QuestDB Time-Series Engine & MCP Server · Window Join & Core Fixes
Dual-repository upstream contribution to the QuestDB ecosystem: fixed SQL compiler validation for deferred symbol filters in WINDOW JOIN clauses inside the core Java engine (questdb/questdb#7850) and resolved Python packaging dependencies in the official QuestDB MCP server (questdb/mcp-server-questdb#7, merged).
High-Throughput Time-Series SQL & AI Agent Tooling
[QuestDB](https://github.com/questdb/questdb) is a high-performance open-source time-series database written in zero-GC Java, C++, and Rust, engineered for financial tick data, IoT telemetry, and real-time analytics. Alongside the core engine, [mcp-server-questdb](https://github.com/questdb/mcp-server-questdb) exposes time-series querying to AI coding assistants via the Model Context Protocol (MCP).
Technical Comparison Across QuestDB Layers
| Repository & PR | Language / Layer | Technical Issue | Upstream Fix |
|---|---|---|---|
| questdb/questdb (#7850) | Java (Zero-GC SQL Compiler) | `WINDOW JOIN` threw false-positive exceptions on deferred non-existent symbol keys | Validated symbol table existence and deferred symbol resolution in `SqlCompilerImpl` |
| questdb/mcp-server-questdb (#7) | Python (MCP Server) | Missing runtime dependency declarations in `pyproject.toml` | Restructured PEP 621 dependency metadata (Merged) |
| Vectorized Execution | SIMD Time-Series Joins | Sub-millisecond temporal range matching | Preserved zero-allocation fast path for valid symbols |
*Table 1: QuestDB Core SQL Compiler and MCP Server Contributions*
// QuestDB SQL Compiler: Handling deferred symbol lookup in WINDOW JOIN clauses
int symbolKey = symbolMapReader.keyOf(symbolFilterCharSequence);
if (symbolKey == SymbolTable.VALUE_NOT_FOUND && !symbolMapReader.isDeleted()) {
// Gracefully evaluate empty match without aborting vectorized WINDOW JOIN plan
return EmptyRecordCursorFactory.INSTANCE;
}Results & Ecosystem Integration
- MCP Server PR #7 Merged: Enabled clean `uvx` and `pip` installation of the official QuestDB MCP server for LLM agents. - Core Engine PR #7850: Hardened `WINDOW JOIN` stability on high-cardinality streaming symbol columns.