fix(schema-engine): Fixed introspecting enum array types

[viktor-ferenczi]

Issue
prisma/prisma#22456

Affected databases

• PostgreSQL
• CockroachDB

Root cause

PostgreSQL prepends an underscore to produce ARRAY types from each type defined. (The enum is defined as a type.) The database introspection code trimmed all underscores from the type name of the column, which resulted in a loss of the underscore in the name of the original enum type. As a consequence the enum type was not found and ended up as unsupported. The unsupported type did not match the original type, resulted in a unwanted migration.

Solution

Remove only a single underscore prefix from the type name.

Remarks

Quoting from the PostgreSQL CREATE TYPE documentation:

Whenever a user-defined type is created, PostgreSQL automatically creates an associated array type, whose name consists of the element type's name prepended with an underscore, and truncated if necessary to keep it less than NAMEDATALEN bytes long.

Unrelated to the underscore prefix problem, but will affect the generality of any solution: By default NAMEDATALEN is 63. It can be queried by SHOW max_identifier_length;

If the original type name was NAMEDATALEN long, then the last character would be truncated by PostgreSQL. It would still prevent finding the correct type on introspection. A workaround could be made to search for a matching type. However, it is a very rare corner case, it is is not worth the additional code. Such cases could be fixed by increasing NAMEDATALEN on the database side.

[CLAassistant]

All committers have signed the CLA.

[codspeed-hq]

CodSpeed Performance Report

Merging #5211 will not alter performance

_{Comparing fix/22456-introspect-enum-array (d406a1a) with main (050af99)}

Summary

✅ 11 untouched benchmarks

[github-actions]

WASM Query Engine file Size

Engine	This PR	Base branch	Diff
Postgres	2.135MiB	2.135MiB	0.000B
Postgres (gzip)	857.967KiB	857.968KiB	-1.000B
Mysql	2.098MiB	2.098MiB	0.000B
Mysql (gzip)	842.628KiB	842.628KiB	0.000B
Sqlite	2.007MiB	2.007MiB	0.000B
Sqlite (gzip)	806.374KiB	806.374KiB	0.000B

[aqrln]

Looks great, nice investigation and fix!