# NL2SQL - Natural Language to SQL for ProxySQL

## Overview

NL2SQL (Natural Language to SQL) is a ProxySQL feature that converts natural language questions into SQL queries using Large Language Models (LLMs).

## Features

- **Hybrid Deployment**: Local Ollama + Cloud APIs (OpenAI, Anthropic)
- **Semantic Caching**: Vector-based cache for similar queries using sqlite-vec
- **Schema Awareness**: Understands your database schema for better conversions
- **Multi-Provider**: Switch between LLM providers seamlessly
- **Security**: Generated SQL is returned for review before execution

## Quick Start

### 1. Enable NL2SQL

```sql
-- Via admin interface
SET ai_nl2sql_enabled='true';
LOAD MYSQL VARIABLES TO RUNTIME;
```

### 2. Configure LLM Provider

**Using local Ollama (default):**

```sql
SET ai_nl2sql_model_provider='ollama';
SET ai_nl2sql_ollama_model='llama3.2';
LOAD MYSQL VARIABLES TO RUNTIME;
```

**Using OpenAI:**

```sql
SET ai_nl2sql_model_provider='openai';
SET ai_nl2sql_openai_model='gpt-4o-mini';
SET ai_nl2sql_openai_key='sk-...';
LOAD MYSQL VARIABLES TO RUNTIME;
```

**Using Anthropic:**

```sql
SET ai_nl2sql_model_provider='anthropic';
SET ai_nl2sql_anthropic_model='claude-3-haiku';
SET ai_nl2sql_anthropic_key='sk-ant-...';
LOAD MYSQL VARIABLES TO RUNTIME;
```

### 3. Use NL2SQL

```sql
-- In your SQL client, prefix your query with "NL2SQL:"
mysql> SELECT * FROM runtime_mysql_servers WHERE variable_name='ai_nl2sql_enabled';

-- Query converted to SQL
mysql> NL2SQL: Show top 10 customers by revenue;
```

## Configuration

### Variables

| Variable | Default | Description |
|----------|---------|-------------|
| `ai_nl2sql_enabled` | true | Enable/disable NL2SQL |
| `ai_nl2sql_query_prefix` | NL2SQL: | Prefix for NL2SQL queries |
| `ai_nl2sql_model_provider` | ollama | LLM provider (ollama/openai/anthropic) |
| `ai_nl2sql_ollama_model` | llama3.2 | Ollama model name |
| `ai_nl2sql_openai_model` | gpt-4o-mini | OpenAI model name |
| `ai_nl2sql_anthropic_model` | claude-3-haiku | Anthropic model name |
| `ai_nl2sql_cache_similarity_threshold` | 85 | Semantic similarity threshold (0-100) |
| `ai_nl2sql_timeout_ms` | 30000 | LLM request timeout in milliseconds |
| `ai_nl2sql_prefer_local` | true | Prefer local models when possible |

### Model Selection

The system automatically selects the best model based on:

1. **Latency requirements**: Local Ollama for fast queries (< 500ms)
2. **API key availability**: Falls back to Ollama if keys missing
3. **User preference**: Respects `ai_nl2sql_model_provider` setting

## Examples

### Basic Queries

```
NL2SQL: Show all users
NL2SQL: Find orders with amount > 100
NL2SQL: Count customers by country
```

### Complex Queries

```
NL2SQL: Show top 5 customers by total order amount
NL2SQL: Find customers who placed orders in the last 30 days
NL2SQL: What is the average order value per month?
```

### Schema-Aware Queries

```
-- Switch to your schema first
USE my_database;
NL2SQL: List all products in the Electronics category
NL2SQL: Find orders that contain specific products
```

### Results

NL2SQL returns a resultset with:
- `sql_query`: Generated SQL
- `confidence`: 0.0-1.0 score
- `explanation`: Which model was used
- `cached`: Whether from semantic cache

## Troubleshooting

### NL2SQL returns empty result

1. Check AI module is initialized:
   ```sql
   SELECT * FROM runtime_mysql_servers WHERE variable_name LIKE 'ai_%';
   ```

2. Verify LLM is accessible:
   ```bash
   # For Ollama
   curl http://localhost:11434/api/tags

   # For cloud APIs, check your API keys
   ```

3. Check logs:
   ```bash
   tail -f proxysql.log | grep NL2SQL
   ```

### Poor quality SQL

1. **Try a different model:**
   ```sql
   SET ai_nl2sql_ollama_model='llama3.3';
   ```

2. **Increase timeout for complex queries:**
   ```sql
   SET ai_nl2sql_timeout_ms=60000;
   ```

3. **Check confidence score:**
   - High confidence (> 0.7): Generally reliable
   - Medium confidence (0.4-0.7): Review before using
   - Low confidence (< 0.4): May need manual correction

### Cache Issues

```sql
-- Clear cache (Phase 3 feature)
-- TODO: Add cache clearing command

-- Check cache stats
SELECT * FROM stats_ai_nl2sql_cache;
```

## Performance

| Operation | Typical Latency |
|-----------|-----------------|
| Local Ollama | ~1-2 seconds |
| Cloud API | ~2-5 seconds |
| Cache hit | < 50ms |

**Tips for better performance:**
- Use local Ollama for faster responses
- Enable caching for repeated queries
- Use `ai_nl2sql_timeout_ms` to limit wait time
- Consider pre-warming cache with common queries

## Security

### Important Notes

- NL2SQL queries are **NOT executed automatically**
- Generated SQL is returned for **review first**
- Always validate generated SQL before execution
- Keep API keys secure (use environment variables)

### Best Practices

1. **Review generated SQL**: Always check the output before running
2. **Use read-only accounts**: Test with limited permissions first
3. **Monitor confidence scores**: Low confidence may indicate errors
4. **Keep API keys secure**: Don't commit them to version control
5. **Use caching wisely**: Balance speed vs. data freshness

## API Reference

For complete API documentation, see [API.md](API.md).

## Architecture

For system architecture details, see [ARCHITECTURE.md](ARCHITECTURE.md).

## Testing

For testing information, see [TESTING.md](TESTING.md).

## Version History

- **0.1.0** (2025-01-16): Initial release with Ollama, OpenAI, Anthropic support

## License

This feature is part of ProxySQL and follows the same license.