chore(release): update package version to 1.0.71

* Implemented `Concurrent` field in index model
* Updated index creation template to support `CREATE INDEX CONCURRENTLY`
* Added tests for concurrent index creation in migration writer

cmd/relspec/diff.go

@@ -16,6 +16,7 @@ import (
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/drawdb"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/json"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/pgsql"
+	"git.warky.dev/wdevs/relspecgo/pkg/readers/sqldir"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/sqlite"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/yaml"
 )
@@ -87,11 +88,11 @@ Examples:
 }
 
 func init() {
-	diffCmd.Flags().StringVar(&sourceType, "from", "", "Source database format (dbml, dctx, drawdb, json, yaml, pgsql)")
+	diffCmd.Flags().StringVar(&sourceType, "from", "", "Source database format (dbml, dctx, drawdb, json, yaml, pgsql, sqldir)")
 	diffCmd.Flags().StringVar(&sourcePath, "from-path", "", "Source file path (for file-based formats)")
 	diffCmd.Flags().StringVar(&sourceConn, "from-conn", "", "Source connection string (for database formats)")
 
-	diffCmd.Flags().StringVar(&targetType, "to", "", "Target database format (dbml, dctx, drawdb, json, yaml, pgsql)")
+	diffCmd.Flags().StringVar(&targetType, "to", "", "Target database format (dbml, dctx, drawdb, json, yaml, pgsql, sqldir)")
 	diffCmd.Flags().StringVar(&targetPath, "to-path", "", "Target file path (for file-based formats)")
 	diffCmd.Flags().StringVar(&targetConn, "to-conn", "", "Target connection string (for database formats)")
 
@@ -129,10 +130,12 @@ func runDiff(cmd *cobra.Command, args []string) error {
 
 	fmt.Fprintf(os.Stderr, "      ✓ Successfully read database '%s'\n", sourceDB.Name)
 	sourceTables := 0
+	sourceScripts := 0
 	for _, schema := range sourceDB.Schemas {
 		sourceTables += len(schema.Tables)
+		sourceScripts += len(schema.Scripts)
 	}
-	fmt.Fprintf(os.Stderr, "      Found: %d schema(s), %d table(s)\n\n", len(sourceDB.Schemas), sourceTables)
+	fmt.Fprintf(os.Stderr, "      Found: %d schema(s), %d table(s), %d script(s)\n\n", len(sourceDB.Schemas), sourceTables, sourceScripts)
 
 	// Read target database
 	fmt.Fprintf(os.Stderr, "[2/3] Reading target schema...\n")
@@ -151,10 +154,12 @@ func runDiff(cmd *cobra.Command, args []string) error {
 
 	fmt.Fprintf(os.Stderr, "      ✓ Successfully read database '%s'\n", targetDB.Name)
 	targetTables := 0
+	targetScripts := 0
 	for _, schema := range targetDB.Schemas {
 		targetTables += len(schema.Tables)
+		targetScripts += len(schema.Scripts)
 	}
-	fmt.Fprintf(os.Stderr, "      Found: %d schema(s), %d table(s)\n\n", len(targetDB.Schemas), targetTables)
+	fmt.Fprintf(os.Stderr, "      Found: %d schema(s), %d table(s), %d script(s)\n\n", len(targetDB.Schemas), targetTables, targetScripts)
 
 	// Compare databases
 	fmt.Fprintf(os.Stderr, "[3/3] Comparing schemas...\n")
@@ -165,7 +170,8 @@ func runDiff(cmd *cobra.Command, args []string) error {
 		summary.Tables.Missing + summary.Tables.Extra + summary.Tables.Modified +
 		summary.Columns.Missing + summary.Columns.Extra + summary.Columns.Modified +
 		summary.Indexes.Missing + summary.Indexes.Extra + summary.Indexes.Modified +
-		summary.Constraints.Missing + summary.Constraints.Extra + summary.Constraints.Modified
+		summary.Constraints.Missing + summary.Constraints.Extra + summary.Constraints.Modified +
+		summary.Scripts.Missing + summary.Scripts.Extra + summary.Scripts.Modified
 
 	fmt.Fprintf(os.Stderr, "      ✓ Comparison complete\n")
 	fmt.Fprintf(os.Stderr, "      Found: %d difference(s)\n\n", totalDiffs)
@@ -249,6 +255,12 @@ func readDatabase(dbType, filePath, connString, label string) (*models.Database,
 		}
 		reader = yaml.NewReader(&readers.ReaderOptions{FilePath: filePath})
 
+	case "sqldir", "scripts", "scriptdir":
+		if filePath == "" {
+			return nil, fmt.Errorf("%s: file path is required for SQL directory format", label)
+		}
+		reader = sqldir.NewReader(&readers.ReaderOptions{FilePath: filePath})
+
 	case "pgsql", "postgres", "postgresql":
 		if connString == "" {
 			return nil, fmt.Errorf("%s: connection string is required for PostgreSQL format", label)

cmd/relspec/diff_sqldir_test.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestReadDatabaseSupportsSQLDir(t *testing.T) {
+	tempDir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(tempDir, "1_001_create_users.sql"), []byte("CREATE TABLE users (id int);"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(tempDir, "1_002_seed_users.pgsql"), []byte("INSERT INTO users (id) VALUES (1);"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	db, err := readDatabase("sqldir", tempDir, "", "source")
+	if err != nil {
+		t.Fatalf("readDatabase failed: %v", err)
+	}
+	if len(db.Schemas) != 1 {
+		t.Fatalf("expected 1 schema, got %d", len(db.Schemas))
+	}
+	if got := len(db.Schemas[0].Scripts); got != 2 {
+		t.Fatalf("expected 2 scripts, got %d", got)
+	}
+}

cmd/relspec/merge.go

@@ -117,7 +117,7 @@ func init() {
 	// Output flags
 	mergeCmd.Flags().StringVar(&mergeOutputType, "output", "", "Output format (required): dbml, dctx, drawdb, graphql, json, yaml, gorm, bun, drizzle, prisma, typeorm, pgsql")
 	mergeCmd.Flags().StringVar(&mergeOutputPath, "output-path", "", "Output file path (required for file-based formats)")
-	mergeCmd.Flags().StringVar(&mergeOutputConn, "output-conn", "", "Output connection string (for pgsql)")
+	mergeCmd.Flags().StringVar(&mergeOutputConn, "output-conn", "", "Output connection string (for pgsql) or database file path (for sqlite, to execute DDL directly instead of writing a .sql file)")
 
 	// Merge options
 	mergeCmd.Flags().BoolVar(&mergeSkipDomains, "skip-domains", false, "Skip domains during merge")
@@ -427,7 +427,15 @@ func writeDatabaseForMerge(dbType, filePath, connString string, db *models.Datab
 		}
 		writer = wtypeorm.NewWriter(newWriterOptions(filePath, "", flattenSchema, "", "", false))
 	case "sqlite", "sqlite3":
-		writer = wsqlite.NewWriter(newWriterOptions(filePath, "", flattenSchema, "", "", false))
+		writerOpts := newWriterOptions(filePath, "", flattenSchema, "", "", false)
+		if connString != "" {
+			// Execute DDL directly against the SQLite database file instead
+			// of writing a .sql script.
+			writerOpts.Metadata = map[string]interface{}{
+				"connection_string": connString,
+			}
+		}
+		writer = wsqlite.NewWriter(writerOpts)
 	case "pgsql":
 		writerOpts := newWriterOptions(filePath, "", flattenSchema, "", "", false)
 		if connString != "" {

linux/arch/PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Hein (Warky Devs) <hein@warky.dev>
 pkgname=relspec
-pkgver=1.0.67
+pkgver=1.0.71
 pkgrel=1
 pkgdesc="RelSpec is a comprehensive database relations management tool that reads, transforms, and writes database table specifications across multiple formats and ORMs."
 arch=('x86_64' 'aarch64')

linux/centos/relspec.spec

@@ -1,5 +1,5 @@
 Name:           relspec
-Version:        1.0.67
+Version:        1.0.71
 Release:        1%{?dist}
 Summary:        RelSpec is a comprehensive database relations management tool that reads, transforms, and writes database table specifications across multiple formats and ORMs.
 

pkg/diff/diff.go

@@ -1,6 +1,7 @@
 package diff
 
 import (
+	"fmt"
 	"reflect"
 	"sort"
 
@@ -96,6 +97,13 @@ func compareSchemaDetails(source, target *models.Schema) *SchemaChange {
 		hasChanges = true
 	}
 
+	// Compare scripts
+	scriptDiff := compareScripts(source.Scripts, target.Scripts)
+	if !isEmpty(scriptDiff) {
+		change.Scripts = scriptDiff
+		hasChanges = true
+	}
+
 	if !hasChanges {
 		return nil
 	}
@@ -543,6 +551,79 @@ func compareSequenceDetails(source, target *models.Sequence) map[string]any {
 	return changes
 }
 
