Support indexing a column partially, i.e. indexing a subset of a text field in MySQL

Problem

I’m trying out Prisma new native types feature.

generator client {
  provider        = "prisma-client-js"
  previewFeatures = ["nativeTypes"]
}

After I introspect the db, I get the following error.

But actually mediumtext can be used as unique if you specify a length to it.

Suggested solution

Maybe Prisma could support something like the following:

model StatusUpdate {
  id         String               @id @db.Char(30)
  uid        String               @unique(191) @db.MediumText
}

Additional context

Prisma 1 @unique uses mediumtext unique with 191 length.

[kgoggin]

I ran into this also. Our DB started life with Prisma 1, and so we’ve got several places where P1 created tables with mediumtext columns marked as @unique that have an index defined that selects a sub part of that field, so that it can be unique. See shortName column in the sql below, which was exported from our P1 DB:

CREATE TABLE `Theme` (
  `id` char(30) CHARACTER SET utf8 NOT NULL,
  `shortName` mediumtext COLLATE utf8mb4_unicode_ci NOT NULL,
  `displayName` mediumtext COLLATE utf8mb4_unicode_ci NOT NULL,
  `primaryColor` mediumtext COLLATE utf8mb4_unicode_ci NOT NULL,
  `logoUrl` mediumtext COLLATE utf8mb4_unicode_ci,
  `createdAt` datetime(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
  `updatedAt` datetime(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
  PRIMARY KEY (`id`),
  UNIQUE KEY `shortName_UNIQUE` (`shortName`(191))
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

We’ve since switched over to P2, and now we’re trying to start using the native DB types via introspect, and then switch over to prisma migrate. But, when I introspect it strips the @unique from the schema and won’t let me re-add it. I see the same error @chanlito posted above. This is blocking us from being able to upgrade to the latest Prisma version, and from using Prisma Migrate. Any idea if/when the suggested approach might be implemented?

[janpio]

We released support for this in https://github.com/prisma/prisma/releases/tag/3.5.0 - please test it out @kgoggin @chanlito and let us know if this works for you - or not. Thanks!