Hello It is redundant to current FETCH_COUNT implementation, so I don't see sense to use it together. Maybe we can drop FETCH_COUNT and replace it by --single-row mode and probably it can simplify code.
Regards Pavel 2013/4/23 Christopher Manning <c...@christophermanning.org> > psql currently collects the query result rows in memory before writing > them to a file and can cause out of memory problems for large results in > low memory environments like ec2. I can't use COPY TO STDOUT or FETCH_COUNT > since I'm using Redshift and it doesn't support [writing to STDOUT]( > http://docs.aws.amazon.com/redshift/latest/dg/r_COPY.html) or [CURSOR]( > https://forums.aws.amazon.com/thread.jspa?threadID=122664). > > [Single Row Mode is available in Postgres 9.2]( > http://www.postgresql.org/docs/9.2/static/libpq-single-row-mode.html) but > [it doesn't look like]( > http://www.postgresql.org/docs/9.2/static/app-psql.html) you can tell > psql to use single row mode when writing to a file (using --output). > > I'm proposing to add a --single-row option to psql that would allow the > result rows of a query to be streamed to a file without collecting them in > memory first. > > I'm new to the postgres source, but I was considering doing this by adding > an elseif at [this line in bin/psql/common.c]( > https://github.com/postgres/postgres/blob/master/src/bin/psql/common.c#L955) > that > would call [PQsetSingleRowMode]( > https://github.com/postgres/postgres/blob/master/src/interfaces/libpq/fe-exec.c#L1581) > and > ideally use something very similar to [ExecQueryUsingCursor]( > https://github.com/postgres/postgres/blob/master/src/bin/psql/common.c#L1081 > ) > > Please let me know if that would be an acceptable addition and if there's > anything in particular I should be aware of when adding the feature. > > Thank you, > Christopher > >