+func compareScripts(source, target []*models.Script) *ScriptDiff {
+	diff := &ScriptDiff{
+		Missing:  make([]*models.Script, 0),
+		Extra:    make([]*models.Script, 0),
+		Modified: make([]*ScriptChange, 0),
+	}
+
+	sourceMap := make(map[string]*models.Script)
+	targetMap := make(map[string]*models.Script)
+
+	for _, s := range source {
+		sourceMap[scriptCompareKey(s)] = s
+	}
+	for _, s := range target {
+		targetMap[scriptCompareKey(s)] = s
+	}
+
+	for _, name := range sortedKeys(sourceMap) {
+		srcScript := sourceMap[name]
+		if tgtScript, exists := targetMap[name]; !exists {
+			diff.Missing = append(diff.Missing, srcScript)
+		} else if changes := compareScriptDetails(srcScript, tgtScript); len(changes) > 0 {
+			diff.Modified = append(diff.Modified, &ScriptChange{
+				Name:    srcScript.Name,
+				Source:  srcScript,
+				Target:  tgtScript,
+				Changes: changes,
+			})
+		}
+	}
+
+	for _, name := range sortedKeys(targetMap) {
+		tgtScript := targetMap[name]
+		if _, exists := sourceMap[name]; !exists {
+			diff.Extra = append(diff.Extra, tgtScript)
+		}
+	}
+
+	return diff
+}
+
+func scriptCompareKey(script *models.Script) string {
+	return fmt.Sprintf("%d:%d:%s", script.Priority, script.Sequence, script.SQLName())
+}
+
+func compareScriptDetails(source, target *models.Script) map[string]any {
+	changes := make(map[string]any)
+
+	if source.SQL != target.SQL {
+		changes["sql"] = map[string]string{"source": source.SQL, "target": target.SQL}
+	}
+	if source.Rollback != target.Rollback {
+		changes["rollback"] = map[string]string{"source": source.Rollback, "target": target.Rollback}
+	}
+	if !reflect.DeepEqual(source.RunAfter, target.RunAfter) {
+		changes["run_after"] = map[string][]string{"source": source.RunAfter, "target": target.RunAfter}
+	}
+	if source.Schema != target.Schema {
+		changes["schema"] = map[string]string{"source": source.Schema, "target": target.Schema}
+	}
+	if source.Version != target.Version {
+		changes["version"] = map[string]string{"source": source.Version, "target": target.Version}
+	}
+	if source.Priority != target.Priority {
+		changes["priority"] = map[string]int{"source": source.Priority, "target": target.Priority}
+	}
+	if source.Sequence != target.Sequence {
+		changes["sequence"] = map[string]uint{"source": source.Sequence, "target": target.Sequence}
+	}
+
+	return changes
+}
+
 // Helper function to check if a diff is empty
 func isEmpty(v any) bool {
 	switch d := v.(type) {
@@ -560,6 +641,8 @@ func isEmpty(v any) bool {
 		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
 	case *SequenceDiff:
 		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
+	case *ScriptDiff:
+		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
 	default:
 		return false
 	}
@@ -616,6 +699,11 @@ func ComputeSummary(result *DiffResult) *Summary {
 				summary.Sequences.Extra += len(schemaChange.Sequences.Extra)
 				summary.Sequences.Modified += len(schemaChange.Sequences.Modified)
 			}
+			if schemaChange.Scripts != nil {
+				summary.Scripts.Missing += len(schemaChange.Scripts.Missing)
+				summary.Scripts.Extra += len(schemaChange.Scripts.Extra)
+				summary.Scripts.Modified += len(schemaChange.Scripts.Modified)
+			}
 		}
 	}
 

pkg/diff/diff_test.go

@@ -525,6 +525,78 @@ func TestCompareSchemas(t *testing.T) {
 	}
 }
 
+func TestCompareScripts(t *testing.T) {
+	tests := []struct {
+		name   string
+		source []*models.Script
+		target []*models.Script
+		want   func(*ScriptDiff) bool
+	}{
+		{
+			name:   "identical scripts",
+			source: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);", Priority: 1, Sequence: 1}},
+			target: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);", Priority: 1, Sequence: 1}},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
+			},
+		},
+		{
+			name:   "missing script",
+			source: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);"}},
+			target: []*models.Script{},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Missing) == 1 && d.Missing[0].Name == "create_users"
+			},
+		},
+		{
+			name:   "extra script",
+			source: []*models.Script{},
+			target: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);"}},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Extra) == 1 && d.Extra[0].Name == "create_users"
+			},
+		},
+		{
+			name:   "modified script sql",
+			source: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);"}},
+			target: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id bigint);"}},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Modified) == 1 && d.Modified[0].Name == "create_users" && d.Modified[0].Changes["sql"] != nil
+			},
+		},
+		{
+			name:   "different script order is different identity",
+			source: []*models.Script{{Name: "create_users", SQL: "SELECT 1;", Priority: 1, Sequence: 1}},
+			target: []*models.Script{{Name: "create_users", SQL: "SELECT 1;", Priority: 2, Sequence: 3}},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Missing) == 1 && len(d.Extra) == 1 && len(d.Modified) == 0
+			},
+		},
+		{
+			name: "same descriptive names remain distinct",
+			source: []*models.Script{
+				{Name: "alter_users", SQL: "SELECT 1;", Priority: 1, Sequence: 1},
+				{Name: "alter_users", SQL: "SELECT 2;", Priority: 1, Sequence: 2},
+			},
+			target: []*models.Script{
+				{Name: "alter_users", SQL: "SELECT 1;", Priority: 1, Sequence: 1},
+			},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Missing) == 1 && d.Missing[0].Sequence == 2
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := compareScripts(tt.source, tt.target)
+			if !tt.want(got) {
+				t.Errorf("compareScripts() result doesn't match expectations")
+			}
+		})
+	}
+}
+
 func TestIsEmpty(t *testing.T) {
 	tests := []struct {
 		name string
@@ -540,6 +612,8 @@ func TestIsEmpty(t *testing.T) {
 		{"TableDiff with extra", &TableDiff{Missing: []*models.Table{}, Extra: []*models.Table{{Name: "users"}}, Modified: []*TableChange{}}, false},
 		{"empty ConstraintDiff", &ConstraintDiff{Missing: []*models.Constraint{}, Extra: []*models.Constraint{}, Modified: []*ConstraintChange{}}, true},
 		{"empty RelationshipDiff", &RelationshipDiff{Missing: []*models.Relationship{}, Extra: []*models.Relationship{}, Modified: []*RelationshipChange{}}, true},
+		{"empty ScriptDiff", &ScriptDiff{Missing: []*models.Script{}, Extra: []*models.Script{}, Modified: []*ScriptChange{}}, true},
+		{"ScriptDiff with modified", &ScriptDiff{Missing: []*models.Script{}, Extra: []*models.Script{}, Modified: []*ScriptChange{{Name: "create_users"}}}, false},
 	}
 
 	for _, tt := range tests {
@@ -586,6 +660,26 @@ func TestComputeSummary(t *testing.T) {
 				return s.Schemas.Missing == 1 && s.Schemas.Extra == 2 && s.Schemas.Modified == 1
 			},
 		},
+		{
+			name: "scripts with differences",
+			result: &DiffResult{
+				Schemas: &SchemaDiff{
+					Modified: []*SchemaChange{
+						{
+							Name: "public",
+							Scripts: &ScriptDiff{
+								Missing:  []*models.Script{{Name: "missing_script"}},
+								Extra:    []*models.Script{{Name: "extra_script"}, {Name: "seed_data"}},
+								Modified: []*ScriptChange{{Name: "changed_script"}},
+							},
+						},
+					},
+				},
+			},
+			want: func(s *Summary) bool {
+				return s.Scripts.Missing == 1 && s.Scripts.Extra == 2 && s.Scripts.Modified == 1
+			},
+		},
 	}
 
 	for _, tt := range tests {

pkg/diff/formatters.go

@@ -158,6 +158,21 @@ func formatSummary(result *DiffResult, w io.Writer) error {
 		fmt.Fprintf(w, "\n")
 	}
 
+	// Scripts
+	if summary.Scripts.Missing > 0 || summary.Scripts.Extra > 0 || summary.Scripts.Modified > 0 {
+		fmt.Fprintf(w, "Scripts:\n")
+		if summary.Scripts.Missing > 0 {
+			fmt.Fprintf(w, "  Missing:  %d\n", summary.Scripts.Missing)
+		}
+		if summary.Scripts.Extra > 0 {
+			fmt.Fprintf(w, "  Extra:    %d\n", summary.Scripts.Extra)
+		}
+		if summary.Scripts.Modified > 0 {
+			fmt.Fprintf(w, "  Modified: %d\n", summary.Scripts.Modified)
+		}
+		fmt.Fprintf(w, "\n")
+	}
+
 	// Check if there are no differences
 	if summary.Schemas.Missing == 0 && summary.Schemas.Extra == 0 && summary.Schemas.Modified == 0 &&
 		summary.Tables.Missing == 0 && summary.Tables.Extra == 0 && summary.Tables.Modified == 0 &&
@@ -166,7 +181,8 @@ func formatSummary(result *DiffResult, w io.Writer) error {
 		summary.Constraints.Missing == 0 && summary.Constraints.Extra == 0 && summary.Constraints.Modified == 0 &&
 		summary.Relationships.Missing == 0 && summary.Relationships.Extra == 0 && summary.Relationships.Modified == 0 &&
 		summary.Views.Missing == 0 && summary.Views.Extra == 0 && summary.Views.Modified == 0 &&
-		summary.Sequences.Missing == 0 && summary.Sequences.Extra == 0 && summary.Sequences.Modified == 0 {
+		summary.Sequences.Missing == 0 && summary.Sequences.Extra == 0 && summary.Sequences.Modified == 0 &&
+		summary.Scripts.Missing == 0 && summary.Scripts.Extra == 0 && summary.Scripts.Modified == 0 {
 		fmt.Fprintf(w, "No differences found.\n")
 	}
 
@@ -448,6 +464,26 @@ const htmlTemplate = `<!DOCTYPE html>
                 </div>
             </div>
             {{end}}
+
+            {{if or .Summary.Scripts.Missing .Summary.Scripts.Extra .Summary.Scripts.Modified}}
+            <div class="summary-item">
+                <h3>Scripts</h3>
+                <div class="count-group">
+                    <div class="count">
+                        <span class="count-label">Missing</span>
+                        <span class="count-value missing">{{.Summary.Scripts.Missing}}</span>
+                    </div>
+                    <div class="count">
+                        <span class="count-label">Extra</span>
+                        <span class="count-value extra">{{.Summary.Scripts.Extra}}</span>
+                    </div>
+                    <div class="count">
+                        <span class="count-label">Modified</span>
+                        <span class="count-value modified">{{.Summary.Scripts.Modified}}</span>
+                    </div>
+                </div>
+            </div>
+            {{end}}
         </div>
     </div>
 
