Value and ValueRef relation

[bobozaur]

There are these two traits that represent a database value, yet it seems that most of SQLx relies on ValueRef and I struggled to find the use of Value implementors when developing sqlx-exasol.

My question is really about how is this relationship between implementors of Value and the ones of ValueRef supposed to work? In sqlx-exasol, Value contains a serde_json::Value (the data communicated in JSON format over a websocket) and ValueRef contains a reference to that serde_json::Value.

However, if the ownership of the data would be transferred to the ValueRef, that would remove the need to clone the value when deserializing it to a concrete type. The only reason I didn't directly go with that is because there's also the Row API, which can theoretically allow you to retrieve the same column value multiple times. If the ownership of the serde_json::Value is transferred (leaving maybe a Value::Null in its place) then that would provide inconsistent results.

I don't know how much the Row API is used though, or if this "gimme the value at row[2] multiple times" is even something that's expected to work (personally I don't think so), so I'd like to understand the proper way to go about this and what the expectations are.