Configuring Data Sources

Data sources are configured via a JSON config file that you pass to PlyDB with the --config flag. You can configure multiple data sources in a single file and query across all of them.

If you have the PlyDB Agent Skill installed, you can ask your agent to help you with data source configuration instead of writing a config file manually.

Config file structure

The config file has three top-level objects:

credentials — Shared authentication profiles for cloud providers (S3, Google Sheets).
databases — A map of data source configurations. Each key is a unique identifier that becomes the catalog name in SQL queries.
semantic_context — (Optional) Semantic context overlay configuration.

Database keys must consist of lowercase letters, digits, and underscores only.

PostgreSQL

{
  "databases": {
    "analytics": {
      "metadata": {
        "name": "Production Analytics",
        "description": "Primary read-replica for data warehousing."
      },
      "type": "postgresql",
      "host": "db-prod-01.example.com",
      "port": 5432,
      "database_name": "analytics_main",
      "username": "bi_user",
      "password_env_var": "DB_PROD_PASSWORD"
    }
  }
}

Field	Type	Description
`host`	String	Server address
`port`	Integer	Network port
`database_name`	String	Target database name
`username`	String	Login identity
`password_env_var`	String	Name of the environment variable holding the password

Tables are referenced as catalog.schema.table, e.g. analytics.public.orders.

MySQL

MySQL uses the same fields as PostgreSQL:

{
  "databases": {
    "app": {
      "metadata": {
        "name": "Application Database",
        "description": "Main application MySQL instance."
      },
      "type": "mysql",
      "host": "mysql.example.com",
      "port": 3306,
      "database_name": "myapp",
      "username": "readonly",
      "password_env_var": "MYSQL_PASSWORD"
    }
  }
}

SQLite

{
  "databases": {
    "shop": {
      "metadata": {
        "name": "Shop Database",
        "description": "SQLite database backing the app."
      },
      "type": "sqlite",
      "path": "/data/shop.sqlite"
    }
  }
}

Field	Type	Description
`path`	String	Path to the SQLite database file

SQLite uses main as its default schema, so tables are referenced as shop.main.customers.

DuckDB

{
  "databases": {
    "analytics": {
      "metadata": {
        "name": "Analytics Database",
        "description": "DuckDB with pre-aggregated metrics."
      },
      "type": "duckdb",
      "path": "/data/analytics.duckdb"
    }
  }
}

Field	Type	Description
`path`	String	Path to the DuckDB database file

Like SQLite, DuckDB uses main as its default schema.

Local files (CSV, JSON, Parquet, Excel)

{
  "databases": {
    "budget": {
      "metadata": {
        "name": "FY2026 Budget",
        "description": "Department budget allocations."
      },
      "type": "file",
      "path": "/Documents/Finance/budget_2026.xlsx",
      "sheet_name": "Final_Approval",
      "header_row": true
    }
  }
}

Field	Type	Description
`path`	String	Path to the file
`format`	String	(Optional) `csv`, `xlsx`, `parquet`, or `json`. Inferred from extension if omitted.
`delimiter`	String	(CSV only) Separator character
`header_row`	Boolean	(CSV/XLSX) Whether row 1 is the header
`sheet_name`	String	(XLSX only) Tab name to read

S3

{
  "credentials": {
    "aws_user": {
      "access_key_env": "AWS_ACCESS_KEY_ID",
      "secret_key_env": "AWS_SECRET_ACCESS_KEY"
    }
  },
  "databases": {
    "sensor_data": {
      "metadata": {
        "name": "IoT Sensor Data",
        "description": "Partitioned sensor data in S3."
      },
      "type": "s3",
      "credential_profile": "aws_user",
      "uri": "s3://iot-bucket/2026/*/sensor_*.parquet",
      "format": "parquet",
      "region": "us-west-2"
    }
  }
}

Field	Type	Description
`uri`	String	S3 URI. Supports glob patterns (`*`, `?`, `[]`).
`credential_profile`	String	Key matching an entry in the `credentials` map
`region`	String	AWS region (e.g. `us-east-1`)
`format`	String	Required. File format (`csv`, `parquet`, etc.)
`delimiter`	String	(CSV only) Separator character
`header_row`	Boolean	(CSV/XLSX) Whether row 1 is the header

Credentials are defined in the top-level credentials object and referenced by name via credential_profile.

Google Sheets

PlyDB supports two authentication methods for Google Sheets:

Service account — for server-side, non-interactive use.
Browser OAuth — for interactive, ad-hoc use. PlyDB opens a browser for Google login with no credentials needed in the config.

