bloom_filter_fp_chance needs to be validated up front

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.