Elasticsearch re-index all vs join - elasticsearch

Question

I'm pretty new on Elasticsearch and all its concepts. I would like to understand how I could accomplish what I have in my Relational DB in an Elasticsearch architecture.
The scenario is the following
I have a index "data":
{
"id": "00001",
"content" : "some text here ..",
"type": "T1",
"categories: ["A", "A1", "B"]
}
The requirement says that data can be queried by:
some text search in the context field
that belongs to a specific type or category
So far, so simple, so good.
This data will not be completed from the creating time. It might happen that new categories will be added/removed to the data later. So, many data uploads/re-indexes might happen along the way
For example:
create the data
{
"id": "00001",
"content" : "some text here ..",
"type": "T1",
"categories: ["A"]
}
Then it was decided that all data with type=T1 must belong to both A & B categories.
{
"id": "00001",
"content" : "some text here ..",
"type": "T1",
"categories: ["A", "B"]
}
If I have a billion hits for type=T1 I would have to update/re-index a billion entries. Maybe it is how things should work and this where my question lands on.
Is ok to re-index all the data just to add/remove a new category, or would it be possible to have a second much smaller index just to do this association and somehow join both indexes at time to query?
Something like it:
Data:
{
"id": "00001",
"content" : "some text here ..",
"type": "T1"
}
DataCategories:
{
"type": "T1"
"categories" : ["A", "B"]
}
Is it acceptable/possible?

Answer 1

This is a common scenario - but unfortunately, there is no 1:1 mapping for RDBMS features in text search engines like Lucene/elasticsearch.
Possible options:
1 - For the best performance, reindex. It may not be practical depending on the velocity of your change
2 - Consider Parent-Child; Though it's a slower option - often will meet performance requirements. The category could be a parent document, each having several thousands of children.
3 - If its category renaming - Consider using IDs for the category and translating it to text in the application.
4 - Update document depends on the number of documents to be updated; maybe for few thousand - run an update query, if more - reindex.
Suggested reading - https://www.elastic.co/blog/managing-relations-inside-elasticsearch