Re: What is the relationship between checkpoint and wal

高健 escribió:

> ...
> Checkpoints are fairly expensive, first because they require writing out
> all currently dirty buffers, and second because they result in extra
> subsequent WAL traffic as discussed above.
> ...
>
> What confused me is that:  (checkpoint)result in extra subsequent WAL
> traffic as discussed above...
>
> I haven't found any more information can describe it in the "above" of that
> page.

It means that the first change following the checkpoint that affects any
particular page will require a full page image of that page to be
written to WAL.  See the discussion in the preceding paragraph about
"full_page_writes".  It's not the checkpoint itself that writes this
extra WAL, but the rest of the system.

--
Álvaro Herrera                http://www.2ndQuadrant.com/
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