@@ -588,6 +624,35 @@ const htmlTemplate = `<!DOCTYPE html>
                 </ul>
                 {{end}}
             {{end}}
+
+            {{if .Scripts}}
+                {{if .Scripts.Missing}}
+                <h4>Missing Scripts</h4>
+                <ul class="item-list">
+                    {{range .Scripts.Missing}}
+                    <li class="missing">{{.Name}}</li>
+                    {{end}}
+                </ul>
+                {{end}}
+
+                {{if .Scripts.Extra}}
+                <h4>Extra Scripts</h4>
+                <ul class="item-list">
+                    {{range .Scripts.Extra}}
+                    <li class="extra">{{.Name}}</li>
+                    {{end}}
+                </ul>
+                {{end}}
+
+                {{if .Scripts.Modified}}
+                <h4>Modified Scripts</h4>
+                <ul class="item-list">
+                    {{range .Scripts.Modified}}
+                    <li class="modified">{{.Name}}</li>
+                    {{end}}
+                </ul>
+                {{end}}
+            {{end}}
         </div>
         {{end}}
     </div>

pkg/diff/formatters_test.go

@@ -104,6 +104,26 @@ func TestFormatSummary(t *testing.T) {
 			},
 			wantStr: []string{"Tables:", "Missing:  1", "Extra:    1", "Modified: 1"},
 		},
+		{
+			name: "with script differences",
+			result: &DiffResult{
+				Source: "source",
+				Target: "target",
+				Schemas: &SchemaDiff{
+					Modified: []*SchemaChange{
+						{
+							Name: "public",
+							Scripts: &ScriptDiff{
+								Missing:  []*models.Script{{Name: "create_users"}},
+								Extra:    []*models.Script{{Name: "seed_users"}},
+								Modified: []*ScriptChange{{Name: "add_indexes"}},
+							},
+						},
+					},
+				},
+			},
+			wantStr: []string{"Scripts:", "Missing:  1", "Extra:    1", "Modified: 1"},
+		},
 	}
 
 	for _, tt := range tests {
@@ -237,6 +257,31 @@ func TestFormatHTML(t *testing.T) {
 				"text",
 			},
 		},
+		{
+			name: "with script modifications",
+			result: &DiffResult{
+				Source: "source",
+				Target: "target",
+				Schemas: &SchemaDiff{
+					Modified: []*SchemaChange{
+						{
+							Name: "public",
+							Scripts: &ScriptDiff{
+								Missing:  []*models.Script{{Name: "create_users"}},
+								Extra:    []*models.Script{{Name: "seed_users"}},
+								Modified: []*ScriptChange{{Name: "add_indexes"}},
+							},
+						},
+					},
+				},
+			},
+			wantStr: []string{
+				"Scripts",
+				"create_users",
+				"seed_users",
+				"add_indexes",
+			},
+		},
 	}
 
 	for _, tt := range tests {

pkg/diff/types.go

@@ -22,6 +22,7 @@ type SchemaChange struct {
 	Tables    *TableDiff    `json:"tables,omitempty"`
 	Views     *ViewDiff     `json:"views,omitempty"`
 	Sequences *SequenceDiff `json:"sequences,omitempty"`
+	Scripts   *ScriptDiff   `json:"scripts,omitempty"`
 }
 
 // TableDiff represents differences in tables
@@ -131,6 +132,21 @@ type SequenceChange struct {
 	Changes map[string]any   `json:"changes"`
 }
 
+// ScriptDiff represents differences in migration scripts.
+type ScriptDiff struct {
+	Missing  []*models.Script `json:"missing"`  // Scripts in source but not in target
+	Extra    []*models.Script `json:"extra"`    // Scripts in target but not in source
+	Modified []*ScriptChange  `json:"modified"` // Scripts that exist in both but differ
+}
+
+// ScriptChange represents a modified migration script.
+type ScriptChange struct {
+	Name    string         `json:"name"`
+	Source  *models.Script `json:"source"`
+	Target  *models.Script `json:"target"`
+	Changes map[string]any `json:"changes"`
+}
+
 // Summary provides counts for quick overview
 type Summary struct {
 	Schemas       SchemaSummary       `json:"schemas"`
@@ -141,6 +157,7 @@ type Summary struct {
 	Relationships RelationshipSummary `json:"relationships"`
 	Views         ViewSummary         `json:"views"`
 	Sequences     SequenceSummary     `json:"sequences"`
+	Scripts       ScriptSummary       `json:"scripts"`
 }
 
 type SchemaSummary struct {
@@ -190,3 +207,9 @@ type SequenceSummary struct {
 	Extra    int `json:"extra"`
 	Modified int `json:"modified"`
 }
+
+type ScriptSummary struct {
+	Missing  int `json:"missing"`
+	Extra    int `json:"extra"`
+	Modified int `json:"modified"`
+}

pkg/merge/merge.go

@@ -492,7 +492,12 @@ func extractTypeParts(col *models.Column) (baseType string, length, precision, s
 		}
 	}
 
-	typeName = pgsql.NormalizePGType(typeName)
+	// serial/bigserial/smallserial are sugar over an integer column plus a
+	// sequence default; PostgreSQL itself reports the underlying integer
+	// type back for such columns, so treat them as equivalent here to avoid
+	// spurious conflicts between a DBML "bigserial" source and a live-read
+	// "bigint" target (or vice versa).
+	typeName = pgsql.SerialUnderlyingType(typeName)
 
 	return typeName, length, precision, scale
 }

pkg/merge/merge_test.go

@@ -196,6 +196,50 @@ func TestMergeColumns_TypeConflictIsDetected(t *testing.T) {
 	}
 }
 
+func TestMergeColumns_SerialVsUnderlyingIntegerIsNotAConflict(t *testing.T) {
+	target := &models.Database{
+		Schemas: []*models.Schema{
+			{
+				Name: "public",
+				Tables: []*models.Table{
+					{
+						Name:   "users",
+						Schema: "public",
+						Columns: map[string]*models.Column{
+							// As reported back by a live PostgreSQL read of an
+							// existing serial primary key column.
+							"id": {Name: "id", Type: "bigint"},
+						},
+					},
+				},
+			},
+		},
+	}
+	source := &models.Database{
+		Schemas: []*models.Schema{
+			{
+				Name: "public",
+				Tables: []*models.Table{
+					{
+						Name:   "users",
+						Schema: "public",
+						Columns: map[string]*models.Column{
+							// As declared in a DBML source spec.
+							"id": {Name: "id", Type: "bigserial"},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	result := MergeDatabases(target, source, nil)
+
+	if len(result.TypeConflicts) != 0 {
+		t.Fatalf("Expected no type conflicts for bigserial vs bigint, got %d: %+v", len(result.TypeConflicts), result.TypeConflicts)
+	}
+}
+
 func TestMergeConstraints_NewConstraint(t *testing.T) {
 	target := &models.Database{
 		Schemas: []*models.Schema{

pkg/pgsql/datatypes.go

@@ -193,6 +193,28 @@ func IsKnownPGBaseType(baseType string) bool {
 	return ok
 }
 
+// serialUnderlyingType maps each serial pseudo-type to the integer type
+// PostgreSQL actually stores the column as. serial/bigserial/smallserial are
+// not real types: they are sugar for an integer column plus a sequence
+// default, and pg_catalog (and information_schema) always reports the
+// underlying integer type back for such columns.
+var serialUnderlyingType = map[string]string{
+	"serial":      "integer",
+	"bigserial":   "bigint",
+	"smallserial": "smallint",
+}
+
+// SerialUnderlyingType returns the underlying integer type for a serial
+// pseudo-type (e.g. "bigserial" -> "bigint"). If baseType (after
+// NormalizePGType) is not a serial type, it is returned unchanged.
+func SerialUnderlyingType(baseType string) string {
+	normalized := NormalizePGType(baseType)
+	if underlying, ok := serialUnderlyingType[normalized]; ok {
+		return underlying
+	}
+	return normalized
+}
+
 func IsGoType(pTypeName string) bool {
 	for k := range GoToStdTypes {
 		if strings.EqualFold(pTypeName, k) {

pkg/writers/pgsql/README.md

@@ -169,6 +169,7 @@ When `include_audit` is enabled, adds:
 - Constraint actions (CASCADE, RESTRICT, SET NULL)
 - Partial indexes
 - Function-based indexes
+- Concurrent index creation (`CREATE INDEX CONCURRENTLY`) via `Index.Concurrent`
 - Check constraints with expressions
 
 ## Data Types

pkg/writers/pgsql/migration_writer.go

@@ -409,14 +409,7 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 
 		if !exists {
 			// Column doesn't exist, add it
-			defaultVal := ""
-			if modelCol.Default != nil {
-				if value, ok := modelCol.Default.(string); ok {
-					defaultVal = writers.QuoteDefaultValue(value, modelCol.Type)
-				} else {
-					defaultVal = fmt.Sprintf("%v", modelCol.Default)
-				}
-			}
+			_, defaultVal := formatColumnDefaultSQL(modelCol)
 
 			sql, err := w.executor.ExecuteAddColumn(AddColumnData{
 				SchemaName: schema.Name,
@@ -443,13 +436,13 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 			// Column exists but properties changed
 			if !columnTypesEqual(modelCol, currentCol) {
 				newType := effectiveAlterColumnSQLType(modelCol)
-				sql, err := w.executor.ExecuteAlterColumnTypeWithFallback(AlterColumnTypeWithFallbackData{
-					SchemaName:    schema.Name,
-					TableName:     modelTable.Name,
-					ColumnName:    modelCol.Name,
-					NewType:       newType,
-					UsingExpr:     buildAlterColumnUsingExpression(modelCol.Name, newType),
-					OldColumnName: renamedColumnName(modelCol.Name, effectiveAlterColumnSQLType(currentCol)),
+				sql, err := w.executor.ExecuteAlterColumnTypeWithCheck(AlterColumnTypeWithCheckData{
+					SchemaName:      schema.Name,
+					TableName:       modelTable.Name,
+					ColumnName:      modelCol.Name,
+					NewType:         newType,
+					EquivalentTypes: equivalentTypeListSQL(newType),
+					UsingExpr:       buildAlterColumnUsingExpression(modelCol.Name, newType),
 				})
 				if err != nil {
 					return nil, err
@@ -467,18 +460,10 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 			}
 
 			// Check default value changes
-			if fmt.Sprintf("%v", modelCol.Default) != fmt.Sprintf("%v", currentCol.Default) {
-				setDefault := modelCol.Default != nil
-				defaultVal := ""
-				if setDefault {
-					if value, ok := modelCol.Default.(string); ok {
-						defaultVal = writers.QuoteDefaultValue(value, modelCol.Type)
-					} else {
-						defaultVal = fmt.Sprintf("%v", modelCol.Default)
-					}
-				}
+			if !columnDefaultsEqual(modelCol.Default, currentCol.Default) {
+				setDefault, defaultVal := formatColumnDefaultSQL(modelCol)
 
-				sql, err := w.executor.ExecuteAlterColumnDefault(AlterColumnDefaultData{
+				sql, err := w.executor.ExecuteAlterColumnDefaultWithCheck(AlterColumnDefaultWithCheckData{
 					SchemaName:   schema.Name,
 					TableName:    modelTable.Name,
 					ColumnName:   modelCol.Name,
@@ -502,7 +487,7 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 
 			// Check nullability changes
 			if modelCol.NotNull != currentCol.NotNull {
-				sql, err := w.executor.ExecuteAlterColumnNullability(AlterColumnNullabilityData{
+				sql, err := w.executor.ExecuteAlterColumnNullabilityWithCheck(AlterColumnNullabilityWithCheckData{
 					SchemaName: schema.Name,
 					TableName:  modelTable.Name,
 					ColumnName: modelCol.Name,
@@ -667,6 +652,7 @@ func (w *MigrationWriter) generateIndexScripts(model *models.Schema, current *mo
 					IndexType:  indexType,
 					Columns:    strings.Join(columnExprs, ", "),
 					Unique:     modelIndex.Unique,
+					Concurrent: modelIndex.Concurrent,
 				})
 				if err != nil {
 					return nil, err
@@ -964,32 +950,6 @@ func (w *MigrationWriter) generateAuditScripts(schema *models.Schema, auditConfi
 
