1 | #pragma once |
2 | |
3 | #include <Common/HashTable/StringHashTable.h> |
4 | |
5 | template <typename SubMaps, typename ImplTable = StringHashTable<SubMaps>, size_t BITS_FOR_BUCKET = 8> |
6 | class TwoLevelStringHashTable : private boost::noncopyable |
7 | { |
8 | protected: |
9 | using HashValue = size_t; |
10 | using Self = TwoLevelStringHashTable; |
11 | |
12 | public: |
13 | using Key = StringRef; |
14 | using Impl = ImplTable; |
15 | |
16 | static constexpr size_t NUM_BUCKETS = 1ULL << BITS_FOR_BUCKET; |
17 | static constexpr size_t MAX_BUCKET = NUM_BUCKETS - 1; |
18 | |
19 | // TODO: currently hashing contains redundant computations when doing distributed or external aggregations |
20 | size_t hash(const Key & x) const |
21 | { |
22 | return const_cast<Self &>(*this).dispatch(*this, x, [&](const auto &, const auto &, size_t hash) { return hash; }); |
23 | } |
24 | |
25 | size_t operator()(const Key & x) const { return hash(x); } |
26 | |
27 | /// NOTE Bad for hash tables with more than 2^32 cells. |
28 | static size_t getBucketFromHash(size_t hash_value) { return (hash_value >> (32 - BITS_FOR_BUCKET)) & MAX_BUCKET; } |
29 | |
30 | public: |
31 | using key_type = typename Impl::key_type; |
32 | using mapped_type = typename Impl::mapped_type; |
33 | using value_type = typename Impl::value_type; |
34 | using cell_type = typename Impl::cell_type; |
35 | |
36 | using LookupResult = typename Impl::LookupResult; |
37 | using ConstLookupResult = typename Impl::ConstLookupResult; |
38 | |
39 | Impl impls[NUM_BUCKETS]; |
40 | |
41 | TwoLevelStringHashTable() {} |
42 | |
43 | template <typename Source> |
44 | TwoLevelStringHashTable(const Source & src) |
45 | { |
46 | if (src.m0.hasZero()) |
47 | impls[0].m0.setHasZero(*src.m0.zeroValue()); |
48 | |
49 | for (auto & v : src.m1) |
50 | { |
51 | size_t hash_value = v.getHash(src.m1); |
52 | size_t buck = getBucketFromHash(hash_value); |
53 | impls[buck].m1.insertUniqueNonZero(&v, hash_value); |
54 | } |
55 | for (auto & v : src.m2) |
56 | { |
57 | size_t hash_value = v.getHash(src.m2); |
58 | size_t buck = getBucketFromHash(hash_value); |
59 | impls[buck].m2.insertUniqueNonZero(&v, hash_value); |
60 | } |
61 | for (auto & v : src.m3) |
62 | { |
63 | size_t hash_value = v.getHash(src.m3); |
64 | size_t buck = getBucketFromHash(hash_value); |
65 | impls[buck].m3.insertUniqueNonZero(&v, hash_value); |
66 | } |
67 | for (auto & v : src.ms) |
68 | { |
69 | size_t hash_value = v.getHash(src.ms); |
70 | size_t buck = getBucketFromHash(hash_value); |
71 | impls[buck].ms.insertUniqueNonZero(&v, hash_value); |
72 | } |
73 | } |
74 | |
75 | // This function is mostly the same as StringHashTable::dispatch, but with |
76 | // added bucket computation. See the comments there. |
77 | template <typename Self, typename Func, typename KeyHolder> |
78 | static auto ALWAYS_INLINE dispatch(Self & self, KeyHolder && key_holder, Func && func) |
79 | { |
80 | const StringRef & x = keyHolderGetKey(key_holder); |
81 | const size_t sz = x.size; |
82 | if (sz == 0) |
83 | { |
84 | keyHolderDiscardKey(key_holder); |
85 | return func(self.impls[0].m0, VoidKey{}, 0); |
86 | } |
87 | |
88 | const char * p = x.data; |
89 | // pending bits that needs to be shifted out |
90 | const char s = (-sz & 7) * 8; |
91 | union |
92 | { |
93 | StringKey8 k8; |
94 | StringKey16 k16; |
95 | StringKey24 k24; |
