vacuum_max_eager_freeze_failure_rate

doc html

<p>
        Specifies the maximum number of pages (as a fraction of total pages in
        the relation) that <code class="command">VACUUM</code> may scan and
        <span class="emphasis"><em>fail</em></span> to set all-frozen in the visibility map
        before disabling eager scanning. A value of <code class="literal">0</code>
        disables eager scanning altogether. The default is
        <code class="literal">0.03</code> (3%).
       </p><p>
        Note that when eager scanning is enabled, only freeze failures
        count against the cap, not successful freezing. Successful page
        freezes are capped internally at 20% of the all-visible but not
        all-frozen pages in the relation. Capping successful page freezes helps
        amortize the overhead across multiple normal vacuums and limits the
        potential downside of wasted eager freezes of pages that are modified
        again before the next aggressive vacuum.
       </p><p>
        The setting can be overridden for individual tables by changing the
        <a class="link" href="/docs/18/sql-createtable.html#RELOPTION-VACUUM-MAX-EAGER-FREEZE-FAILURE-RATE">
        corresponding table storage parameter</a>.
        For more information on tuning vacuum's freezing behavior,
        see <a class="xref" href="/docs/18/routine-vacuuming.html#VACUUM-FOR-WRAPAROUND" title="24.1.5. Preventing Transaction ID Wraparound Failures">Section 24.1.5</a>.
       </p>

documentation revision

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extra desc

A value of 0.0 disables eager scanning and a value of 1.0 will eagerly scan up to 100 percent of the all-visible pages in the relation. If vacuum successfully freezes these pages, the cap is lower than 100 percent, because the goal is to amortize page freezing across multiple vacuums.