < toAdds.size(); i++)
+ {
+ SSTableReader toRemove = toRemoves.get(i);
+ SSTableReader toAdd = toAdds.get(i);
+ // optimization: here we don't check the descriptor. If we're able
to match those to be removed with those
+ // to be added, we ensure that the pairs have the same (first,
last) range
+ if (toRemove.first.equals(toAdd.first) &&
toRemove.last.equals(toAdd.last))
Review Comment:
IntervalTree only search with `searchInterval.min` and `searchInterval.max`,
all sstables intersect with this will be returned. It's safe if we properly
construct this map to ensure that toAdd and toRemove is 1-to-1 mapping with
same [first,last], and in the replace method we do check on `toRemove` equals
to the interval in the tree.
e.g.
Say T1, T2, T3 all share [1,4]
We replace T2 with T2' also share with [1,4]
toAdd = T2', toRemove=T2
The map here will be {T2: T2'}
When actually figuring the intervals to do replacement, we do check:
`node.intersectsLeft.get(i).equals(intervalToRemove)`
That we start checking from T1, but `!T1.equals(T2)` and we continue to the
correct place T2.
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