Scripting: Cache script results if deterministic

[stu-elastic]

Cache results from queries that use scripts if they use only
deterministic API calls. Nondeterministic API calls are marked in the
whitelist with the @nondeterministic annotation. Examples are
Math.random() and new Date().

Refs: #49466

[elasticmachine]

Pinging @elastic/es-core-infra (:Core/Infra/Scripting)

[jdconrad]

LGTM once we address the couple of comments I left that require further discussion.

[rjernst]

LGTM. Left a few suggestions.

[stu-elastic]

Currently debugging NPE when using scripts for weighted avg, fieldName coming in as null.

[stu-elastic]

Ok, now that scripts are cachable, here's what's causing the NPE

SearchService.loadOrExecuteQueryPhase

calls into

IndicesService.loadIntoContext (instead of queryPhase.execute)

which calls

ShardSearchRequest.cacheKey

which eventually calls

MultiValuesSourceFieldConfig.writeTo

which nulls out because there is no fieldName.

Here's the series of calls to reproduce:

curl -H 'Content-Type: application/json' -XPUT --user 'elastic-admin:elastic-password' localhost:9200/exams -d '{ "mappings": { "properties": { "grade": { "type": "byte" } } } }'

curl -H 'Content-Type: application/json' -XPOST --user 'elastic-admin:elastic-password' localhost:9200/exams/_doc -d '{"grade": 100, "weight": 2}'

curl -H 'Content-Type: application/json' -XPOST --user 'elastic-admin:elastic-password' localhost:9200/exams/_doc -d '{"grade": 50, "weight": 3}'

curl -H 'Content-Type: application/json' -XPOST --user 'elastic-admin:elastic-password' localhost:9200/exams/_search -d '{
    "size": 0,
    "aggs" : {
        "weighted_grade": {
            "weighted_avg": {
                "value": {
                    "script": "doc.grade.value + 1"
                },
                "weight": {
                    "script": "doc.weight.value + 1"
                }
            }
        }
    }
}'

[stu-elastic]

This just happened to be caught by a test. Are there other places where cacheKey calls writeTo with fields that are not available if a script is used?

[stu-elastic]

@elasticmachine run elasticsearch-ci/1

[jdconrad]

@stu-elastic Thanks again for all the work getting this done. The tests look especially good.