quotient filter: merge test mismatch hash strategies

barrust · Jan 13, 2024 · 7522c02 · 7522c02
1 parent c1b8310
commit 7522c02
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diff --git a/probables/quotientfilter/quotientfilter.py b/probables/quotientfilter/quotientfilter.py
@@ -265,6 +265,8 @@ def merge(self, second: "QuotientFilter") -> None:
             The hashing function between the two filters should match
         Note:
             Errors can occur if the quotient filter being inserted into does not expand (i.e., auto_expand=False)"""
+        if self._hash_func("test", 0) != second._hash_func("test", 0):
+            raise QuotientFilterError("Hash functions do not match")
 
         for _h in second.hashes():
             self.add_alt(_h)

diff --git a/tests/quotientfilter_test.py b/tests/quotientfilter_test.py
@@ -227,3 +227,12 @@ def test_qf_merge_error(self):
             fq.add(str(i))
 
         self.assertRaises(QuotientFilterError, lambda: qf.merge(fq))
+
+        # test mismatch hashes
+        def useless_hash(key, seed) -> int:
+            return 99999999
+
+        qq = QuotientFilter(quotient=8, hash_function=useless_hash)
+        qq.add("999")
+
+        self.assertRaises(QuotientFilterError, lambda: fq.merge(qq))