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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-14400] Using $min and $max on shard key doesn&apos;t target queries</title>
                <link>https://jira.mongodb.org/browse/SERVER-14400</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;Using &lt;tt&gt;$gte&lt;/tt&gt; and &lt;tt&gt;$lt&lt;/tt&gt; on the shard key fields inside a query will cause it the query to be targeted to only the appropriate shards.&lt;/p&gt;

&lt;p&gt;However, using the &lt;tt&gt;$min&lt;/tt&gt; and &lt;tt&gt;$max&lt;/tt&gt; query operators (while hinting on the shard key) doesn&apos;t target the query to the relevant shard(s) in the same way.  The explain()  is missing indexBounds in this case, which may be the cause or at least related?&lt;/p&gt;

&lt;p&gt;I also tested 2.4.10 and 2.7.2 and the issue is present both.&lt;/p&gt;</description>
                <environment></environment>
        <key id="144760">SERVER-14400</key>
            <summary>Using $min and $max on shard key doesn&apos;t target queries</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="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="kevin.pulo@mongodb.com">Kevin Pulo</reporter>
                        <labels>
                            <label>QFB</label>
                            <label>asya</label>
                            <label>neweng</label>
                            <label>query-44-grooming</label>
                    </labels>
                <created>Tue, 1 Jul 2014 03:03:09 +0000</created>
                <updated>Wed, 18 Oct 2023 00:06:47 +0000</updated>
                                            <version>2.4.10</version>
                    <version>2.6.3</version>
                    <version>2.7.2</version>
                                                    <component>Querying</component>
                    <component>Sharding</component>
                                        <votes>4</votes>
                                    <watches>15</watches>
                                                                                                                <comments>
                            <comment id="5786516" author="JIRAUSER1275507" created="Wed, 18 Oct 2023 00:06:47 +0000"  >&lt;p&gt;Using $min/$max/$hint may be useful for operations that need to process all documents in a collection that uses hashed sharding, especially when the collection is very large and the operation needs to be split into many smaller pieces.&lt;/p&gt;

&lt;p&gt;For example, consider a collection foo that is sharded by {_id: &quot;hashed&quot;}. The collection has millions of documents, and we want to gradually visit them all, in small (but potentially parallel) batches - say 100 at a time.&lt;/p&gt;

&lt;p&gt;We can do this by partitioning the range of a 64-bit long (used for hashed sharding) into sub-ranges such that each sub-range should have approximately 100 documents in it. Then the query for a single batch might look like this:&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.foo.find().min({_id: &lt;/span&gt;&lt;span style=&quot;color: #009900; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;3989082343&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;}).max({_id: &lt;/span&gt;&lt;span style=&quot;color: #009900; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;43985498398&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;}).hint(_id: &lt;/span&gt;&lt;span style=&quot;color: blue; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;&quot;hashed&quot;&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;)&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;Another benefit of doing it this way is that each batch can theoretically be targeted to a small number of shards - but that doesn&apos;t actually happen.&lt;/p&gt;

&lt;p&gt;The impact of this scales with the size of the MongoDB deployment, and can be quite significant in clusters with 100+ shards and collections with billions of documents.&lt;/p&gt;</comment>
                            <comment id="646677" author="kevin.pulo@10gen.com" created="Thu, 3 Jul 2014 00:25:24 +0000"  >&lt;blockquote&gt;&lt;p&gt;results are correct ... the only issue is that the query is not targeted when it could be.&lt;/p&gt;&lt;/blockquote&gt;

&lt;p&gt;Yes, exactly.&lt;/p&gt;

&lt;p&gt;I also tested against a standalone, and the behaviour (wrt indexBounds) is the same - with $gte/$lt, there are indexBounds, with $min/$max there are no indexBounds.  Despite this, in both cases, only the relevant range of the index is scanned.&lt;/p&gt;

&lt;p&gt;The use case (for me) is trying to write (simple) mongo shell code that works with documents within each chunk range.  I could look up the shard and connect directly to it (and that&apos;s what orphanage.js does), but it&apos;s a pain and complicates the code considerably.  For example, I would like to be be able to write the following code (to check for empty chunks - yes, I know 2.6 has features for this, but this is for 2.4, and this is just one example) and have it correctly scale by numchunks, not numchunks * numshards.&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;cfg = db.getSiblingDB(&lt;/span&gt;&lt;span style=&quot;color: blue; font-family: &apos;Consolas&apos;, &apos;Bitstream Vera Sans Mono&apos;, &apos;Courier New&apos;, Courier, monospace !important;&quot;&gt;&quot;config&quot;&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;);&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;cfg.chunks.find().forEach(&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;function&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;(c) { &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;if&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; ( ! db.getMongo().getCollection(c.ns).find().hint(cfg.collections.findOne({_id:c.ns}).key).min(c.min).max(c.max).hasNext()) printjson(c) })&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;To do this by connecting to each shard individually, or trying to rewrite the chunk min/max as $gte/$lt on each component, would stop this from being a simple one-liner.&lt;/p&gt;</comment>
                            <comment id="641101" author="asya" created="Tue, 1 Jul 2014 21:04:45 +0000"  >
&lt;p&gt;Just tested this - the query is correct, results are correct and the explain looks correct to me as well, except for index bounds being missing, however, that matches the explain run directly on a primary of the shard so all mongos is doing is merging the results of explain.&lt;/p&gt;

&lt;p&gt;I think the only issue is that the query is not targeted when it could be.&lt;/p&gt;
</comment>
                            <comment id="640912" author="greg_10gen" created="Tue, 1 Jul 2014 18:48:49 +0000"  >&lt;p&gt;This is a pretty rarely-used query (and one with strange semantics) - is there a certain type of client operation this impacts badly?  Generally this would result in very fast index lookups with no results on all but one shard.&lt;/p&gt;

&lt;p&gt;Also, just to clarify, there&apos;s no correctness problem aside from bounds not showing up in explain?  Do they show up when run against a single server?&lt;/p&gt;</comment>
                    </comments>
                <issuelinks>
                            <issuelinktype id="10011">
                    <name>Depends</name>
                                                                <inwardlinks description="is depended on by">
                                        <issuelink>
            <issuekey id="332523">SPARK-98</issuekey>
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                            <issuelinktype id="10012">
                    <name>Related</name>
                                            <outwardlinks description="related to">
                                        <issuelink>
            <issuekey id="371891">SERVER-28667</issuekey>
        </issuelink>
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