chore(release): update package version to 1.0.70

Merge conflict detection compared bigserial (DBML) against bigint (live
PostgreSQL read of an existing serial column) as incompatible types, since
serial is sugar over an integer column plus a sequence default and
PostgreSQL always reports back the underlying integer type. Add
SerialUnderlyingType and use it when comparing column types for conflicts.

QuoteDefaultValue also wrapped bare keyword expressions like CURRENT_DATE
in string quotes because they contain no parentheses, unlike function-call
defaults such as now(). Recognize known bare keyword defaults and leave
them unquoted across CREATE TABLE, ALTER TABLE ADD COLUMN, and
ALTER COLUMN SET DEFAULT generation.

linux/arch/PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Hein (Warky Devs) <hein@warky.dev>
 pkgname=relspec
-pkgver=1.0.67
+pkgver=1.0.70
 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:        1.0.70
 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/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/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{
+				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),
-					OldColumnName: renamedColumnName(modelCol.Name, effectiveAlterColumnSQLType(currentCol)),
 				})
 				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,
@@ -964,32 +949,6 @@ 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 +956,24 @@ 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)

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
@@ -322,27 +309,9 @@ 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 +321,25 @@ 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 +530,7 @@ 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/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)

pkg/writers/pgsql/writer_test.go

@@ -1106,6 +1106,71 @@ 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 +1207,43 @@ 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/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 {