 // Helper functions for comparing database objects
 
-// renamedColumnName builds the fallback column name used when an in-place
-// type conversion fails: "<column>_<oldtype>", with the old type sanitized
-// to a valid identifier fragment (e.g. "varchar(50)" -> "varchar_50").
-func renamedColumnName(columnName, oldType string) string {
-	sanitized := strings.Map(func(r rune) rune {
-		switch {
-		case r >= 'a' && r <= 'z', r >= '0' && r <= '9':
-			return r
-		case r >= 'A' && r <= 'Z':
-			return r + ('a' - 'A')
-		default:
-			return '_'
-		}
-	}, oldType)
-
-	for strings.Contains(sanitized, "__") {
-		sanitized = strings.ReplaceAll(sanitized, "__", "_")
-	}
-	sanitized = strings.Trim(sanitized, "_")
-
-	if sanitized == "" {
-		return columnName + "_old"
-	}
-	return columnName + "_" + sanitized
-}
-
 // columnsEqual checks if two columns have the same definition
 func columnsEqual(col1, col2 *models.Column) bool {
 	if col1 == nil || col2 == nil {
@@ -997,7 +957,24 @@ func columnsEqual(col1, col2 *models.Column) bool {
 	}
 	return columnTypesEqual(col1, col2) &&
 		col1.NotNull == col2.NotNull &&
-		fmt.Sprintf("%v", col1.Default) == fmt.Sprintf("%v", col2.Default)
+		columnDefaultsEqual(col1.Default, col2.Default)
+}
+
+// columnDefaultsEqual compares column defaults for drift detection, stripping
+// MySQL-style backticks (e.g. from GORM tags) so a model default of
+// "`now()`" is recognised as equal to a live default of "now()".
+func columnDefaultsEqual(default1, default2 interface{}) bool {
+	return normalizeDefaultForCompare(default1) == normalizeDefaultForCompare(default2)
+}
+
+func normalizeDefaultForCompare(value interface{}) string {
+	if value == nil {
+		return ""
+	}
+	if s, ok := value.(string); ok {
+		return strings.TrimSpace(stripBackticks(s))
+	}
+	return fmt.Sprintf("%v", value)
 }
 
 func columnTypesEqual(col1, col2 *models.Column) bool {

pkg/writers/pgsql/migration_writer_test.go

@@ -170,8 +170,11 @@ func TestWriteMigration_AltersColumnTypeFallsBackToRenameAndAddOnConversionFailu
 	if !strings.Contains(output, "EXCEPTION WHEN OTHERS THEN") {
 		t.Fatalf("expected migration to guard the type conversion with an exception handler, got:\n%s", output)
 	}
-	if !strings.Contains(output, "RENAME COLUMN details TO details_varchar_50") {
-		t.Fatalf("expected migration to rename the old column on conversion failure, got:\n%s", output)
+	if !strings.Contains(output, "RENAME COLUMN details TO %I") {
+		t.Fatalf("expected migration to rename the old column (derived from the live type) on conversion failure, got:\n%s", output)
+	}
+	if !strings.Contains(output, "renamed_column := 'details_' || trim(both '_' from regexp_replace(lower(current_type)") {
+		t.Fatalf("expected migration to derive the renamed column name from the live type, got:\n%s", output)
 	}
 	if !strings.Contains(output, "ADD COLUMN details integer") {
 		t.Fatalf("expected migration to add a fresh column with the new type on conversion failure, got:\n%s", output)
@@ -331,6 +334,46 @@ func TestWriteMigration_DoesNotAlterEquivalentNormalizedColumnType(t *testing.T)
 	}
 }
 
+func TestWriteMigration_ConcurrentIndex(t *testing.T) {
+	current := models.InitDatabase("testdb")
+	currentSchema := models.InitSchema("public")
+	current.Schemas = append(current.Schemas, currentSchema)
+
+	model := models.InitDatabase("testdb")
+	modelSchema := models.InitSchema("public")
+
+	table := models.InitTable("articles", "public")
+	titleCol := models.InitColumn("title", "articles", "public")
+	titleCol.Type = "text"
+	table.Columns["title"] = titleCol
+
+	index := &models.Index{
+		Name:       "idx_articles_title",
+		Columns:    []string{"title"},
+		Concurrent: true,
+	}
+	table.Indexes[index.Name] = index
+
+	modelSchema.Tables = append(modelSchema.Tables, table)
+	model.Schemas = append(model.Schemas, modelSchema)
+
+	var buf bytes.Buffer
+	writer, err := NewMigrationWriter(&writers.WriterOptions{})
+	if err != nil {
+		t.Fatalf("Failed to create writer: %v", err)
+	}
+	writer.writer = &buf
+
+	if err := writer.WriteMigration(model, current); err != nil {
+		t.Fatalf("WriteMigration failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "CREATE INDEX CONCURRENTLY IF NOT EXISTS") {
+		t.Fatalf("expected CONCURRENTLY create index statement, got:\n%s", output)
+	}
+}
+
 func TestWriteMigration_GinIndexOnTextUsesTrigramOperatorClass(t *testing.T) {
 	current := models.InitDatabase("testdb")
 	currentSchema := models.InitSchema("public")

pkg/writers/pgsql/templates.go

@@ -89,27 +89,10 @@ type AddColumnData struct {
 	NotNull    bool
 }
 
-// AlterColumnTypeData contains data for alter column type template
-type AlterColumnTypeData struct {
-	SchemaName string
-	TableName  string
-	ColumnName string
-	NewType    string
-	UsingExpr  string
-}
-
-// AlterColumnTypeWithFallbackData contains data for the alter column type
-// template that falls back to renaming the old column and adding a fresh
-// one when the in-place type conversion is not possible.
-type AlterColumnTypeWithFallbackData struct {
-	SchemaName    string
-	TableName     string
-	ColumnName    string
-	NewType       string
-	UsingExpr     string
-	OldColumnName string
-}
-
+// AlterColumnTypeWithCheckData contains data for the guarded alter column
+// type template, which only alters existing columns whose live type
+// differs from the desired one, and falls back to renaming the old column
+// and adding a fresh one when the in-place conversion is not possible.
 type AlterColumnTypeWithCheckData struct {
 	SchemaName      string
 	TableName       string
@@ -119,8 +102,10 @@ type AlterColumnTypeWithCheckData struct {
 	UsingExpr       string
 }
 
-// AlterColumnDefaultData contains data for alter column default template
-type AlterColumnDefaultData struct {
+// AlterColumnDefaultWithCheckData contains data for the guarded alter
+// column default template, which only alters existing columns whose live
+// default differs from the desired one.
+type AlterColumnDefaultWithCheckData struct {
 	SchemaName   string
 	TableName    string
 	ColumnName   string
@@ -128,8 +113,10 @@ type AlterColumnDefaultData struct {
 	DefaultValue string
 }
 
-// AlterColumnNullabilityData contains data for alter column nullability template
-type AlterColumnNullabilityData struct {
+// AlterColumnNullabilityWithCheckData contains data for the guarded alter
+// column nullability template, which only alters existing columns whose
+// live NOT NULL state differs from the desired one.
+type AlterColumnNullabilityWithCheckData struct {
 	SchemaName string
 	TableName  string
 	ColumnName string
@@ -152,6 +139,7 @@ type CreateIndexData struct {
 	IndexType  string
 	Columns    string
 	Unique     bool
+	Concurrent bool
 }
 
 // CreateForeignKeyData contains data for create foreign key template
@@ -322,27 +310,9 @@ func (te *TemplateExecutor) ExecuteAddColumn(data AddColumnData) (string, error)
 	return buf.String(), nil
 }
 
-// ExecuteAlterColumnType executes the alter column type template
-func (te *TemplateExecutor) ExecuteAlterColumnType(data AlterColumnTypeData) (string, error) {
-	var buf bytes.Buffer
-	err := te.templates.ExecuteTemplate(&buf, "alter_column_type.tmpl", data)
-	if err != nil {
-		return "", fmt.Errorf("failed to execute alter_column_type template: %w", err)
-	}
-	return buf.String(), nil
-}
-
-// ExecuteAlterColumnTypeWithFallback executes the alter column type template
-// that renames the old column and adds a new one when the conversion fails.
-func (te *TemplateExecutor) ExecuteAlterColumnTypeWithFallback(data AlterColumnTypeWithFallbackData) (string, error) {
-	var buf bytes.Buffer
-	err := te.templates.ExecuteTemplate(&buf, "alter_column_type_with_fallback.tmpl", data)
-	if err != nil {
-		return "", fmt.Errorf("failed to execute alter_column_type_with_fallback template: %w", err)
-	}
-	return buf.String(), nil
-}
-
+// ExecuteAlterColumnTypeWithCheck executes the guarded alter column type
+// template shared by the full-schema writer and the diff-based migration
+// writer.
 func (te *TemplateExecutor) ExecuteAlterColumnTypeWithCheck(data AlterColumnTypeWithCheckData) (string, error) {
 	var buf bytes.Buffer
 	err := te.templates.ExecuteTemplate(&buf, "alter_column_type_with_check.tmpl", data)
@@ -352,22 +322,25 @@ func (te *TemplateExecutor) ExecuteAlterColumnTypeWithCheck(data AlterColumnType
 	return buf.String(), nil
 }
 
-// ExecuteAlterColumnDefault executes the alter column default template
-func (te *TemplateExecutor) ExecuteAlterColumnDefault(data AlterColumnDefaultData) (string, error) {
+// ExecuteAlterColumnDefaultWithCheck executes the guarded alter column
+// default template shared by the full-schema writer and the diff-based
+// migration writer.
+func (te *TemplateExecutor) ExecuteAlterColumnDefaultWithCheck(data AlterColumnDefaultWithCheckData) (string, error) {
 	var buf bytes.Buffer
-	err := te.templates.ExecuteTemplate(&buf, "alter_column_default.tmpl", data)
+	err := te.templates.ExecuteTemplate(&buf, "alter_column_default_with_check.tmpl", data)
 	if err != nil {
-		return "", fmt.Errorf("failed to execute alter_column_default template: %w", err)
+		return "", fmt.Errorf("failed to execute alter_column_default_with_check template: %w", err)
 	}
 	return buf.String(), nil
 }
 
