Class: Langchain::Tool::Database

Inherits:
Object
  • Object
show all
Extended by:
Langchain::ToolDefinition
Includes:
DependencyHelper
Defined in:
lib/langchain/tool/database.rb

Overview

Connects to a SQL database, executes SQL queries, and outputs DB schema for Agents to use

Gem requirements:

gem "sequel", "~> 5.68.0"

Usage:

database = Langchain::Tool::Database.new(connection_string: "postgres://user:password@localhost:5432/db_name")

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Langchain::ToolDefinition

define_function, function_schemas, tool_name

Methods included from DependencyHelper

#depends_on

Constructor Details

#initialize(connection_string:, tables: [], exclude_tables: []) ⇒ Database

Establish a database connection

Parameters:

  • connection_string (String) —

    Database connection info, e.g. ‘postgres://user:password@localhost:5432/db_name’

  • tables (Array<Symbol>) (defaults to: []) —

    The tables to use. Will use all if empty.

  • except_tables (Array<Symbol>) —

    The tables to exclude. Will exclude none if empty.

Raises:

  • (StandardError) 


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# File 'lib/langchain/tool/database.rb', line 39

def initialize(connection_string:, tables: [], exclude_tables: [])
  depends_on "sequel"

  raise StandardError, "connection_string parameter cannot be blank" if connection_string.empty?

  @db = Sequel.connect(connection_string)
  # TODO: This is a bug, these 2 parameters are completely ignored.
  @requested_tables = tables
  @excluded_tables = exclude_tables
end

Instance Attribute Details

#db ⇒ Object (readonly)

Returns the value of attribute db.



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# File 'lib/langchain/tool/database.rb', line 31

def db
  @db
end

#excluded_tables ⇒ Object (readonly)

Returns the value of attribute excluded_tables.



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# File 'lib/langchain/tool/database.rb', line 31

def excluded_tables
  @excluded_tables
end

#requested_tables ⇒ Object (readonly)

Returns the value of attribute requested_tables.



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# File 'lib/langchain/tool/database.rb', line 31

def requested_tables
  @requested_tables
end

Instance Method Details

#describe_tables(tables: []) ⇒ String

Database Tool: Returns the schema for a list of tables

Parameters:

  • tables (Array<String>) (defaults to: []) —

    The tables to describe.

Returns:

  • (String) —

    The schema for the tables



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# File 'lib/langchain/tool/database.rb', line 61

def describe_tables(tables: [])
  return "No tables specified" if tables.empty?

  Langchain.logger.debug("#{self.class} - Describing tables: #{tables}")

  tables
    .map do |table|
      describe_table(table)
    end
    .join("\n")
end

#dump_schema ⇒ String

Database Tool: Returns the database schema

Returns:

  • (String) —

    Database schema



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# File 'lib/langchain/tool/database.rb', line 76

def dump_schema
  Langchain.logger.debug("#{self.class} - Dumping schema tables and keys")

  schemas = db.tables.map do |table|
    describe_table(table)
  end
  schemas.join("\n")
end

#execute(input:) ⇒ Array

Database Tool: Executes a SQL query and returns the results

Parameters:

  • input (String) —

    SQL query to be executed

Returns:

  • (Array) —

    Results from the SQL query



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# File 'lib/langchain/tool/database.rb', line 89

def execute(input:)
  Langchain.logger.debug("#{self.class} - Executing \"#{input}\"")

  db[input].to_a
rescue Sequel::DatabaseError => e
  Langchain.logger.error("#{self.class} - #{e.message}")
  e.message # Return error to LLM
end

#list_tables ⇒ Array<Symbol>

Database Tool: Returns a list of tables in the database

Returns:

  • (Array<Symbol>) —

    List of tables in the database



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# File 'lib/langchain/tool/database.rb', line 53

def list_tables
  db.tables
end