96 | UInt64 n[3]; |
97 | }; |
98 | StringHashTableHash hash; |
99 | switch ((sz - 1) >> 3) |
100 | { |
101 | case 0: |
102 | { |
103 | // first half page |
104 | if ((reinterpret_cast<uintptr_t>(p) & 2048) == 0) |
105 | { |
106 | memcpy(&n[0], p, 8); |
107 | n[0] &= -1ul >> s; |
108 | } |
109 | else |
110 | { |
111 | const char * lp = x.data + x.size - 8; |
112 | memcpy(&n[0], lp, 8); |
113 | n[0] >>= s; |
114 | } |
115 | auto res = hash(k8); |
116 | auto buck = getBucketFromHash(res); |
117 | keyHolderDiscardKey(key_holder); |
118 | return func(self.impls[buck].m1, k8, res); |
119 | } |
120 | case 1: |
121 | { |
122 | memcpy(&n[0], p, 8); |
123 | const char * lp = x.data + x.size - 8; |
124 | memcpy(&n[1], lp, 8); |
125 | n[1] >>= s; |
126 | auto res = hash(k16); |
127 | auto buck = getBucketFromHash(res); |
128 | keyHolderDiscardKey(key_holder); |
129 | return func(self.impls[buck].m2, k16, res); |
130 | } |
131 | case 2: |
132 | { |
133 | memcpy(&n[0], p, 16); |
134 | const char * lp = x.data + x.size - 8; |
135 | memcpy(&n[2], lp, 8); |
136 | n[2] >>= s; |
137 | auto res = hash(k24); |
138 | auto buck = getBucketFromHash(res); |
139 | keyHolderDiscardKey(key_holder); |
140 | return func(self.impls[buck].m3, k24, res); |
141 | } |
142 | default: |
143 | { |
144 | auto res = hash(x); |
145 | auto buck = getBucketFromHash(res); |
146 | return func(self.impls[buck].ms, std::forward<KeyHolder>(key_holder), res); |
147 | } |
148 | } |
149 | } |
150 | |
151 | template <typename KeyHolder> |
152 | void ALWAYS_INLINE emplace(KeyHolder && key_holder, LookupResult & it, bool & inserted) |
153 | { |
154 | dispatch(*this, key_holder, typename Impl::EmplaceCallable{it, inserted}); |
155 | } |
156 | |
157 | LookupResult ALWAYS_INLINE find(const Key x) |
158 | { |
159 | return dispatch(*this, x, typename Impl::FindCallable{}); |
160 | } |
161 | |
162 | ConstLookupResult ALWAYS_INLINE find(const Key x) const |
163 | { |
164 | return dispatch(*this, x, typename Impl::FindCallable{}); |
165 | } |
166 | |
167 | void write(DB::WriteBuffer & wb) const |
168 | { |
169 | for (size_t i = 0; i < NUM_BUCKETS; ++i) |
170 | impls[i].write(wb); |
171 | } |
172 | |
173 | void writeText(DB::WriteBuffer & wb) const |
174 | { |
175 | for (size_t i = 0; i < NUM_BUCKETS; ++i) |
176 | { |
177 | if (i != 0) |
178 | DB::writeChar(',', wb); |
179 | impls[i].writeText(wb); |
180 | } |
181 | } |
182 | |
183 | void read(DB::ReadBuffer & rb) |
184 | { |
185 | for (size_t i = 0; i < NUM_BUCKETS; ++i) |
186 | impls[i].read(rb); |
187 | } |
188 | |
189 | void readText(DB::ReadBuffer & rb) |
190 | { |
191 | for (size_t i = 0; i < NUM_BUCKETS; ++i) |
192 | { |
193 | if (i != 0) |
194 | DB::assertChar(',', rb); |
195 | impls[i].readText(rb); |
196 | } |
197 | } |
198 | |
199 | size_t size() const |
200 | { |
201 | size_t res = 0; |
202 | for (size_t i = 0; i < NUM_BUCKETS; ++i) |
203 | res += impls[i].size(); |
204 | |
205 | return res; |
206 | } |
207 | |
208 | bool empty() const |
209 | { |
210 | for (size_t i = 0; i < NUM_BUCKETS; ++i) |
211 | if (!impls[i].empty()) |
212 | return false; |
213 | |
214 | return true; |
215 | } |
216 | |
217 | size_t getBufferSizeInBytes() const |
218 | { |
219 | size_t res = 0; |
220 | for (size_t i = 0; i < NUM_BUCKETS; ++i) |
221 | res += impls[i].getBufferSizeInBytes(); |
222 | |
223 | return res; |
224 | } |
225 | }; |
226 | |