Re: Why doesn't GiST VACUUM require a super-exclusive lock, like nbtree VACUUM?

<div> </div><div> </div><div>04.11.2021, 04:33, "Peter Geoghegan" &lt;pg@bowt.ie&gt;:</div><blockquote><p>But what about index-only scans, which GiST also supports? I think<br />that the rules are different there, even though index-only scans use<br />an MVCC snapshot.</p></blockquote><p>Let's enumerate steps how things can go wrong.</p><p>Backend1: Index-Only scan returns tid and xs_hitup with index_tuple1 on index_page1 pointing to heap_tuple1 on page1</p><p>Backend2: Remove index_tuple1 and heap_tuple1</p><div><div>Backend3: Mark page1 all-visible</div><div>Backend1: Thinks that page1 is all-visible and shows index_tuple1 as visible</div><div> </div><div>To avoid this Backend1 must hold pin on index_page1 until it's done with checking visibility, and Backend2 must do LockBufferForCleanup(index_page1). Do I get things right?</div><div> </div><div>Best regards, Andrey Borodin.</div></div><div> </div>