The relation between "checkpoint_timeout" and "checkpoint_warning" is missing
От
Tianyin Xu
Тема
The relation between "checkpoint_timeout" and
"checkpoint_warning" is missing
Дата
Msg-id
CABBDWwfVg275EjUd0daBN7Vd9yaCZewSgbzd3_8ciEXY5XK0tQ@mail.gmail.com
Список
Дерево обсуждения
The relation between "checkpoint_timeout" and
"checkpoint_warning" is missing Tianyin Xu <tixu@cs.ucsd.edu>
Re: The relation between "checkpoint_timeout" and
"checkpoint_warning" is missing Peter Eisentraut <peter_e@gmx.net>
Hi, PG,
In "18.5.2. Checkpoints" (http://www.postgresql.org/docs/9.2/static/runtime-config-wal.html#RUNTIME-CONFIG-WAL-CHECKPOINTS), the relation between "checkpoint_timeout" and "checkpoint_warning" is missing.
According to the code, "checkpoint_timeout" should be set larger than "checkpoint_warning", otherwise the warnings will not be generated. The comments in function: CheckpointerMain() also tell such behavior, which is in line#473 in "src/backend/postmaster/checkpointer.c":
/*
* We will warn if (a) too soon since last checkpoint (whatever
* caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
* since the last checkpoint start. Note in particular that this
* implementation will not generate warnings caused by
* CheckPointTimeout < CheckPointWarning.
*/
I think this's should definitely specified in the documentation.
Best,
Tianyin
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