Add multitenancy support

Makefile

@@ -0,0 +1,11 @@
+
+startup-pg-docker:
+	docker run \
+		--name pg-test \
+		-v "$$PWD"/examples/pg/script.sql:/docker-entrypoint-initdb.d/init.sql:ro \
+		-e POSTGRES_PASSWORD=pass \
+		-e POSTGRES_USER=user \
+		-e POSTGRES_DB=testdb \
+		-p 5432:5432 \
+		-d \
+		postgres:15

cmd/scima/main.go

@@ -3,14 +3,12 @@ package main
 
 import (
 	"context"
-	"database/sql"
 	"fmt"
 	"os"
 	"time"
 
 	_ "github.com/lib/pq" // postgres driver
 	"github.com/scima/scima/internal/config"
-	"github.com/scima/scima/internal/dialect"
 	"github.com/scima/scima/internal/migrate"
 	"github.com/spf13/cobra"
 )
@@ -28,6 +26,7 @@ func addGlobalFlags(cmd *cobra.Command) {
 	cmd.PersistentFlags().StringVar(&dsn, "dsn", "", "Database DSN / connection string")
 	cmd.PersistentFlags().StringVar(&migrationsDir, "migrations-dir", "./migrations", "Directory containing migration files")
 	cmd.PersistentFlags().StringVar(&schema, "schema", "", "Optional database schema for migration tracking table and SQL placeholders ({{schema}}, {{schema?}})")
+	cmd.PersistentFlags().StringVar(&configPath, "config", "", "Path to config file")
 }
 
 func init() {
@@ -40,9 +39,9 @@ func init() {
 	downCmd.Flags().IntVar(&steps, "steps", 1, "Number of migration steps to revert (default 1, 0=all)")
 }
 
-var initCmd = &cobra.Command{Use: "init", Short: "Initialize migration tracking table", RunE: func(_ *cobra.Command, _ []string) error {
-	cfg := gatherConfig()
-	migr, db, err := buildMigrator(cfg)
+var initCmd = &cobra.Command{Use: "init", Short: "Initialize migration tracking table", RunE: func(cmd *cobra.Command, _ []string) error {
+	cfg := gatherConfig(cmd)
+	migr, db, err := migrate.BuildMigrator(cfg)
 	if err != nil {
 		return err
 	}
@@ -58,9 +57,9 @@ var initCmd = &cobra.Command{Use: "init", Short: "Initialize migration tracking
 	return nil
 }}
 
-var statusCmd = &cobra.Command{Use: "status", Short: "Show current and pending migrations", RunE: func(_ *cobra.Command, _ []string) error {
-	cfg := gatherConfig()
-	migr, db, err := buildMigrator(cfg)
+var statusCmd = &cobra.Command{Use: "status", Short: "Show current and pending migrations", RunE: func(cmd *cobra.Command, _ []string) error {
+	cfg := gatherConfig(cmd)
+	migr, db, err := migrate.BuildMigrator(cfg)
 	if err != nil {
 		return err
 	}
@@ -84,9 +83,9 @@ var statusCmd = &cobra.Command{Use: "status", Short: "Show current and pending m
 	return nil
 }}
 
-var upCmd = &cobra.Command{Use: "up", Short: "Apply pending up migrations", RunE: func(_ *cobra.Command, _ []string) error {
-	cfg := gatherConfig()
-	migr, db, err := buildMigrator(cfg)
+var upCmd = &cobra.Command{Use: "up", Short: "Apply pending up migrations", RunE: func(cmd *cobra.Command, _ []string) error {
+	cfg := gatherConfig(cmd)
+	migr, db, err := migrate.BuildMigrator(cfg)
 	if err != nil {
 		return err
 	}
@@ -116,9 +115,9 @@ var upCmd = &cobra.Command{Use: "up", Short: "Apply pending up migrations", RunE
 }}
 
 var steps int
-var downCmd = &cobra.Command{Use: "down", Short: "Revert migrations (default 1 step)", RunE: func(_ *cobra.Command, _ []string) error {
-	cfg := gatherConfig()
-	migr, db, err := buildMigrator(cfg)
+var downCmd = &cobra.Command{Use: "down", Short: "Revert migrations (default 1 step)", RunE: func(cmd *cobra.Command, _ []string) error {
+	cfg := gatherConfig(cmd)
+	migr, db, err := migrate.BuildMigrator(cfg)
 	if err != nil {
 		return err
 	}
@@ -151,7 +150,7 @@ var downCmd = &cobra.Command{Use: "down", Short: "Revert migrations (default 1 s
 	return nil
 }}
 
