ESQL: Push down StartsWith and EndsWith functions to Lucene

[ivancea]

Fixes #123067

Just like WildcardLike and RLike, some functions can be converted to Lucene queries. Here it's those two, which are nearly identical to WildcardLike

This, like some other functions, needs a FoldContext. I'm using the static one for this here, but it's fixed in #123398, which I kept separated as it changes many files

[elasticsearchmachine]

Hi @ivancea, I've created a changelog YAML for you.

[elasticsearchmachine]

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

[astefan]

This is a good start in terms of testing this, but the tests are the bare minimum.
Let's make this functionality more robust by having stronger tests, please. For CSV (notice also the _index metadata which is a feature of pushable attributes):

• from employees | where starts_with(first_name, "A") | keep first_name, last_name | where ends_with(last_name, "g")
• from employees* metadata _index | where starts_with(first_name::keyword, "A") | keep first_name, last_name, _index | where ends_with(last_name::keyword, "g") and starts_with(_index, "e")
• from e* metadata _index | where starts_with(first_name::keyword, "A") | keep first_name, last_name, languages.long, _index | where ends_with(last_name::keyword, "g") and starts_with(_index, "e")
• from e* metadata _index | where starts_with(first_name::keyword, "A") | keep first_name, last_name, languages.long, _index | where ends_with(last_name::keyword, "g") and ends_with(_index, "e")
• from employees metadata _index | where starts_with(first_name, "A") | keep first_name, last_name, languages.long, _index | where ends_with(_index, "s") and (ends_with(last_name, "e") or ends_with(last_name, "m")
• from employees metadata _index | where starts_with(first_name, "A") | keep first_name, last_name, languages.long, _index | where ends_with(_index, "s") and not (ends_with(last_name, "e") or ends_with(last_name, "m")

For unit testing, please look at PhysicalPlanOptimizerTests.testPushAndInequalitiesFilter and make sure that the EsQueryExec that gets created includes the actual wildcard query in its proper form. Please, also use a query with two statements so we can see the bool query getting created as well.

[ivancea]

@astefan Just added some extra CSV tests with some combinations, with and without _index and wildcards.
For the PhysicalPlanOptimizerTests tests, I just added one with a combination of ANDs and ORs, to ensure it works as it should. I didn't add much more here, as it's generic, already tested code (AND and OR functions), and the StartsWith and EndsWith functions already have unit tests for translations.
WDYT?

[astefan]

Please, add as a javadoc the expected physicalplan tree. I know some methods in this class do not have this, but I (or we) try to have this consistent throughout the class. Thanks.

[astefan]

LGTM with a minor comment regarding the unit test.

[elasticsearchmachine]

💚 Backport successful

Status	Branch	Result
✅	8.x
✅	9.0

[ivancea]

Also backporting to 8.18 in #124871