Hey Tomas! Gentle nudge on the patch. I have rebased the changes and attached the new v4 patch. There are no actual changes from the previous patch; I have just rebased the changes on top of the latest head.
Thanks, Siddharth
From 99d1fb5f47f79597b11c09a4f105cd44483cd1f7 Mon Sep 17 00:00:00 2001 From: Siddharth Kothari <[email protected]> Date: Tue, 17 Feb 2026 12:23:56 +0000 Subject: [PATCH v4] Add parallel instrumentation hooks for CustomScan providers CustomScan providers currently lack a standard method to aggregate instrumentation data from parallel workers back to the leader process before the Dynamic Shared Memory segment is destroyed. Furthermore, unlike built-in scans, they are missing the callbacks required to allocate instrumentation DSM when they are in the parallel part of a plan but not necessarily parallel-aware. This patch introduces four optional callbacks to CustomExecMethods: - EstimateDSMCustomScanInstrumentation - InitializeDSMCustomScanInstrumentation - InitializeWorkerCustomScanInstrumentation - RetrieveInstrumentationCustomScan This allows custom scan providers to fully support parallel EXPLAIN ANALYZE metrics and consolidate instrumentation from shared memory similarly to built-in scan nodes. --- doc/src/sgml/custom-scan.sgml | 43 +++++++++++++++++++++++++++++ src/backend/executor/execParallel.c | 12 ++++++++ src/backend/executor/nodeCustom.c | 37 +++++++++++++++++++++++++ src/include/executor/nodeCustom.h | 7 +++++ src/include/nodes/extensible.h | 13 +++++++++ 5 files changed, 112 insertions(+) diff --git a/doc/src/sgml/custom-scan.sgml b/doc/src/sgml/custom-scan.sgml index a200d502cdd..8c2a4f82041 100644 --- a/doc/src/sgml/custom-scan.sgml +++ b/doc/src/sgml/custom-scan.sgml @@ -409,6 +409,49 @@ void (*ShutdownCustomScan) (CustomScanState *node); <para> <programlisting> +void (*EstimateDSMCustomScanInstrumentation) (CustomScanState *node, + ParallelContext *pcxt); +</programlisting> + Estimate the amount of dynamic shared memory that will be required + for parallel operation's instrumentation (for <literal>EXPLAIN ANALYZE</literal>). + This callback is optional, and need only be supplied if this custom + scan provider supports parallel execution and needs custom instrumentation. + </para> + + <para> +<programlisting> +void (*InitializeDSMCustomScanInstrumentation) (CustomScanState *node, + ParallelContext *pcxt); +</programlisting> + Initialize the dynamic shared memory that will be required for parallel + operation's instrumentation. + This callback is optional, and need only be supplied if this custom + scan provider supports parallel execution and needs custom instrumentation. + </para> + + <para> +<programlisting> +void (*InitializeWorkerCustomScanInstrumentation) (CustomScanState *node, + ParallelWorkerContext *pwcxt); +</programlisting> + Initialize a parallel worker's local state based on the shared state + set up by the leader during <function>InitializeDSMCustomScanInstrumentation</function>. + This callback is optional, and need only be supplied if this custom + scan provider supports parallel execution and needs custom instrumentation. + </para> + + <para> +<programlisting> +void (*RetrieveInstrumentationCustomScan) (CustomScanState *node); +</programlisting> + Retrieve parallel instrumentation data from dynamic shared memory into local + memory when the custom-scan plan node finishes execution. + This callback is optional, and need only be supplied if this custom + scan provider supports parallel execution and needs custom instrumentation. + </para> + + <para> +<programlisting> void (*ExplainCustomScan) (CustomScanState *node, List *ancestors, ExplainState *es); diff --git a/src/backend/executor/execParallel.c b/src/backend/executor/execParallel.c index 6b85508a696..f01ace0db03 100644 --- a/src/backend/executor/execParallel.c +++ b/src/backend/executor/execParallel.c @@ -304,6 +304,9 @@ ExecParallelEstimate(PlanState *planstate, ExecParallelEstimateContext *e) if (planstate->plan->parallel_aware) ExecCustomScanEstimate((CustomScanState *) planstate, e->pcxt); + /* even when not parallel-aware, for EXPLAIN ANALYZE */ + ExecCustomScanInstrumentEstimate((CustomScanState *) planstate, + e->pcxt); break; case T_BitmapHeapScanState: if (planstate->plan->parallel_aware) @@ -552,6 +555,9 @@ ExecParallelInitializeDSM(PlanState *planstate, if (planstate->plan->parallel_aware) ExecCustomScanInitializeDSM((CustomScanState *) planstate, d->pcxt); + /* even when not parallel-aware, for EXPLAIN ANALYZE */ + ExecCustomScanInstrumentInitDSM((CustomScanState *) planstate, + d->pcxt); break; case T_BitmapHeapScanState: if (planstate->plan->parallel_aware) @@ -1164,6 +1170,9 @@ ExecParallelRetrieveInstrumentation(PlanState *planstate, case T_TidRangeScanState: ExecTidRangeScanRetrieveInstrumentation((TidRangeScanState *) planstate); break; + case T_CustomScanState: + ExecCustomScanRetrieveInstrumentation((CustomScanState *) planstate); + break; default: break; } @@ -1449,6 +1458,9 @@ ExecParallelInitializeWorker(PlanState *planstate, ParallelWorkerContext *pwcxt) if (planstate->plan->parallel_aware) ExecCustomScanInitializeWorker((CustomScanState *) planstate, pwcxt); + /* even when not parallel-aware, for EXPLAIN ANALYZE */ + ExecCustomScanInstrumentInitWorker((CustomScanState *) planstate, + pwcxt); break; case T_BitmapHeapScanState: if (planstate->plan->parallel_aware) diff --git a/src/backend/executor/nodeCustom.c b/src/backend/executor/nodeCustom.c index b7cc890cd20..04a043543d1 100644 --- a/src/backend/executor/nodeCustom.c +++ b/src/backend/executor/nodeCustom.c @@ -217,6 +217,43 @@ ExecCustomScanInitializeWorker(CustomScanState *node, } } +void +ExecCustomScanInstrumentEstimate(CustomScanState *node, ParallelContext *pcxt) +{ + const CustomExecMethods *methods = node->methods; + + if (methods->EstimateDSMCustomScanInstrumentation) + methods->EstimateDSMCustomScanInstrumentation(node, pcxt); +} + +void +ExecCustomScanInstrumentInitDSM(CustomScanState *node, ParallelContext *pcxt) +{ + const CustomExecMethods *methods = node->methods; + + if (methods->InitializeDSMCustomScanInstrumentation) + methods->InitializeDSMCustomScanInstrumentation(node, pcxt); +} + +void +ExecCustomScanInstrumentInitWorker(CustomScanState *node, + ParallelWorkerContext *pwcxt) +{ + const CustomExecMethods *methods = node->methods; + + if (methods->InitializeWorkerCustomScanInstrumentation) + methods->InitializeWorkerCustomScanInstrumentation(node, pwcxt); +} + +void +ExecCustomScanRetrieveInstrumentation(CustomScanState *node) +{ + const CustomExecMethods *methods = node->methods; + + if (methods->RetrieveInstrumentationCustomScan) + methods->RetrieveInstrumentationCustomScan(node); +} + void ExecShutdownCustomScan(CustomScanState *node) { diff --git a/src/include/executor/nodeCustom.h b/src/include/executor/nodeCustom.h index fb0acc6e414..f702ef01709 100644 --- a/src/include/executor/nodeCustom.h +++ b/src/include/executor/nodeCustom.h @@ -37,6 +37,13 @@ extern void ExecCustomScanReInitializeDSM(CustomScanState *node, ParallelContext *pcxt); extern void ExecCustomScanInitializeWorker(CustomScanState *node, ParallelWorkerContext *pwcxt); +extern void ExecCustomScanInstrumentEstimate(CustomScanState *node, + ParallelContext *pcxt); +extern void ExecCustomScanInstrumentInitDSM(CustomScanState *node, + ParallelContext *pcxt); +extern void ExecCustomScanInstrumentInitWorker(CustomScanState *node, + ParallelWorkerContext *pwcxt); +extern void ExecCustomScanRetrieveInstrumentation(CustomScanState *node); extern void ExecShutdownCustomScan(CustomScanState *node); #endif /* NODECUSTOM_H */ diff --git a/src/include/nodes/extensible.h b/src/include/nodes/extensible.h index b4fc6067807..21d7110cbbb 100644 --- a/src/include/nodes/extensible.h +++ b/src/include/nodes/extensible.h @@ -153,6 +153,19 @@ typedef struct CustomExecMethods void *coordinate); void (*ShutdownCustomScan) (CustomScanState *node); + /* Optional: estimate parallel instrumentation size */ + void (*EstimateDSMCustomScanInstrumentation) (CustomScanState *node, + ParallelContext *pcxt); + /* Optional: initialize parallel instrumentation DSM */ + void (*InitializeDSMCustomScanInstrumentation) (CustomScanState *node, + ParallelContext *pcxt); + /* Optional: initialize parallel instrumentation worker */ + void (*InitializeWorkerCustomScanInstrumentation) (CustomScanState *node, + ParallelWorkerContext *pwcxt); + + /* Optional: retrieve parallel instrumentation */ + void (*RetrieveInstrumentationCustomScan) (CustomScanState *node); + /* Optional: print additional information in EXPLAIN */ void (*ExplainCustomScan) (CustomScanState *node, List *ancestors, -- 2.55.0.1003.g10538fe699-goog
