How do I map combination keys

Question

I am working on the Apache CouchDB using the cURL. I have created a database added database files & created a view. I have made the following configurations for mapping the keys to the view.

function (doc) { emit([doc.key1, doc.key2, doc.key3], doc); }

I would like to access the database file using a combination of keys. i.e. In the above case, key1 is fixed in my URL's get request. but I don't have control over key2 & key3(sometimes I have key2 & rest I have key3).

Will you please help me to know, How can I access the database with a combination of key1-key2 OR key1-key3?

Will a document ever have both key2 and key3? Is it important to differentiate the two keys in a query? — RamblinRose
– RamblinRose, Commented Aug 5, 2021 at 13:21

Rea · Accepted Answer · 2022-02-02 10:01:18Z

Have a look at this Guide with compound keys: https://docs.couchdb.org/en/stable/ddocs/views/collation.html#examples

Thus, you could try something like this:

startkey=[<val_key1>]&endkey[<val_key1>,{}]

or

startkey=[<val_key1>,<val_key2>]&endkey[<val_key1>,<val_key2>,{}]

If you use cURL, don't forget to encode the curly brackets or use option -g/--globoff (Passing a URL with brackets to curl).

EDIT:

There is no space between the keys (write [<val_key1>,{}] instead of [<val_key1>, {}])
Likely, you have to create multiple views for each of your available key combination (key1-key2, key2-key3, key1-key3) combination because e.g. [{},<val_key2>,<val_key3>] does not work and will return you no rows. If you want to group by <val_key2> or <val_key3> you have to emit them first. (see also https://forums.couchbase.com/t/how-to-give-muliple-composite-keys-in-startkey-and-endkey-to-search-in-views/629)

fynnlyte · Accepted Answer · 2021-08-06 12:06:09Z

How can I access the database with a combination of key1-key2 OR key1-key3?

If you want to access documents based on the existence or value of key1, key2, key3, you most likely don't want to create a View that simply emits all them as keys.

Instead, first have a look at Mango queries using the _find-API and construct them s.t. the desired documents are returned. For example:

{ "selector": { "key1": { "$gt": null }, "key2" { "$lt": "too high" } }

The, create a matching index or view for your queries.

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