[Known Issue] Detect JSON columns in Azure SQL

[yorek]

We should be able to automatically detect if a column contains JSON data and avoid escaping it in the output. Right now if I have the following table:

create table s003b.todos
(
	id int not null constraint pk__s003b_todos primary key default (next value for s003b.globalId),
	category_id varchar(3) collate Latin1_General_BIN2 not null constraint fk__s003b_todos__s003b_categories references s003b.categories(id),
	title nvarchar(100) not null,
	[description] nvarchar(1000) null,
	tags nvarchar(max) null check ( isjson(tags)= 1 ),
	completed bit not null default(0)
)

and I store JSON data in the "tags" column, I get the following output:

{ data": {
		"todos": {
			"items": [
				{
					"id": 10000,
					"title": "item-001",
					"completed": false,
					"tags": "[{\"tag\":\"red\"}]",
					"category": {
						"id": "f",
						"category": "Family"
					}
				}

where tags contains encoded JSON...even if the content is valid JSON itself. Right now Azure SQL DB doesn't have a native JSON data type, but we can check if a column contains JSON data by checking the check constraint that should have been created to allow only JSON data to be inserted (see table definition above). This query can return which columns should be treated as JSON:

select 
	s.[name] as [schema_name],
	t.[name] as [table_name],
	c.[name] as [columne_name],
	ck.[definition],
	case when (ck.[definition] like '%isjson(/[' + trim(c.[name]) + '/])=(1)%' escape '/') then 1 else 0 end as [isjson]
from 
	sys.check_constraints ck
inner join
	sys.tables t on ck.[parent_object_id] = t.[object_id]
inner join
	sys.columns c on t.[object_id] = c.[object_id] and ck.parent_column_id = c.[column_id]
inner join
	sys.schemas s on t.[schema_id] = s.[schema_id]

[jarupatj]

@gledis69 can you please take a look at this issue?

[gledis69]

@yorek what would be the desired output for "tags" in this scenario?
The " need to be escaped otherwise they will terminate the string that represents the json.
Another question that comes to mind is what the use case scenario is here. Most libraries that work with string should be able to handle escaped quotes.

[yorek]

@gledis69 given that in the tags columns there can only be valid JSON content, the expected output would be:

{
  "data": {
    "todos": {
      "items": [
        {
          "id": 10000,
          "title": "item-001",
          "completed": false,
          "tags": [
            {
              "tag": "red"
            }
          ],
          "category": {
            "id": "f",
            "category": "Family"
          }
        }
      }
    }
  }
}

basically: just pass the JSON as is, without encoding it.

[Aniruddh25]

Not need to have support for Filter, Order but for Mutation for JSON type

[Aniruddh25]

From @gledis69 : This turned out to be more involved that I imagined, The core problem is that our DbDataAdapter approach that we use to detect column types just doesn't detect json-s, so we'd have to rewrite column type detection to querying the db and analyzing the response similarly to what we do to detect fk-s.