Hi Japin,
> When we write a extension using C language, we often add the dynamic library
> into shared_preload_libraries, however, I found that the bloom, btree_gist and
> btree_gin do not follow this rule. I'm a bit confused with this, could anybody
> explain it for me?
In the general case, you don't need to modify shared_preload_libraries to use an extension, regardless of the language in which it's implemented. That's it.
Some extensions may however require this. See the description of the GUC [1].
[1]:
https://www.postgresql.org/docs/13/runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES
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Best regards,
Aleksander Alekseev