JSON document does not report error even exceeds the maximum depth.

[xiongjiwei]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

select json_valid(repeat('[', 1000));
Error 3157: The JSON document exceeds the maximum depth.

2. What did you expect to see? (Required)

Error 3157: The JSON document exceeds the maximum depth.

3. What did you see instead (Required)

0

4. What is your TiDB version? (Required)

[windtalker]

There is a hard limit of max depth(100) of json type in MySQL, while TiDB does not have such limits, so TiDB does not throw error.
I think it should be a moderate or minor bug.

[YangKeao]

See golang/go#31789

The standard library of golang has a default max depth for 10000, (but as I know, it doesn't provide a way to specify the depth). We can verify this limitation through:

In TiDB:

MySQL [test]> select json_valid(concat(repeat('[', 1001), repeat(']', 10001)));
+-----------------------------------------------------------+
| json_valid(concat(repeat('[', 1001), repeat(']', 10001))) |
+-----------------------------------------------------------+
|                                                         0 |
+-----------------------------------------------------------+
1 row in set (0.001 sec)

MySQL [test]> select json_valid(concat(repeat('[', 10001), repeat(']', 10001)));
+------------------------------------------------------------+
| json_valid(concat(repeat('[', 10001), repeat(']', 10001))) |
+------------------------------------------------------------+
|                                                          0 |
+------------------------------------------------------------+
1 row in set (0.001 sec)

See serde-rs/json#162

The default recursion depth used in TiKV is 128 (by default), which is so different from the TiDB. Also, it's not configurable, but this limitation can be turned off: https://docs.rs/serde_json/latest/serde_json/struct.Deserializer.html#method.disable_recursion_limit .

[YangKeao]

We could handle this special error everywhere, if it's needed.