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POMongoDB performance: newsfeed architecture, subscribers, comments
 

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  1. POMongoDB performance: newsfeed architecture, subscribers, comments
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    <p>I use MongoDB + PHP for a "facebookish" newsfeed with different kinds of feeds (post, photo, poll, etc.) and with comments.</p> <p>Each feed belongs to some "channel" - currently it could be <em>user</em> or <em>group</em> (there may be more containers in future).</p> <p>Any user can subscribe for any channel or unsibscribe from it.</p> <p>Now let's say there're tons of channels and tons of feeds. What is the best structure for channels/feeds/comments?</p> <p>I'm thinking about two approaches:</p> <p><strong>1) Feeds collection with list of subscribers in each feed:</strong></p> <pre><code>feeds: [ {date_added: ..., last_update: ..., title: ..., text: ..., channel: ..., channel_subscribers: [...], comments_subscribers: [...], comments: [...] }, {...}, {...}, {...} ] </code></pre> <p>If I want to get last feeds: </p> <pre><code>db.feeds.find({date_added: "this week", channel_subscribers: "my_login"}); </code></pre> <p>If I want to get feeds with new comments:</p> <pre><code>db.feeds.find({last_update: "this week", comments_subscribers: "my_login"}); </code></pre> <p><em>Pros:</em></p> <ul> <li>Simple and fast readings?</li> </ul> <p><em>Cons:</em></p> <ul> <li>When I want to subscribe/unsibscribe for/from a channel, I have to run trough all feeds and push/pull my name from list of channel_subscribers; it could be slow if I have tons of feeds</li> </ul> <p><strong>2) Separate "channels" collection:</strong> Same thing but keep list of subscribers in channel collection: </p> <pre><code>channels: [ {channel_id:..., last_update: ..., subscribers: [...]}, {channel_id:..., last_update: ..., subscribers: [...]} ] </code></pre> <p>First I have to query last updated channels:</p> <pre><code>subscribes = db.channels.find({last_update: "today", subscribers: "my_login"}) </code></pre> <p>Now find my feeds:</p> <pre><code>db.feeds.find({channel: {$in: subscribes}], date_added: "today"}) </code></pre> <p><em>Pros:</em></p> <ul> <li>Simple, fast and more safe subscribing/unsubsribing;</li> </ul> <p><em>Cons:</em></p> <ul> <li>I feel I should avoid <strong>$in</strong> because it's slow(?), especially when I have lots of subscribes to put inside of this operator.</li> </ul> <p><strong>3) Keep user subscribes in users collection (so each user has an array of his own subscribes)</strong> </p> <pre><code>users: [ {_id: ..., login: ..., email: ..., subscribes: [...]} ] </code></pre> <p><em>Cons:</em> - in this case we'll have even bigger array to put inside of $in than in previous (#2) approach.</p> <p><strong>4) Your suggestions?</strong></p>
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      1. POMongoDB performance: newsfeed architecture, subscribers, comments
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    1. COMongoDB recommends that they data structure you use is geared toward your most common use case. Still having a bit of difficulty understanding your current structure though. Can you elaborate on your structure a bit more?
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      1. USJohnP
    2. COOK let me simplify my question. What would be faster: keep a list of my subscribes and then put that big array inside of "$in" operator and get my feeds by that; OR - get feeds by my login name - when every feed has a big (~2000) array of subscribers in it? (is it good practise to create multikey index on such big arrays?)
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      1. USoyatek
    3. COI think it's a bad idea to keep the subscribers in the feeds itself. Might be better to link them. This looks a bit SQLey, but it makes for easy searching and removal as well.
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      1. USJohnP
 

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