WaitForOlderSnapshots refactoring

Hi,

On 2018-08-20 14:35:34 +0200, Peter Eisentraut wrote:

The attached patch factors out the CREATE INDEX CONCURRENTLY code that
waits for transactions with older snapshots to finish into a new
function WaitForOlderSnapshots().

This refactoring was part of a previously posted REINDEX CONCURRENTLY
patch. But this code is now also appearing as a copy-and-paste in the
ATTACH/DETACH PARTITION CONCURRENTLY thread, so it might be worth making
it an official thing.

I'm doubtful that ATTACH should use this, but I think the refactoring is
a good idea regardless.

The question is where to put it. This patch just leaves it static in
indexcmds.c, which doesn't help other uses. A sensible place might be a
new src/backend/commands/common.c. Or we make it non-static in
indexcmds.c when the need arises.

Why not move it to procarray.c? Most of the referenced functionality
resides there IIRC.

Greetings,

Andres Freund

On 20/08/2018 14:39, Andres Freund wrote:

The question is where to put it. This patch just leaves it static in
indexcmds.c, which doesn't help other uses. A sensible place might be a
new src/backend/commands/common.c. Or we make it non-static in
indexcmds.c when the need arises.

Why not move it to procarray.c? Most of the referenced functionality
resides there IIRC.

I was thinking about that, too. I thought that that would create a
circular dependency between lock.c and procarray.c, but seeing that
that's already the case, I guess it's OK. (lock.c includes procarray.h,
but procarray.c uses stuff from lock.h, even though it doesn't include
it directly.) I'll rework the patch accordingly.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services