# `PhoenixKit.Migrations.Postgres.V30`
[🔗](https://github.com/BeamLabEU/phoenix_kit/blob/v1.7.71/lib/phoenix_kit/migrations/postgres/v30.ex#L1)

Migration V30: Move preferred_locale from column to custom_fields JSONB.

This migration removes the dedicated `preferred_locale` column and stores
the value in the existing `custom_fields` JSONB column instead. This reduces
schema complexity by leveraging the flexible JSONB storage for user preferences.

## Changes
- Migrates existing `preferred_locale` values into `custom_fields` JSONB
- Drops the `preferred_locale` index
- Drops the `preferred_locale` column

## Requirements
- PostgreSQL database
- PhoenixKit V29 or higher
- The `custom_fields` JSONB column must exist (added in V18)

## Data Migration
Existing preferred_locale values are preserved by copying them into custom_fields:
- `user.preferred_locale = "en-GB"` becomes `user.custom_fields["preferred_locale"] = "en-GB"`
- NULL values are not migrated (same behavior: use system default)

## Backward Compatibility
- Reading: `get_in(user.custom_fields, ["preferred_locale"])` or `user.custom_fields["preferred_locale"]`
- Writing: Merge into custom_fields map
- NULL handling: Missing key = use system default (same as before)

## Rollback
The down migration restores the column and migrates data back from custom_fields.

# `down`
[🔗](https://github.com/BeamLabEU/phoenix_kit/blob/v1.7.71/lib/phoenix_kit/migrations/postgres/v30.ex#L59)

# `up`
[🔗](https://github.com/BeamLabEU/phoenix_kit/blob/v1.7.71/lib/phoenix_kit/migrations/postgres/v30.ex#L35)

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*Consult [api-reference.md](api-reference.md) for complete listing*