Will the synchronized seq scan patch be able to do this by issuing all the CREATE INDEX commands at the same time from several different database connections ?No, but it could someday.
Actually I tested, it does it right now, albeit unconsciously (pg doesn't do anything to synchronize the scans, but if you launch the concurrent connections at the same time and issue all your "create index" at the same time, only 1 table scan is needed). Maybe if the tables were bigger, it would lose sync between the 3 concurrent scans and would end up going slower. That's why I spoke about the "synchronized scan" patch.
Or would a "CREATE MANY INDEXES" (where in one statement you specify all the indexes on a single table) command be easier to implement?
You can get the effect right now by using concurrent connections it seems. Not very practical in a psql script, though...
