gem-hunter
Language: Go
An MCP server to query any Postgres database in natural language.
PGMCP connects AI assistants to any PostgreSQL database through natural language queries. Ask questions in plain English and get structured SQL results with automatic streaming and robust error handling.
Works with: Cursor, Claude Desktop, VS Code extensions, and any MCP-compatible client
PGMCP connects to your existing PostgreSQL database and makes it accessible to AI assistants through natural language queries.
# Set up environment variables export DATABASE_URL="postgres://user:password@localhost:5432/your-existing-db" export OPENAI_API_KEY="your-api-key" # Optional # Run server (using pre-compiled binary) ./pgmcp-server # Test with client in another terminal ./pgmcp-client -ask "What tables do I have?" -format table ./pgmcp-client -ask "Who is the customer that has placed the most orders?" -format table ./pgmcp-client -search "john" -format table
Here is how it works:
👤 User / AI Assistant
│
│ "Who are the top customers?"
▼
┌─────────────────────────────────────────────────────────────┐
│ Any MCP Client │
│ │
│ PGMCP CLI │ Cursor │ Claude Desktop │ VS Code │ ... │
│ JSON/CSV │ Chat │ AI Assistant │ Editor │ │
└─────────────────────────────────────────────────────────────┘
│
│ Streamable HTTP / MCP Protocol
▼
┌─────────────────────────────────────────────────────────────┐
│ PGMCP Server │
│ │
│ 🔒 Security 🧠 AI Engine 🌊 Streaming │
│ • Input Valid • Schema Cache • Auto-Pagination │
│ • Audit Log • OpenAI API • Memory Management │
│ • SQL Guard • Error Recovery • Connection Pool │
└─────────────────────────────────────────────────────────────┘
│
│ Read-Only SQL Queries
▼
┌─────────────────────────────────────────────────────────────┐
│ Your PostgreSQL Database │
│ │
│ Any Schema: E-commerce, Analytics, CRM, etc. │
│ Tables • Views • Indexes • Functions │
└─────────────────────────────────────────────────────────────┘
External AI Services:
OpenAI API • Anthropic • Local LLMs (Ollama, etc.)
Key Benefits:
✅ Works with ANY PostgreSQL database (no assumptions about schema)
✅ No schema modifications required
✅ Read-only access (100% safe)
✅ Automatic streaming for large results
✅ Intelligent query understanding (singular vs plural)
✅ Robust error handling (graceful AI failure recovery)
✅ PostgreSQL case sensitivity support (mixed-case tables)
✅ Production-ready security and performance
✅ Universal database compatibility
✅ Multiple output formats (table, JSON, CSV)
✅ Free-text search across all columns
✅ Authentication support
✅ Comprehensive testing suite
Required:
DATABASE_URL: PostgreSQL connection string to your existing databaseOptional:
OPENAI_API_KEY: OpenAI API key for AI-powered SQL generationOPENAI_MODEL: Model to use (default: "gpt-4o-mini")HTTP_ADDR: Server address (default: ":8080")HTTP_PATH: MCP endpoint path (default: "/mcp")AUTH_BEARER: Bearer token for authentication# Example for macOS/Linux tar xzf pgmcp_*.tar.gz cd pgmcp_* ./pgmcp-server
# Homebrew (macOS/Linux) - Available after first release brew tap subnetmarco/homebrew-tap brew install pgmcp # Build from source go build -o pgmcp-server ./server go build -o pgmcp-client ./client
Add -ldflags="-s -w -extldflags=-static" -trimpath if you want to get stripped executables (no debug info):
go build -ldflags="-s -w -extldflags=-static" -trimpath -o pgmcp-server ./server go build -ldflags="-s -w -extldflags=-static" -trimpath -o pgmcp-client ./client
# Docker docker run -e DATABASE_URL="postgres://user:pass@host:5432/db" \ -p 8080:8080 ghcr.io/subnetmarco/pgmcp:latest # Kubernetes (see examples/ directory for full manifests) kubectl create secret generic pgmcp-secret \ --from-literal=database-url="postgres://user:pass@host:5432/db" kubectl apply -f examples/k8s/
# Set up database (optional - works with any existing PostgreSQL database) export DATABASE_URL="postgres://user:password@localhost:5432/mydb" psql $DATABASE_URL < schema.sql # Run server export OPENAI_API_KEY="your-api-key" ./pgmcp-server # Test with client ./pgmcp-client -ask "Who is the user that places the most orders?" -format table ./pgmcp-client -ask "Show me the top 40 most reviewed items in the marketplace" -format table
Required:
DATABASE_URL: PostgreSQL connection stringOptional:
OPENAI_API_KEY: OpenAI API key for SQL generationOPENAI_MODEL: Model to use (default: "gpt-4o-mini")HTTP_ADDR: Server address (default: ":8080")HTTP_PATH: MCP endpoint path (default: "/mcp")AUTH_BEARER: Bearer token for authentication# Ask questions in natural language ./pgmcp-client -ask "What are the top 5 customers?" -format table ./pgmcp-client -ask "How many orders were placed today?" -format json # Search across all text fields ./pgmcp-client -search "john" -format table # Multiple questions at once ./pgmcp-client -ask "Show tables" -ask "Count users" -format table # Different output formats ./pgmcp-client -ask "Export all data" -format csv -max-rows 1000
The project includes two schemas:
schema.sql: Full Amazon-like marketplace with 5,000+ recordsschema_minimal.sql: Minimal test schema with mixed-case "Categories" tableKey features:
"Categories") for testing case sensitivityorder_items) for testing AI assumptionsUse your own database:
export DATABASE_URL="postgres://user:pass@host:5432/your_db" ./pgmcp-server ./pgmcp-client -ask "What tables do I have?"
When AI generates incorrect SQL, PGMCP handles it gracefully:
{
"error": "Column not found in generated query",
"suggestion": "Try rephrasing your question or ask about specific tables",
"original_sql": "SELECT non_existent_column FROM table..."
}Instead of crashing, the system provides helpful feedback and continues operating.
# Start server export DATABASE_URL="postgres://user:pass@localhost:5432/your_db" ./pgmcp-server
Add to Cursor settings:
{
"mcp.servers": {
"pgmcp": {
"transport": {
"type": "http",
"url": "http://localhost:8080/mcp"
}
}
}
}Edit ~/.config/claude-desktop/claude_desktop_config.json:
{
"mcpServers": {
"pgmcp": {
"transport": {
"type": "http",
"url": "http://localhost:8080/mcp"
}
}
}
}ask: Natural language questions → SQL queries with automatic streamingsearch: Free-text search across all database text columnsstream: Advanced streaming for very large result sets with pagination# Unit tests go test ./server -v # Integration tests (requires PostgreSQL) go test ./server -tags=integration -v
Apache 2.0 - See LICENSE file for details.
PGMCP makes your PostgreSQL database accessible to AI assistants through natural language while maintaining security through read-only access controls.