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MCP Catalog

The MCP Catalog is a local SQLite database (mcp_catalog.db) where ProxySQL stores all metadata discovered from backend servers. This metadata is essential for providing LLMs with the context they need to generate accurate SQL queries.

Catalog Tables​

Core Structure​

  • schemas: Stores discovered database schemas.
  • objects: Stores tables and views.
  • columns: Detailed column metadata (type, nullable, etc.).
  • indexes: Index definitions.
  • index_columns: Mapping of columns to indexes.
  • foreign_keys: Foreign key relationships.
  • view_dependencies: Tracks which tables a view depends on.

AI & Agent Context​

  • runs: Tracks every execution of the discovery process.
  • agent_runs: Tracks individual LLM agent sessions.
  • agent_events: Log of actions performed by an agent during a run.
  • llm_object_summaries: Stores natural language summaries of tables/views generated by LLMs.
  • llm_notes: Miscellaneous observations about the schema.
  • llm_search_log: Tracks semantic searches performed by agents.

Advanced Relationships​

  • inferred_relationships: Relationships not explicitly defined by foreign keys but detected by ProxySQL.
  • llm_domains: Logical groupings of tables (e.g., "Finance", "Users").
  • llm_domain_members: Mapping of tables to logical domains.

Location​

The catalog file is stored in the ProxySQL data directory, defined by the datadir variable. A common location on Linux systems is:

/var/lib/proxysql/mcp_catalog.db

Management​

The catalog is managed via MCP Tools like catalog.init and catalog.search, or by directly querying the ProxySQL Admin interface.