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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-68520] Investigate performance of push down of low-selectivity per-path filters</title>
                <link>https://jira.mongodb.org/browse/SERVER-68520</link>
                <project id="10000" key="SERVER">Core Server</project>
                    <description>&lt;p&gt;Zig-zag search naturally favors high-selectivity filters, however, if &lt;em&gt;all&lt;/em&gt; filters are low selectivity, the perf of zig-zag search might be worse than iterating over the filtered columns in parallel. We should investigate how bad it becomes and whether we need to take any mitigating actions (e.g. replacing short-distance seeks with iterating either inside the stage or at the storage level).&lt;/p&gt;

&lt;p&gt;&amp;#8212;&lt;/p&gt;

&lt;p&gt;From my experiments on small datasets, the cost of a &quot;seek&quot; is about twice the cost of a &quot;next&quot; which means that the filters have to have really low selectivity to benefit from replacing seeks with next (on a collection with 10^5 docs, a query with 7 always true filters and one filter that let through 30% of records performed about the same with seeks and nexts). The seeks would likely be more relatively expensive on indexes that don&apos;t fit into memory but we&apos;d still have to use heuristics in the column_scan stage to pick between the two, such as the distance between the record ids, and I doubt the heuristics can be reliable enough to be useful.&#160;&lt;/p&gt;</description>
                <environment></environment>
        <key id="2105153">SERVER-68520</key>
            <summary>Investigate performance of push down of low-selectivity per-path filters</summary>
                <type id="3" iconUrl="https://jira.mongodb.org/secure/viewavatar?size=xsmall&amp;avatarId=14718&amp;avatarType=issuetype">Task</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="9">Done</resolution>
                                        <assignee username="irina.yatsenko@mongodb.com">Irina Yatsenko</assignee>
                                    <reporter username="irina.yatsenko@mongodb.com">Irina Yatsenko</reporter>
                        <labels>
                    </labels>
                <created>Tue, 2 Aug 2022 21:31:54 +0000</created>
                <updated>Wed, 19 Oct 2022 16:06:28 +0000</updated>
                            <resolved>Wed, 19 Oct 2022 16:06:28 +0000</resolved>
                                                                                        <votes>0</votes>
                                    <watches>2</watches>
                                                                                                                <comments>
                            <comment id="4913054" author="JIRAUSER1259274" created="Wed, 19 Oct 2022 16:06:28 +0000"  >&lt;p&gt;Per the completed investigation have decided not to optimize &quot;seeks&quot; vs &quot;nexts&quot; at this time.&lt;/p&gt;</comment>
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