sqldb: add support for custom in-code migrations

This commit introduces support for custom, in-code migrations, allowing
a specific Go function to be executed at a designated database version
during sqlc migrations. If the current database version surpasses the
specified version, the migration will be skipped.

sqldb/postgres.go

@@ -1,6 +1,7 @@
 package sqldb
 
 import (
+	"context"
 	"database/sql"
 	"fmt"
 	"net/url"
@@ -32,6 +33,9 @@ var (
 		"BIGINT PRIMARY KEY":  "BIGSERIAL PRIMARY KEY",
 		"TIMESTAMP":           "TIMESTAMP WITHOUT TIME ZONE",
 	}
+
+	// Make sure PostgresStore implements the MigrationExecutor interface.
+	_ MigrationExecutor = (*PostgresStore)(nil)
 )
 
 // replacePasswordInDSN takes a DSN string and returns it with the password
@@ -85,43 +89,62 @@ type PostgresStore struct {
 
 // NewPostgresStore creates a new store that is backed by a Postgres database
 // backend.
-func NewPostgresStore(cfg *PostgresConfig) (*PostgresStore, error) {
+func NewPostgresStore(cfg *PostgresConfig, migrations []MigrationConfig) (
+	*PostgresStore, error) {
+
 	sanitizedDSN, err := replacePasswordInDSN(cfg.Dsn)
 	if err != nil {
 		return nil, err
 	}
 	log.Infof("Using SQL database '%s'", sanitizedDSN)
 
-	rawDB, err := sql.Open("pgx", cfg.Dsn)
+	db, err := sql.Open("pgx", cfg.Dsn)
 	if err != nil {
 		return nil, err
 	}
 
+	// Ensure the migration tracker table exists before running migrations.
+	// This table tracks migration progress and ensures compatibility with
+	// SQLC query generation. If the table is already created by an SQLC
+	// migration, this operation becomes a no-op.
+	migrationTrackerSQL := `
+	CREATE TABLE IF NOT EXISTS migration_tracker (
+		version INTEGER UNIQUE NOT NULL,
+		migration_time TIMESTAMP NOT NULL
+	);`
+
+	_, err = db.Exec(migrationTrackerSQL)
+	if err != nil {
+		return nil, fmt.Errorf("error creating migration tracker: %w",
+			err)
+	}
+
 	maxConns := defaultMaxConns
 	if cfg.MaxConnections > 0 {
 		maxConns = cfg.MaxConnections
 	}
 
-	rawDB.SetMaxOpenConns(maxConns)
-	rawDB.SetMaxIdleConns(maxConns)
-	rawDB.SetConnMaxLifetime(connIdleLifetime)
+	db.SetMaxOpenConns(maxConns)
+	db.SetMaxIdleConns(maxConns)
+	db.SetConnMaxLifetime(connIdleLifetime)
 
-	queries := sqlc.New(rawDB)
+	queries := sqlc.New(db)
 
 	s := &PostgresStore{
 		cfg: cfg,
 		BaseDB: &BaseDB{
-			DB:      rawDB,
+			DB:      db,
 			Queries: queries,
 		},
 	}
 
 	// Execute migrations unless configured to skip them.
 	if !cfg.SkipMigrations {
-		err := s.ExecuteMigrations(TargetLatest)
+		err := ApplyMigrations(
+			context.Background(), s.BaseDB, s, migrations,
+		)
 		if err != nil {
-			return nil, fmt.Errorf("error executing migrations: %w",
-				err)
+			return nil, err
 		}
 	}