Ent API: count() by Expression

Count API is similar to select(), but instead of loading the matching Ents, it counts them.

Ent.count(vc, { field: "...", ... }): number

Returns the number of Ents matching the where condition. Works across multiple microshards.

As usual, if multiple count() calls for the same Ent are run in parallel, they are internally batched into a single SQL query:

const [count1, count2] = await Promise.all([
  EntTopic.count(vc, { creator_id: "123" }),
  EntTopic.count(vc, { updated_at: { $gt: new Date("2024-01-01") } }),
]);

This sends the following SQL query to the underlying database:

SELECT count(1) FROM topics WHERE creator_id='123'
  UNION ALL
SELECT count(1) FROM topics WHERE created_at>'...'

As opposed to select(), load*() and loadBy*() calls, count() is privacy-unaware: it does not run privacy checks. This is partially a technical limitation (to recheck privacy, one needs to load the actual rows from the database, and count() doesn’t do it). But also, it’s an intended behavior: with count(), it’s convenient to build custom privacy checks and avoid "chicken and egg" problem (to build a privacy check, you eventually need to run a privacy-unaware calls at the very bottom of the stack).