CouchDB many-to-many fetching with dynamic sorting - couchdb

Question

I have a CouchDB index where documents are music files with fields artist, album, title, etc. I also want to store playlists of tracks and be able to fetch all of a playlist's tracks and optionally sort the results by arbitrary fields.
I've read through the documentation on joins and the blog post/comment example is basically the same architecture as my playlist/track one, so I already have the ability to fetch a playlist's tracks and sort them by some predetermined key.
Is there any way to combine a view (like in those docs) with post-hoc sorting by some other arbitrary field (artist, title, etc.)?
I don't mind using multiple queries, but collecting all of the returned document IDs and using them in a subsequent /_find query like {"_id": {"$in": [...]}} query is extremely slow. Sorting them client side is always an option, but then I'd need to implement sorting logic twice in my app: a server-side version for when I'm using /_find on all tracks and a client-side version for tracks returned from a playlist view.
(This would be trivially easy to accomplish with an RDBMS but my use case involves syncing data between mobile and desktop versions of the same app (which might be offline), which is what led me to CouchDB+PouchDB.)

Answer 1

This belongs in a comment but would be an ugly mess.
When not to use map/reduce is a must read blog post by Nolan Lawson. There the point made is to leverage document _id's as much as possible, and demonstrates that denormalization isn't always the answer.
I believe if you are able to refactor your id's and documents, it will be evident how a secondary index (or two!) will fill in the gaps.
I won't go further because it would be plagiarism - it can't be explained in simpler terms. Read that article, toy with this code.
const g_view_result = 'view_result';
const getAllArtists = async() => {
const options = {
include_docs: true,
startkey: 'artist_',
endkey: 'artist_\uffff'
};
allDocs(["name"], options);
}
const getAllAlbums = async() => {
const options = {
include_docs: true,
startkey: 'album_',
endkey: 'album_\uffff'
};
allDocs(["title"], options);
}
const getAllBowieAlbums = async() => {
const options = {
include_docs: true,
startkey: 'album_bowie_',
endkey: 'album_bowie_\uffff'
};
allDocs(["title"], options);
}
const allDocs = async(fields, options) => {
let html = [];
const results = getEl('results');
results.innerText = '';
let docs = await db.allDocs(options);
docs.rows.forEach(row => {
html.push(fields.map(f => row.doc[f]).join(", "));
})
results.innerText = html.join('\n');
}
// canned test documents
const getDocsToInstall = () => {
return [
/*---- artist ----*/
{
_id: 'artist_bowie',
type: 'artist',
name: 'David Bowie',
age: 67
},
{
_id: 'artist_dylan',
type: 'artist',
name: 'Bob Dylan',
age: 72
},
{
_id: 'artist_joni',
type: 'artist',
name: 'Joni Mitchell',
age: 70
},
/*---- albums ----*/
{
_id: 'album_bowie_1971_hunky_dory',
artist: 'artist_bowie',
title: 'Hunky Dory',
type: 'album',
year: 1971
},
{
_id: 'album_bowie_1972_ziggy_stardust',
artist: 'artist_bowie',
title: 'The Rise and Fall of Ziggy Stardust and the Spiders from Mars',
type: 'album',
year: 1972
},
{
_id: 'album_dylan_1964_times_they_are_changin',
artist: 'artist_dylan',
title: 'The Times They Are a-Changin\'',
type: 'album',
year: 1964
},
{
_id: 'album_dylan_1965_highway_61',
artist: 'artist_dylan',
title: 'Highway 61 Revisited',
type: 'album',
year: 1965
},
{
_id: 'album_dylan_1969_nashville_skyline',
artist: 'artist_dylan',
title: 'Nashville Skyline',
type: 'album',
year: 1969
},
{
_id: 'album_joni_1974_court_and_spark',
artist: 'artist_joni',
title: 'Court and Spark',
type: 'album',
year: 1974
}
]
}
//
// boilerplate code
//
let db;
// init example db instance
const initDb = async() => {
db = new PouchDB('test', {
adapter: 'memory'
});
await db.bulkDocs(getDocsToInstall());
}
initDb().then(() => {
document.querySelectorAll('.hide').forEach(el => el.classList.remove('hide'));
});
const getEl = id => document.getElementById(id);
.hide {
display: none
}
.label {
text-align: right;
margin-right: 1em;
}
.hints {
font-size: smaller;
}
<script src="https://cdn.jsdelivr.net/npm/pouchdb#7.1.1/dist/pouchdb.min.js"></script>
<script src="https://github.com/pouchdb/pouchdb/releases/download/7.1.1/pouchdb.memory.min.js"></script>
<table id='actions' class='hide'>
<tr>
<td>
<button onclick='getAllArtists()'>All artists</button>
</td>
<td>
<button onclick='getAllAlbums()'>All albums</button>
</td>
<td>
<button onclick='getAllBowieAlbums()'>All albums by David Bowie</button>
</td>
</tr>
</table>
<div style='margin-top:2em'></div>
<pre id='results'></pre>