Query Runners Overview

Legion Query Runners provides a unified interface for connecting to and querying different database systems. Each query runner is designed to handle the specific features and requirements of its respective database system while providing a consistent API.

Available Query Runners

Legion Query Runners supports the following database systems:

Database System	Type Identifier	Description
SQLite	sqlite	Lightweight file-based database
Microsoft SQL Server	mssql	Microsoft SQL Server databases
MySQL	mysql	MySQL and MariaDB databases
MySQL (RDS)	rds_mysql	Amazon RDS MySQL instances
PostgreSQL	pg	PostgreSQL databases
Redshift	redshift	Amazon Redshift data warehouse
Redshift IAM	redshift_iam	Redshift with IAM authentication
CockroachDB	cockroach	CockroachDB distributed SQL database
Oracle	oracle	Oracle databases
BigQuery	big_query	Google BigQuery data warehouse

Common Features

All query runners provide a standard set of features:

1. Connection Management: Establish and maintain database connections
2. Query Execution: Run SQL queries and process results
3. Schema Retrieval: Get information about tables and columns
4. Type Mapping: Convert database-specific types to standardized types
5. Error Handling: Handle and report database errors

Basic Usage Pattern

All query runners follow the same basic usage pattern:

from legion_query_runner.query_runner import QueryRunner

# Create a query runner with a specific type and configuration
runner = QueryRunner('database_type', {
    # Configuration options specific to the database type
    'option1': 'value1',
    'option2': 'value2'
})

# Test the connection
runner.test_connection()

# Execute a query
results, error = runner.run_query("SELECT * FROM table LIMIT 10", user=None)

if error:
    print(f"Error: {error}")
else:
    # Process results
    for column in results['columns']:
        print(f"Column: {column['name']} ({column['type']})")
    
    print(f"Row count: {len(results['rows'])}")
    
    # Access the first row
    if results['rows']:
        first_row = results['rows'][0]
        print(first_row)

Selection Guide

When choosing a query runner for your application, consider:

1. Database Type: Use the corresponding query runner for your database
2. Feature Requirements: Some runners provide database-specific features
3. Performance Needs: Different runners have different performance characteristics
4. Authentication Method: Consider the authentication requirements

Refer to the specific documentation for each query runner to understand their unique capabilities and configuration options.