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    <title>MongoDB Jira</title>
    <link>https://jira.mongodb.org</link>
    <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-15083] Indexing $exists</title>
                <link>https://jira.mongodb.org/browse/DOCS-15083</link>
                <project id="10380" key="DOCS">Documentation</project>
                    <description>&lt;p&gt;Due to &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-12869&quot; title=&quot;Index null values and missing values differently&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-12869&quot;&gt;SERVER-12869&lt;/a&gt;, normal indexes require a FETCH for exists:false and exists:true queries.&lt;/p&gt;

&lt;p&gt;We have a section in our documentation on &lt;a href=&quot;https://docs.mongodb.com/manual/reference/operator/query/exists/#use-a-sparse-index-to-improve--exists-performance&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;Using sparse indexes to improve exists performance&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;As &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-12869&quot; title=&quot;Index null values and missing values differently&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-12869&quot;&gt;SERVER-12869&lt;/a&gt; has been open since 2014, would it make sense to expand the discussion of indexing exists to include the implications of that ticket:&lt;/p&gt;
&lt;p/&gt;
&lt;div id=&quot;syntaxplugin&quot; class=&quot;syntaxplugin&quot; style=&quot;border: 1px dashed #bbb; border-radius: 5px !important; overflow: auto; max-height: 30em;&quot;&gt;
&lt;table cellspacing=&quot;0&quot; cellpadding=&quot;0&quot; border=&quot;0&quot; width=&quot;100%&quot; style=&quot;font-size: 1em; line-height: 1.4em !important; font-weight: normal; font-style: normal; color: black;&quot;&gt;
		&lt;tbody &gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;  margin-top: 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;We can safely use an index on $exists queries in the following cases:&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;{a:{ $exists:&lt;/span&gt;&lt;span style=&quot;color: #006699; font-weight: bold; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;true&lt;/span&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt; }} - normal index helps, but we must still fetch&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;{a:{ $exists:&lt;/span&gt;&lt;span style=&quot;color: #006699; font-weight: bold; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;true&lt;/span&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt; }} - sparse index is exact&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;{a:{ $exists:&lt;/span&gt;&lt;span style=&quot;color: #006699; font-weight: bold; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;false&lt;/span&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt; }} - normal index requires a fetch&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
				&lt;tr id=&quot;syntaxplugin_code_and_gutter&quot;&gt;
						&lt;td  style=&quot; line-height: 1.4em !important; padding: 0em; vertical-align: top;&quot;&gt;
					&lt;pre style=&quot;font-size: 1em; margin: 0 10px;   margin-bottom: 10px;  width: auto; padding: 0;&quot;&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;{a:{ $exists:&lt;/span&gt;&lt;span style=&quot;color: #006699; font-weight: bold; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;false&lt;/span&gt;&lt;span style=&quot;color: black; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt; }} - never &lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
			&lt;/tbody&gt;
&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;Based on customer feedback, this was not clear from the documentation.&lt;/p&gt;</description>
                <environment></environment>
        <key id="1975960">DOCS-15083</key>
            <summary>Indexing $exists</summary>
                <type id="4" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14710&amp;avatarType=issuetype">Improvement</type>
                                            <priority id="4" iconUrl="https://jira.mongodb.org/images/icons/priorities/minor.svg">Minor - P4</priority>
                        <status id="6" iconUrl="https://jira.mongodb.org/images/icons/statuses/closed.png" description="The issue is considered finished, the resolution is correct. Issues which are closed can be reopened.">Closed</status>
                    <statusCategory id="3" key="done" colorName="success"/>
                                    <resolution id="13201">Fixed</resolution>
                                        <assignee username="joseph.dougherty@mongodb.com">Joseph Dougherty</assignee>
                                    <reporter username="ronan.merrick@mongodb.com">Ronan Merrick</reporter>
                        <labels>
                            <label>Onboarding</label>
                    </labels>
                <created>Wed, 2 Feb 2022 17:28:50 +0000</created>
                <updated>Mon, 30 Oct 2023 22:14:13 +0000</updated>
                            <resolved>Fri, 29 Apr 2022 15:11:24 +0000</resolved>
                                                    <fixVersion>Server_Docs_20231030</fixVersion>
                                    <component>manual</component>
                    <component>Server</component>
                        <due>Fri, 29 Apr 2022 00:00:00 +0000</due>
                            <votes>0</votes>
                                    <watches>2</watches>
                                                                                                                <comments>
                            <comment id="4516351" author="xgen-internal-githook" created="Fri, 29 Apr 2022 14:49:38 +0000"  >&lt;p&gt;Author:&lt;/p&gt;
{&apos;name&apos;: &apos;jmd-mongo&apos;, &apos;email&apos;: &apos;73852296+jmd-mongo@users.noreply.github.com&apos;, &apos;username&apos;: &apos;jmd-mongo&apos;}
&lt;p&gt;Message: &lt;a href=&quot;https://jira.mongodb.org/browse/DOCS-15083&quot; title=&quot;Indexing $exists&quot; class=&quot;issue-link&quot; data-issue-key=&quot;DOCS-15083&quot;&gt;&lt;del&gt;DOCS-15083&lt;/del&gt;&lt;/a&gt; clarifies how sparse/non-sparse indexes affect exists queries (#1016)&lt;/p&gt;

&lt;ul&gt;
	&lt;li&gt;clarifies how sparse/non-sparse indexes affect exists queries&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;combine into one paragraph&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;review feedback&lt;/li&gt;
&lt;/ul&gt;


&lt;ul&gt;
	&lt;li&gt;external review&lt;br/&gt;
Branch: master&lt;br/&gt;
&lt;a href=&quot;https://github.com/10gen/docs-mongodb-internal/commit/ab76d8f88b6ac8f0808719c270a0c5cd2e6b1675&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;https://github.com/10gen/docs-mongodb-internal/commit/ab76d8f88b6ac8f0808719c270a0c5cd2e6b1675&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
</comment>
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