Re: glist: _Generic wrapper for selective dlist/dclist usage

On Wed, 02 Sep 2026 at 13:36, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com> wrote:
> Hi,
>
> I'd like to track the size of a dlist for data structure validation
> purposes[^0]. Normally, one would use a dclist, as this tracks a
> count of list elements contained therein, but because this code would
> not be called in most normal production builds using a dclist would
> waste precious memory.
> Manually tracking the length is possible, but tedious, and a local
> wrapper around the used dclist/dlist APIs (with different
> implementations conditioned with #ifdefs to use the right types) would
> also be a significant amount of effort, that'd be duplicated every
> time .
>
> Attached is a patch that adds glist_* macros, which wrap several
> dlist/dclist_* APIs, so that developers can use dlist/dclist
> selectively in different environments, without significant visual
> overhead in the code. I'm planning to use this in the Proxy memory
> contexts over at [1].
>
> I've considered also adding slist_* to the macros, but I've never
> needed selective slist vs dlist/dclist before, so I ignored that list
> type for now.
>

+1 for this idea.

Should we adopt the new glist interface in the existing code to better
showcase its intended use?

>
> Kind regards,
>
> Matthias van de Meent
> Databricks (https://www.databricks.com)
>
>
> [^0]: This case for builds with MEMORY_CONTEXT_CHECKING, but builds
> with USE_ASSERT_CHECKING or WRITE_READ_PARSE_PLAN_TREES -like options
> may also want this.
>
> [1]: https://www.postgresql.org/message-id/flat/CAEze2WiPyruOtUOSyRUV8mQssjmYwno0M6hkxC_iUpH-=W8WcA(at)mail(dot)gmail(dot)com

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Regards,
Japin Li
ChengDu WenWu Information Technology Co., Ltd.