ERROR: no builtin aggregate for SUM_INT on [unknown]

[bajinsheng]

Describe the problem

An error was encountered when using NULL in sum_int function.

To Reproduce

SELECT sum_int(NULL+1); --ERROR: no builtin aggregate for SUM_INT on [unknown]

Expected behavior
No error.

Additional data / screenshots

Environment:

• CockroachDB version [02dcb38]
• Server OS: [Ubuntu 20.04]
• Client app [cockroach sql]

Additional context

Jira issue: CRDB-17325

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[mgartner]

To start, we should probably make the error match that of sum:

defaultdb> select sum(NULL+1);
ERROR: ambiguous call: sum(unknown), candidates are:
sum(float) -> float
sum(decimal) -> decimal
sum(interval) -> interval
sum(int) -> decimal
SQLSTATE: 42725

Ideally, sum_int wouldn't exist. It's only necessary because sum(int) returns a decimal rather than an integer.

[github-actions]

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18 months. If this issue is still relevant, removing the stale label
or adding a comment will keep it active. Otherwise, we'll close it in
10 days to keep the issue queue tidy. Thank you for your contribution
to CockroachDB!

[mgartner]

To start, we should probably make the error match that of sum:

I don't think this last comment of mine is quite right. It won't have the same error message because there is only one overload for sum_int.

To match Postgres's behavior here, we need to match Postgres's function resolution logic, which is tracked in #75101. I'm going to close this as a duplicate of that.