fk_vs_ed

.gitignore

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+_site

_includes/fk_vs_ed/1.html

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+<div id="main">Inevitably, everyone who uses MongoDB comes to a choice between using multiple collections with id references or embedded documents</div>

_includes/fk_vs_ed/10.html

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+<div id="main">
+  <p>So, separate collections are good if you need to select individual documents, need more control over querying.</p>
+  <p>Embedded documents are good when you want the entire document, the document with a $slice of comments, or with no comments at all</p>
+</div>

_includes/fk_vs_ed/11.html

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+<div id="main">
+  <p>As a general rule, if you have a lot of "comments" or if they are large, a separate collection might be best.</p>
+  <p>Smaller documents tend to be a natural fit for embedding</p>
+</div>
+
+<div class="note">Virtual collection + positional field selection are relevant upcoming[ish] features</div>

_includes/fk_vs_ed/12.html

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+<div id="main">Remember, you can always change your mind. Trying each out is the best way to learn.</div>

_includes/fk_vs_ed/2.html

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+<h2>Use separate collections</h2>
+<pre>
+  &gt; db.posts.find();
+  {_id: 1, title: 'unicorns are awesome', ...}
+
+  &gt; db.comments.find();
+  {_id: 1, post_id: 1, title: 'i agree', ...}
+  {_id: 2, post_id: 1, title: 'they kill vampires too!', ...}
+</pre>
+
+<div id="or">- or -</div>
+
+<h2>Use embedded documents</h2>
+<pre>
+  &gt; db.posts.find();
+  {_id: 1, title: 'unicorns are awesome', ..., comments: [
+    {title: 'i agree', ...},
+    {title: 'they kill vampires too!', ...}
+  ]}
+</pre>

_includes/fk_vs_ed/3.html

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+<div id="main">
+  Don't worry, this means that <em>you get it</em>
+</div>
+
+<div class="note">Both solutions have their strengths and weaknesses. Learn to use both</div>

_includes/fk_vs_ed/4.html

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+<div id="main">Separate collections offer the greatest querying flexibility</div>
+
+<pre>
+  // sort comments however you want
+  > db.comments.find({post_id: 3}).sort({votes: -1}).limit(5)
+
+  // pull out one or more specific comment(s)
+  > db.comments.find({post_id: 3, user: 'leto'})
+
+  // get a all of a user's comments joining the posts to get the title
+  > var comments = db.comments.find({user: 'leto'}, {post_id: true, votes: true})
+  > var postIds = comments.map(function(c) { return c.post_id; });
+  > db.posts.find({_id: {$in: postIds}}, {title: true});
+</pre>

_includes/fk_vs_ed/5.html

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+<div id="main">Selecting embedded documents is more limited</div>
+
+<pre>
+  // you can select a range (useful for paging)
+  // but can't sort, so you are limited to the insertion order
+  > db.posts.find({_id: 3}, {comments: {$slice: [0, 5]}})
+
+  // you can select the post without any comments also
+  > db.posts.find({_id: 54}, {comments: -1})
+
+  // you <em>can't</em> use the update's position operator ($) for field selections
+  > db.posts.find({'comments.user': 'leto'}, {title: 1, 'comments.$': 1})
+</pre>
+
+<div class="note">(there are two separate features, currently in planning/development, which should address this)</div>

_includes/fk_vs_ed/6.html

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+<div id="main">A document, including all its embedded documents and arrays, cannot exceed 16MB</div>
+
+<div class="note">Don't freak out, The Complete Works of William Shakespeare is around 5.5MB</div>

_includes/fk_vs_ed/7.html

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+<div id="main">Separate collections require more work</div>
+
+<pre>
+  // finding a post + its comments is two queries and require extra work
+  // in your code to make it all pretty (or your ODM might do it for you)
+  > db.posts.find({_id: 9001});
+  > db.comments.find({post_id: 9001})
+</pre>
+
+<div class="note">this also takes [a bit] more space (+1 field, +1 index)</div>

_includes/fk_vs_ed/8.html

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+<div id="main">Embedded documents are easy and fast (single seek)</div>
+
+<pre>
+  // finding a post + its comments
+  > db.posts.find({_id: 9001});
+</pre>

_includes/fk_vs_ed/9.html

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+<div id="main">No big differences for inserts and updates</div>
+
+<pre>
+  // separate collection insert and update
+  > db.comments.insert({post_id: 43, title: 'i hate unicrons', user: 'dracula'});
+  > db.comments.update({_id: 4949}, {$set : {tiltle: 'i hate unicorns'}});
+
+  // embedded document insert and update
+  > db.posts.update({_id: 43}, {$push: {title: 'lol @ emo vampire', user: 'paul'}})
+  // this specific update requires that we store an _id with each comment
+  > db.posts.update( {'comments._id': 4949}, {$inc:{'comments.$.votes':1}})
+</pre>
+
+<div class="note">documents that grow, like inserting new comments, will have a <a href="/whats-a-padding-factor">padding factor</a></div>

