Time-Travel Queries with Multi-Modal AS OF Clause for Embedded Databases

We present a comprehensive time-travel query system for embedded SQL databases that enables point-in-time data access through three complementary resolution modes: wall-clock timestamps (AS OF TIMESTAMP), transaction identifiers (AS OF TRANSACTION), and Oracle-compatible system change numbers (AS OF SCN). Our implementation combines MVCC-integrated versioning, LRU-cached snapshot retrieval with O(log N) complexity using reverse timestamp indexing, and configurable garbage collection policies optimized for embedded deployments. This approach addresses the gap between heavy-weight enterprise solutions (Oracle Flashback, SQL Server Temporal Tables) and the needs of embedded databases by providing Oracle-compatible syntax with lightweight resource management suitable for edge computing and IoT scenarios.