-func gatherConfig() config.Config {
+func gatherConfig(cmd *cobra.Command) config.Config {
 	// Try config file first if provided or default locations
 	var cfg *config.Config
 	if configPath != "" {
@@ -169,47 +168,21 @@ func gatherConfig() config.Config {
 		}
 	}
 	// CLI flags override config file
-	if driver != "" {
+	if driver != "" && cmd.Flags().Changed("driver") {
 		cfg.Driver = driver
 	}
-	if dsn != "" {
+	if dsn != "" && cmd.Flags().Changed("dsn") {
 		cfg.DSN = dsn
 	}
-	if migrationsDir != "" {
+	if migrationsDir != "" && cmd.Flags().Changed("migrations-dir") {
 		cfg.MigrationsDir = migrationsDir
 	}
-	if schema != "" {
+	if schema != "" && cmd.Flags().Changed("schema") {
 		cfg.Schema = schema
 	}
 	return *cfg
 }
 
-func buildMigrator(cfg config.Config) (*migrate.Migrator, *sql.DB, error) {
-	dial, err := dialect.Get(cfg.Driver)
-	if err != nil {
-		return nil, nil, err
-	}
-	if cfg.DSN == "" {
-		return nil, nil, fmt.Errorf("dsn required")
-	}
-	db, err := sql.Open(driverNameFor(cfg.Driver), cfg.DSN)
-	if err != nil {
-		return nil, nil, err
-	}
-	return migrate.NewMigrator(dial, dialect.SQLConn{DB: db}, schema), db, nil
-}
-
-func driverNameFor(driver string) string {
-	switch driver {
-	case "hana":
-		return "hdb"
-	case "postgres", "pg":
-		return "postgres"
-	default:
-		return driver // assume same
-	}
-}
-
 func main() {
 	if err := rootCmd.Execute(); err != nil {
 		fmt.Fprintf(os.Stderr, "error: %v\n", err)

cmd/scima/tenants.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"github.com/scima/scima/internal/config"
+	"github.com/scima/scima/internal/migrate"
+	"github.com/spf13/cobra"
+)
+
+var tenantsCmd = &cobra.Command{
+	Use:   "tenants",
+	Short: "Multi-tenant schema migrations",
+}
+
+var tenantsUpCmd = &cobra.Command{
+	Use:   "up",
+	Short: "Apply pending up migrations for all tenants",
+	RunE: func(cmd *cobra.Command, _ []string) error {
+		cfg := gatherConfig(cmd)
+		if len(cfg.Tenants) == 0 {
+			return fmt.Errorf("no tenants configured")
+		}
+		pairs, err := migrate.ScanDir(cfg.MigrationsDir)
+		if err != nil {
+			return err
+		}
+		if err := migrate.Validate(pairs); err != nil {
+			return err
+		}
+		mtMigr := migrate.NewMultiTenantMigrator(cfg.Tenants, func(t config.Tenant) (*migrate.Migrator, io.Closer, error) {
+			return migrate.BuildTenantMigrator(cfg.Driver, t)
+		})
+		start := time.Now()
+		results := mtMigr.ApplyUpAll(context.Background(), pairs)
+		for tenant, err := range results {
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "tenant %s: error: %v\n", tenant, err)
+			} else {
+				fmt.Printf("tenant %s: migrations applied successfully\n", tenant)
+			}
+		}
+		fmt.Printf("completed in %s\n", time.Since(start))
+		return nil
+	},
+}
+
+// Register the tenants command and its subcommands in main.go's init()
+func init() {
+	rootCmd.AddCommand(tenantsCmd)
+	tenantsCmd.AddCommand(tenantsUpCmd)
+}

examples/pg/migrations/0010_init.down.sql

@@ -0,0 +1 @@
+DROP TABLE {{schema}}users;

examples/pg/migrations/0010_init.up.sql

@@ -0,0 +1,5 @@
+CREATE TABLE {{schema}}users (
+    id BIGSERIAL PRIMARY KEY,
+    username VARCHAR(255) NOT NULL,
+    created_at TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
+);

