type inference for ValArg doesn't work for some expressions: CASE, function application

[andreimatei]

No description provided.

[petermattis]

Can you provide some concrete examples? I recall there are difficulties in doing type inference for CASE expressions, though not the details.

[JackKrupansky]

A function with a single argument which is a ValArg. Normally type check would infer the type of the ValArg from other, non-ValArg function arguments. Or, a function where all arguments are ValArgs.

[vivekmenezes]

In the bank example while using the pgwire protocol the following doesn't work:

from := rand.Intn(*numAccounts)
to := rand.Intn(*numAccounts - 1)
if from == to {
    to = *numAccounts - 1
}
amount := rand.Intn(*maxTransfer)

update := `                                                                           
    UPDATE bank.accounts                                                                            
    SET balance = CASE id WHEN $1 THEN balance-$3 WHEN $2 THEN balance+$3 END
    WHERE id IN ($1, $2) AND (SELECT balance >= $3 FROM bank.accounts WHERE id = $1)`
if _, err := clients[i].db.Exec(update, from, to, amount); err != nil {
    return err
}

I see the error

incompatible condition types int, valarg

Looking into the code this appears to be the type checker while evaluating the WHEN clause.

[maddyblue]

The fix I have for this only fixes CASE statements. Please make single issues for the other kinds of statements with examples for which prepare fails.

@vivekmenezes the bank example is now closer to working. Subqueries are failing with prepare. Working on that now.