[question] difference between vm_extend and fsm_extend

From: Junwang Zhao <zhjwpku(at)gmail(dot)com>
To: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: [question] difference between vm_extend and fsm_extend
Date: 2023-08-10 08:36:21
Message-ID: CAEG8a3K_zajxhWMpJO=f1Z70kBjwe3RiMb9_Jyv4=8M9sSJEow@mail.gmail.com
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Hey hacks,

I'm looking the code of free space map and visibility map, both the module
call `ExtendBufferedRelTo` to extend its file when necessary, what confused
me is that `vm_extend` has an extra step that send a shared message to force
other backends to close other smgr references.

My question is why does `fsm_extend` not need the invalidation step?

--
Regards
Junwang Zhao

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