Improve buffer manager API for backend pin limits.
Previously the support functions assumed that the caller needed one pin
to make progress, and could optionally use some more, allowing enough
for every connection to do the same. Add a couple more functions for
callers that want to know:
* what the maximum possible number could be, irrespective of currently
held pins, for space planning purposes
* how many additional pins they could acquire right now, without the
special case allowing one pin, for callers that already hold pins and
could already make progress even if no extra pins are available
The pin limit logic began in commit 31966b15. This refactoring is
better suited to read_stream.c, which will be adjusted to respect the
remaining limit as it changes over time in a follow-up commit. It also
computes MaxProportionalPins up front, to avoid performing divisions
whenever a caller needs to check the balance.
Reviewed-by: Andres Freund <andres@anarazel.de> (earlier versions)
Discussion: https://postgr.es/m/CA%2BhUKGK_%3D4CVmMHvsHjOVrK6t4F%3DLBpFzsrr3R%2BaJYN8kcTfWg%40mail.gmail.com
Branch
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master
Details
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https://git.postgresql.org/pg/commitdiff/01261fb07888642efa98ba8d4117654bfd2a413d
Modified Files
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src/backend/storage/buffer/bufmgr.c | 80 ++++++++++++++++++++++++-----------
src/backend/storage/buffer/localbuf.c | 16 +++++++
src/include/storage/bufmgr.h | 4 ++
3 files changed, 75 insertions(+), 25 deletions(-)
