On 05/12/2023 05:40, Richard Guo wrote:
> On Tue, Dec 5, 2023 at 12:31 AM Tristan Partin <tristan@neon.tech> wrote:
> On Mon Dec 4, 2023 at 6:49 AM CST, Heikki Linnakangas wrote:
> > Here's a patch to allocate and initialize it with a pair of
> ShmemSize
> > and ShmemInit functions, like all other shared memory structs.
> >
> > + if (!IsUnderPostmaster)
> > + {
> > + Assert(!found);
> > + memset(ShmemVariableCache, 0,
> sizeof(VariableCacheData));
> > + }
> > + else
> > + Assert(found);
>
>> Should the else branch instead be a fatal log?
>
> The Assert here seems OK to me. We do the same when initializing
> commitTsShared/MultiXactState. I think it would be preferable to adhere
> to this convention.
Right. I'm not 100% happy with that pattern either, but better be
consistent.
There's a brief comment about this in CreateOrAttachShmemStructs():
> * This is called by the postmaster or by a standalone backend.
> * It is also called by a backend forked from the postmaster in the
> * EXEC_BACKEND case. In the latter case, the shared memory segment
> * already exists and has been physically attached to, but we have to
> * initialize pointers in local memory that reference the shared structures,
> * because we didn't inherit the correct pointer values from the postmaster
> * as we do in the fork() scenario. The easiest way to do that is to run
> * through the same code as before. (Note that the called routines mostly
> * check IsUnderPostmaster, rather than EXEC_BACKEND, to detect this case.
> * This is a bit code-wasteful and could be cleaned up.)
The last sentence refers to this pattern.
>> Patches look good to me.
>
> Also +1 to the patches.
Committed, thanks!
--
Heikki Linnakangas
Neon (https://neon.tech)