Doc'd that Count("*") is equivalent to COUNT(*) SQL.

[orf]

I've always known that Count("*") is a valid shorthand for expression=Star(), but I'm surprised that it's not documented. This was added by #2496 / f59fd15 back in 2014.

If we do want to document this, because it is quite useful, then this seems like a simple way to do it. However I'm open to a larger snippet if needed?

[orf]

One other thing to possibly note here is what COUNT(*) actually does? Not sure if this is the right place for a detailed description, but I could add a note about how it differs in counting null values?

Mabe:

Count("*") is shorthand for Count(expression=Star()), which counts NULL values as opposed to Count() which does not

It's a tricky one to word though. Happy to keep it as-is and skip that.

[shangxiao]

Hi Tom,

Not sure if this is the right place for a detailed description, but I could add a note about how it differs in counting null values?

It's a nice idea but I reckon it's probably fine to leave it out… afterall this is an SQL fundamental (eg it's documented in the pg docs see below).

If anything I feel like explicitly stating that Count('*') yields the SQL expression "COUNT(*)" would close the gap for folks who are learning SQL and may not know what a "count(*)" even is :)… from here they can google "What is a count(*)?"

pg docs:

Most aggregate functions ignore null inputs, so that rows in which one or more of the expression(s) yield null are discarded. This can be assumed to be true, unless otherwise specified, for all built-in aggregates.

For example, count(*) yields the total number of input rows; count(f1) yields the number of input rows in which f1 is non-null, since count ignores nulls; and count(distinct f1) yields the number of distinct non-null values of f1.

https://www.postgresql.org/docs/current/sql-expressions.html#SYNTAX-AGGREGATES

[orf]

Makes sense @shangxiao. I've reworded it slightly: Count('*') is shorthand for the SQL expression COUNT(*), how does that sound?

[shangxiao]

@orf Good idea :) I was originally thinking of them both… but now that I think about it I'm not even sure if folks would ever even use the Star() object… so yep I reckon this is better 👍

[felixxm]

@orf Thanks 👍