Expressions executor caching

[streamich]

• Memoize result of functions given the same arguments
• Allow functions to opt-out of memoization

Parent issue: #46909

[elasticmachine]

Pinging @elastic/kibana-app-arch

[ppisljar]

we looked at expression executor caching and figured we would need to solve a couple of issues first:

1. cases where expression would not change, but we would actually be requesting new data

examples:

• using datemath now (possible solution: non cachable function providing now)
• something accessing uiSettings internally (possible solution: provide non cachable uiSettings function)

2. cases where expression would change, but the request would not

example:

• changing label of a column (possible solution: allow functions to provide a function to determine if cache should be hit (instead of executor doing this internally)

3. working with search sessions

example:

• in application we do something that triggers re-execution of expression. as expression figures out it doesn't need to do the data fetching part the request is never made and search collector will not put it in the session. (possible solution: support backgrounding expressions or support reporting of search ids from expressions (for the cached ones))

4. memory consumption
The problem is that we don't know what to cache and if we cache everything we will be using a lot of memory.

possible solutions:

• cache just specific functions (the ones fetching data)
• make user responsible for deciding what to cache (use variables!)

examples:

• esaggs ... | addColumn | addColumn | addColumn | ..... | pie we wouldn't want to cache every step of inexpensive addColumn perations

[streamich]

Maybe when expression is run, the consumer could specify for how long data is cached.

expressions.createExecution('esaggs ... | render', {
  cacheDataFor: 60000,
})

And then the esaggs function can see if the user wants to cache data requests. Then the functions that want to support data caching, like esaags, could be wrapped into a higher order function.

let esaggs = /* ... */;

esaggs = withCachedDataSupport(esaggs);

export { esaggs };

[ppisljar]

Thank you for contributing to this issue, however, we are closing this issue due to inactivity as part of a backlog grooming effort. If you believe this feature/bug should still be considered, please reopen with a comment.