I’m just checking in to see if anyone has had a chance to look at this or if there’s any further information I should provide to help with the review. I have also added the patch to PG20-1 CF queue, the link is https://commitfest.postgresql.org/patch/6524/.
Thanks, Siddharth
On Wed, Feb 18, 2026 at 3:09 PM Siddharth Kothari <sidkot@google.com> wrote:
Dear PostgreSQL Hackers,
This email proposes a patch to enhance the CustomScan provider interface. The patch file, 0001-Add-RetrieveInstrumentationCustomScan-hook-for-Custo.patch, is attached.
Problem:
CustomScan providers currently lack a standard method to aggregate instrumentation data from parallel workers back to the leader process before the Dynamic Shared Memory (DSM) segment is unlinked. This makes it difficult to gather comprehensive performance metrics from parallelized custom scans.
Solution:
This patch introduces a new optional hook, RetrieveInstrumentationCustomScan, to the CustomExecMethods struct. This hook allows custom scan providers to implement logic to collect and consolidate instrumentation from shared memory or worker states during the parallel query cleanup phase. This hook is invoked via the new ExecCustomScanRetrieveInstrumentation function, called from ExecParallelRetrieveInstrumentation for T_CustomScanState nodes. Since the hook is optional (checked for NULL before calling), it maintains full backward compatibility.
Testing & Compatibility:
The patch compiles and passes all core regression tests (make check-world) on my x86_64 instance.
The changes are not platform-specific.
Regression Tests: This patch provides a new capability for custom scan providers. Since the hook's functionality is only realized when implemented by an extension, specific tests would naturally reside within that extension rather than in the core regression suite.
This patch does not directly address a specific item on the official TODO list but enhances the extensibility framework.
I believe this patch is complete and ready for review. I look forward to any feedback and am happy to make revisions. I will also add this patch to the next CommitFest.
