PlainTable hard codes num_probes=6 for Bloom filter, regardless of bloom_bits_per_key

[pdillinger]

Expected behavior

When using PlainTable with Bloom filter, expect it to choose reasonable num_probes based on bloom_bits_per_key setting.

Actual behavior

Always uses num_probes = 6 even when that's really bad for speed and false positive rate.

Steps to reproduce the behavior

Just based on code inspection:

rocksdb/table/plain/plain_table_factory.cc

Line 47 in 62829ff

table_builder_options.column_family_name, 6,

[pdillinger]

And here:

rocksdb/table/plain/plain_table_reader.cc

Line 108 in 1d6a10f

bloom_(6),

[liam-thunder]

I prepared a PR for this issue
#5833