test(drawdb): add test for converting column types with modifiers

* Implement tests to ensure explicit type modifiers are preserved during conversion.
* Validate behavior for varchar, numeric, and custom vector types.

pkg/readers/pgsql/reader.go

@@ -259,12 +259,14 @@ func (r *Reader) close() {
 	}
 }
 
-// mapDataType maps PostgreSQL data types to canonical types
-func (r *Reader) mapDataType(pgType, udtName string, hasNextval bool) string {
+// mapDataType maps PostgreSQL data types while preserving exact type text when available.
+func (r *Reader) mapDataType(pgType, udtName, formattedType string, hasNextval bool) string {
+	normalizedPGType := strings.ToLower(strings.TrimSpace(pgType))
+
 	// If the column has a nextval default, it's likely a serial type
 	// Map to the appropriate serial type instead of the base integer type
 	if hasNextval {
-		switch strings.ToLower(pgType) {
+		switch normalizedPGType {
 		case "integer", "int", "int4":
 			return "serial"
 		case "bigint", "int8":
@@ -274,6 +276,17 @@ func (r *Reader) mapDataType(pgType, udtName string, hasNextval bool) string {
 		}
 	}
 
+	// Prefer the database-provided formatted type; this preserves arrays/custom
+	// types/modifiers like text[], vector(1536), numeric(10,2), etc.
+	if strings.TrimSpace(formattedType) != "" {
+		return formattedType
+	}
+
+	// information_schema reports arrays generically as "ARRAY" with udt_name like "_text".
+	if strings.EqualFold(pgType, "ARRAY") && strings.HasPrefix(udtName, "_") && len(udtName) > 1 {
+		return udtName[1:] + "[]"
+	}
+
 	// Map common PostgreSQL types
 	typeMap := map[string]string{
 		"integer":                     "integer",
@@ -320,7 +333,7 @@ func (r *Reader) mapDataType(pgType, udtName string, hasNextval bool) string {
 	}
 
 	// Try mapped type first
-	if mapped, exists := typeMap[pgType]; exists {
+	if mapped, exists := typeMap[normalizedPGType]; exists {
 		return mapped
 	}
 
@@ -329,8 +342,11 @@ func (r *Reader) mapDataType(pgType, udtName string, hasNextval bool) string {
 		return pgsql.GetSQLType(pgType)
 	}
 
-	// Return UDT name for custom types
+	// Return UDT name for custom types (including array fallback when needed)
 	if udtName != "" {
+		if strings.HasPrefix(udtName, "_") && len(udtName) > 1 {
+			return udtName[1:] + "[]"
+		}
 		return udtName
 	}