Re: [BUGS] Breakage with VACUUM ANALYSE + partitions

Hi,

On 2016-05-03 00:05:35 +0200, Fabien COELHO wrote:
> Maybe consider checking for the exclusivity explicitely?

I thought about it, and decided it's not worth it. Requiring one of
those to be specified seems stringent enough.

> I'm unsure about switching enum to #define, could be an enum still with
> explicit values set, something like:
>
> enum {
> EXTENSION_RETURN_NULL = (1 << 0),
> ...
> } extension_behavior;

An enum doesn't have a benefit for a bitmask imo - you can't "legally"
use it as a type for functions accepting the bitmask.

> I'm fuzzy about the _OPEN_DELETED part because it is an oxymoron. Is it
> RECREATE really?

No. The relevant explanation is at the top of the file:
* On disk, a relation must consist of consecutively numbered segment
* files in the pattern
* -- Zero or more full segments of exactly RELSEG_SIZE blocks each
* -- Exactly one partial segment of size 0 <= size < RELSEG_SIZE blocks
* -- Optionally, any number of inactive segments of size 0 blocks.
* The full and partial segments are collectively the "active" segments.
* Inactive segments are those that once contained data but are currently
* not needed because of an mdtruncate() operation. The reason for leaving
* them present at size zero, rather than unlinking them, is that other
* backends and/or the checkpointer might be holding open file references to
* such segments. If the relation expands again after mdtruncate(), such
* that a deactivated segment becomes active again, it is important that
* such file references still be valid --- else data might get written
* out to an unlinked old copy of a segment file that will eventually
* disappear.

- Andres