_layouts/bare.html

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+<!DOCTYPE html>
+<html>
+  <head>
+    <title>{{ page.title }}</title>
+    <link href="/assets/css/main.css" rel="stylesheet" type="text/css">
+    {% for font in page.fonts %}
+      <link href="http://fonts.googleapis.com/css?family={{ font }}" rel="stylesheet" type="text/css">
+    {% endfor %}
+    {% if page.css %}<link href="styles.css" rel="stylesheet" type="text/css">{% endif %}
+    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.3/jquery.min.js" type="text/javascript"></script>
+    <script src="/assets/js/main.js" type="text/javascript"></script>
+    {% if page.multi %}<script src="/assets/js/multi.js" type="text/javascript"></script>{% endif %}
+  </head>
+  <body>
+    <div id="page">{{ content }}</div>
+    <img src="/assets/i/leaf.png" id="leaf" />
+    <div id="footer">
+      <a href="https://github.com/karlseguin/mongohelp">fork it</a>
+      <a href="http://openmymind.net">openmymind.net</a>
+    </div>
+  </body>
+</html>
+

assets/css/main.css

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+*{padding:0;margin:0;border:none;}
+body{font-family:verdana;background:#222;color:#fff;}
+a{text-decoration:none;color:#c35617;}
+
+#page a:hover{text-decoration:underline;}
+#multi{display:none;}
+#leaf{position:fixed;bottom:0;width:23px;height:50px;right:50px;cursor:pointer}
+#footer{height:35px;width:100%;position:absolute;bottom:0;display:none;text-align:right;}
+#footer a{color:#fff;padding:2px 0;margin-right:40px;text-decoration:none;border:2px solid transparent;}
+#footer a:hover{border-bottom-color:#fff}
+
+#next, #prev{position:absolute;top:0;right:0;height:100%;width:50px;color:#222;font-size:32px;}
+#prev{left:0;}
+#next:hover, #prev:hover {color:#111;background:#333;text-shadow:0 0 20px #fff;}
+#next:hover{border-left:1px solid #444;}
+#prev:hover{border-right:1px solid #444;}
+#next span, #prev span{position:absolute;top:50%;width:100%;text-align:center;}
+#next span:after{content:'\276f'}
+#prev span:after{content:'\276e'}
+#pager{position:fixed;bottom:25px;left:25px;color:#888;font-size:80%;}

assets/js/main.js

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+$(document).ready(function() {
+  //footer code
+  var $footer = $('#footer');  
+  var $leaf = $('#leaf').click(function() {
+    if ($footer.visible()) { hideFooter(); }
+    else { showFooter(); }
+  });
+  function hideFooter() {
+     $footer.slideUp();
+     $leaf.animate({bottom: '0px'}, 'normal');
+  }
+  function showFooter() {
+     $footer.slideDown();
+     $leaf.animate({bottom: '45px'}, 'normal');
+  }
+  $(document).keydown(function(e) {
+     if (e.keyCode == 27 && $footer.visible()) { 
+       hideFooter();
+     }
+  });
+
+  $('pre').each(function(i, pre) {
+    var $pre = $(pre);
+    $pre.html($pre.html().replace(/( *\/\/.*)/g, '<span class="comment">$1</span>'))
+  })
+});
+
+$.fn.visible = function() {
+  return this.is(':visible');
+};

foreign-keys-versus-embedded-documents/index.html

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+---
+layout: bare
+title: Foreign Keys vs Embedded Documents
+css: true
+multi: true
+fonts: [Chivo]
+---
+
+<div id="multi">
+  <div>{% include fk_vs_ed/1.html %}</div>
+  <div>{% include fk_vs_ed/2.html %}</div>
+  <div>{% include fk_vs_ed/3.html %}</div>
+  <div>{% include fk_vs_ed/4.html %}</div>
+  <div>{% include fk_vs_ed/5.html %}</div>
+  <div>{% include fk_vs_ed/6.html %}</div>
+  <div>{% include fk_vs_ed/7.html %}</div>
+  <div>{% include fk_vs_ed/8.html %}</div>
+  <div>{% include fk_vs_ed/9.html %}</div>
+  <div>{% include fk_vs_ed/10.html %}</div>
+  <div>{% include fk_vs_ed/11.html %}</div>
+  <div>{% include fk_vs_ed/12.html %}</div>
+</div>

foreign-keys-versus-embedded-documents/styles.css

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+h2{color:#ddd;font-weight:normal;margin-bottom:10px;}
+p{margin-bottom:35px;}
+pre{line-height:26px;margin-bottom:50px;}
+pre .comment{color:#5a5;}
+
+#page{font-family:Chivo,verdana;width:960px;margin:100px auto;font-size:16px;}
+#main{font-size:32px;text-align:center;line-height:50px;margin-bottom:50px;}
+body.first #main, body.last #main{padding:50px 0;border:solid #444;border-width:6px 0;}
+body.first #main:first-letter, body.last #main:first-letter{font-size:75px;}
+#or{font-size:50px;text-align:center;margin-bottom:50px;color:#ccc;text-shadow:0 0 3px #000;}
+
+.note{font-size:20px;color:#ccc;text-align:right;margin-top:10px;font-style:italic;}

index.html

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-My GitHub Page
+---
+layout: bare
+title: MongoDB Help
+---