fix(mysql): show inherited charset and collation in structure editor

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

@@ -0,0 +1,30 @@
+import { describe, expect, it } from "vitest";
+import type { QueryResult } from "@/types/database";
+import { mysqlTableCollationSql, parseMysqlTableCollation } from "@/lib/table/mysqlTableCollation";
+
+function result(columns: string[], rows: QueryResult["rows"]): QueryResult {
+  return { columns, rows, affected_rows: 0, execution_time_ms: 1 };
+}
+
+describe("mysqlTableCollation", () => {
+  it("builds mode-independent lookup SQL for quoted and Unicode names", () => {
+    const sql = mysqlTableCollationSql("db'x", "订单\\archive");
+    expect(sql).toContain("TABLE_COLLATION AS table_collation");
+    expect(sql).toContain("TABLE_SCHEMA = CONVERT(X'64622778' USING utf8mb4)");
+    expect(sql).toContain("TABLE_NAME = CONVERT(X'e8aea2e58d955c61726368697665' USING utf8mb4)");
+    expect(sql).not.toContain("db'x");
+  });
+
+  it("reads the reported collation regardless of column-name casing", () => {
+    expect(parseMysqlTableCollation(result(["TABLE_COLLATION"], [["utf8mb4_0900_ai_ci"]]))).toBe("utf8mb4_0900_ai_ci");
+    expect(parseMysqlTableCollation(result(["table_collation"], [[" utf8mb4_bin "]]))).toBe("utf8mb4_bin");
+  });
+
+  it("falls back to no table default when the server reports nothing usable", () => {
+    // MySQL reports TABLE_COLLATION as NULL for views, and the lookup itself may fail.
+    expect(parseMysqlTableCollation(result(["table_collation"], [[null]]))).toBe("");
+    expect(parseMysqlTableCollation(result(["table_collation"], []))).toBe("");
+    expect(parseMysqlTableCollation(result(["engine"], [["InnoDB"]]))).toBe("");
+    expect(parseMysqlTableCollation(undefined)).toBe("");
+  });
+});

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

@@ -0,0 +1,23 @@
+import type { QueryResult } from "@/types/database";
+import { mysqlUtf8Literal } from "@/lib/table/mysqlTableEngine";
+
+/**
+ * Reads the table's default collation. MySQL reports the *effective* collation on every
+ * character column and never records whether it was written out explicitly, so a column
+ * matching this value is one that simply inherits the table default. The structure editor
+ * passes it to the SQL builder, which then leaves the redundant `CHARACTER SET`/`COLLATE`
+ * clauses out of the generated DDL — the column metadata itself keeps the real values so
+ * the charset and collation pickers can show what the column currently uses.
+ */
+export function mysqlTableCollationSql(database: string, table: string): string {
+  return ["SELECT TABLE_COLLATION AS table_collation", "FROM information_schema.TABLES", `WHERE TABLE_SCHEMA = ${mysqlUtf8Literal(database)}`, `  AND TABLE_NAME = ${mysqlUtf8Literal(table)}`, "LIMIT 1"].join("\n");
+}
+
+/** Empty string when the server reported nothing usable — MySQL returns NULL for views. */
+export function parseMysqlTableCollation(result: QueryResult | undefined): string {
+  if (!result) return "";
+  const index = result.columns.findIndex((column) => column.trim().toLowerCase() === "table_collation");
+  if (index < 0) return "";
+  const value = result.rows[0]?.[index];
+  return value === null || value === undefined ? "" : String(value).trim();
+}

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

@@ -13,7 +13,9 @@ export interface MysqlTableEngineDraft {
 
 export const MYSQL_STORAGE_ENGINES_SQL = "SHOW ENGINES";
 
-function mysqlUtf8Literal(value: string): string {
+/** Encodes a schema/table name as a byte literal so non-ASCII names survive whatever
+ *  charset the session happens to use. Shared with the table collation lookup. */
+export function mysqlUtf8Literal(value: string): string {
   const bytes = new TextEncoder().encode(value);
   const hex = Array.from(bytes, (byte) => byte.toString(16).padStart(2, "0")).join("");
   return `CONVERT(X'${hex}' USING utf8mb4)`;

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

@@ -84,6 +84,10 @@ export interface BuildTableStructureChangeSqlOptions {
   tableComment?: string;
   originalTableComment?: string;
   mysqlEngine?: string;
+  /** MySQL only: the table's current default collation. Columns whose collation merely
+   * matches it inherit the table default, so the backend leaves their redundant
+   * `CHARACTER SET`/`COLLATE` clauses out of the generated DDL. */
+  tableCollation?: string;
   /** The target table is a PostgreSQL partitioned parent (`relkind = 'p'`);
    * the backend rejects `CREATE INDEX CONCURRENTLY` on such tables (fail
    * closed) instead of downgrading to a blocking `CREATE INDEX`. */