From 2fdde4ba5539f17496f9ba2b77c94d47325c6ada Mon Sep 17 00:00:00 2001
From: Anton Popov <anton@clickhouse.com>
Date: Fri, 30 Aug 2024 00:29:46 +0000
Subject: [PATCH] unroll loop in bloom filter

---
 src/Interpreters/BloomFilter.cpp          | 35 +++++++++++++++++++++--
 src/Interpreters/BloomFilter.h            | 13 +++++++++
 tests/performance/ngram_filter_insert.xml |  9 ++++++
 3 files changed, 54 insertions(+), 3 deletions(-)
 create mode 100644 tests/performance/ngram_filter_insert.xml

diff --git a/src/Interpreters/BloomFilter.cpp b/src/Interpreters/BloomFilter.cpp
index 7bf50a0312b..0bb46b1f0a8 100644
--- a/src/Interpreters/BloomFilter.cpp
+++ b/src/Interpreters/BloomFilter.cpp
@@ -71,10 +71,39 @@ void BloomFilter::add(const char * data, size_t len)
     size_t hash1 = CityHash_v1_0_2::CityHash64WithSeed(data, len, seed);
     size_t hash2 = CityHash_v1_0_2::CityHash64WithSeed(data, len, SEED_GEN_A * seed + SEED_GEN_B);
 
-    for (size_t i = 0; i < hashes; ++i)
+    switch (hashes)
     {
-        size_t pos = (hash1 + i * hash2 + i * i) % (8 * size);
-        filter[pos / (8 * sizeof(UnderType))] |= (1ULL << (pos % (8 * sizeof(UnderType))));
+        case 1:
+        {
+            addHashesImpl<1>(hash1, hash2);
+            break;
+        }
+        case 2:
+        {
+            addHashesImpl<2>(hash1, hash2);
+            break;
+        }
+        case 3:
+        {
+            addHashesImpl<3>(hash1, hash2);
+            break;
+        }
+        case 4:
+        {
+            addHashesImpl<4>(hash1, hash2);
+            break;
+        }
+        default:
+        {
+            addHashesImpl<4>(hash1, hash2);
+
+            for (size_t i = 4; i < hashes; ++i)
+            {
+                size_t pos = (hash1 + i * hash2 + i * i) % (8 * size);
+                filter[pos / (8 * sizeof(UnderType))] |= (1ULL << (pos % (8 * sizeof(UnderType))));
+            }
+            break;
+        }
     }
 }
 
diff --git a/src/Interpreters/BloomFilter.h b/src/Interpreters/BloomFilter.h
index 8ebdfd879e6..76a0a76e247 100644
--- a/src/Interpreters/BloomFilter.h
+++ b/src/Interpreters/BloomFilter.h
@@ -8,6 +8,7 @@
 #include <Columns/IColumn.h>
 #include <Columns/ColumnVector.h>
 #include <DataTypes/IDataType.h>
+#include <base/constexpr_helpers.h>
 
 
 namespace DB
@@ -56,7 +57,19 @@ public:
     UInt64 isEmpty() const;
 
     friend bool operator== (const BloomFilter & a, const BloomFilter & b);
+
 private:
+    template <size_t num_hashes>
+    ALWAYS_INLINE void addHashesImpl(size_t hash1, size_t hash2)
+    {
+        static_assert(num_hashes >= 1 && num_hashes <= 4);
+
+        for (size_t i = 0; i < num_hashes; ++i)
+        {
+            size_t pos = (hash1 + i * hash2 + i * i) % (8 * size);
+            filter[pos / (8 * sizeof(UnderType))] |= (1ULL << (pos % (8 * sizeof(UnderType))));
+        }
+    }
 
     size_t size;
     size_t hashes;
diff --git a/tests/performance/ngram_filter_insert.xml b/tests/performance/ngram_filter_insert.xml
new file mode 100644
index 00000000000..e426a64bb81
--- /dev/null
+++ b/tests/performance/ngram_filter_insert.xml
@@ -0,0 +1,9 @@
+<test>
+    <create_query>DROP TABLE IF EXISTS test_ngram</create_query>
+    <create_query>CREATE TABLE test_ngram (s String, INDEX idx_s s TYPE ngrambf_v1(5, 10000, 3, 0) GRANULARITY 1) ENGINE = MergeTree ORDER BY tuple()</create_query>
+    <create_query>SYSTEM STOP MERGES test_ngram</create_query>
+
+    <query>INSERT INTO test_ngram SELECT randomPrintableASCII(128) FROM numbers(100000)</query>
+
+    <drop_query>DROP TABLE IF EXISTS test_ngram</drop_query>
+</test>