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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>[SERVER-17266] count command performance optimization should support more complex queries</title>
                <link>https://jira.mongodb.org/browse/SERVER-17266</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;With a valid index to cover the queries, the following in the shell:&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;
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						&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;   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;db.coll.count({foo:{$&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;in&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;:[1,2]}});&lt;/span&gt;&lt;/pre&gt;
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&lt;p/&gt;
&lt;p&gt;Is consistently upwards of an order of magnitude slower than:&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;   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;db.coll.count({foo:1}) + db.coll.count({foo:2})&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
		&lt;/tr&gt;
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&lt;/table&gt;
&lt;/div&gt;
&lt;p/&gt;

&lt;p&gt;In my test, where 700k documents match each predicate, the first variant takes ~1500ms to run, the second variant (without $in) takes ~120ms.&lt;/p&gt;

&lt;p&gt;To reproduce requires no special documents, surrounding indexes don&apos;t matter, the index in use can be compound (include other fields), other documents present in the collection don&apos;t matter (overall cardinality is irrelevant, though the effect requires low cardinality for the items in test purely to measure it temporally).&lt;/p&gt;

&lt;p&gt;The effect described above does not apply to a regular query, it applies only to the count command. Thus, &quot;explain&quot; does not reveal the reason why in 2.6.5, however, it is possible to observe a difference in the plans by running count a newfangled 3.0 explainable collection.&lt;/p&gt;</description>
                <environment></environment>
        <key id="183854">SERVER-17266</key>
            <summary>count command performance optimization should support more complex queries</summary>
                <type id="4" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14710&amp;avatarType=issuetype">Improvement</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="10038" iconUrl="https://jira.mongodb.org/images/icons/subtask.gif" description="">Backlog</status>
                    <statusCategory id="2" key="new" colorName="default"/>
                                    <resolution id="-1">Unresolved</resolution>
                                        <assignee username="backlog-query-optimization">Backlog - Query Optimization</assignee>
                                    <reporter username="andrew.ryder@mongodb.com">Andrew Ryder</reporter>
                        <labels>
                            <label>graphquery</label>
                    </labels>
                <created>Thu, 12 Feb 2015 04:28:00 +0000</created>
                <updated>Tue, 6 Dec 2022 04:55:44 +0000</updated>
                                            <version>2.6.5</version>
                    <version>3.0.0-rc8</version>
                                                    <component>Querying</component>
                                        <votes>6</votes>
                                    <watches>33</watches>
                                                                                                                <comments>
                            <comment id="3634239" author="JIRAUSER1258833" created="Thu, 25 Feb 2021 03:13:28 +0000"  >&lt;p&gt;Hello, I am also using mongodb. Encountered a similar problem, why does my table count of one million data take 3 seconds.&lt;/p&gt;</comment>
                            <comment id="2492123" author="asya" created="Mon, 21 Oct 2019 09:17:25 +0000"  >&lt;p&gt;Reopening this ticket specifically to track the optimization for $in when the index is NOT multikey.&lt;/p&gt;</comment>
                            <comment id="1675109" author="asya" created="Mon, 18 Sep 2017 07:42:11 +0000"  >&lt;p&gt;All the examples in this ticket are fixed, probably via work in &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-27822&quot; title=&quot;Count plans sometimes don&amp;#39;t need a FETCH&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-27822&quot;&gt;&lt;del&gt;SERVER-27822&lt;/del&gt;&lt;/a&gt;.&lt;/p&gt;

&lt;p&gt;Closing as dup, please re-open if I missed any cases.&lt;/p&gt;</comment>
                            <comment id="831318" author="andrew.ryder@10gen.com" created="Wed, 18 Feb 2015 02:24:53 +0000"  >&lt;p&gt;To apply the optimization to &lt;tt&gt;$in&lt;/tt&gt; would need to check the &lt;tt&gt;isMultiKey&lt;/tt&gt; flag on the indexstats to ensure there is no possibility of duplicate matches.&lt;/p&gt;</comment>
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                    <name>Duplicate</name>
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            <issuekey id="349439">SERVER-27822</issuekey>
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                                        <issuelink>
            <issuekey id="327745">SERVER-26831</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="264634">SERVER-22574</issuekey>
        </issuelink>
            <issuelink>
            <issuekey id="970620">SERVER-44032</issuekey>
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                    <name>Related</name>
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                                                        </outwardlinks>
                                                                <inwardlinks description="is related to">
                                        <issuelink>
            <issuekey id="182012">SERVER-17148</issuekey>
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