feat(expander): Add star expander for SELECT * and RETURNING * (PostgreSQL, MySQL, SQLite) (#4203)

* feat(postgresql): Add star expander for SELECT * and RETURNING *

Adds a new expander package that expands * expressions in SQL queries
to explicit column names by preparing the query against a PostgreSQL
database.

Features:
- Expands SELECT * to explicit column list
- Preserves table prefix for qualified stars (e.g., table.*)
- Handles RETURNING * in INSERT/UPDATE/DELETE statements
- Recursively expands CTEs, including dependent CTEs
- Supports subqueries in FROM clause
- Works with both cgo (pganalyze/pg_query_go) and non-cgo
  (wasilibs/go-pgquery) builds

Example:
  SELECT * FROM authors
  → SELECT id, name, bio FROM authors

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* feat(expander): port expander to use internal AST types

Move expander from internal/engine/postgresql/expander to internal/x/expander
and port it to use the internal AST types instead of pg_query nodes.

Key changes:
- Use internal AST types (*ast.SelectStmt, *ast.InsertStmt, etc.)
- Use astutils.Search for star detection
- Use ast.Format instead of pg_query deparse
- Add Parser interface for dependency injection
- Add test cases for COUNT(*) (should not be expanded)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* feat(expander): add MySQL support and use ColumnGetter interface

- Rename TestExpand to TestExpandPostgreSQL
- Add TestExpandMySQL for MySQL database support
- Replace pgxpool.Pool with ColumnGetter interface for database-agnostic column resolution
- Add PostgreSQLColumnGetter and MySQLColumnGetter implementations
- MySQL tests skip edge cases (double star, star in middle) due to intermediate query formatting issues

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* fix(expander): use valid MySQL syntax for edge case tests

MySQL doesn't support unqualified `*` mixed with other columns (e.g.,
`SELECT *, *` or `SELECT id, *, name`). These are valid PostgreSQL
but invalid MySQL syntax.

Update MySQL tests to use table-qualified stars which are valid:
- `SELECT authors.*, authors.*` instead of `SELECT *, *`
- `SELECT id, authors.*, name` instead of `SELECT id, *, name`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* feat(expander): add SQLite support

- Add TestExpandSQLite with 8 test cases using in-memory SQLite database
- Rename MySQLColumnGetter to SQLColumnGetter since both MySQL and SQLite
  use the same database/sql-based implementation
- SQLite supports the same star syntax as PostgreSQL (including `SELECT *, *`
  and `SELECT id, *, name`)

Test results:
- PostgreSQL: 14 tests
- MySQL: 8 tests
- SQLite: 8 tests

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* refactor(expander): use PrepareContext in SQLColumnGetter

Use PrepareContext to validate the query before executing it to get
column metadata. While database/sql doesn't expose column names from
prepared statements directly (unlike pgx), this at least validates
the SQL syntax before execution.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* refactor(expander): use native ncruces/go-sqlite3 API for column names

Use the native sqlite3.Conn.Prepare and stmt.ColumnName/ColumnCount APIs
to get column names without executing the query. This is more efficient
and consistent with how PostgreSQL handles it.

Changes:
- Add SQLiteColumnGetter using native sqlite3.Conn
- Rename SQLColumnGetter to MySQLColumnGetter (MySQL still needs to execute)
- SQLite test now uses sqlite3.Open instead of sql.Open

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

* refactor(expander): use forked MySQL driver and fix list formatting

- Update MySQLColumnGetter to use github.com/sqlc-dev/mysql fork with
  StmtMetadata interface for getting column names via prepare
- Add replace directive to go.mod for the forked MySQL driver
- Fix list formatting to use ", " separator instead of "," for proper
  SQL spacing (e.g., "SELECT id, name, bio" instead of "SELECT id,name,bio")
- Update test expectations to reflect proper spacing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: kyleconroy

go.mod

@@ -64,3 +64,5 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20251022142026-3a174f9686a8 // indirect
 	gopkg.in/natefinch/lumberjack.v2 v2.2.1 // indirect
 )
+
+replace github.com/go-sql-driver/mysql => github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2

go.sum

@@ -26,8 +26,6 @@ github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
 github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
 github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
-github.com/go-sql-driver/mysql v1.9.3 h1:U/N249h2WzJ3Ukj8SowVFjdtZKfu9vlLZxjPXV1aweo=
-github.com/go-sql-driver/mysql v1.9.3/go.mod h1:qn46aNg1333BRMNU69Lq93t8du/dwxI64Gl8i5p1WMU=
 github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=
 github.com/gofrs/uuid v4.0.0+incompatible h1:1SD/1F5pU8p29ybwgQSwpQk+mwdRrXCYuPhW6m+TnJw=
 github.com/gofrs/uuid v4.0.0+incompatible/go.mod h1:b2aQJv3Z4Fp6yNu3cdSllBxTCLRxnplIgP/c0N/04lM=
@@ -159,6 +157,8 @@ github.com/spf13/cobra v1.10.1/go.mod h1:7SmJGaTHFVBY0jW4NXGluQoLvhqFQM+6XSKD+P4
 github.com/spf13/pflag v1.0.9/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
 github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2 h1:kmCAKKtOgK6EXXQX9oPdEASIhgor7TCpWxD8NtcqVcU=
+github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2/go.mod h1:TrDMWzjNTKvJeK2GC8uspG+PWyPLiY9QKvwdWpAdlZE=
 github.com/stoewer/go-strcase v1.2.0 h1:Z2iHWqGXH00XYgqDmNgQbIBxf3wrNq0F3feEy0ainaU=
 github.com/stoewer/go-strcase v1.2.0/go.mod h1:IBiWB2sKIp3wVVQ3Y035++gc+knqhUQag1KpM8ahLw8=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

internal/sql/ast/list.go

@@ -14,5 +14,5 @@ func (n *List) Format(buf *TrackedBuffer, d format.Dialect) {
 	if n == nil {
 		return
 	}
-	buf.join(n, d, ",")
+	buf.join(n, d, ", ")
 }