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Re: Stack-based tracking of per-node WAL/buffer usage

Zsolt Parragi <zsolt.parragi@percona.com>

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From: Zsolt Parragi <zsolt.parragi@percona.com>
To: Lukas Fittl <lukas@fittl.com>
Cc: Tomas Vondra <tomas@vondra.me>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andres Freund <andres@anarazel.de>, Peter Smith <smithpb2250@gmail.com>
Date: 2026-03-18T20:49:37Z
Lists: pgsql-hackers 
+ instr_stack.stack_space *= 2;
+ instr_stack.entries = repalloc_array(instr_stack.entries,
Instrumentation *, instr_stack.stack_space);

Can't this also cause issues with OOM? repalloc_array failing, but we
already doubled stack_space.
The initialization above uses the same order, but that should be safe
as entries is initially NULL.


+ * 2) Accumulate all instrumentation to the currently active instrumentation,
+ *    so that callers get a complete picture of activity, even after an abort
...
+ if (idx >= 0)
+ {
+ while (instr_stack.stack_size > idx + 1)
+ instr_stack.stack_size--;
+
+ InstrPopStack(instr);
+ }

There seems to be one more bug in this:

1. EXPLAIN ANALYZE fires a trigger
2. The trigger function throws ERROR, InstrStopTrigger never runs
3. ResOwnerReleaseInstrumentation runs but only checks
unfinalized_children, not triggers
4. InstrStopFinalize discards the trigger entry
5. Trigger instrumentation information shows 0

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. instrumentation: Allocate query level instrumentation in ExecutorStart

  2. instrumentation: Move ExecProcNodeInstr to allow inlining

  3. instrumentation: Separate per-node logic from other uses

  4. instrumentation: Separate trigger logic from other uses

  5. instrumentation: Rename INSTR_TIME_LT macro to INSTR_TIME_GT

  6. instrumentation: Keep time fields as instrtime, convert in callers