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LibSQL: Hash index implementation for the SQL storage layer
This patch implements a basic hash index. It uses the extendible hashing algorith. Also includes a test file.
This commit is contained in:
Jan de Visser
Andreas Kling
parent
224804b424
commit
267eb3b329
5 changed files with 945 additions and 0 deletions
423
Userland/Libraries/LibSQL/HashIndex.cpp
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423
Userland/Libraries/LibSQL/HashIndex.cpp
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/*
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* Copyright (c) 2021, Jan de Visser <jan@de-visser.net>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibSQL/HashIndex.h>
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#include <LibSQL/Heap.h>
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#include <LibSQL/Key.h>
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#include <LibSQL/Serialize.h>
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namespace SQL {
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HashDirectoryNode::HashDirectoryNode(HashIndex& index, u32 node_number, size_t offset)
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: IndexNode(index.node_pointer(node_number))
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, m_hash_index(index)
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, m_node_number(node_number)
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, m_offset(offset)
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{
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}
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HashDirectoryNode::HashDirectoryNode(HashIndex& index, u32 pointer, ByteBuffer& buffer)
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: IndexNode(pointer)
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, m_hash_index(index)
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{
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dbgln_if(SQL_DEBUG, "Deserializing Hash Directory Node");
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size_t offset = 0;
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deserialize_from<u32>(buffer, offset, index.m_global_depth);
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u32 size;
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deserialize_from<u32>(buffer, offset, size);
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dbgln_if(SQL_DEBUG, "Global Depth {}, #Bucket pointers {}", index.global_depth(), size);
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u32 next_node;
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deserialize_from<u32>(buffer, offset, next_node);
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if (next_node) {
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dbgln_if(SQL_DEBUG, "Next node {}", next_node);
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m_hash_index.m_nodes.append(next_node);
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} else {
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dbgln_if(SQL_DEBUG, "This is the last directory node");
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m_is_last = true;
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}
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for (auto ix = 0u; ix < size; ix++) {
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u32 bucket_pointer;
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deserialize_from(buffer, offset, bucket_pointer);
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u32 local_depth;
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deserialize_from(buffer, offset, local_depth);
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dbgln_if(SQL_DEBUG, "Bucket pointer {} local depth {}", bucket_pointer, local_depth);
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index.append_bucket(ix, local_depth, bucket_pointer);
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}
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}
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void HashDirectoryNode::serialize(ByteBuffer& buffer) const
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{
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dbgln_if(SQL_DEBUG, "Serializing directory node #{}. Offset {}", m_node_number, m_offset);
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serialize_to(buffer, m_hash_index.global_depth());
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serialize_to(buffer, number_of_pointers());
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dbgln_if(SQL_DEBUG, "Global depth {}, #bucket pointers {}", m_hash_index.global_depth(), number_of_pointers());
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u32 next_node;
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if (m_node_number < (m_hash_index.m_nodes.size() - 1)) {
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next_node = m_hash_index.m_nodes[m_node_number + 1];
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dbgln_if(SQL_DEBUG, "Next directory node pointer {}", next_node);
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} else {
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next_node = 0u;
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dbgln_if(SQL_DEBUG, "This is the last directory node");
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}
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serialize_to(buffer, next_node);
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for (auto ix = 0u; ix < number_of_pointers(); ix++) {
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auto& bucket = m_hash_index.m_buckets[m_offset + ix];
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dbgln_if(SQL_DEBUG, "Bucket pointer {} local depth {}", bucket->pointer(), bucket->local_depth());
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serialize_to(buffer, bucket->pointer());
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serialize_to(buffer, bucket->local_depth());
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}
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}
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HashBucket::HashBucket(HashIndex& hash_index, u32 index, u32 local_depth, u32 pointer)
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: IndexNode(pointer)
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, m_hash_index(hash_index)
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, m_local_depth(local_depth)
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, m_index(index)
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{
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}
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void HashBucket::serialize(ByteBuffer& buffer) const
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{
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dbgln_if(SQL_DEBUG, "Serializing bucket: pointer {}, index #{}, local depth {} size {}",
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pointer(), index(), local_depth(), size());
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dbgln_if(SQL_DEBUG, "key_length: {} max_entries: {}", m_hash_index.descriptor().data_length(), max_entries_in_bucket());
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serialize_to(buffer, local_depth());
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serialize_to(buffer, size());
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dbgln_if(SQL_DEBUG, "buffer size after prolog {}", buffer.size());
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for (auto& key : m_entries) {
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key.serialize(buffer);
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dbgln_if(SQL_DEBUG, "Key {} buffer size {}", key.to_string(), buffer.size());
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}
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}
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void HashBucket::inflate()
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{
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if (m_inflated || !pointer())
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return;
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dbgln_if(SQL_DEBUG, "Inflating Hash Bucket {}", pointer());
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auto buffer = m_hash_index.read_block(pointer());
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size_t offset = 0;
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deserialize_from(buffer, offset, m_local_depth);
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dbgln_if(SQL_DEBUG, "Bucket Local Depth {}", m_local_depth);
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u32 size;
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deserialize_from(buffer, offset, size);
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dbgln_if(SQL_DEBUG, "Bucket has {} keys", size);
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for (auto ix = 0u; ix < size; ix++) {
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Key key(m_hash_index.descriptor(), buffer, offset);
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dbgln_if(SQL_DEBUG, "Key {}: {}", ix, key.to_string());
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m_entries.append(key);
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}
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m_inflated = true;
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}
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size_t HashBucket::max_entries_in_bucket() const
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{
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auto key_size = m_hash_index.descriptor().data_length() + sizeof(u32);
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return (BLOCKSIZE - 2 * sizeof(u32)) / key_size;
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}
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Optional<u32> HashBucket::get(Key& key)
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{
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auto optional_index = find_key_in_bucket(key);
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if (optional_index.has_value()) {
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auto& k = m_entries[optional_index.value()];
