fix(postgres): improve view column save guidance

apps/desktop/src/lib/__tests__/table/objectSourceEditor.spec.ts

@@ -1,6 +1,6 @@
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import * as api from "@/lib/backend/api";
-import { executeObjectSourceSave } from "@/lib/table/objectSourceEditor";
+import { executeObjectSourceSave, formatObjectSourceSaveError } from "@/lib/table/objectSourceEditor";
 
 vi.mock("@/lib/backend/api", () => ({
   executeInTransaction: vi.fn().mockResolvedValue({}),
@@ -32,3 +32,33 @@ describe("executeObjectSourceSave", () => {
     expect(api.executeScript).not.toHaveBeenCalled();
   });
 });
+
+describe("formatObjectSourceSaveError", () => {
+  const hint = "Keep existing view columns unchanged and append new columns at the end.";
+
+  it.each(["ERROR: cannot drop columns from view", 'ERROR: cannot change name of view column "old_name" to "new_name"', 'ERROR: cannot change data type of view column "amount" from integer to bigint', "ERROR: ビューからは列を削除できません", "错误：无法从视图中删除列"])(
+    "appends guidance for PostgreSQL view column replacement errors: %s",
+    (message) => {
+      expect(formatObjectSourceSaveError(new Error(message), "postgres", "VIEW", hint)).toBe(`${message}\n\n${hint}`);
+    },
+  );
+
+  it("supports PostgreSQL-compatible databases", () => {
+    expect(formatObjectSourceSaveError("cannot change name of view column", "kingbase", "VIEW", hint)).toBe(`cannot change name of view column\n\n${hint}`);
+  });
+
+  it("leaves unrelated errors unchanged", () => {
+    expect(formatObjectSourceSaveError(new Error("syntax error at or near SELECT"), "postgres", "VIEW", hint)).toBe("syntax error at or near SELECT");
+    expect(formatObjectSourceSaveError(new Error("SQLSTATE 42P16"), "mysql", "VIEW", hint)).toBe("SQLSTATE 42P16");
+    expect(formatObjectSourceSaveError(new Error("SQLSTATE 42P16"), "postgres", "PROCEDURE", hint)).toBe("SQLSTATE 42P16");
+  });
+
+  it.each(["Agent RPC error: SQLSTATE 42P16", "ERROR: ON COMMIT can only be used on temporary tables (SQLSTATE 42P16)"])("does not treat unrelated invalid_table_definition errors as view column changes: %s", (message) => {
+    expect(formatObjectSourceSaveError(new Error(message), "postgres", "VIEW", hint)).toBe(message);
+  });
+
+  it("does not append the same guidance twice", () => {
+    const formatted = formatObjectSourceSaveError("ERROR: cannot drop columns from view", "postgres", "VIEW", hint);
+    expect(formatObjectSourceSaveError(formatted, "postgres", "VIEW", hint)).toBe(formatted);
+  });
+});

apps/desktop/src/lib/table/objectSourceEditor.ts

@@ -16,9 +16,32 @@ export type BuildRoutineRenameObjectSourceInput = BuildEditableObjectSourceSqlIn
 export type ObjectSourceSaveExecutionMode = "single" | "script";
 
 const postgresLikeRoutineRenameTypes = new Set<DatabaseType>(["postgres", "redshift", "gaussdb", "kwdb", "kingbase", "highgo", "vastbase"]);
+const postgresLikeViewTypes = new Set<DatabaseType>(["postgres", "redshift", "gaussdb", "kwdb", "opengauss", "questdb", "kingbase", "highgo", "vastbase"]);
 const mysqlLikeRoutineRenameTypes = new Set<DatabaseType>(["mysql", "goldendb"]);
 const oracleLikeRoutineRenameTypes = new Set<DatabaseType>(["oracle", "dameng"]);
 
+// SQLSTATE 42P16 covers unrelated invalid table definitions, so only match the
+// confirmed PostgreSQL view-column errors and their localized equivalents.
+const postgresViewColumnChangeErrorPatterns = [/cannot drop columns? from view/i, /cannot change name of view column/i, /cannot change data type of view column/i, /ビューからは列を削除できません/, /(?:无法|不能)从视图中删除列/];
+
+function errorMessage(error: unknown): string {
+  if (error instanceof Error) return error.message;
+  if (error && typeof error === "object" && "message" in error) {
+    const message = (error as { message?: unknown }).message;
+    if (message !== undefined && message !== null) return String(message);
+  }
+  return String(error);
+}
+
+export function formatObjectSourceSaveError(error: unknown, databaseType: DatabaseType, objectType: ObjectSourceKind, postgresViewColumnChangeHint: string): string {
+  const message = errorMessage(error);
+  if (objectType !== "VIEW" || !postgresLikeViewTypes.has(databaseType) || !postgresViewColumnChangeErrorPatterns.some((pattern) => pattern.test(message)) || message.includes(postgresViewColumnChangeHint)) {
+    return message;
+  }
+
+  return `${message}\n\n${postgresViewColumnChangeHint}`;
+}
+
 export function supportsSourceBackedRoutineRename(databaseType: DatabaseType | undefined, objectType: ObjectSourceKind): boolean {
   if (objectType !== "FUNCTION" && objectType !== "PROCEDURE") return false;
   if (!databaseType || databaseType === "sqlserver") return false;