[ES|QL] Implicit numeric casting for CASE/GREATEST/LEAST

[fang-xing-esql]

Resolves #121890

#111917 supports implicit casting for numeric values and fields in COALEASE, the subsequent numeric arguments are casted to the first not null numeric type argument. This PR follow the same path to support CASE, GREATEST and LEAST to have the same behavior as COALESCE.

For example,

1. GREATEST(Long, Int) returns a Long

2. LEAST(null, Long, Int) returns a Long

3. CASE(condition1, Double, condition2, Long, Int) returns a Double

4. GREATEST(Int, Long) returns VerificationException, because Long cannot be casted to Int.

Technically, we can make the implicit casting independent of the sequence how the numeric values and fields are coded in the query, so that the query #4 above can run to completion, if this is the desired behavior.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[elasticsearchmachine]

Hi @fang-xing-esql, I've created a changelog YAML for you.

[costin]

LGTM however we should look into generalizing this by looking at the param declaration instead of specific functions.

[fang-xing-esql]

LGTM however we should look into generalizing this by looking at the param declaration instead of specific functions.

Thanks for reviewing @costin , #123088 is created for using annotation to tag function parameters that are eligible for implicit casting.

[elasticsearchmachine]

💔 Backport failed

Status	Branch	Result
❌	9.0	Commit could not be cherrypicked due to conflicts
❌	8.x	Commit could not be cherrypicked due to conflicts

You can use sqren/backport to manually backport by running backport --upstream elastic/elasticsearch --pr 122601

[fang-xing-esql]

💚 All backports created successfully

Status	Branch	Result
✅	8.x
✅	9.0

Questions ?

Please refer to the Backport tool documentation

[alex-spies]

@fang-xing-esql just to double check, since we're backporting this to 9.0, did we intend to also backport this to 8.18 (which is kinda-sorta in sync with 9.0)? Not that this is a technical requirement, just something that stood out to me.

[fang-xing-esql]

@fang-xing-esql just to double check, since we're backporting this to 9.0, did we intend to also backport this to 8.18 (which is kinda-sorta in sync with 9.0)? Not that this is a technical requirement, just something that stood out to me.

Good point! I'll back port this to 8.18 as well.

[fang-xing-esql]

💚 All backports created successfully

Status	Branch	Result
✅	8.18

Questions ?

Please refer to the Backport tool documentation