database_system

Database System / 数据库系统

Technical Requirements for C++ Database System Developer

Core Components / 核心组件

SQL Engine / SQL引擎

• SQL parser and lexer
• Query analyzer and semantic checker
• Query optimizer (cost-based, rule-based)
• Query execution engine

Storage Engine / 存储引擎

• B+ tree and LSM-tree implementations
• Buffer pool management
• Page management and eviction strategies
• Write-Ahead Logging (WAL)

Query Processing / 查询处理

Operators / 算子

• Scan Operator / 扫描算子: Full table scan, index scan
• Aggregation Operator / 聚集算子: GROUP BY, DISTINCT, aggregate functions
• Join Operator: Nested loop, hash join, merge join
• Sort Operator: External sorting for large datasets

Query Optimization / 查询优化

• Predicate Pushdown / 谓词下推: Push filters down to reduce data movement
• Constant Folding / 常量折叠: Evaluate constant expressions at compile time
• Join Reordering: Find optimal join order
• Index Selection: Choose best index for query

Transaction Management / 事务管理

Two-Phase Locking / 两阶段锁

• Strong Two-Phase Locking / 强两阶段锁: Locks held until transaction commits
• Strict Two-Phase Locking / 严格两阶段锁: Write locks held until transaction ends

MVCC (Multi-Version Concurrency Control)

• Snapshot Isolation / 快照隔离: Read consistent snapshot of data
• Version chain management
• Garbage collection of old versions

Logging and Recovery / 日志与恢复

Log Types / 日志类型

• Undo Log: For rollback and MVCC
• Redo Log: For crash recovery
• Batch Write / 批量写入: Group commit for performance

Recovery Mechanisms

• Checkpointing
• ARIES recovery algorithm
• Point-in-time recovery

Compression / 压缩

• ZSTD: Facebook's Zstandard compression
• Snappy: Google's fast compression
• Dictionary compression
• Page-level compression

Replication / 复制

• Logical Replication: Row-based or statement-based
• Physical Replication: Block-level streaming replication
• Synchronous vs asynchronous replication
• Multi-master replication

Index Structures / 索引结构

索引是数据库中对表的字段进行排序的一种数据结构。

Index Types / 索引类型

1. B+ Tree: Default balanced tree, efficient for range queries
2. Hash Index: O(1) lookup, not suitable for range queries / 哈希表不利于范围查找
3. AVL Tree: Self-balancing binary search tree
4. Red-Black Tree: Balanced BST, performance degrades with large data / 红黑树在数据量大的时候性能会下降

Composite Index / 联合索引

• Multiple column indexing
• Leftmost prefix matching
• Index intersection

C++ Skills Required / C++技能要求

Language Features

• Modern C++ (C++11/14/17/20)
• Template metaprogramming for type-safe operators
• Lock-free data structures for high concurrency
• Memory pools for buffer management
• Zero-copy I/O techniques

Performance Optimization

• Cache-friendly data structures
• SIMD vectorization for data processing
• NUMA-aware memory allocation
• Async I/O (io_uring)

Tools & Technologies

• RocksDB/LevelDB for storage engine reference
• PostgreSQL/MySQL internals study
• Jemalloc/Tcmalloc for memory allocation
• Protocol Buffers for internal communication