Re: Replication slot stats misgivings

On Tue, Apr 20, 2021 at 7:54 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>

I have one question:

+ /*
+ * Create the replication slot stats hash table if we don't have
+ * it already.
+ */
+ if (replSlotStats == NULL)
{
- if (namestrcmp(&replSlotStats[i].slotname, name) == 0)
- return i; /* found */
+ HASHCTL hash_ctl;
+
+ hash_ctl.keysize = sizeof(NameData);
+ hash_ctl.entrysize = sizeof(PgStat_StatReplSlotEntry);
+ hash_ctl.hcxt = pgStatLocalContext;
+
+ replSlotStats = hash_create("Replication slots hash",
+ PGSTAT_REPLSLOT_HASH_SIZE,
+ &hash_ctl,
+ HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
}

It seems to me that the patch is always creating a hash table in
pgStatLocalContext? AFAIU, we need to create it in pgStatLocalContext
when we read stats via backend_read_statsfile so that we can clear it
at the end of the transaction. The db/function stats seems to be doing
the same. Is there a reason why here we need to always create it in
pgStatLocalContext?

--
With Regards,
Amit Kapila.