Can avoid list_copy in recomputeNamespacePath() conditionally?

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От amul sul
Тема Can avoid list_copy in recomputeNamespacePath() conditionally?
Дата
Msg-id CAAJ_b94dGU4BYFtVCKkj58hNuPL9hwP4p1a9Eqq+e+v8GP8KoQ@mail.gmail.com
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Ответы Re: Can avoid list_copy in recomputeNamespacePath() conditionally?  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-hackers
Hi all,

I wondered can we have a shortcut somewhat similar to following POC
in recomputeNamespacePath () when the recomputed path is the same as the
previous baseSearchPath/activeSearchPath :

== POC patch ==
diff --git a/src/backend/catalog/namespace.c b/src/backend/catalog/namespace.c
index e251f5a9fdc..b25ef489e47 100644
--- a/src/backend/catalog/namespace.c
+++ b/src/backend/catalog/namespace.c
@@ -3813,6 +3813,9 @@ recomputeNamespacePath(void)
        !list_member_oid(oidlist, myTempNamespace))
        oidlist = lcons_oid(myTempNamespace, oidlist);
 
+   /* TODO: POC */
+   if (equal(oidlist, baseSearchPath))
+       return;
    /*
     * Now that we've successfully built the new list of namespace OIDs, save
     * it in permanent storage.

== POC patch end ==

It can have two advantages as:

1. Avoid unnecessary list_copy() in TopMemoryContext context &
2. Global pointers like activeSearchPath/baseSearchPath will not change if some
    implementation end up with cascaded call to recomputeNamespacePath().

Thoughts/Comments?

Regards,
Amul

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