> Mark Woodward wrote: >>> Mark Woodward wrote: >>>> Tom had posted a question about file compression with copy. I thought >>>> about it, and I want to through this out and see if anyone things it >>>> is >>>> a >>>> good idea. >>>> >>>> Currently, the COPY command only copies a table, what if it could >>>> operate >>>> with a query, as: >>>> >>>> COPY (select * from mytable where foo='bar') as BAR TO stdout >>>> >>>> I have no idea if it is doable, but I can see uses for replication >>> I doubt it be really usefull (apart from maybe saving some work >>> coding a client app) but did you actually test it with >>> >>> create table as select ...; followed by a copy of that table >>> if it really is faster then just the usual select & fetch? >> >> Why "create table?" > > Just to simulate and time the proposal. > SELECT ... already works over the network and if COPY from a > select (which would basically work like yet another wire > protocol) isnt significantly faster, why bother?
Because the format of COPY is a common transmiter/receiver for PostgreSQL, like this: pg_dump -t mytable | psql -h target -c "COPY mytable FROM STDIN" With a more selective copy, you can use pretty much this mechanism to limit a copy to a sumset of the records in a table. > >> The idea is that you would have one or more redundent databases and use >> the COPY TO/FROM to keep them up to date. > > Well, if you have databases you would have regular tables - and > can use copy as it is now :-) But COPY copies all the records, not some of the records. > > Regards > Tino > ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