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key.set_pointer(k.pointer());
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return k.pointer();
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}
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return {};
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}
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bool HashBucket::insert(Key const& key)
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{
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inflate();
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if (find_key_in_bucket(key).has_value()) {
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return false;
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}
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if (size() >= max_entries_in_bucket()) {
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return false;
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}
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m_entries.append(key);
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m_hash_index.add_to_write_ahead_log(this);
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return true;
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}
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Optional<size_t> HashBucket::find_key_in_bucket(Key const& key)
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{
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for (auto ix = 0u; ix < size(); ix++) {
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auto& k = entries()[ix];
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if (k == key) {
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return ix;
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}
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}
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return {};
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}
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HashBucket const* HashBucket::next_bucket()
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{
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for (auto ix = m_index + 1; ix < m_hash_index.size(); ix++) {
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auto bucket = m_hash_index.get_bucket_by_index(ix);
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bucket->inflate();
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if (bucket->size())
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return bucket;
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}
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return nullptr;
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}
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HashBucket const* HashBucket::previous_bucket()
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{
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for (auto ix = m_index - 1; ix > 0; ix--) {
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auto bucket = m_hash_index.get_bucket_by_index(ix);
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if (bucket->pointer())
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return bucket;
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}
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return nullptr;
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}
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Key const& HashBucket::operator[](size_t ix)
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{
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inflate();
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VERIFY(ix < size());
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return m_entries[ix];
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}
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void HashBucket::list_bucket()
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{
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warnln("Bucket #{} size {} local depth {} pointer {}{}",
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index(), size(), local_depth(), pointer(), (pointer() ? "" : " (VIRTUAL)"));
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for (auto& key : entries()) {
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warnln(" {} hash {}", key.to_string(), key.hash());
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}
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}
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HashIndex::HashIndex(Heap& heap, TupleDescriptor const& descriptor, u32 first_node)
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: Index(heap, descriptor, true, first_node)
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, m_nodes()
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, m_buckets()
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{
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if (!first_node) {
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set_pointer(new_record_pointer());
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}
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if (this->heap().has_block(first_node)) {
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u32 pointer = first_node;
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do {
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VERIFY(this->heap().has_block(pointer));
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auto buffer = read_block(pointer);
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auto node = HashDirectoryNode(*this, pointer, buffer);
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if (node.is_last())
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break;
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pointer = m_nodes.last(); // FIXME Ugly
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} while (pointer);
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} else {
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auto bucket = append_bucket(0u, 1u, new_record_pointer());
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bucket->m_inflated = true;
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add_to_write_ahead_log(bucket);
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bucket = append_bucket(1u, 1u, new_record_pointer());
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bucket->m_inflated = true;
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add_to_write_ahead_log(bucket);
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m_nodes.append(first_node);
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write_directory_to_write_ahead_log();
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}
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}
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HashBucket* HashIndex::get_bucket(u32 index)
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{
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VERIFY(index < m_buckets.size());
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auto divisor = size() / 2;
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while (!m_buckets[index]->pointer()) {
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VERIFY(divisor > 1);
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index = index % divisor;
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divisor /= 2;
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}
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auto& bucket = m_buckets[index];
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return bucket;
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}
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HashBucket* HashIndex::get_bucket_for_insert(Key const& key)
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{
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auto key_hash = key.hash();
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do {
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auto bucket = get_bucket(key_hash % size());
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if (bucket->size() < bucket->max_entries_in_bucket()) {
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return bucket;
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}
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// We previously doubled the directory but the target bucket is
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// still at an older depth. Create new buckets at the current global
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// depth and allocate the contents of the existing buckets to the
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// newly created ones:
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while (bucket->local_depth() < global_depth()) {
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auto base_index = bucket->index();
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auto step = 1 << (global_depth() - bucket->local_depth());
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for (auto ix = base_index + step; ix < size(); ix += step) {
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auto& sub_bucket = m_buckets[ix];
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sub_bucket->set_local_depth(bucket->local_depth() + 1);
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for (auto entry_index = (int)bucket->m_entries.size() - 1; entry_index >= 0; entry_index--) {
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if (bucket->m_entries[entry_index].hash() % size() == ix) {
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if (!sub_bucket->pointer()) {
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sub_bucket->set_pointer(new_record_pointer());
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}
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sub_bucket->insert(bucket->m_entries.take(entry_index));
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}
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}
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if (m_buckets[ix]->pointer())
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add_to_write_ahead_log(m_buckets[ix]);
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}
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bucket->set_local_depth(bucket->local_depth() + 1);
