feat: draft partial index support

[jkomyno]

DRAFT

This PR is a quick attempt at providing Partial Index support for PostgreSQL and CockroachDB.
This is not a planned feature, but I figured I'd give it a shot.

Index expressions like

CREATE TABLE "Order" (
    id SERIAL PRIMARY KEY,
    user_id INT NOT NULL,
    status VARCHAR(20) NOT NULL
);

-- Partial index
CREATE INDEX "Order_user_status_idx" ON "Order" (user_id, status) WHERE status IN ('pending', 'processing');

are stored in PSL like

model Order {
  id         Int    @id @default(autoincrement())
  user_id    Int
  status     String @db.VarChar(20)

  @@index([user_id, status], where: "status IN ('pending', 'processing')")
}

This feature is gated behind previewFeatures = ["partialIndexes"].

---

Limitations:

• only provider = "postgresql" and provider = "cockroachdb" are supported
• users have to write raw SQL in PSL, with no SQL autocompletion / compile-time syntax check
• the SQL written by users may not correspond to the SQL stored in the database. For example:
  • user-defined:

    @@index([user_id, status], where: "status IN ('pending', 'processing')")

  • re-introspected:

    @@index([user_id, status], map: "Order_user_status_idx", where: "((status)::text = ANY ((ARRAY['pending'::character varying, 'processing'::character varying])::text[]))")

[codspeed-hq]

CodSpeed Performance Report

Merging #5567 will not alter performance

_{Comparing feat/partial-index (d5a0491) with main (361e86d)}

Summary

✅ 11 untouched benchmarks

[github-actions]

WASM Query Engine File Size

Engine	This PR	Base branch	Diff
Postgres	2.203MiB	2.203MiB	355.000B
Postgres (gzip)	873.197KiB	873.061KiB	139.000B
Mysql	2.169MiB	2.169MiB	363.000B
Mysql (gzip)	858.697KiB	858.689KiB	8.000B
Sqlite	2.078MiB	2.078MiB	363.000B
Sqlite (gzip)	822.377KiB	822.276KiB	104.000B
SQL Server	2.135MiB	2.135MiB	363.000B
SQL Server (gzip)	846.997KiB	846.988KiB	9.000B
CockroachDB	2.225MiB	2.225MiB	355.000B
CockroachDB (gzip)	882.047KiB	882.025KiB	23.000B

WASM Query Compiler File Size

Engine	This PR	Base branch	Diff
Postgres	1.832MiB	1.831MiB	369.000B
Postgres (gzip)	723.528KiB	723.581KiB	-54.000B
Mysql	1.797MiB	1.796MiB	369.000B
Mysql (gzip)	713.159KiB	713.029KiB	133.000B
Sqlite	1.749MiB	1.749MiB	369.000B
Sqlite (gzip)	693.619KiB	693.602KiB	17.000B
SQL Server	1.835MiB	1.834MiB	370.000B
SQL Server (gzip)	728.916KiB	728.917KiB	-2.000B
CockroachDB	1.855MiB	1.854MiB	367.000B
CockroachDB (gzip)	732.532KiB	732.501KiB	31.000B