One word fields (keyword vs text types)

If, for example, I have a field in which I know that the data ingested to it is only one-word strings. Why would I still use type "text" and not type "keyword" for this field's mapping?
Setting it to be of type "keyword" will both allow me to search it (since it's a one-word, the results will be the same, compared to the "text" type), use it in filters, and use it for aggregations.

I'm trying to understand if there's a catch here.
How does the data ingested if the mapping set to multi-field "text" and "keyword"? does it get ingested twice, even if it's a one-word? Once for the text and once for the keyword?

Slightly confused.

Thank you in advance.

Welcome!

Setting it to be of type "keyword" will both allow me to search it

Yes but only for exact match unless you apply also a lowercase normalizer or may be an asciifolding normalizer...

But you're right, if you need to do sorting, aggregation and exact match search, then using a keyword is the good option.

That's correct. It's "indexed" twice.

Thank you for the response and for your time!

Few more questions, further to your response:

Yes but only for exact match unless you apply also a lowercase normalizer or may be an asciifolding normalized...
But you're right, if you need to do sorting, aggregation and exact match search, then using a keyword is the good option.

Is there a catch there?
Does using the keyword with a lowercase normalizer will be the same as using the text type? (when speaking about one-words, of course)

I'm trying to understand if there will be an improvement in terms of performance/storage.
I'm asking because you said that it does get indexed twice when setting the field's mapping to multi-field (text + keyword).
I wonder if the fact that I choose to index a field only as keyword and not as text as well will save me some disk storage space (or whether the performance will improve).

Additionally, I've been wondering, if I set a field to be of type only keyword, will it appear in the "Available Fields" (the nav bar on the side, please see the screenshot below).

*I'm asking because the field there seems to be only of type not-keyword.

Much appreciation in advance, David!
Aviad.

It will probably same some disk space but won't change performance IMO.

Yes.

Thank you!

So the only question left is this:

Much appreciation!
Aviad

I guess it is similar.

@dadoonet

ill there be a difference in terms of performance? Or not something significant?

Because I want to append this normalizer to each only-keyword field I have in my mapping file and there are many of them; so I wonder whether that matters.

Much appreciation for your time,
Aviad

May be @jpountz can tell exactly. I don't think you'll see a lot of difference, performance wise.