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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-54750] [SBE] Rename cmp3w VM instruction and inspect usages in the SBE codebase</title>
                <link>https://jira.mongodb.org/browse/SERVER-54750</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;SBE VM has two types of comparison instructions:&lt;/p&gt;
&lt;ul&gt;
	&lt;li&gt;&lt;tt&gt;less, lessEq, greater, greaterEq, eq, neq&lt;/tt&gt; implemented using &lt;a href=&quot;https://github.com/mongodb/mongo/blob/322d0734542dc6f140902eea1d4ed5c5b28b596a/src/mongo/db/exec/sbe/vm/vm.h#L46&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;genericCompare&lt;/a&gt; function. These instructions compare values using MQL semantics.&lt;/li&gt;
	&lt;li&gt;&lt;tt&gt;cmp3w&lt;/tt&gt; implemented using &lt;a href=&quot;https://github.com/mongodb/mongo/blob/322d0734542dc6f140902eea1d4ed5c5b28b596a/src/mongo/db/exec/sbe/values/value.cpp#L699&quot; class=&quot;external-link&quot; target=&quot;_blank&quot; rel=&quot;nofollow noopener&quot;&gt;value::compareValue&lt;/a&gt; function. This instructions performs 3-way comparison (spaceship operator), but does &lt;b&gt;not&lt;/b&gt; follow MQL semantics. The behaviour of this instruction is closer to SQL comparison semantics.&lt;/li&gt;
&lt;/ul&gt;


&lt;p&gt;Having two kinds of instructions is intentional because we want to keep SBE VM generic to be extendable and (possibly) execute non-MQL queries in the future. But it can be misleading for the developer since &lt;tt&gt;cmp3w&lt;/tt&gt; and other comparison instructions are not interchangeable. We should rename &lt;tt&gt;cmp3w&lt;/tt&gt; to make it clear that this instruction does &lt;b&gt;not&lt;/b&gt; implement MQL semantics. We should also add documentation to the respective places and expect all usages of &lt;tt&gt;cmp3w&lt;/tt&gt; in the SBE codebase for correctness purposes.&lt;/p&gt;

&lt;p&gt;It seems that they are certain types supported by &lt;tt&gt;value::compareValue&lt;/tt&gt; and not supported by &lt;tt&gt;genericCompare&lt;/tt&gt;. We should also fix this in the scope of this ticket.&lt;/p&gt;</description>
                <environment></environment>
        <key id="1632026">SERVER-54750</key>
            <summary>[SBE] Rename cmp3w VM instruction and inspect usages in the SBE codebase</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-execution">Backlog - Query Execution</assignee>
                                    <reporter username="nikita.lapkov@mongodb.com">Nikita Lapkov</reporter>
                        <labels>
                            <label>sbe-post-v1</label>
                    </labels>
                <created>Wed, 24 Feb 2021 11:31:44 +0000</created>
                <updated>Tue, 6 Dec 2022 01:33:48 +0000</updated>
                                                                                                <votes>0</votes>
                                    <watches>1</watches>
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            <issuekey id="1643164">SERVER-55029</issuekey>
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