-// ExecuteAlterColumnNullability executes the alter column nullability template
-func (te *TemplateExecutor) ExecuteAlterColumnNullability(data AlterColumnNullabilityData) (string, error) {
+// ExecuteAlterColumnNullabilityWithCheck executes the guarded alter column
+// nullability template.
+func (te *TemplateExecutor) ExecuteAlterColumnNullabilityWithCheck(data AlterColumnNullabilityWithCheckData) (string, error) {
 	var buf bytes.Buffer
-	err := te.templates.ExecuteTemplate(&buf, "alter_column_nullability.tmpl", data)
+	err := te.templates.ExecuteTemplate(&buf, "alter_column_nullability_with_check.tmpl", data)
 	if err != nil {
-		return "", fmt.Errorf("failed to execute alter_column_nullability template: %w", err)
+		return "", fmt.Errorf("failed to execute alter_column_nullability_with_check template: %w", err)
 	}
 	return buf.String(), nil
 }
@@ -558,7 +531,7 @@ func BuildCreateTableData(schemaName string, table *models.Table) CreateTableDat
 		}
 		if col.Default != nil {
 			if value, ok := col.Default.(string); ok {
-				colData.Default = writers.QuoteDefaultValue(value, col.Type)
+				colData.Default = writers.QuoteDefaultValue(stripBackticks(value), col.Type)
 			} else {
 				colData.Default = fmt.Sprintf("%v", col.Default)
 			}

pkg/writers/pgsql/templates/alter_column_default.tmpl

@@ -1,7 +0,0 @@
-{{- if .SetDefault -}}
-ALTER TABLE {{qual_table .SchemaName .TableName}}
-  ALTER COLUMN {{quote_ident .ColumnName}} SET DEFAULT {{.DefaultValue}};
-{{- else -}}
-ALTER TABLE {{qual_table .SchemaName .TableName}}
-  ALTER COLUMN {{quote_ident .ColumnName}} DROP DEFAULT;
-{{- end -}}

pkg/writers/pgsql/templates/alter_column_default_with_check.tmpl

@@ -0,0 +1,29 @@
+DO $$
+DECLARE
+  current_default text;
+BEGIN
+  SELECT pg_catalog.pg_get_expr(d.adbin, d.adrelid)
+    INTO current_default
+  FROM pg_attribute a
+  JOIN pg_class t ON t.oid = a.attrelid
+  JOIN pg_namespace n ON n.oid = t.relnamespace
+  LEFT JOIN pg_attrdef d ON d.adrelid = a.attrelid AND d.adnum = a.attnum
+  WHERE n.nspname = '{{.SchemaName}}'
+    AND t.relname = '{{.TableName}}'
+    AND a.attname = '{{.ColumnName}}'
+    AND a.attnum > 0
+    AND NOT a.attisdropped;
+
+{{- if .SetDefault }}
+  IF current_default IS DISTINCT FROM {{quote .DefaultValue}} THEN
+    ALTER TABLE {{qual_table .SchemaName .TableName}}
+      ALTER COLUMN {{quote_ident .ColumnName}} SET DEFAULT {{.DefaultValue}};
+  END IF;
+{{- else }}
+  IF current_default IS NOT NULL THEN
+    ALTER TABLE {{qual_table .SchemaName .TableName}}
+      ALTER COLUMN {{quote_ident .ColumnName}} DROP DEFAULT;
+  END IF;
+{{- end }}
+END;
+$$;

pkg/writers/pgsql/templates/alter_column_nullability.tmpl

@@ -1,7 +0,0 @@
-{{- if .NotNull -}}
-ALTER TABLE {{qual_table .SchemaName .TableName}}
-  ALTER COLUMN {{quote_ident .ColumnName}} SET NOT NULL;
-{{- else -}}
-ALTER TABLE {{qual_table .SchemaName .TableName}}
-  ALTER COLUMN {{quote_ident .ColumnName}} DROP NOT NULL;
-{{- end -}}

pkg/writers/pgsql/templates/alter_column_nullability_with_check.tmpl

@@ -0,0 +1,26 @@
+DO $$
+DECLARE
+  current_not_null boolean;
+BEGIN
+  SELECT a.attnotnull
+    INTO current_not_null
+  FROM pg_attribute a
+  JOIN pg_class t ON t.oid = a.attrelid
+  JOIN pg_namespace n ON n.oid = t.relnamespace
+  WHERE n.nspname = '{{.SchemaName}}'
+    AND t.relname = '{{.TableName}}'
+    AND a.attname = '{{.ColumnName}}'
+    AND a.attnum > 0
+    AND NOT a.attisdropped;
+
+  IF current_not_null IS NOT NULL AND current_not_null IS DISTINCT FROM {{.NotNull}} THEN
+{{- if .NotNull }}
+    ALTER TABLE {{qual_table .SchemaName .TableName}}
+      ALTER COLUMN {{quote_ident .ColumnName}} SET NOT NULL;
+{{- else }}
+    ALTER TABLE {{qual_table .SchemaName .TableName}}
+      ALTER COLUMN {{quote_ident .ColumnName}} DROP NOT NULL;
+{{- end }}
+  END IF;
+END;
+$$;

pkg/writers/pgsql/templates/alter_column_type.tmpl

@@ -1,2 +0,0 @@
-ALTER TABLE {{qual_table .SchemaName .TableName}}
-  ALTER COLUMN {{quote_ident .ColumnName}} TYPE {{.NewType}}{{if .UsingExpr}} USING {{.UsingExpr}}{{end}};

pkg/writers/pgsql/templates/alter_column_type_with_fallback.tmpl

@@ -1,13 +0,0 @@
-DO $$
-BEGIN
-  BEGIN
-    ALTER TABLE {{qual_table .SchemaName .TableName}}
-      ALTER COLUMN {{quote_ident .ColumnName}} TYPE {{.NewType}}{{if .UsingExpr}} USING {{.UsingExpr}}{{end}};
-  EXCEPTION WHEN OTHERS THEN
-    ALTER TABLE {{qual_table .SchemaName .TableName}}
-      RENAME COLUMN {{quote_ident .ColumnName}} TO {{quote_ident .OldColumnName}};
-    ALTER TABLE {{qual_table .SchemaName .TableName}}
-      ADD COLUMN {{quote_ident .ColumnName}} {{.NewType}};
-  END;
-END;
-$$;

pkg/writers/pgsql/templates/create_index.tmpl

@@ -1,2 +1,2 @@
-CREATE {{if .Unique}}UNIQUE {{end}}INDEX IF NOT EXISTS {{quote_ident .IndexName}}
+CREATE {{if .Unique}}UNIQUE {{end}}INDEX {{if .Concurrent}}CONCURRENTLY {{end}}IF NOT EXISTS {{quote_ident .IndexName}}
   ON {{qual_table .SchemaName .TableName}} USING {{.IndexType}} ({{.Columns}});

pkg/writers/pgsql/writer.go

@@ -475,6 +475,75 @@ func (w *Writer) GenerateAlterColumnTypeStatements(schema *models.Schema) ([]str
 	return statements, nil
 }
 
+// GenerateAlterColumnDefaultStatements generates guarded ALTER TABLE
+// statements to bring existing columns' DEFAULT clause in line with the
+// model, safe to run against a database that already has the columns.
+func (w *Writer) GenerateAlterColumnDefaultStatements(schema *models.Schema) ([]string, error) {
+	statements := []string{}
+
+	statements = append(statements, fmt.Sprintf("-- Alter column defaults for schema: %s", schema.Name))
+
+	for _, table := range schema.Tables {
+		columns := getSortedColumns(table.Columns)
+		for _, col := range columns {
+			setDefault, defaultVal := formatColumnDefaultSQL(col)
+			stmt, err := w.executor.ExecuteAlterColumnDefaultWithCheck(AlterColumnDefaultWithCheckData{
+				SchemaName:   schema.Name,
+				TableName:    table.Name,
+				ColumnName:   col.Name,
+				SetDefault:   setDefault,
+				DefaultValue: defaultVal,
+			})
+			if err != nil {
+				return nil, fmt.Errorf("failed to generate alter column default for %s.%s.%s: %w", schema.Name, table.Name, col.Name, err)
+			}
+			statements = append(statements, stmt)
+		}
+	}
+
+	return statements, nil
+}
+
+// formatColumnDefaultSQL renders a column's model-level default into the
+// SQL literal/expression used by ALTER COLUMN ... SET DEFAULT, shared by
+// the full-schema writer and the diff-based migration writer.
+func formatColumnDefaultSQL(col *models.Column) (setDefault bool, defaultVal string) {
+	if col.Default == nil {
+		return false, ""
+	}
+	if value, ok := col.Default.(string); ok {
+		return true, writers.QuoteDefaultValue(stripBackticks(value), col.Type)
+	}
+	return true, fmt.Sprintf("%v", col.Default)
+}
+
+// GenerateAlterColumnNullabilityStatements generates guarded ALTER TABLE
+// statements to bring existing columns' NOT NULL state in line with the
+// model, safe to run against a database that already has the columns.
+func (w *Writer) GenerateAlterColumnNullabilityStatements(schema *models.Schema) ([]string, error) {
+	statements := []string{}
+
+	statements = append(statements, fmt.Sprintf("-- Alter column nullability for schema: %s", schema.Name))
+
+	for _, table := range schema.Tables {
+		columns := getSortedColumns(table.Columns)
+		for _, col := range columns {
+			stmt, err := w.executor.ExecuteAlterColumnNullabilityWithCheck(AlterColumnNullabilityWithCheckData{
+				SchemaName: schema.Name,
+				TableName:  table.Name,
+				ColumnName: col.Name,
+				NotNull:    col.NotNull,
+			})
+			if err != nil {
+				return nil, fmt.Errorf("failed to generate alter column nullability for %s.%s.%s: %w", schema.Name, table.Name, col.Name, err)
+			}
+			statements = append(statements, stmt)
+		}
+	}
+
+	return statements, nil
+}
+
 // GenerateAddColumnsForDatabase generates ALTER TABLE ADD COLUMN statements for the entire database
 func (w *Writer) GenerateAddColumnsForDatabase(db *models.Database) ([]string, error) {
 	statements := []string{}
@@ -641,6 +710,14 @@ func (w *Writer) WriteSchema(schema *models.Schema) error {
 		return err
 	}
 
+	if err := w.writeAlterColumnDefaults(schema); err != nil {
+		return err
+	}
+
+	if err := w.writeAlterColumnNullability(schema); err != nil {
+		return err
+	}
+
 	// Phase 4: Create primary keys (priority 160)
 	if err := w.writePrimaryKeys(schema); err != nil {
 		return err
@@ -859,6 +936,36 @@ func (w *Writer) writeAlterColumnTypes(schema *models.Schema) error {
 	return nil
 }
 
