[DOC] Clarify meaning of term suggester's suggest_mode "missing"

[snikoyo]

What do you want to do?

• Request a change to existing documentation

The page "Did You Mean" states the meaning of the term suggester's suggest_mode parameter as follows:

The suggest mode specifies the terms for which suggestions should be included in the response. Valid values are:

• missing: Return suggestions only for the input text terms that are not in the index.

"not in the index" is not exact enough. The missing mode is field specific: It will only suggest those terms that have zero occurrences in the given field of the index. This is a huge difference in most practical applications. In fact, it would be a huge improvement of the term suggester if there was a mode that would consider the complete index to find out if a term is missing or not.

Version: all

[Naarcha-AWS]

@snikoyo: This sounds like both a documentation change and a potential piece of feedback for the Term suggester behavior. Do we need to make an issue in the Core or Search Plugin repos as well?

[snikoyo]

@Naarcha-AWS It would be very helpful to change the term suggester so that it considers the complete index and not only the field. I could imagine that this would better match the spell check use cases of most users. I guess that many have implemented a workaround using a copyTo field.

[snikoyo]

Instead of changing the behaviour of the "MISSING" mode, it could just be an additional mode like "MISSING_INDEX".

[krisfreedain]

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