Description

In ESQL it is possible to have aggregations working on a constant as long as it comes from a source, however pushing it into the aggregation fails.

This works: row a = 1 | stats m = min(a) but the query stats m = min(1) does not.
We've been looking at adding a dedicated rule for optimizing this ( #100182) however the issue is rather related to folding aggregations.

A somewhat variant of this is folding the aggregation when the argument is the group key itself:
stats mi = min(k), ma = max(k), c = count(k), a = avg(k) by k which is the same as stats by k | keep k as mi, k as ma, k as c, k as a, k

• Implement for aggs where agg(const) can be expressed using a multi-value function as mv_...(const) ESQL: Sum, Min, Max and Avg of constants #105454 ESQL: median, count and count_distinct over constants #107414
• Remove corresponding awaitsFixes from tests, and enable commented-out code
• Implement for aggs without corresponding multi-value functions (PERCENTILE, MEDIAN_ABSOLUTE_DEVIATION ST_CENTROID_AGG)
• Enable PropagateEvalFoldables for aggregates