# Product Lot Sequence Per Product

This module extends Odoo's lot and serial number generation to support unique sequences per product, aligning Odoo 18 with the behavior introduced in Odoo 19.

## Features

- **Per-Product Sequence Configuration**: Define a unique sequence for lot/serial number generation for each product.
- **Inventory Tab Integration**: Configure the custom sequence directly on the product form under the Inventory tab.
- **Automatic Generation**: Lot/serial numbers generated during incoming receipts and manufacturing orders follow the product-specific sequence.
- **Performance Optimized**: Batch generation for large quantities (500,000+ units) using optimized database queries.
- **Fallback Mechanism**: If no sequence is defined for a product, it falls back to the global lot/serial sequence.
- **UI Enhancements**: Avoids generation of invalid "0" lot numbers in manual and wizard flows.

## Configuration

1. Navigate to **Inventory > Products**.
2. Open or create a product.
3. Go to the **Inventory** tab.
4. Set the **Custom Lot/Serial** prefix to define a new sequence or select an existing sequence from the **Lot Sequence** field.
5. The **Next Number** field displays the next lot/serial number that will be generated.

## Behavior

- **Incoming Shipments**: When receiving products, if a product has a custom sequence, the generated lot/serial numbers will follow this sequence.
- **Manufacturing Orders**: When producing products, the finished lots/serials will be generated using the product's custom sequence.
- **Manual Creation**: Creating lots/serials manually or via "Generate Serials/Lots" will respect the product's sequence if configured.

## Performance Optimizations

The module includes several performance optimizations for handling large quantities:

### Batch Sequence Allocation
- Uses PostgreSQL's `generate_series()` to allocate multiple sequence numbers in a single database query
- Reduces database operations from N queries to 1 query for N lots
- Automatically activated for quantities > 10 units

### Batch Lot Creation
- Creates all lot records in a single `create()` operation
- Significantly faster for large quantities (100+ units)
- Maintains data integrity and uniqueness

### Performance Benchmarks
- **Small batch (10 units)**: < 5 seconds
- **Medium batch (100 units)**: < 10 seconds
- **Large batch (500 units)**: < 30 seconds
- **Very large batch (5,000 units)**: < 2 minutes
- **Extreme batch (500,000 units)**: Optimized for production use

### When Optimizations Apply
- Batch allocation: Automatically used when generating > 10 lots at once
- Applies to: Incoming shipments, manufacturing orders, and manual generation

## Technical Details

- The module adds a `lot_sequence_id` field to `product.template` to link the sequence.
- It overrides the `stock.lot` creation to use the product's sequence with batch optimization.
- It extends `stock.move` and `stock.move.line` to handle UI inputs and normalize "0" or empty inputs.
- It overrides `mrp.production._prepare_stock_lot_values` to ensure manufacturing flows use the product sequence.

- Uses `_allocate_sequence_batch()` method for efficient sequence number allocation.

## Testing

The module includes comprehensive test suites:

### Performance Tests
Run performance tests to verify optimization:
```bash
odoo-bin -c odoo.conf -d your_database --test-tags product_lot_sequence_per_product.performance
```

### Inventory Adjustment Tests
Test auto-generation in inventory adjustments:
```bash
odoo-bin -c odoo.conf -d your_database --test-tags product_lot_sequence_per_product
```

## Dependencies

- `stock`
- `mrp`

## Compatibility

- Odoo 18
- Requires `mrp` module for manufacturing order support