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        <version>9.7.1</version>
        <build-number>970001</build-number>
        <build-date>13-04-2023</build-date>
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<item>
            <title>[SERVER-9370] Optimize $match $unwind $match sequence in pipeline</title>
                <link>https://jira.mongodb.org/browse/SERVER-9370</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;When looking to do aggregations on a subset of documents in arrays, the current &quot;best&quot; practice is to do $match first, then $unwind then $match again.&lt;/p&gt;

&lt;p&gt;In other words, if our pipeline is:&lt;br/&gt;
{$match:{array.Member:&quot;value&quot;}},{$unwind:&quot;$array&quot;},{$match:{&quot;array.Member&quot;:&quot;value&quot;}}&lt;/p&gt;

&lt;p&gt;if we can optimize this into something that eliminates unneeded array elements along with unneeded fields this could be reduced to one $match and no $unwind.&lt;/p&gt;

&lt;p&gt;&lt;a href=&quot;https://jira.mongodb.org/secure/ViewProfile.jspa?name=redbeard0531&quot; class=&quot;user-hover&quot; rel=&quot;redbeard0531&quot;&gt;redbeard0531&lt;/a&gt; this is what we talked about yesterday, please re-write the description if I didn&apos;t capture what we were discussing accurately.&lt;/p&gt;</description>
                <environment></environment>
        <key id="72103">SERVER-9370</key>
            <summary>Optimize $match $unwind $match sequence in pipeline</summary>
                <type id="4" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14710&amp;avatarType=issuetype">Improvement</type>
                                            <priority id="3" iconUrl="https://jira.mongodb.org/images/icons/priorities/major.svg">Major - P3</priority>
                        <status id="6" iconUrl="https://jira.mongodb.org/images/icons/statuses/closed.png" description="The issue is considered finished, the resolution is correct. Issues which are closed can be reopened.">Closed</status>
                    <statusCategory id="3" key="done" colorName="success"/>
                                    <resolution id="3">Duplicate</resolution>
                                        <assignee username="-1">Unassigned</assignee>
                                    <reporter username="asya.kamsky@mongodb.com">Asya Kamsky</reporter>
                        <labels>
                            <label>optimization</label>
                    </labels>
                <created>Wed, 17 Apr 2013 15:47:38 +0000</created>
                <updated>Thu, 16 Mar 2023 11:03:26 +0000</updated>
                            <resolved>Wed, 20 May 2015 18:47:24 +0000</resolved>
                                                                    <component>Aggregation Framework</component>
                                        <votes>0</votes>
                                    <watches>5</watches>
                                                                                                                <comments>
                            <comment id="1884059" author="clemilsonbar@gmail.com" created="Sun, 6 May 2018 01:25:44 +0000"  >&lt;p&gt;Good evening!&lt;br/&gt;
What would be the solution to the case &lt;tt&gt;match: {array.Member: &quot;value&quot;&lt;/tt&gt;, {$ unwind: &quot;$ array&quot;}, {$ match: {&quot;array.&lt;/p&gt;</comment>
                            <comment id="876289" author="asya" created="Wed, 8 Apr 2015 20:25:44 +0000"  >&lt;p&gt;This is related to request to have $elemMatch or $filter in support of $map so it may become redundant in light of other possible optimizations.&lt;/p&gt;</comment>
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            <issuekey id="194912">SERVER-17943</issuekey>
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