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Chat with a PostgreSQL DB using SQLChatAgent

The SQLChatAgent is designed to facilitate interactions with an SQL database using natural language. A ready-to-use script based on the SQLChatAgent is available in the langroid-examples repo at examples/data-qa/sql-chat/ (and also in a similar location in the main langroid repo). This tutorial walks you through how you might use the SQLChatAgent if you were to write your own script from scratch. We also show some of the internal workings of this Agent.

The agent uses the schema context to generate SQL queries based on a user's input. Here is a tutorial on how to set up an agent with your PostgreSQL database. The steps for other databases are similar. Since the agent implementation relies on SqlAlchemy, it should work with any SQL DB that supports SqlAlchemy. It offers enhanced functionality for MySQL and PostgreSQL by automatically extracting schemas from the database.

Before you begin

Data Privacy Considerations

Since the SQLChatAgent uses the OpenAI GPT-4 as the underlying language model, users should be aware that database information processed by the agent may be sent to OpenAI's API and should therefore be comfortable with this.

  1. Install PostgreSQL dev libraries for your platform, e.g.

    • sudo apt-get install libpq-dev on Ubuntu,
    • brew install postgresql on Mac, etc.
  2. Follow the general setup guide to get started with Langroid (mainly, install langroid into your virtual env, and set up suitable values in the .env file). Note that to use the SQLChatAgent with a PostgreSQL database, you need to install the langroid[postgres] extra, e.g.:

    • pip install langroid[postgres] or
    • poetry add langroid[postgres] or
    • poetry install -E postgres.

    If this gives you an error, try pip install psycopg2-binary in your virtualenv.

Initialize the agent

from langroid.agent.special.sql.sql_chat_agent import (

agent = SQLChatAgent(


The following components of SQLChatAgentConfig are optional but strongly recommended for improved results:

  • context_descriptions: A nested dictionary that specifies the schema context for the agent to use when generating queries, for example:
  "table1": {
    "description": "description of table1",
    "columns": {
      "column1": "description of column1 in table1",
      "column2": "description of column2 in table1"
  "employees": {
    "description": "The 'employees' table contains information about the employees. It relates to the 'departments' and 'sales' tables via foreign keys.",
    "columns": {
      "id": "A unique identifier for an employee. This ID is used as a foreign key in the 'sales' table.",
      "name": "The name of the employee.",
      "department_id": "The ID of the department the employee belongs to. This is a foreign key referencing the 'id' in the 'departments' table."

By default, if no context description json file is provided in the config, the agent will automatically generate the file using the built-in Postgres table/column comments.

  • schema_tools: When set to True, activates a retrieval mode where the agent systematically requests only the parts of the schemas relevant to the current query. When this option is enabled, the agent performs the following steps:

    1. Asks for table names.
    2. Asks for table descriptions and column names from possibly relevant table names.
    3. Asks for column descriptions from possibly relevant columns.
    4. Writes the SQL query.

Setting schema_tools=True is especially useful for large schemas where it is costly or impossible to include the entire schema in a query context. By selectively using only the relevant parts of the context descriptions, this mode reduces token usage, though it may result in 1-3 additional OpenAI API calls before the final SQL query is generated.

Putting it all together

In the code below, we will allow the agent to generate the context descriptions from table comments by excluding the context_descriptions config option. We set schema_tools to True to enable the retrieval mode.

from langroid.agent.special.sql.sql_chat_agent import (

# Initialize SQLChatAgent with a PostgreSQL database URI and enable schema_tools
agent = SQLChatAgent(gi
config = SQLChatAgentConfig(

# Run the task to interact with the SQLChatAgent
task = Task(agent)

By following these steps, you should now be able to set up an SQLChatAgent that interacts with a PostgreSQL database, making querying a seamless experience.

In the langroid repo we have provided a ready-to-use script based on the above, that you can use right away to interact with your PostgreSQL database:

python3 examples/data-qa/sql-chat/

This script will prompt you for the database URI, and then start the agent.