From: Chao Li <li.evan.chao@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Rahila Syed <rahilasyed90@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: show size of DSAs and dshash tables in pg_dsm_registry_allocations
Date: Tue, 2 Dec 2025 05:35:34 +0800
Message-ID: <E4CEC5F7-BCCE-47D7-B206-48FD31F06F3C@gmail.com> (raw)
In-Reply-To: <aS20Z42rPHecTljS@nathan>
References: <aSeEDeznAsHR1_YF@nathan>
<CAH2L28tr5q965MbD2TroyTc-Ey+b-z3=3kpWAuGg6w7qQwwChA@mail.gmail.com>
<aS20Z42rPHecTljS@nathan>
Hi Nathan,
V2 overall looks good to me. I just got a question and a few nit comments.
> On Dec 1, 2025, at 23:29, Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> --
> nathan
> <v2-0001-rework-DSM-registry-view.patch>
1 - dsa.c
```
+size_t
+dsa_get_total_size_from_handle(dsa_handle handle)
+{
+ size_t size;
+ bool already_attached;
+ dsm_segment *segment;
+ dsa_area_control *control;
+
+ already_attached = dsa_is_attached(handle);
+ if (already_attached)
+ segment = dsm_find_mapping(handle);
+ else
+ segment = dsm_attach(handle);
+
+ if (segment == NULL)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("could not attach to dynamic shared area")));
```
Why do you error out instead of reporting 0/NULL usage here? When users call this function as shown in the test script:
```
CREATE VIEW pg_dsm_registry_allocations AS
SELECT * FROM pg_get_dsm_registry_allocations();
```
User doesn’t pass in a handle, if the DSA has been released, it should treat a missing mapping as “no size available” and maybe return NULL.
2
```
+ else if (entry->type == DSMR_ENTRY_TYPE_DSH &&
+ entry->dsh.dsa_handle !=DSA_HANDLE_INVALID)
```
Missing a white space after !=.
3
```
- Size of the allocation in bytes. NULL for entries of type
- <literal>area</literal> and <literal>hash</literal>.
+ Size of the allocation in bytes. NULL for entries that failed
+ initialization.
```
“Failed initialization”, I guess “to” is needed after “failed”.
4
```
-SELECT name, type, size IS DISTINCT FROM 0 AS size
+SELECT name, type, size > 0 AS size
```
As you changed the third column from “size” to “size > 0”, now it’s a bool column, so maybe rename the column alias from “size” to something indicating a bool type, such as “size_ok”, “has_size”, etc.
Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/
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To: pgsql-hackers@postgresql.org
Cc: li.evan.chao@gmail.com, nathandbossart@gmail.com, rahilasyed90@gmail.com, robertmhaas@gmail.com, pgsql-hackers@lists.postgresql.org
Subject: Re: show size of DSAs and dshash tables in pg_dsm_registry_allocations
In-Reply-To: <E4CEC5F7-BCCE-47D7-B206-48FD31F06F3C@gmail.com>
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