[BUG] Range query with `now` on date fields skips Approximation Path

[prudhvigodithi]

Describe the bug

Currently, range queries on date fields that use now bypass the ApproximatePointRangeQuery optimization path and instead wrap the underlying query in a DateRangeIncludingNowQuery. This results in full execution rather than benefiting from approximation.

Example the following query does not go through the approximation path

curl -X POST "http://localhost:9200/logs-*/_search" -H "Content-Type: application/json" -d '
{
  "query": {
    "range": {
      "@timestamp": {
        "gte": "1998-05-15T00:00:00Z",
        "lt": "now"
      }
    }
  }       
}'

Related component

Search:Performance

To Reproduce

Once we have this #18318 implemented, using profile would be straight forward to see if the query is using the approximation path.

For now add a print statements in canApproximate and run a range query with now and see it does print the statements as it does not go through the ApproximateScoreQuery.

Expected behavior

Update handleNow or the surrounding logic (DateRangeIncludingNowQuery) to ensure that ApproximatePointRangeQuery is still used even when now is present.

[prudhvigodithi]

Adding @harshavamsi @getsaurabh02 @kkewwei.

[sawansri]

Can I tackle this issue?

[prudhvigodithi]

Thanks @sawansri I have assigned this to you, please take a look and and tag me if you have any questions.