Re: Improving REINDEX for system indexes (long)

Here is the proposed patch. This fixes the problems that prevented the
relcache from coping with relfilenode changes for nailed-in-cache
indexes. Accordingly, REINDEX is now crash-safe and transaction-safe
for all cases except reindexing shared system catalogs. That case is
permitted only in a standalone backend (!IsUnderPostmaster). We no
longer require -O to reindex system tables, and since -P now suppresses
only reads not writes of system indexes, it is safe to allow from the
client side. Upshot: reindexing system catalogs can be done without a
standalone backend for all cases except shared catalogs.

regards, tom lane