ADARSH KUMAR created CASSANDRA-11920:
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Summary: Not able to set bloom_filter_fp_chance as .00001
Key: CASSANDRA-11920
URL: https://issues.apache.org/jira/browse/CASSANDRA-11920
Project: Cassandra
Issue Type: Bug
Components: Lifecycle, Local Write-Read Paths
Reporter: ADARSH KUMAR
Hi,
I was doing some bench-marking on bloom_filter_fp_chance values. Everything
worked fine for values .01(default for STCS), .001, .0001. But when I set
bloom_filter_fp_chance = .00001 i observed following behaviour:
1). Reads and writes looked normal from cqlsh.
2). SSttables are never created.
3). It just creates two files (*-Data.db and *-index.db) of size 0kb.
4). nodetool flush does not work and produce following exception:
java.lang.UnsupportedOperationException: Unable to satisfy 1.0E-5 with 20
buckets per element
at
org.apache.cassandra.utils.BloomCalculations.computeBloomSpec(BloomCalculations.java:150)
.....
I checked BloomCalculations class and following lines are responsible for this
exception:
if (maxFalsePosProb < probs[maxBucketsPerElement][maxK]) {
throw new UnsupportedOperationException(String.format("Unable to satisfy
%s with %s buckets per element",
maxFalsePosProb,
maxBucketsPerElement));
}
>From the code it looks like a hard coaded validation (unless we can change
>the nuber of buckets).
So, if this validation is hard coaded then why it is even allowed to set such
value of bloom_fileter_fp_chance, that can prevent ssTable generation?
Please correct this issue.
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