feat: Enhance PostgreSQL type handling and migration scripts

- Introduced equivalent base types and variants for PostgreSQL types to normalize type comparisons.
- Added functions for normalizing SQL types and retrieving equivalent type variants.
- Updated migration writer to handle type alterations with checks for existing types.
- Implemented logic to create necessary extensions (e.g., pg_trgm) based on schema requirements.
- Enhanced tests to cover new functionality for type normalization and migration handling.
- Improved handling of GIN indexes to use appropriate operator classes based on column types.

pkg/writers/pgsql/migration_writer.go

@@ -160,6 +160,17 @@ func (w *MigrationWriter) WriteMigration(model *models.Database, current *models
 func (w *MigrationWriter) generateSchemaScripts(model *models.Schema, current *models.Schema) ([]MigrationScript, error) {
 	scripts := make([]MigrationScript, 0)
 
+	if schemaRequiresPGTrgm(model) {
+		scripts = append(scripts, MigrationScript{
+			ObjectName: "extension.pg_trgm",
+			ObjectType: "create extension",
+			Schema:     model.Name,
+			Priority:   80,
+			Sequence:   len(scripts),
+			Body:       "CREATE EXTENSION IF NOT EXISTS pg_trgm;",
+		})
+	}
+
 	// Phase 1: Drop constraints and indexes that changed (Priority 11-50)
 	if current != nil {
 		dropScripts, err := w.generateDropScripts(model, current)
@@ -361,7 +372,7 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 				SchemaName: schema.Name,
 				TableName:  modelTable.Name,
 				ColumnName: modelCol.Name,
-				ColumnType: pgsql.ConvertSQLType(modelCol.Type),
+				ColumnType: effectiveColumnSQLType(modelCol),
 				Default:    defaultVal,
 				NotNull:    modelCol.NotNull,
 			})
@@ -380,12 +391,13 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 			scripts = append(scripts, script)
 		} else if !columnsEqual(modelCol, currentCol) {
 			// Column exists but properties changed
-			if modelCol.Type != currentCol.Type {
+			if !columnTypesEqual(modelCol, currentCol) {
 				sql, err := w.executor.ExecuteAlterColumnType(AlterColumnTypeData{
 					SchemaName: schema.Name,
 					TableName:  modelTable.Name,
 					ColumnName: modelCol.Name,
-					NewType:    pgsql.ConvertSQLType(modelCol.Type),
+					NewType:    effectiveAlterColumnSQLType(modelCol),
+					UsingExpr:  buildAlterColumnUsingExpression(modelCol.Name, effectiveAlterColumnSQLType(modelCol)),
 				})
 				if err != nil {
 					return nil, err
@@ -606,12 +618,11 @@ func buildIndexColumnExpressions(table *models.Table, index *models.Index, index
 		if table != nil {
 			if col, ok := resolveIndexColumn(table, 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"
+				if strings.EqualFold(indexType, "gin") {
+					opClass := ginOperatorClassForColumn(col, index.Comment)
+					if opClass != "" {
+						colExpr = fmt.Sprintf("%s %s", col.SQLName(), opClass)
 					}
-					colExpr = fmt.Sprintf("%s %s", col.SQLName(), opClass)
 				}
 			}
 		}
@@ -875,11 +886,21 @@ func columnsEqual(col1, col2 *models.Column) bool {
 	if col1 == nil || col2 == nil {
 		return false
 	}
-	return strings.EqualFold(col1.Type, col2.Type) &&
+	return columnTypesEqual(col1, col2) &&
 		col1.NotNull == col2.NotNull &&
 		fmt.Sprintf("%v", col1.Default) == fmt.Sprintf("%v", col2.Default)
 }
 
+func columnTypesEqual(col1, col2 *models.Column) bool {
+	if col1 == nil || col2 == nil {
+		return false
+	}
+	return strings.EqualFold(
+		pgsql.NormalizeEquivalentSQLType(effectiveColumnSQLType(col1)),
+		pgsql.NormalizeEquivalentSQLType(effectiveColumnSQLType(col2)),
+	)
+}
+
 // constraintsEqual checks if two constraints are equal
 func constraintsEqual(c1, c2 *models.Constraint) bool {
 	if c1 == nil || c2 == nil {