@iflow-mcp/garethcott_enhanced-postgres-mcp-server

Executes arbitrary SQL queries (SELECT, INSERT, UPDATE, DELETE) against PostgreSQL databases through the Model Context Protocol, translating LLM-generated SQL into database operations. Implements MCP resource and tool handlers that parse SQL strings, execute them via node-postgres driver, and return structured result sets with row counts and column metadata. Supports both read and write operations with connection pooling managed by the underlying pg library.

Exposes PostgreSQL database schema (tables, columns, constraints, indexes) as MCP resources that Claude can query to understand database structure. Implements information_schema queries to retrieve table definitions, column types, primary keys, foreign keys, and indexes, returning structured metadata that helps LLMs generate correct SQL. Resources are registered with the MCP server and made available as queryable endpoints without requiring separate schema documentation.

Registers SQL execution as MCP tools that Claude can invoke with natural language intent, translating LLM tool calls into parameterized SQL queries. Implements tool schemas that define input parameters (table name, WHERE conditions, column selections), validates them against the database schema, and executes the resulting SQL through the node-postgres driver. Supports both simple CRUD operations and complex queries with filtering, sorting, and pagination parameters.

Manages PostgreSQL connection pooling using the node-postgres (pg) library, maintaining a pool of reusable database connections to reduce connection overhead. Implements connection initialization on MCP server startup, health checks to validate connections, and graceful shutdown that closes all pooled connections. Pool size and timeout parameters are configurable, allowing tuning for different workload patterns (high-concurrency agents vs. low-frequency queries).

Catches PostgreSQL errors (syntax errors, constraint violations, permission errors) and formats them as structured MCP responses with error context and SQL details. Implements error classification to distinguish between client errors (malformed SQL), constraint violations (unique key, foreign key), and server errors (connection loss, out of memory). Result formatting converts PostgreSQL result objects into JSON-serializable structures with column metadata, row counts, and execution time.

Enforces write operation safety through configurable constraints: read-only mode to disable INSERT/UPDATE/DELETE, table whitelisting to restrict which tables can be modified, and operation-level permissions (e.g., allow SELECT but deny DELETE). Implements constraint checking at the MCP tool handler level before executing queries, rejecting unsafe operations with clear error messages. Supports environment-based configuration to enable/disable write modes per deployment.