+func (w *Writer) writeAlterColumnDefaults(schema *models.Schema) error {
+	fmt.Fprintf(w.writer, "-- Alter column defaults for schema: %s\n", schema.Name)
+
+	statements, err := w.GenerateAlterColumnDefaultStatements(schema)
+	if err != nil {
+		return err
+	}
+	for _, stmt := range statements[1:] {
+		fmt.Fprint(w.writer, stmt)
+		fmt.Fprint(w.writer, "\n")
+	}
+
+	return nil
+}
+
+func (w *Writer) writeAlterColumnNullability(schema *models.Schema) error {
+	fmt.Fprintf(w.writer, "-- Alter column nullability for schema: %s\n", schema.Name)
+
+	statements, err := w.GenerateAlterColumnNullabilityStatements(schema)
+	if err != nil {
+		return err
+	}
+	for _, stmt := range statements[1:] {
+		fmt.Fprint(w.writer, stmt)
+		fmt.Fprint(w.writer, "\n")
+	}
+
+	return nil
+}
+
 // writePrimaryKeys generates ALTER TABLE statements for primary keys
 func (w *Writer) writePrimaryKeys(schema *models.Schema) error {
 	fmt.Fprintf(w.writer, "-- Primary keys for schema: %s\n", schema.Name)
@@ -990,8 +1097,13 @@ func (w *Writer) writeIndexes(schema *models.Schema) error {
 				whereClause = fmt.Sprintf(" WHERE %s", index.Where)
 			}
 
-			fmt.Fprintf(w.writer, "CREATE %sINDEX IF NOT EXISTS %s\n",
-				unique, indexName)
+			concurrently := ""
+			if index.Concurrent {
+				concurrently = "CONCURRENTLY "
+			}
+
+			fmt.Fprintf(w.writer, "CREATE %sINDEX %sIF NOT EXISTS %s\n",
+				unique, concurrently, indexName)
 			fmt.Fprintf(w.writer, "  ON %s USING %s (%s)%s;\n\n",
 				w.qualTable(schema.SQLName(), table.SQLName()), indexType, strings.Join(columnExprs, ", "), whereClause)
 		}

pkg/writers/pgsql/writer_test.go

@@ -87,6 +87,41 @@ func TestWriteDatabase(t *testing.T) {
 	}
 }
 
+func TestWriteDatabase_ConcurrentIndex(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("users", "public")
+
+	emailCol := models.InitColumn("email", "users", "public")
+	emailCol.Type = "text"
+	table.Columns["email"] = emailCol
+
+	concurrentIndex := &models.Index{
+		Name:       "idx_users_email",
+		Columns:    []string{"email"},
+		Concurrent: true,
+	}
+	table.Indexes["idx_users_email"] = concurrentIndex
+
+	schema.Tables = append(schema.Tables, table)
+	db.Schemas = append(db.Schemas, schema)
+
+	var buf bytes.Buffer
+	writer := NewWriter(&writers.WriterOptions{})
+	writer.writer = &buf
+
+	if err := writer.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+
+	if !strings.Contains(output, "CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_users_email") {
+		t.Errorf("Output missing CONCURRENTLY index creation:\n%s", output)
+	}
+}
+
 func TestWriteDatabase_GinIndexOnTextArrayDoesNotUseTrigramOperatorClass(t *testing.T) {
 	db := models.InitDatabase("testdb")
 	schema := models.InitSchema("public")
@@ -1106,6 +1141,71 @@ func TestWriteSchema_EmitsGuardedAlterColumnTypeStatements(t *testing.T) {
 	}
 }
 
+func TestWriteSchema_EmitsGuardedAlterColumnDefaultStatements(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("agent_skills", "public")
+
+	statusCol := models.InitColumn("status", "agent_skills", "public")
+	statusCol.Type = "text"
+	statusCol.Default = "active"
+	table.Columns["status"] = statusCol
+
+	schema.Tables = append(schema.Tables, table)
+	db.Schemas = append(db.Schemas, schema)
+
+	var buf bytes.Buffer
+	writer := NewWriter(&writers.WriterOptions{})
+	writer.writer = &buf
+
+	if err := writer.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "-- Alter column defaults for schema: public") {
+		t.Fatalf("expected alter column default section, got:\n%s", output)
+	}
+	if !strings.Contains(output, "pg_get_expr(d.adbin, d.adrelid)") {
+		t.Fatalf("expected guarded live-default check, got:\n%s", output)
+	}
+	if !strings.Contains(output, "ALTER COLUMN status SET DEFAULT 'active'") {
+		t.Fatalf("expected guarded SET DEFAULT for status column, got:\n%s", output)
+	}
+}
+
+func TestWriteSchema_AlterColumnDefaultStripsBackticksFromFunctionExpression(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("agent_skills", "public")
+
+	updatedAtCol := models.InitColumn("updatedat", "agent_skills", "public")
+	updatedAtCol.Type = "timestamp"
+	updatedAtCol.Default = "`now()`"
+	table.Columns["updatedat"] = updatedAtCol
+
+	schema.Tables = append(schema.Tables, table)
+	db.Schemas = append(db.Schemas, schema)
+
+	var buf bytes.Buffer
+	writer := NewWriter(&writers.WriterOptions{})
+	writer.writer = &buf
+
+	if err := writer.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+	if strings.Contains(output, "`") {
+		t.Fatalf("expected no backticks in generated SQL, got:\n%s", output)
+	}
+	if !strings.Contains(output, "ALTER COLUMN updatedat SET DEFAULT now()") {
+		t.Fatalf("expected guarded SET DEFAULT now() without backticks, got:\n%s", output)
+	}
+}
+
 func TestWriteSchema_GuardedAlterColumnTypeFallsBackOnConversionFailure(t *testing.T) {
 	db := models.InitDatabase("testdb")
 	schema := models.InitSchema("public")
@@ -1142,6 +1242,43 @@ func TestWriteSchema_GuardedAlterColumnTypeFallsBackOnConversionFailure(t *testi
 	}
 }
 
+func TestWriteSchema_EmitsGuardedAlterColumnNullabilityStatements(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("origin")
+
+	table := models.InitTable("service_instance", "origin")
+
+	typeCol := models.InitColumn("rid_service_instance_type", "service_instance", "origin")
+	typeCol.Type = "text"
+	typeCol.NotNull = false
+	table.Columns["rid_service_instance_type"] = typeCol
+
+	schema.Tables = append(schema.Tables, table)
+	db.Schemas = append(db.Schemas, schema)
+
+	var buf bytes.Buffer
+	writer := NewWriter(&writers.WriterOptions{})
+	writer.writer = &buf
+
+	if err := writer.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "-- Alter column nullability for schema: origin") {
+		t.Fatalf("expected alter column nullability section, got:\n%s", output)
+	}
+	if !strings.Contains(output, "a.attnotnull") {
+		t.Fatalf("expected guarded live-nullability check, got:\n%s", output)
+	}
+	if !strings.Contains(output, "current_not_null IS DISTINCT FROM false") {
+		t.Fatalf("expected guard comparing live nullability against desired value, got:\n%s", output)
+	}
+	if !strings.Contains(output, "ALTER COLUMN rid_service_instance_type DROP NOT NULL") {
+		t.Fatalf("expected guarded DROP NOT NULL for nullable column, got:\n%s", output)
+	}
+}
+
 func TestWriteSchema_UsesStorageTypeForSerialAlterStatements(t *testing.T) {
 	db := models.InitDatabase("testdb")
 	schema := models.InitSchema("public")

pkg/writers/sqlite/README.md

@@ -4,13 +4,14 @@ SQLite DDL (Data Definition Language) writer for RelSpec. Converts database sche
 
 ## Features
 
-- **Automatic Schema Flattening** - SQLite doesn't support PostgreSQL-style schemas, so table names are automatically flattened (e.g., `public.users` → `public_users`)
+- **Schema Flattening** - SQLite doesn't support PostgreSQL-style schemas. Non-default schema names are flattened into table name prefixes (e.g., `auth.sessions` → `auth_sessions`); the default schema (`public`/`main`) is left as bare table names (e.g., `public.users` → `users`)
 - **Type Mapping** - Converts PostgreSQL data types to SQLite type affinities (TEXT, INTEGER, REAL, NUMERIC, BLOB)
 - **Auto-Increment Detection** - Automatically converts SERIAL types and auto-increment columns to `INTEGER PRIMARY KEY AUTOINCREMENT`
 - **Function Translation** - Converts PostgreSQL functions to SQLite equivalents (e.g., `now()` → `CURRENT_TIMESTAMP`)
 - **Boolean Handling** - Maps boolean values to INTEGER (true=1, false=0)
-- **Constraint Generation** - Creates indexes, unique constraints, and documents foreign keys
+- **Constraint Generation** - Creates indexes, unique constraints, and inline `FOREIGN KEY` clauses in `CREATE TABLE`
 - **Identifier Quoting** - Properly quotes identifiers using double quotes
+- **Direct Execution** - Can execute the generated DDL directly against a `.db` file instead of writing a `.sql` script (see below)
 
 ## Usage
 
@@ -30,15 +31,26 @@ relspec convert --from dbml --from-path schema.dbml \
 
 ### Multi-Schema Databases
 
-SQLite doesn't support schemas, so multi-schema databases are automatically flattened:
+SQLite doesn't support schemas, so multi-schema databases are automatically flattened. The default schema (`public`/`main`) keeps bare table names; other schemas are prefixed to avoid collisions:
 
 ```bash
 # Input has auth.users and public.posts
-# Output will have auth_users and public_posts
+# Output will have auth_users and posts
 relspec convert --from json --from-path multi_schema.json \
                 --to sqlite --to-path flattened.sql
 ```
 
+### Direct Execution Against a Database File
+
+`relspec merge` can execute the generated DDL directly against a SQLite file instead of writing a `.sql` script, by passing the file path as `--output-conn`:
+
+```bash
+relspec merge --source dbml --source-path schema.dbml \
+              --output sqlite --output-conn ./app.db
+```
+
+Passing `--output-conn` opens `./app.db` and applies the schema directly; passing `--output-path` instead (or omitting `--output-conn`) writes a `.sql` script as before.
+
 ## Type Mapping
 
 | PostgreSQL Type | SQLite Affinity | Examples |
@@ -87,17 +99,17 @@ CREATE TABLE "users" (
 
 ## Foreign Keys
 
-Foreign keys are generated as commented-out ALTER TABLE statements for reference:
+SQLite has no `ALTER TABLE ADD CONSTRAINT`, so foreign keys are generated as inline `FOREIGN KEY` clauses inside `CREATE TABLE`, exactly as SQLite requires:
 
 ```sql
--- Foreign key: fk_posts_user_id
--- ALTER TABLE "posts" ADD CONSTRAINT "posts_fk_posts_user_id"
---   FOREIGN KEY ("user_id")
---   REFERENCES "users" ("id");
--- Note: Foreign keys should be defined in CREATE TABLE for better SQLite compatibility
+CREATE TABLE "posts" (
+    "id" INTEGER PRIMARY KEY AUTOINCREMENT,
+    "user_id" INTEGER NOT NULL,
+    FOREIGN KEY ("user_id") REFERENCES "users" ("id") ON DELETE CASCADE
+);
 ```
 
-For production use, define foreign keys directly in the CREATE TABLE statement or execute the ALTER TABLE commands after creating all tables.
+`PRAGMA foreign_keys = ON;` is emitted at the top of the output (and executed first in direct-execution mode) so these constraints are actually enforced.
 
