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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-3892] consider multiple candidate index scans, potentially with intersection, in cases of distinct ranges on a multikey index</title>
                <link>https://jira.mongodb.org/browse/SERVER-3892</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;When an index is multikey and a query specifies two predicates on an indexed field, and the index bounds produced by one predicate do not entirely include the index bounds produced by the other predicate, the index bounds for only one predicate will be used for the query.  Generally the index bounds for the first predicate parsed are chosen, while the index bounds for the other predicate are ignored.&lt;/p&gt;

&lt;p&gt;This behavior was requested here &amp;lt;&lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-958?focusedCommentId=19122&amp;amp;page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-19122&quot; class=&quot;external-link&quot; rel=&quot;nofollow&quot;&gt;https://jira.mongodb.org/browse/SERVER-958?focusedCommentId=19122&amp;amp;page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-19122&lt;/a&gt;&amp;gt;.&lt;/p&gt;

&lt;p&gt;We could instead attempt to use the index bounds for both predicates to evaluate a query like this.  For example we could create a separate query plan for each predicate&apos;s index bounds and analyze/run each plan in the query optimizer.  Or we could create a plan with an index and over ranges for both index bounds.&lt;/p&gt;

&lt;p&gt;In the example below, the predicate a:2 produces index bounds [[ 2, 2 ]] while the predicate a:{ $gt:5 } produces index bounds [[ 5, max_number ]].  Currently the first query only uses the index bounds [[ 2, 2 ]] only while the second query uses the index bounds [[ 5, max_number ]] only.&lt;/p&gt;

&lt;p&gt;Aaron&lt;/p&gt;

&lt;p&gt;--------------------------------------------------&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;db.foo.save({a: [1, 2, 3, 4, 5]})&lt;/span&gt;&lt;/pre&gt;
			&lt;/td&gt;
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				&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;db.foo.save({a: [1, 2, 3, 4, 5, 6]})&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;db.foo.ensureIndex({a: 1})&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;&amp;nbsp;&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;db.foo.find({$and: [{a: 2}, {a: {$gt: 5}}]}).explain()&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;db.foo.find({$and: [{a: {$gt: 5}, {a: 2}}]}).explain()&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;The first of these queries scans two objects, while the second scans only one. Is there a way to implement this that provides a more consistent result? If we had a million documents with {a: 2}, then the first query would scan a lot of documents.&lt;/p&gt;</description>
                <environment></environment>
        <key id="22461">SERVER-3892</key>
            <summary>consider multiple candidate index scans, potentially with intersection, in cases of distinct ranges on a multikey index</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="david.storch@mongodb.com">David Storch</assignee>
                                    <reporter username="kbanker">Kyle Banker</reporter>
                        <labels>
                    </labels>
                <created>Fri, 16 Sep 2011 20:27:28 +0000</created>
                <updated>Thu, 14 Apr 2016 15:19:17 +0000</updated>
                            <resolved>Mon, 26 Jan 2015 19:40:24 +0000</resolved>
                                                                    <component>Querying</component>
                                        <votes>0</votes>
                                    <watches>3</watches>
                                                                                                                <comments>
                            <comment id="813444" author="david.storch" created="Mon, 26 Jan 2015 19:39:58 +0000"  >&lt;p&gt;This ticket describes a problem that still exists in the new query system written for 2.6. For the new query system, this issue is being tracked under &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-16042&quot; title=&quot;Optimise $all/$and to select smallest subset as initial index bounds&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-16042&quot;&gt;&lt;del&gt;SERVER-16042&lt;/del&gt;&lt;/a&gt;. Since &lt;a href=&quot;https://jira.mongodb.org/browse/SERVER-16042&quot; title=&quot;Optimise $all/$and to select smallest subset as initial index bounds&quot; class=&quot;issue-link&quot; data-issue-key=&quot;SERVER-16042&quot;&gt;&lt;del&gt;SERVER-16042&lt;/del&gt;&lt;/a&gt; ticket is newer and has more context, I am closing this one as a duplicate.&lt;/p&gt;</comment>
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                            <issuelinktype id="10012">
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            <issuekey id="66858">SERVER-8790</issuekey>
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