Nullable Test

1import { describe, expect, it } from "vitest";
2import { query } from "./clickhouse.js";
3import { readNullable } from "../src/readers/composite.js";
4import { NeedMoreData, Cursor } from "../src/readers/core.js";
5import { readUInt32, readUInt8 } from "../src/readers/integers.js";
6import { readString } from "../src/readers/strings.js";
7
8async function reader(expr: string): Promise<Cursor> {
9  return new Cursor(await query(`SELECT ${expr} FORMAT RowBinary`));
10}
11
12describe("readNullable", () => {
13  it("decodes a present value (flag 0 + value)", async () => {
14    const r = await reader("CAST(42 AS Nullable(UInt32))");
15    expect(readNullable(readUInt32)(r)).toBe(42);
16    expect(r.pos).toBe(5); // 1 flag + 4 value
17  });
18
19  it("decodes NULL as the lone flag byte (no value follows)", async () => {
20    const r = await reader("CAST(NULL AS Nullable(UInt32))");
21    expect(readNullable(readUInt32)(r)).toBeNull();
22    expect(r.pos).toBe(1); // just the flag — the inner reader must not run
23  });
24
25  // Framing across rows: NULL then 1 -> bytes 01 00 01.
26  it("keeps the cursor aligned across NULL and non-NULL rows", async () => {
27    const r = await reader(
28      "CAST(number = 0 ? NULL : number AS Nullable(UInt8)) FROM numbers(2)",
29    );
30    expect(readNullable(readUInt8)(r)).toBeNull();
31    expect(r.pos).toBe(1);
32    expect(readNullable(readUInt8)(r)).toBe(1);
33    expect(r.pos).toBe(3);
34  });
35
36  // A variable-length inner type: the inner reader must not run on NULL.
37  it("works with a variable-length inner type (String)", async () => {
38    const r = await reader("CAST('hi' AS Nullable(String))");
39    expect(readNullable(readString)(r)).toBe("hi");
40  });
41
42  describe("advance() edge cases", () => {
43    it("throws NeedMoreData for every incomplete prefix (0 .. full.length-1)", async () => {
44      const full = await query(
45        "SELECT CAST(42 AS Nullable(UInt32)) FORMAT RowBinary",
46      );
47      for (let len = 0; len < full.length; len++) {
48        const r = new Cursor(full.subarray(0, len));
49        let thrown: unknown;
50        try {
51          readNullable(readUInt32)(r);
52        } catch (e) {
53          thrown = e;
54        }
55        expect(thrown, `prefix length ${len} of ${full.length}`).toBe(
56          NeedMoreData,
57        );
58      }
59    });
60  });
61});