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base repository: postgresql-cfbot/postgresql
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base: cf/6023~1
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head repository: postgresql-cfbot/postgresql
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compare: cf/6023
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  • 8 commits
  • 29 files changed
  • 2 contributors

Commits on Dec 25, 2025

  1. Instrumentation: Keep time fields as instrtime, require caller to con… 

    …vert

Previously the Instrumentation logic always converted to seconds, only for many
of the callers to do unnecessary division to get to milliseconds. Since an upcoming
refactoring will split the Instrumentation struct, utilize instrtime always to
keep things simpler.
    @lfittl
    lfittl authored and Commitfest Bot committed Dec 25, 2025
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  2. Separate node and trigger instrumentation from other use of Instrumen… 

    …tation struct

Previously different places (e.g. query "total time") were repurposing
the Instrumentation struct initially introduced for capturing per-node
statistics during execution. This overuse of the same struct is confusing,
e.g. by cluttering calls of InstrStartNode/InstrStopNode in unrelated
code paths, and prevents future refactorings.

Instead, simplify the Instrumentation struct to only track time and
WAL/buffer usage. Similarly, drop the use of InstrEndLoop outside of
per-node instrumentation - these calls were added without any apparent
benefit since the relevant fields were never read.

Introduce the NodeInstrumentation struct to carry forward the per-node
instrumentation information, and introduce TriggerInstrumentation to
capture trigger timing and firings (previously counted in "ntuples").
    @lfittl
    lfittl authored and Commitfest Bot committed Dec 25, 2025
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  3. Replace direct changes of pgBufferUsage/pgWalUsage with INSTR_* macros 

    This encapsulates the ownership of these globals better, and will allow
a subsequent refactoring.
    @lfittl
    lfittl authored and Commitfest Bot committed Dec 25, 2025
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  4. Optimize measuring WAL/buffer usage through stack-based instrumentation 

    Previously, in order to determine the buffer/WAL usage of a given code section,
we utilized continuously incrementing global counters that get updated when the
actual activity (e.g. shared block read) occurred, and then calculated a diff when
the code section ended. This resulted in a bottleneck for executor node instrumentation
specifically, with the function BufferUsageAccumDiff showing up in profiles and
in some cases adding up to 10% overhead to an EXPLAIN (ANALYZE, BUFFERS) run.

Instead, introduce a stack-based mechanism, where the actual activity writes
into the current stack entry. In the case of executor nodes, this means that
each node gets its own stack entry that is pushed at InstrStartNode, and popped
at InstrEndNode. Stack entries are zero initialized (avoiding the diff mechanism)
and get added to their parent entry when they are finalized, i.e. no more
modifications can occur.

To correctly handle abort situations, any use of instrumentation stacks must
involve either a top-level Instrumentation struct, and its associated InstrStart/
InstrStop helpers (which use resource owners to handle aborts), or dedicated
PG_TRY/PG_FINALLY calls that ensure the stack is in a consistent state after
an abort.
    @lfittl
    lfittl authored and Commitfest Bot committed Dec 25, 2025
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  5. Use Instrumentation stack for parallel query aggregation in workers

    @lfittl
    lfittl authored and Commitfest Bot committed Dec 25, 2025
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  6. Convert remaining users of pgBufferUsage to use InstrStart/InstrStop,… 

    … drop the global
    @lfittl
    lfittl authored and Commitfest Bot committed Dec 25, 2025
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  7. Index scans: Split heap and index buffer access reporting in EXPLAIN 

    This makes it clear whether activity was on the index directly, or
on the table based on heap fetches.
    @lfittl
    lfittl authored and Commitfest Bot committed Dec 25, 2025
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  8. [CF 6023] v4 - Stack-based tracking of per-node WAL/buffer usage 

    This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/6023

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CAP53PkzZ3UotnRrrnXWAv=F4avRq9MQ8zU+bxoN9tpovEu6fGQ@mail.gmail.com
Author(s): Lukas Fittl
    Commitfest Bot committed Dec 25, 2025
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