# Identifier Normalization Pattern Notes

This file keeps examples. The normative rules live in `contract.md`.

## Go — сравнение

```go
import "strings"

func SameIdentifier(a, b string) bool {
    return strings.EqualFold(a, b)
}
```

## Go — дедупликация

```go
func deduplicateBySerial(items []Device) []Device {
    seen := make(map[string]struct{})
    result := items[:0]
    for _, item := range items {
        key := strings.ToLower(item.SerialNumber)
        if _, exists := seen[key]; !exists {
            seen[key] = struct{}{}
            result = append(result, item)
        }
    }
    return result
}
```

## SQL — поиск и уникальность

Поиск:

```sql
SELECT * FROM devices WHERE LOWER(serial_number) = LOWER(?);
```

Уникальный индекс (MySQL / MariaDB):

```sql
-- Collation ci обеспечивает case-insensitive уникальность
ALTER TABLE devices MODIFY serial_number VARCHAR(255)
    CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

ALTER TABLE devices ADD UNIQUE INDEX uniq_serial (serial_number);
```

SQLite:

```sql
CREATE UNIQUE INDEX uniq_serial ON devices (LOWER(serial_number));
```