examples/pg/migrations/0020_add_email.down.sql

@@ -0,0 +1 @@
+ALTER TABLE {{schema}}users DROP COLUMN email;

examples/pg/migrations/0020_add_email.up.sql

@@ -0,0 +1 @@
+ALTER TABLE {{schema}}users ADD COLUMN email VARCHAR(320);

examples/pg/migrations/0030_add_tenant1_schema.down.sql

@@ -0,0 +1 @@
+DROP SCHEMA tenant1 CASCADE;

examples/pg/migrations/0030_add_tenant1_schema.up.sql

@@ -0,0 +1 @@
+CREATE SCHEMA IF NOT EXISTS tenant1;

examples/pg/migrations/0040_add_tenant2_schema.down.sql

@@ -0,0 +1 @@
+DROP SCHEMA tenant2 CASCADE;

examples/pg/migrations/0040_add_tenant2_schema.up.sql

@@ -0,0 +1 @@
+CREATE SCHEMA IF NOT EXISTS tenant2;

examples/pg/scima.yaml

@@ -0,0 +1,12 @@
+driver: postgres
+dsn: postgres://user:pass@localhost:5432/testdb?sslmode=disable
+schema: public
+migrationsdir: ./examples/pg/migrations
+
+tenants:
+  - name: tenant1
+    dsn: postgres://user:pass@localhost:5432/testdb?sslmode=disable
+    schema: tenant1
+  - name: tenant2
+    dsn: postgres://user:pass@localhost:5432/testdb?sslmode=disable
+    schema: tenant2

internal/config/config.go

@@ -7,10 +7,18 @@ import (
 
 // Config holds runtime configuration for migrations.
 type Config struct {
-	Driver        string `mapstructure:"driver"`
-	DSN           string `mapstructure:"dsn"`
-	MigrationsDir string `mapstructure:"migrationsdir"`
-	Schema        string `mapstructure:"schema"`
+	Driver        string   `mapstructure:"driver"`
+	DSN           string   `mapstructure:"dsn"`
+	MigrationsDir string   `mapstructure:"migrationsdir"`
+	Schema        string   `mapstructure:"schema"`
+	Tenants       []Tenant `mapstructure:"tenants"`
+}
+
+// Tenant holds configuration for a single tenant.
+type Tenant struct {
+	Name   string `mapstructure:"name"`
+	DSN    string `mapstructure:"dsn"`
+	Schema string `mapstructure:"schema"`
 }
 
 // LoadConfig uses Viper to load config from file, env, and flags.

internal/migrate/migrator.go

@@ -3,9 +3,13 @@ package migrate
 
 import (
 	"context"
+	"database/sql"
 	"fmt"
+	"io"
+	"os"
 	"strings"
 
+	"github.com/scima/scima/internal/config"
 	"github.com/scima/scima/internal/dialect"
 )
 
@@ -110,6 +114,7 @@ func expandPlaceholders(sql string, schema string) (string, error) {
 				return "", fmt.Errorf("%s used but schema not set", requiredSchemaToken)
 			}
 			b.WriteString(schema)
+			b.WriteByte('.')
 			i += len(req)
 			continue
 		}
@@ -119,3 +124,38 @@ func expandPlaceholders(sql string, schema string) (string, error) {
 	}
 	return b.String(), nil
 }
+
+// BuildMigrator constructs a Migrator and underlying sql.DB from config.
+func BuildMigrator(cfg config.Config) (*Migrator, *sql.DB, error) {
+	dial, err := dialect.Get(cfg.Driver)
+	if err != nil {
+		return nil, nil, err
+	}
+	if cfg.DSN == "" {
+		return nil, nil, fmt.Errorf("dsn required")
+	}
+	db, err := sql.Open(driverNameFor(cfg.Driver), cfg.DSN)
+	if err != nil {
+		return nil, nil, err
+	}
+	return NewMigrator(dial, dialect.SQLConn{DB: db}, cfg.Schema), db, nil
+}
+
+func driverNameFor(driver string) string {
+	switch driver {
+	case "hana":
+		return "hdb"
+	case "postgres", "pg":
+		return "postgres"
+	default:
+		return driver // assume same
+	}
+}
+
+func closeDb(db io.Closer) {
+	if db != nil {
+		if err := db.Close(); err != nil {
+			fmt.Fprintf(os.Stderr, "error closing db: %v\n", err)
+		}
+	}
+}