feat(migration): enhance primary key handling and add GIN index support in migration writer

pkg/writers/pgsql/migration_writer.go

@@ -31,6 +31,10 @@ type MigrationWriter struct {
 
 // NewMigrationWriter creates a new templated migration writer
 func NewMigrationWriter(options *writers.WriterOptions) (*MigrationWriter, error) {
+	if options == nil {
+		options = &writers.WriterOptions{}
+	}
+
 	executor, err := NewTemplateExecutor(options.FlattenSchema)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create template executor: %w", err)
@@ -44,6 +48,16 @@ func NewMigrationWriter(options *writers.WriterOptions) (*MigrationWriter, error
 
 // WriteMigration generates migration scripts using templates
 func (w *MigrationWriter) WriteMigration(model *models.Database, current *models.Database) error {
+	if model == nil {
+		return fmt.Errorf("model database is required")
+	}
+	if w.options == nil {
+		w.options = &writers.WriterOptions{}
+	}
+	if current == nil {
+		current = models.InitDatabase(model.Name)
+	}
+
 	var writer io.Writer
 	var file *os.File
 	var err error
@@ -86,9 +100,16 @@ func (w *MigrationWriter) WriteMigration(model *models.Database, current *models
 
 	// Process each schema in the model
 	for _, modelSchema := range model.Schemas {
+		if modelSchema == nil {
+			continue
+		}
+
 		// Find corresponding schema in current database
 		var currentSchema *models.Schema
 		for _, cs := range current.Schemas {
+			if cs == nil {
+				continue
+			}
 			if strings.EqualFold(cs.Name, modelSchema.Name) {
 				currentSchema = cs
 				break
@@ -545,12 +566,17 @@ func (w *MigrationWriter) generateIndexScripts(model *models.Schema, current *mo
 					indexType = modelIndex.Type
 				}
 
+				columnExprs := buildIndexColumnExpressions(modelTable, modelIndex, indexType)
+				if len(columnExprs) == 0 {
+					continue
+				}
+
 				sql, err := w.executor.ExecuteCreateIndex(CreateIndexData{
 					SchemaName: model.Name,
 					TableName:  modelTable.Name,
 					IndexName:  indexName,
 					IndexType:  indexType,
-					Columns:    strings.Join(modelIndex.Columns, ", "),
+					Columns:    strings.Join(columnExprs, ", "),
 					Unique:     modelIndex.Unique,
 				})
 				if err != nil {
@@ -573,6 +599,27 @@ func (w *MigrationWriter) generateIndexScripts(model *models.Schema, current *mo
 	return scripts, nil
 }
 
+func buildIndexColumnExpressions(table *models.Table, index *models.Index, indexType string) []string {
+	columnExprs := make([]string, 0, len(index.Columns))
+	for _, colName := range index.Columns {
+		colExpr := colName
+		if table != nil {
+			if col, ok := table.Columns[colName]; ok && col != nil {
+				colExpr = col.SQLName()
+				if strings.EqualFold(indexType, "gin") && isTextType(col.Type) {
+					opClass := extractOperatorClass(index.Comment)
+					if opClass == "" {
+						opClass = "gin_trgm_ops"
+					}
+					colExpr = fmt.Sprintf("%s %s", col.SQLName(), opClass)
+				}
+			}
+		}
+		columnExprs = append(columnExprs, colExpr)
+	}
+	return columnExprs
+}
+
 // generateForeignKeyScripts generates ADD CONSTRAINT FOREIGN KEY scripts using templates
 func (w *MigrationWriter) generateForeignKeyScripts(model *models.Schema, current *models.Schema) ([]MigrationScript, error) {
 	scripts := make([]MigrationScript, 0)