 ## Constraints
 
@@ -112,11 +124,10 @@ Generated SQL follows this order:
 
 1. Header comments
 2. `PRAGMA foreign_keys = ON;`
-3. CREATE TABLE statements (sorted by schema, then table)
+3. CREATE TABLE statements (sorted by schema, then table), with primary keys and foreign keys defined inline
 4. CREATE INDEX statements
 5. CREATE UNIQUE INDEX statements (for unique constraints)
 6. Check constraint comments
-7. Foreign key comments
 
 ## Example
 
@@ -145,7 +156,7 @@ CREATE TABLE public.posts (
 -- SQLite Database Schema
 -- Database: mydb
 -- Generated by RelSpec
--- Note: Schema names have been flattened (e.g., public.users -> public_users)
+-- Note: SQLite has no schema concept; non-default schema names are flattened into table name prefixes (e.g., auth.sessions -> auth_sessions)
 
 -- Enable foreign key constraints
 PRAGMA foreign_keys = ON;
@@ -160,22 +171,17 @@ CREATE TABLE "auth_users" (
 
 CREATE UNIQUE INDEX "auth_users_users_username_key" ON "auth_users" ("username");
 
--- Schema: public (flattened into table names)
-
-CREATE TABLE "public_posts" (
+CREATE TABLE "posts" (
     "id" INTEGER PRIMARY KEY AUTOINCREMENT,
     "user_id" INTEGER NOT NULL,
     "title" TEXT NOT NULL,
-    "published" INTEGER DEFAULT 0
+    "published" INTEGER DEFAULT 0,
+    FOREIGN KEY ("user_id") REFERENCES "auth_users" ("id")
 );
-
--- Foreign key: posts_user_id_fkey
--- ALTER TABLE "public_posts" ADD CONSTRAINT "public_posts_posts_user_id_fkey"
---   FOREIGN KEY ("user_id")
---   REFERENCES "auth_users" ("id");
--- Note: Foreign keys should be defined in CREATE TABLE for better SQLite compatibility
 ```
 
+Note that `public.posts` becomes bare `posts` (the default schema isn't prefixed), while `auth.users` becomes `auth_users` (a non-default schema is), and the foreign key to `auth_users` is defined inline rather than as a separate statement.
+
 ## Programmatic Usage
 
 ```go
@@ -208,8 +214,9 @@ func main() {
 
 ## Notes
 
-- Schema flattening is **always enabled** for SQLite output (cannot be disabled)
+- Schema flattening is **always enabled** for SQLite output (cannot be disabled); the default schema (`public`/`main`) produces bare table names, other schemas are prefixed
 - Constraint and index names are prefixed with the flattened table name to avoid collisions
 - Generated SQL is compatible with SQLite 3.x
-- Foreign key constraints require `PRAGMA foreign_keys = ON;` to be enforced
+- Foreign key constraints require `PRAGMA foreign_keys = ON;` to be enforced, which is emitted (and, in direct-execution mode, run) before any `CREATE TABLE`
+- Setting `Metadata["connection_string"]` to a `.db` file path (or passing `--output-conn` to `relspec merge`) executes the DDL directly against that file instead of writing a `.sql` script
 - For complex schemas, review and test the generated SQL before use in production

pkg/writers/sqlite/templates.go

@@ -40,10 +40,22 @@ func NewTemplateExecutor(opts *writers.WriterOptions) (*TemplateExecutor, error)
 
 // TableTemplateData contains data for table template
 type TableTemplateData struct {
-	Schema     string
-	Name       string
-	Columns    []*models.Column
-	PrimaryKey *models.Constraint
+	Schema      string
+	Name        string
+	Columns     []*models.Column
+	PrimaryKey  *models.Constraint
+	ForeignKeys []ForeignKeyTemplateData
+}
+
+// ForeignKeyTemplateData contains data for an inline FOREIGN KEY clause
+type ForeignKeyTemplateData struct {
+	Name           string
+	Columns        []string
+	ForeignSchema  string
+	ForeignTable   string
+	ForeignColumns []string
+	OnDelete       string
+	OnUpdate       string
 }
 
 // IndexTemplateData contains data for index template
@@ -120,16 +132,6 @@ func (te *TemplateExecutor) ExecuteCreateCheckConstraint(data ConstraintTemplate
 	return buf.String(), nil
 }
 
-// ExecuteCreateForeignKey executes the create foreign key template
-func (te *TemplateExecutor) ExecuteCreateForeignKey(data ConstraintTemplateData) (string, error) {
-	var buf bytes.Buffer
-	err := te.templates.ExecuteTemplate(&buf, "create_foreign_key.tmpl", data)
-	if err != nil {
-		return "", fmt.Errorf("failed to execute create_foreign_key template: %w", err)
-	}
-	return buf.String(), nil
-}
-
 // Helper functions to build template data from models
 
 // BuildTableTemplateData builds TableTemplateData from a models.Table
@@ -162,11 +164,35 @@ func BuildTableTemplateData(schema string, table *models.Table) TableTemplateDat
 		}
 	}
 
+	// Collect foreign keys for inline FOREIGN KEY clauses
+	var fks []ForeignKeyTemplateData
+	for _, constraint := range sortConstraints(table.Constraints) {
+		if constraint.Type != models.ForeignKeyConstraint {
+			continue
+		}
+
+		refSchema := tableSchemaName(constraint.ReferencedSchema)
+		if refSchema == "" {
+			refSchema = schema
+		}
+
+		fks = append(fks, ForeignKeyTemplateData{
+			Name:           constraint.Name,
+			Columns:        constraint.Columns,
+			ForeignSchema:  refSchema,
+			ForeignTable:   constraint.ReferencedTable,
+			ForeignColumns: constraint.ReferencedColumns,
+			OnDelete:       constraint.OnDelete,
+			OnUpdate:       constraint.OnUpdate,
+		})
+	}
+
 	return TableTemplateData{
-		Schema:     schema,
-		Name:       table.Name,
-		Columns:    columns,
-		PrimaryKey: pk,
+		Schema:      schema,
+		Name:        table.Name,
+		Columns:     columns,
+		PrimaryKey:  pk,
+		ForeignKeys: fks,
 	}
 }
 

pkg/writers/sqlite/templates/create_foreign_key.tmpl

@@ -1,6 +0,0 @@
--- Foreign key: {{.Name}}
--- ALTER TABLE {{quote_ident (qualified_table_name .Schema .Table)}} ADD CONSTRAINT {{quote_ident (format_constraint_name .Schema .Table .Name)}}
---   FOREIGN KEY ({{range $i, $col := .Columns}}{{if $i}}, {{end}}{{quote_ident $col}}{{end}})
---   REFERENCES {{quote_ident (qualified_table_name .ForeignSchema .ForeignTable)}} ({{range $i, $col := .ForeignColumns}}{{if $i}}, {{end}}{{quote_ident $col}}{{end}})
---   {{if .OnDelete}}ON DELETE {{.OnDelete}}{{end}}{{if .OnUpdate}} ON UPDATE {{.OnUpdate}}{{end}};
--- Note: Foreign keys should be defined in CREATE TABLE for better SQLite compatibility

pkg/writers/sqlite/templates/create_table.tmpl

@@ -6,4 +6,7 @@ CREATE TABLE {{quote_ident (qualified_table_name .Schema .Name)}} (
 {{- if and .PrimaryKey (not $hasAutoIncrement)}}{{if gt (len .Columns) 0}},{{end}}
     PRIMARY KEY ({{range $i, $colName := .PrimaryKey.Columns}}{{if $i}}, {{end}}{{quote_ident $colName}}{{end}})
 {{- end}}
+{{- range .ForeignKeys}},
+    FOREIGN KEY ({{range $i, $col := .Columns}}{{if $i}}, {{end}}{{quote_ident $col}}{{end}}) REFERENCES {{quote_ident (qualified_table_name .ForeignSchema .ForeignTable)}} ({{range $i, $col := .ForeignColumns}}{{if $i}}, {{end}}{{quote_ident $col}}{{end}}){{if .OnDelete}} ON DELETE {{.OnDelete}}{{end}}{{if .OnUpdate}} ON UPDATE {{.OnUpdate}}{{end}}
+{{- end}}
 );

pkg/writers/sqlite/writer.go

@@ -1,11 +1,15 @@
 package sqlite
 
 import (
+	"context"
+	"database/sql"
 	"fmt"
 	"io"
 	"os"
 	"strings"
 
+	_ "modernc.org/sqlite" // SQLite driver
+
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 )
@@ -30,8 +34,16 @@ func NewWriter(options *writers.WriterOptions) *Writer {
 	}
 }
 
-// WriteDatabase writes the entire database schema as SQLite SQL
+// WriteDatabase writes the entire database schema as SQLite SQL.
+//
+// If Metadata["connection_string"] is set (a path to a SQLite database file),
+// the generated DDL is executed directly against that file instead of being
+// written out as a .sql script.
 func (w *Writer) WriteDatabase(db *models.Database) error {
+	if dbPath, ok := w.options.Metadata["connection_string"].(string); ok && dbPath != "" {
+		return w.executeDatabaseSQL(db, dbPath)
+	}
+
 	var writer io.Writer
 	var file *os.File
 	var err error
@@ -52,12 +64,16 @@ func (w *Writer) WriteDatabase(db *models.Database) error {
 	}
 
 	w.writer = writer
+	return w.writeContent(db)
+}
 
+// writeContent writes the header, pragma, and every schema's DDL to w.writer.
+func (w *Writer) writeContent(db *models.Database) error {
 	// Write header comment
 	fmt.Fprintf(w.writer, "-- SQLite Database Schema\n")
 	fmt.Fprintf(w.writer, "-- Database: %s\n", db.Name)
 	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n")
-	fmt.Fprintf(w.writer, "-- Note: Schema names have been flattened (e.g., public.users -> public_users)\n\n")
+	fmt.Fprintf(w.writer, "-- Note: SQLite has no schema concept; non-default schema names are flattened into table name prefixes (e.g., auth.sessions -> auth_sessions)\n\n")
 
