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    <description>This file is an XML representation of an issue</description>
    <language>en-us</language>    <build-info>
        <version>9.7.1</version>
        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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<item>
            <title>[DOCS-15803] Rename &quot;cardinality&quot; term for shard key considerations</title>
                <link>https://jira.mongodb.org/browse/DOCS-15803</link>
                <project id="10380" key="DOCS">Documentation</project>
                    <description>&lt;p&gt;I was reviewing the design document for an upcoming project &quot;Add and expose metrics to make shard key selection easier&quot;, when I noticed we use the term &quot;cardinality&quot; to mean &quot;number of unique values&quot;: &lt;br/&gt;
&lt;a href=&quot;https://www.mongodb.com/docs/manual/core/sharding-choose-a-shard-key/#std-label-shard-key-range&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://www.mongodb.com/docs/manual/core/sharding-choose-a-shard-key/#std-label-shard-key-range&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;This is mostly fine, and somewhat consistent with set theory (as in &lt;a href=&quot;https://en.wikipedia.org/wiki/Cardinality&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;the wiki page&lt;/a&gt;), but are the shard key values a set? I would think they are more like a multi-set or vector, since values repeat.&lt;/p&gt;

&lt;p&gt;We are underway in making a new query optimizer which will estimate the &quot;cardinality&quot; of different query plan sub-segments. In that context, the &quot;cardinality&quot; will mean &quot;number of values&quot;, &lt;em&gt;not&lt;/em&gt; &quot;number of &lt;b&gt;unique&lt;/b&gt; values&quot;. This is all going to get confusing I think. &lt;/p&gt;

&lt;p&gt;I&apos;m open to suggestions here but I would propose the &quot;choose a shard key&quot; page would use &quot;number of distinct values&quot; instead of cardinality.&lt;/p&gt;</description>
                <environment></environment>
        <key id="2224030">DOCS-15803</key>
            <summary>Rename &quot;cardinality&quot; term for shard key considerations</summary>
                <type id="3" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14718&amp;avatarType=issuetype">Task</type>
                                            <priority id="4" iconUrl="https://jira.mongodb.org/images/icons/priorities/minor.svg">Minor - P4</priority>
                        <status id="10045" iconUrl="https://jira.mongodb.org/images/icons/statuses/generic.png" description="">Ready for Work</status>
                    <statusCategory id="2" key="new" colorName="default"/>
                                    <resolution id="-1">Unresolved</resolution>
                                        <assignee username="joseph.dougherty@mongodb.com">Joseph Dougherty</assignee>
                                    <reporter username="charlie.swanson@mongodb.com">Charlie Swanson</reporter>
                        <labels>
                            <label>query</label>
                            <label>sharding</label>
                    </labels>
                <created>Wed, 4 Jan 2023 19:31:50 +0000</created>
                <updated>Tue, 29 Aug 2023 16:28:42 +0000</updated>
                                                                            <component>manual</component>
                    <component>Server</component>
                        <due></due>
                            <votes>0</votes>
                                    <watches>4</watches>
                                                                                                                <comments>
                            <comment id="5159299" author="JIRAUSER1257483" created="Wed, 1 Feb 2023 16:58:39 +0000"  >&lt;p&gt;Thanks for opening this issue, &lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=charlie.swanson%40mongodb.com&quot; class=&quot;user-hover&quot; rel=&quot;charlie.swanson@mongodb.com&quot;&gt;charlie.swanson@mongodb.com&lt;/a&gt;! I like the idea of simplifying our terminology here a bit. &lt;br/&gt;
I think we should also consider:&lt;/p&gt;
&lt;ul class=&quot;alternate&quot; type=&quot;square&quot;&gt;
	&lt;li&gt;other part of the corpus may still use the &quot;cardinality&quot; terminology&lt;/li&gt;
	&lt;li&gt;there are plenty of supplementary materials that will continue to use this language (for example, &lt;a href=&quot;https://www.youtube.com/watch?v=8sk75-6W0ik&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;Demystifying Sharding in MongoDB&lt;/a&gt; &#8211; See attached screenshot.)&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;Let&apos;s consider making this a discussion point at the next 6WR for this issue. I&apos;d like to hear what folks think about this.&lt;/p&gt;

&lt;p&gt;&lt;span class=&quot;image-wrap&quot; style=&quot;&quot;&gt;&lt;a id=&quot;429429_thumb&quot; href=&quot;https://jira.mongodb.org/secure/attachment/429429/429429_Screen+Shot+2023-02-01+at+11.30.04+AM.png&quot; title=&quot;Screen Shot 2023-02-01 at 11.30.04 AM.png&quot; file-preview-type=&quot;image&quot; file-preview-id=&quot;429429&quot; file-preview-title=&quot;Screen Shot 2023-02-01 at 11.30.04 AM.png&quot;&gt;&lt;img src=&quot;https://jira.mongodb.org/secure/thumbnail/429429/_thumb_429429.png&quot; style=&quot;border: 0px solid black&quot; role=&quot;presentation&quot;/&gt;&lt;/a&gt;&lt;/span&gt;&lt;/p&gt;

&lt;p&gt;Thanks!&lt;br/&gt;
Joe&lt;/p&gt;</comment>
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                            <attachment id="429429" name="Screen Shot 2023-02-01 at 11.30.04 AM.png" size="929488" author="joseph.dougherty@mongodb.com" created="Wed, 1 Feb 2023 16:56:31 +0000"/>
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