On 2024-11-18 Mo 9:25 AM, Yan Chengpeng wrote:
Dear PostgreSQL Hackers,
*Problem Description*
I encountered an issue with the B-Tree ordering of `jsonb` values.
According to the PostgreSQL documentation[1], the ordering should
follow this precedence:
`Object > Array > Boolean > Number > String > Null`
However, empty arrays (`[]`) are currently considered smaller than
`null`, which violates the documented rules. This occurs due to
improper handling of the `rawScalar` flag when comparing arrays in the
`compareJsonbContainers()` function in
`src/backend/utils/adt/jsonb_util.c`.
I agree that this is a (10 year old) bug:
- if (va.val.array.nElems != vb.val.array.nElems)
+ else if (va.val.array.nElems !=
vb.val.array.nElems)
But I don't think we can fix it, because there could well be indexes
that would no longer be valid if we change the sort order. Given that, I
think the best we can do is adjust the documentation to mention the anomaly.
So the actual sort order as implemented is, AIUI,
Object > Non-Empty-Array > Boolean > Number > String > Null > Empty-Array
which is ugly, but fortunately not many apps rely on jsonb sort order.
cheers
andrew
--
Andrew Dunstan
EDB:https://www.enterprisedb.com
