Re: Introduce XID age and inactive timeout based replication slot invalidation

On Tue, Feb 11, 2025 at 8:49 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> Hi Nisha.
>
> Some review comments about v74-0001
>
> ======
> src/backend/replication/slot.c
>
> 1.
> /* Maximum number of invalidation causes */
> -#define RS_INVAL_MAX_CAUSES RS_INVAL_WAL_LEVEL
> -
> -StaticAssertDecl(lengthof(SlotInvalidationCauses) == (RS_INVAL_MAX_CAUSES + 1),
> - "array length mismatch");
> +#define RS_INVAL_MAX_CAUSES (lengthof(InvalidationCauses)-1)
>
> The static assert was here to protect against dev mistakes in keeping
> the lookup table up-to-date with the enum of slot.h. So it's not a
> good idea to remove it...
>
> IMO the RS_INVAL_MAX_CAUSES should be relocated to slot.h where the
> enum is defined and where the devs know exactly how many invalidation
> types there are. Then this static assert can be put back in to do its
> job of ensuring the integrity properly again for this lookup table.
>

How about keeping RS_INVAL_MAX_CAUSES dynamic in slot.c (as it was)
and updating the static assert to ensure the lookup table stays
up-to-date with the enums?
The change has been implemented in v75.

> ~~~
>
> ======

Here are v75 patches addressing comments in [1], [2] and [3].
- A new function, "EvaluateSlotInvalidationCause()", has been
introduced to separate the invalidation_cause evaluation logic from
InvalidatePossiblyObsoleteSlot().
- Also, another new inline function "CalculateTimeDuration()" added
as suggested in [3].

[1] https://www.postgresql.org/message-id/CAHut%2BPvsvHWoiEkGTP4NfVNsADsy-Jan3Dvp%2B_GW3gmPDHf5Qw%40mail.gmail.com
[2] https://www.postgresql.org/message-id/OS0PR01MB57163889BE5F9F30DD3318A394FD2%40OS0PR01MB5716.jpnprd01.prod.outlook.com
[3] https://www.postgresql.org/message-id/CAA4eK1LuvXa6sVj3xuLoe2X%3D0xjbJXrnJePbpXQZaTMws8pZqg%40mail.gmail.com

--
Thanks,
Nisha