Subject: The relation between "checkpoint_timeout" and "checkpoint_warning" is missing

From: Tianyin Xu <[email-masked]>
Date: Fri, 8 Feb 2013 01:38:09 -0800

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

-- 
Tianyin XU,
http://cseweb.ucsd.edu/~tixu/

---

From: Peter Eisentraut <[email-masked]>
Date: Sun, 10 Mar 2013 17:17:51 -0400

> the relation between "checkpoint_timeout" and "checkpoint_warning" is

Fixed.  Thanks for the suggestion.

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