[BUG]: typings are lost when using customType with known dataType

Author: monholmCreated Mar 12, 2024Updated Sep 15, 2026
Labelsbugdb/postgresqb/crudbug/fixed-in-beta

What version of drizzle-orm are you using?

0.30.1

What version of drizzle-kit are you using?

No response

Describe the Bug

Hello.

We're using the customType to do simple overloads of the toDriver/fromDriver methods on well known data types (e.g. uuid) using postgresql. E.g.:

typescript
const customUuid = () =>
  customType<{data: string; driverData: string}>({
    dataType() {
      return 'uuid';
    },

    fromDriver(value: string): string {
      return addPrefix(value);
    },

    toDriver(value: string): string {
      return removePrefix(value);
    },
  });

Doing this, we've discovered that even though the type being returned in the dataType function is a type well known to drizzle, the typing is lost when the query is built, eventually leading to our queries failing, since we're using the AWS Data API that receives no typeHint because of the missing typing here.

Looking at the codebase, this seems to come down to the fact that the typings are infered from the instance of the class (or alternatively from the entityKind field in the class) in

https://github.com/drizzle-team/drizzle-orm/blob/bfc757f2adb843192e1b5508fcb4abd9737edd09/drizzle-orm/src/pg-core/dialect.ts#L494-L512

which will always return none for custom types, since the class is PgCustomColumn.

I'm not familiar enough with the codebase to tell whether the following solution would introduce other issues, but I did some brief testing modifying the prepareTyping function to something like:

typescript
prepareTyping(encoder: DriverValueEncoder<unknown, unknown>): QueryTypingsValue {
if (
	is(encoder, PgJsonb) || is(encoder, PgJson) || (is(encoder, PgCustomColumn) && (encoder.getSQLType() === 'json' || encoder.getSQLType() === 'jsonb'))
) {
	return 'json';
} else if (is(encoder, PgNumeric) || (is(encoder, PgCustomColumn) && encoder.getSQLType() === 'decimal')) {
	return 'decimal';
} else if (is(encoder, PgTime) || (is(encoder, PgCustomColumn) && encoder.getSQLType() === 'time')) {
	return 'time';
} else if (is(encoder, PgTimestamp) || (is(encoder, PgCustomColumn) && encoder.getSQLType() === 'timestamp')) {
	return 'timestamp';
} else if (is(encoder, PgDate) || (is(encoder, PgCustomColumn) && encoder.getSQLType() === 'date')) {
	return 'date';
} else if (is(encoder, PgUUID) || (is(encoder, PgCustomColumn) && encoder.getSQLType() === 'uuid')) {
	return 'uuid';
} else {
	return 'none';
}
}

to maintain the typing if it's well known. This worked successfully.

I was hoping that someone more familiar with the codebase could look into whether a solution like this would be feasible going forward?

Expected behavior

Typings to be preserved when using known data types in customType.

Environment & setup

Postgresql.

Source: drizzle-team/drizzle-orm