Type Alias NonDehydrateable<T>

Wrap your column type to opt-out from dehydration by ShallowDehydrateValue, when used by JSON functions, such as the ones used by the relational helpers.

Why need this?

An edge case surfaced in issues where a numeric string column type was actually not a numeric data type column, but text - and thus shouldn't be dehydrated to number.

Another use case would be, when someone finds a way to keep nested columns hydrated at runtime, e.g. via a plugin, and wants to prevent dehydration of such columns at the type level.

Examples

import type { NonDehydrateable } from 'kysely'
import { jsonArrayFrom } from 'kysely/helpers/postgres'

const result = await db
  .withTables<{
    my_table: {
      a_column: '1' | '2' | '3',
      another_column: NonDehydrateable<'1' | '2' | '3'>,
      column_too: NonDehydrateable<ColumnType<'1' | '2' | '3'>>
    }
  }>()
  .selectFrom('person')
  .select((eb) => [
    'id',
    jsonArrayFrom(
      eb.selectFrom('my_table')
        .select(['a_column', 'another_column', 'column_too'])
    ).as('related')
  ])
  .execute()
Copy

In the example above, "a_column" will be dehydrated to number given it is a numeric string - which is normally a numeric data type column that gets output as a string by underlying database drivers to avoid precision loss or overflow.

"another_column" and "column_too" will remain as '1' | '2' | '3', given they're wrapped in NonDehydrateable, which prevents their dehydration.