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add_to_write_ahead_log(bucket);
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write_directory_to_write_ahead_log();
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auto bucket_after_redistribution = get_bucket(key_hash % size());
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if (bucket_after_redistribution->size() < bucket_after_redistribution->max_entries_in_bucket()) {
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return bucket_after_redistribution;
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}
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}
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expand();
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} while (true);
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}
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void HashIndex::expand()
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{
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auto sz = size();
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for (auto i = 0u; i < sz; i++) {
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auto bucket = get_bucket(i);
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bucket = append_bucket(sz + i, bucket->local_depth(), 0u);
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bucket->m_inflated = true;
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}
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m_global_depth++;
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write_directory_to_write_ahead_log();
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}
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void HashIndex::write_directory_to_write_ahead_log()
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{
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auto num_nodes_required = (size() / HashDirectoryNode::max_pointers_in_node()) + 1;
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while (m_nodes.size() < num_nodes_required)
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m_nodes.append(new_record_pointer());
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size_t offset = 0u;
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size_t num_node = 0u;
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while (offset < size()) {
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HashDirectoryNode node(*this, num_node, offset);
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add_to_write_ahead_log(node.as_index_node());
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offset += node.number_of_pointers();
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}
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}
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HashBucket* HashIndex::append_bucket(u32 index, u32 local_depth, u32 pointer)
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{
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m_buckets.append(make<HashBucket>(*this, index, local_depth, pointer));
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return m_buckets.last();
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}
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HashBucket* HashIndex::get_bucket_by_index(u32 index)
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{
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if (index >= size())
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return nullptr;
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return m_buckets[index];
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}
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Optional<u32> HashIndex::get(Key& key)
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{
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auto hash = key.hash();
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auto bucket_index = hash % size();
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auto bucket = get_bucket(bucket_index);
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return bucket->get(key);
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}
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bool HashIndex::insert(Key const& key)
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{
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auto bucket = get_bucket_for_insert(key);
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bucket->insert(key);
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return true;
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}
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HashIndexIterator HashIndex::begin()
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{
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return HashIndexIterator(get_bucket(0));
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}
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HashIndexIterator HashIndex::end()
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{
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return HashIndexIterator::end();
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}
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HashIndexIterator HashIndex::find(Key const& key)
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{
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auto hash = key.hash();
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auto bucket_index = hash % size();
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auto bucket = get_bucket(bucket_index);
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auto optional_index = bucket->find_key_in_bucket(key);
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if (!optional_index.has_value())
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return end();
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return HashIndexIterator(bucket, optional_index.value());
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}
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void HashIndex::list_hash()
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{
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warnln("Number of buckets: {} (Global depth {})", size(), global_depth());
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warn("Directory pointer(s): ");
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for (auto ptr : m_nodes) {
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warn("{}, ", ptr);
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}
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warnln();
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bool first_bucket = true;
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for (auto& bucket : m_buckets) {
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if (first_bucket) {
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warnln("Max. keys in bucket {}", bucket->max_entries_in_bucket());
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first_bucket = false;
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}
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bucket->list_bucket();
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}
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}
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HashIndexIterator::HashIndexIterator(HashBucket const* bucket, size_t index)
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: m_current(bucket)
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, m_index(index)
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{
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VERIFY(!m_current || !index || (index < m_current->size()));
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while (m_current && (m_current->size() == 0)) {
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m_current = m_current->next_bucket();
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m_index = 0;
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}
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}
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HashIndexIterator HashIndexIterator::next()
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{
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if (is_end())
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return *this;
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if (m_index < (m_current->size() - 1))
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return HashIndexIterator(m_current.ptr(), m_index + 1);
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return HashIndexIterator(m_current->next_bucket());
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}
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HashIndexIterator HashIndexIterator::previous()
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{
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TODO();
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}
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bool HashIndexIterator::operator==(HashIndexIterator const& other) const
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{
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if (is_end())
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return other.is_end();
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if (other.is_end())
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return false;
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VERIFY(&other.m_current->hash_index() == &m_current->hash_index());
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return (m_current.ptr() == other.m_current.ptr()) && (m_index == other.m_index);
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}
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bool HashIndexIterator::operator==(Key const& other) const
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{
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if (is_end())
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return false;
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if (other.is_null())
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return false;
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return (**this).compare(other);
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}
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}
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