 	// Enable foreign keys
 	pragma, err := w.executor.ExecutePragmaForeignKeys()
@@ -76,48 +92,134 @@ func (w *Writer) WriteDatabase(db *models.Database) error {
 	return nil
 }
 
+// statementCollector captures each Write call as a single SQL statement (or
+// comment line), matching the writer's convention of one Fprintf per statement.
+type statementCollector struct {
+	statements []string
+}
+
+func (c *statementCollector) Write(p []byte) (int, error) {
+	if s := strings.TrimSpace(string(p)); s != "" {
+		c.statements = append(c.statements, s)
+	}
+	return len(p), nil
+}
+
+// executeDatabaseSQL generates the DDL for db and executes it directly
+// against the SQLite database file at dbPath.
+func (w *Writer) executeDatabaseSQL(db *models.Database, dbPath string) error {
+	collector := &statementCollector{}
+	w.writer = collector
+	if err := w.writeContent(db); err != nil {
+		return fmt.Errorf("failed to generate SQL statements: %w", err)
+	}
+
+	conn, err := sql.Open("sqlite", dbPath)
+	if err != nil {
+		return fmt.Errorf("failed to open sqlite database %q: %w", dbPath, err)
+	}
+	defer conn.Close()
+
+	ctx := context.Background()
+	ignoreErrors := false
+	if val, ok := w.options.Metadata["ignore_errors"].(bool); ok {
+		ignoreErrors = val
+	}
+
+	total, executed := 0, 0
+	var execErrors []string
+	for _, stmt := range collector.statements {
+		if strings.HasPrefix(stmt, "--") {
+			continue
+		}
+
+		total++
+		if _, err := conn.ExecContext(ctx, stmt); err != nil {
+			execErrors = append(execErrors, fmt.Sprintf("statement %d (%s): %v", total, truncateStatement(stmt), err))
+			if !ignoreErrors {
+				break
+			}
+			continue
+		}
+		executed++
+	}
+
+	w.options.Metadata["execution_total"] = total
+	w.options.Metadata["execution_success"] = executed
+	w.options.Metadata["execution_failed"] = len(execErrors)
+
+	if len(execErrors) > 0 {
+		return fmt.Errorf("failed to execute %d/%d statement(s) against %q:\n%s", len(execErrors), total, dbPath, strings.Join(execErrors, "\n"))
+	}
+
+	return nil
+}
+
+// truncateStatement shortens a SQL statement for error messages.
+func truncateStatement(stmt string) string {
+	const maxLen = 80
+	stmt = strings.Join(strings.Fields(stmt), " ")
+	if len(stmt) > maxLen {
+		return stmt[:maxLen] + "..."
+	}
+	return stmt
+}
+
+// defaultSchemaNames are treated as "no schema" for SQLite output: SQLite has
+// no schema concept, and a lone default schema (e.g. DBML's implicit "public")
+// should produce bare table names rather than a "public_" prefix.
+var defaultSchemaNames = map[string]bool{
+	"public": true,
+	"main":   true,
+}
+
+// tableSchemaName returns the schema name to use for table/constraint naming,
+// collapsing default schema names to "" so they aren't prefixed onto table names.
+func tableSchemaName(schema string) string {
+	if defaultSchemaNames[strings.ToLower(schema)] {
+		return ""
+	}
+	return schema
+}
+
 // WriteSchema writes a single schema as SQLite SQL
 func (w *Writer) WriteSchema(schema *models.Schema) error {
-	// SQLite doesn't have schemas, so we just write a comment
-	if schema.Name != "" {
+	tableSchema := tableSchemaName(schema.Name)
+
+	// SQLite doesn't have schemas, so we just write a comment (skip for the
+	// default schema, since its tables aren't actually being prefixed)
+	if tableSchema != "" {
 		fmt.Fprintf(w.writer, "-- Schema: %s (flattened into table names)\n\n", schema.Name)
 	}
 
 	// Phase 1: Create tables
 	for _, table := range schema.Tables {
-		if err := w.writeTable(schema.Name, table); err != nil {
+		if err := w.writeTable(tableSchema, table); err != nil {
 			return fmt.Errorf("failed to write table %s: %w", table.Name, err)
 		}
 	}
 
 	// Phase 2: Create indexes
 	for _, table := range schema.Tables {
-		if err := w.writeIndexes(schema.Name, table); err != nil {
+		if err := w.writeIndexes(tableSchema, table); err != nil {
 			return fmt.Errorf("failed to write indexes for table %s: %w", table.Name, err)
 		}
 	}
 
 	// Phase 3: Create unique constraints (as unique indexes)
 	for _, table := range schema.Tables {
-		if err := w.writeUniqueConstraints(schema.Name, table); err != nil {
+		if err := w.writeUniqueConstraints(tableSchema, table); err != nil {
 			return fmt.Errorf("failed to write unique constraints for table %s: %w", table.Name, err)
 		}
 	}
 
 	// Phase 4: Check constraints (as comments, since SQLite requires them in CREATE TABLE)
 	for _, table := range schema.Tables {
-		if err := w.writeCheckConstraints(schema.Name, table); err != nil {
+		if err := w.writeCheckConstraints(tableSchema, table); err != nil {
 			return fmt.Errorf("failed to write check constraints for table %s: %w", table.Name, err)
 		}
 	}
 
-	// Phase 5: Foreign keys (as comments for compatibility)
-	for _, table := range schema.Tables {
-		if err := w.writeForeignKeys(schema.Name, table); err != nil {
-			return fmt.Errorf("failed to write foreign keys for table %s: %w", table.Name, err)
-		}
-	}
-
 	return nil
 }
 
@@ -255,37 +357,3 @@ func (w *Writer) writeCheckConstraints(schema string, table *models.Table) error
 	return nil
 }
 
-// writeForeignKeys writes foreign keys as comments
-func (w *Writer) writeForeignKeys(schema string, table *models.Table) error {
-	for _, constraint := range sortConstraints(table.Constraints) {
-		if constraint.Type != models.ForeignKeyConstraint {
-			continue
-		}
-
-		refSchema := constraint.ReferencedSchema
-		if refSchema == "" {
-			refSchema = schema
-		}
-
-		data := ConstraintTemplateData{
-			Schema:         schema,
-			Table:          table.Name,
-			Name:           constraint.Name,
-			Columns:        constraint.Columns,
-			ForeignSchema:  refSchema,
-			ForeignTable:   constraint.ReferencedTable,
-			ForeignColumns: constraint.ReferencedColumns,
-			OnDelete:       constraint.OnDelete,
-			OnUpdate:       constraint.OnUpdate,
-		}
-
-		sql, err := w.executor.ExecuteCreateForeignKey(data)
-		if err != nil {
-			return fmt.Errorf("failed to execute create foreign key template: %w", err)
-		}
-
-		fmt.Fprintf(w.writer, "%s\n", sql)
-	}
-
-	return nil
-}

pkg/writers/sqlite/writer_test.go

@@ -85,8 +85,11 @@ func TestWriteDatabase(t *testing.T) {
 		t.Error("Expected CREATE TABLE statement")
 	}
 
-	if !strings.Contains(output, "\"public_users\"") {
-		t.Error("Expected flattened table name public_users")
+	if !strings.Contains(output, "\"users\"") {
+		t.Error("Expected bare table name users (default schema should not be prefixed)")
+	}
+	if strings.Contains(output, "\"public_users\"") {
+		t.Error("Did not expect flattened table name public_users for the default public schema")
 	}
 
 	if !strings.Contains(output, "INTEGER PRIMARY KEY AUTOINCREMENT") {
@@ -322,13 +325,15 @@ func TestWriteSchema_MultiSchema(t *testing.T) {
 
 	output := buf.String()
 
-	// Check for flattened table names from both schemas
+	// Non-default schemas are still prefixed to avoid name collisions...
 	if !strings.Contains(output, "\"auth_sessions\"") {
 		t.Error("Expected flattened table name auth_sessions")
 	}
 
-	if !strings.Contains(output, "\"public_posts\"") {
-		t.Error("Expected flattened table name public_posts")
+	// ...but the default "public" schema is not, since it's typically the
+	// only schema and bare names read better (and match e.g. DBML output).
+	if !strings.Contains(output, "\"posts\"") {
+		t.Error("Expected bare table name posts")
 	}
 }
 

pkg/writers/writer.go

@@ -148,6 +148,26 @@ func SanitizeFilename(name string) string {
 // Examples (boolean):   "true"         → "true"
 // Examples (bigint):    "0"            → "0"
 // Examples (timestamp): "now()"        → "now()"   (function call – never quoted)
+// bareKeywordDefaults are PostgreSQL default-value keywords that are
+// expressions, not string literals, even though they contain no
+// parentheses (e.g. "CURRENT_DATE" rather than "now()"). They must never be
+// wrapped in quotes.
+var bareKeywordDefaults = map[string]bool{
+	"current_date":      true,
+	"current_time":      true,
+	"current_timestamp": true,
+	"localtime":         true,
+	"localtimestamp":    true,
+	"current_user":      true,
+	"session_user":      true,
+	"current_role":      true,
+	"current_catalog":   true,
+	"current_schema":    true,
+	"null":              true,
+	"true":              true,
+	"false":             true,
+}
+
 func QuoteDefaultValue(value, sqlType string) string {
 	value = strings.TrimSpace(value)
 
@@ -158,6 +178,12 @@ func QuoteDefaultValue(value, sqlType string) string {
 		return value
 	}
 
+	// Bare keyword expressions (e.g. CURRENT_DATE) are never quoted,
+	// regardless of column type.
+	if bareKeywordDefaults[strings.ToLower(value)] {
+		return value
+	}
+
 	// Normalise the SQL type: lowercase, strip length/precision suffix.
 	baseType := strings.ToLower(strings.TrimSpace(sqlType))
 	if idx := strings.Index(baseType, "("); idx > 0 {

pkg/writers/writer_test.go

@@ -41,6 +41,24 @@ func TestQuoteDefaultValue(t *testing.T) {
 			sqlType: "timestamptz",
 			want:    "now()",
 		},
+		{
+			name:    "bare keyword default CURRENT_DATE is not quoted",
+			value:   "CURRENT_DATE",
+			sqlType: "date",
+			want:    "CURRENT_DATE",
+		},
+		{
+			name:    "bare keyword default is case insensitive",
+			value:   "current_timestamp",
+			sqlType: "timestamptz",
+			want:    "current_timestamp",
+		},
+		{
+			name:    "bare keyword default localtime is not quoted",
+			value:   "LOCALTIME",
+			sqlType: "time",
+			want:    "LOCALTIME",
+		},
 	}
 
 	for _, tt := range tests {