Service account

{
  "credentials": {
    "gsheet_sa": {
      "key_file": "/etc/secrets/gsheet-sa-key.json"
    }
  },
  "databases": {
    "sales": {
      "metadata": {
        "name": "Sales Forecast",
        "description": "Q3 sales forecast."
      },
      "type": "gsheet",
      "spreadsheet_id": "1BxiMVs0XRA5nFMdKvBdBZjgmUUqptlbs74OgVE2upms",
      "credential_profile": "gsheet_sa",
      "sheet_name": "Forecast",
      "header_row": true
    }
  }
}

Browser OAuth

{
  "databases": {
    "sales": {
      "metadata": {
        "name": "Personal Tracker",
        "description": "Ad-hoc sheet accessed via browser OAuth."
      },
      "type": "gsheet",
      "spreadsheet_id": "1AbCdEfGhIjKlMnOpQrStUvWxYz0123456789abcdefg"
    }
  }
}

On first query, PlyDB opens your browser for Google login. The OAuth token is cached at ~/.duckdb/stored_secrets/ and reused automatically. To force re-authentication, run plydb auth --config /path/to/config.json.

Field	Type	Description
`spreadsheet_id`	String	The spreadsheet ID from the Google Sheets URL
`credential_profile`	String	(Optional) Key referencing a credential with `key_file`. Omit for browser OAuth.
`sheet_name`	String	(Optional) Tab name. If omitted, PlyDB uses the table name from the SQL query.
`header_row`	Boolean	(Optional) Whether row 1 is the header. Defaults to `true`.

Dynamic sheet names

When sheet_name is omitted, the table name in your SQL query determines which tab is read:

# Read from the "January" tab
plydb query --config config.json \
  "SELECT * FROM sales.default.\"January\""

# Read from the "February" tab
plydb query --config config.json \
  "SELECT * FROM sales.default.\"February\""

SQL lowercases unquoted identifiers. If your sheet tab name contains uppercase letters, either quote the identifier with double quotes (e.g. "Revenue") or set sheet_name in the config to bypass SQL identifier parsing.

Cross-source queries

You can join across any combination of data sources in a single query. Just add all sources to the same config file:

plydb query --config config.json \
  "SELECT c.name, o.product, o.amount
   FROM store.public.orders o
   JOIN products.default.\"table\" p ON o.product_id = p.id"

Semantic context

PlyDB can automatically scan your data sources and provide AI agents with structured semantic context. See the dedicated Semantic Context page for details on automatic discovery, overlays, and how agents build institutional knowledge over time.

Full reference example

Here is a complete config file demonstrating multiple source types:

{
  "credentials": {
    "aws_user": {
      "access_key_env": "AWS_ACCESS_KEY_ID",
      "secret_key_env": "AWS_SECRET_ACCESS_KEY"
    },
    "gsheet_sa": {
      "key_file": "/etc/secrets/gsheet-sa-key.json"
    }
  },
  "databases": {
    "analytics": {
      "metadata": {
        "name": "Production Analytics",
        "description": "Primary read-replica."
      },
      "type": "postgresql",
      "host": "db-prod-01.example.com",
      "port": 5432,
      "database_name": "analytics_main",
      "username": "bi_user",
      "password_env_var": "DB_PROD_PASSWORD"
    },
    "budget": {
      "metadata": {
        "name": "FY2026 Budget",
        "description": "Department budget allocations."
      },
      "type": "file",
      "path": "/Documents/Finance/budget_2026.xlsx",
      "sheet_name": "Final_Approval",
      "header_row": true
    },
    "sensor_data": {
      "metadata": {
        "name": "IoT Sensor Data",
        "description": "Partitioned sensor data."
      },
      "type": "s3",
      "credential_profile": "aws_user",
      "uri": "s3://iot-bucket/2026/*/sensor_*.parquet",
      "format": "parquet",
      "region": "us-west-2"
    },
    "sales": {
      "metadata": {
        "name": "Sales Forecast",
        "description": "Q3 sales forecast."
      },
      "type": "gsheet",
      "spreadsheet_id": "1BxiMVs0XRA5nFMdKvBdBZjgmUUqptlbs74OgVE2upms",
      "credential_profile": "gsheet_sa",
      "sheet_name": "Forecast",
      "header_row": true
    }
  },
  "semantic_context": {
    "overlays": ["/path/to/business_glossary.yaml"]
  }
}

Installation Semantic Context