Re: Support for REINDEX CONCURRENTLY

Andres Freund escribió:
> On 2013-06-22 22:45:26 +0900, Michael Paquier wrote:

> > And I imagine that you have the same problem even with
> > RelationGetIndexList, not only RelationGetIndexListIfInvalid, because
> > this would appear as long as you try to open more than 1 index with an
> > index list.
> 
> No. RelationGetIndexList() returns a copy of the list for exactly that
> reason. The danger is not to see an outdated list - we should be
> protected by locks against that - but looking at uninitialized or reused
> memory.

Are we doing this only to save some palloc traffic?  Could we do this
by, say, teaching list_copy() to have a special case for lists of ints
and oids that allocates all the cells in a single palloc chunk?

(This has the obvious problem that list_free no longer works, of
course.  But I think that specific problem can be easily fixed.  Not
sure if it causes more breakage elsewhere.)

Alternatively, I guess we could grab an uncopied list, then copy the
items individually into a locally allocated array, avoiding list_copy.
We'd need to iterate differently than with foreach().

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services