Can't set threshold=1 when using MinHashLSH?

[brother-darion]

Is it can't set threshold=1 when using MinHashLSH? I got error when I using MinHashLSH and set threshold=1 :

here is the code:

from datasketch import MinHash, MinHashLSH

set1 = set(['minhash', 'is', 'a', 'probabilistic', 'data', 'structure', 'for',
            'estimating', 'the', 'similarity', 'between', 'datasets'])
set2 = set(['minhash', 'is', 'a', 'probability', 'data', 'structure', 'for',
            'estimating', 'the', 'similarity', 'between', 'documents'])
set3 = set(['minhash', 'is', 'probability', 'data', 'structure', 'for',
            'estimating', 'the', 'similarity', 'between', 'documents'])

m1 = MinHash(num_perm=128)
m2 = MinHash(num_perm=128)
m3 = MinHash(num_perm=128)
for d in set1:
    m1.update(d.encode('utf8'))
for d in set2:
    m2.update(d.encode('utf8'))
for d in set3:
    m3.update(d.encode('utf8'))

# Create LSH index
lsh = MinHashLSH(threshold=1, num_perm=128)
lsh.insert("m2", m2)
lsh.insert("m3", m3)
result = lsh.query(m1)
print("Approximate neighbours with Jaccard similarity > 0.5", result)

and got error:

Traceback (most recent call last):
File "/opt/venv/test/lib/python3.8/site-packages/IPython/core/interactiveshell.py", line 3508, in run_code
exec(code_obj, self.user_global_ns, self.user_ns)
File "", line 21, in
lsh = MinHashLSH(threshold=1, num_perm=128)
File "/opt/venv/test/lib/python3.8/site-packages/datasketch/lsh.py", line 174, in init
raise ValueError("The number of bands are too small (b < 2)")
ValueError: The number of bands are too small (b < 2)

[cameron-toy]

There's no need to use LSH for threshold=1.0 since that would only match items with the exact same MinHash. Instead, you can store items in a dict keyed by the hash of the entire MinHash, or even skip using MinHash and just use a single hash of the entire item.