[jarri-abidi]

Closes #3187. Supersedes #3291, which was closed automatically for merge conflicts; this is the same feature rebased onto the current main, with the fixes from running it since.

Problem

With emit_prepared_queries, Prepare prepares every query on one connection. A database user that can only read, such as one connecting to a read replica, can't prepare the INSERT, UPDATE and DELETE statements, so you either prepare everything with a read-write user or generate a second package and duplicate all the models (#3187).

Solution

A new emit_read_only_prepared option (Go, database/sql). When set, sqlc also generates read.go with a ReadQueries type, created with PrepareReadOnly, that prepares only the read-only queries. Prepare is unchanged, and the models are shared.

version: "2"
sql:
  - engine: "postgresql"
    queries: "query.sql"
    schema: "schema.sql"
    gen:
      go:
        package: "db"
        out: "db"
        emit_prepared_queries: true
        emit_read_only_prepared: true

writes, err := db.Prepare(ctx, primary)        // every query
reads, err := db.PrepareReadOnly(ctx, replica) // read-only queries only
user, err := reads.GetUserByID(ctx, id)

A query is read-only if it SELECTs and doesn't INSERT, UPDATE, DELETE or SELECT ... FOR UPDATE, so a DELETE ... WHERE id IN (SELECT ...) stays out of read.go, as asked in the #3291 review. Keywords are matched when followed by any whitespace, so queries written as SELECT\n col1, ... are recognised.

read.go gets its imports from the read-only queries' own argument and result types, including github.com/lib/pq when they bind or scan slices with pq.Array.

pgx isn't supported (no read.go is generated), because emit_prepared_queries doesn't apply to it.

Changes

• emit_read_only_prepared in the Go options, the v1 config, both config JSON schemas and docs/reference/config.md
• readQueriesFile template (stdlib/readonlyCode.tmpl) and the read-only query selection in gen.go
• endtoend fixtures under read_write_segregation: MySQL, PostgreSQL, and PostgreSQL with slice arguments and results

Testing

• go vet ./... and go test --tags=examples ./... pass locally
• This feature has been running in production services generating read.go, which is where the pq import and bare-SELECT fixes came from

🤖 Generated with Claude Code