Which JSON Schema version is being implemented?

Note that MySQL uses Draft 4 - actually a subset of it, as the documentation omits to mention. Draft 4 problems:

• It's old (2013)
• It has annoying problems that have been fixed in later versions, for example one is used id instead of $id, which led to confusion when id is used as an attribute name.
• Not fully compatible with later versions.

Final Patch: https://github.com/MariaDB/server/tree/bb-11.1-MDEV-27128

f_razzoli We support the 2020 draft with some exception.

didn't agree with parts of the design. Comments sent by email.

ok with a couple of corrections discussed on Slack.

Some cases I'm not sure how it should be:

1. I suppose that for all cases where JSON_SCHEMA_VALID returns warning due to incorrect schema the result must be NULL. An example can be taken from MDEV-30689 or use this:

SET @schema = '{

                 "type":"array",

                  "enum": [null]}

                }';

SELECT JSON_SCHEMA_VALID(@schema, 'null');

JSON_SCHEMA_VALID(@schema, 'null')

0

Warnings:

Warning	4038	Syntax error in JSON text in argument 2 to function 'json_schema_valid' at position 86

2. With uniqueItems=true for array I guess 'null' and 'null' should be duplicate items, but that's not the case right now:

SET @schema= '{

                     "type":"array",

                     "uniqueItems":true

              }';

SELECT JSON_SCHEMA_VALID(@schema, '[null, null]');

JSON_SCHEMA_VALID(@schema, '[null, null]')

1

3. All parameters marked as "be a non-negative integer" in the schema must be checked for this condidtion. So, I suppose in cases like the following one should return null and warning or error:

SET @schema_array= '{

                      "type": "array",

                      "contains": {

                                    "type": "string"

                                  },

                      "minContains": -3,

                      "maxContains": 3

}';

SELECT JSON_SCHEMA_VALID(@schema_array, '["string1", "string2", "string3",  "string3", 1, 2, 3]');

JSON_SCHEMA_VALID(@schema_array, '["string1", "string2", "string3",  "string3", 1, 2, 3]')

0

4. Also for parameter "required":

The value of this keyword MUST be an array. Elements of this array, if any, MUST be strings, and MUST be unique.

SET @schema_required='{"type":"object","required":[1,"str1", "str1"]}';

SELECT JSON_SCHEMA_VALID(@schema_required,'{"num1":1, "str1":"abc", "arr1":[1,2,3]}');

JSON_SCHEMA_VALID(@schema_required,'{"num1":1, "str1":"abc", "arr1":[1,2,3]}')

0

After fixing bugs and rebasing on the actual tree, a little rechecking will be required (for checked options).

See comments to the commit
https://github.com/MariaDB/server/commit/abcd161da906bfed1a3e61ce79eae37c16332a58

lstartseva Thanks for the comment. You're right. I've fixed it as part of below patch

1) https://github.com/MariaDB/server/commit/357c208d67fa90b79da013c6cb7fae044af8c1b6
2), 3) and 4): https://github.com/MariaDB/server/commit/0058ac37d31767686cea2816f17b30fe59b6f60d

Comments on slack.
After these addressed i'm ok with making the preview out of this.

( Reassigned after working on review 2 for final check )

commit 70a7de2aed7677ef9e0a14f5734150cbc58023ae
comments on slack.
With at least keyword_map= &empty_map fix i'm ok with the patch to preview.

ok to push