gjacoby126 commented on code in PR #1495:
URL: https://github.com/apache/phoenix/pull/1495#discussion_r957929952
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phoenix-core/src/main/java/org/apache/phoenix/compile/WhereOptimizer.java:
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@@ -308,6 +322,30 @@ public static Expression
pushKeyExpressionsToScan(StatementContext context, Set<
slotSpanArray[cnf.size()] = clipLeftSpan-1;
cnf.add(keyRanges);
}
+
+ // Do not use the skipScanFilter when there is a large IN clause
(for e.g > 50k elements)
+ // Since the generation of point keys for skip scan filter will
blow up the memory usage.
+ // See ScanRanges.getPointKeys(...) where using the various slot
key ranges
+ // to generate point keys will lead to combinatorial explosion.
+ // The following check will ensure the cardinality of generated
point keys
+ // is below the configured max (maxInListSkipScanSize).
+ // We shall force a range scan if the configured max is exceeded.
+ // cnfStartPos => is the start slot of this IN list
+ if (checkMaxSkipScanCardinality) {
Review Comment:
There's already a config param to control how many elements triggers the
conversion, which could be used to turn it off by setting it very high.
However, when we get in this state (high cardinality skip scans) we find that
we get OOM exceptions even with large client-side heaps, which is worse than a
slow query.
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