"David G. Johnston" <david.g.johnston@xxxxxxxxx> writes: > On Thu, May 7, 2020 at 10:49 AM Amarendra Konda <amar.vijaya@xxxxxxxxx> > wrote: >> Can you please explain, why it is getting more columns in output, even >> though we have asked for only one column ? >> * Output: pa.process_activity_id, pa.process_activity_type, pa.voice_url, >> pa.process_activity_user_id, pa.app_id, pa.process_instance_id, pa.alias, >> pa.read_by_user, pa.source, pa.label_category_id, pa.label_id, >> pa.csat_response_id, m.process_activity_fragments, pa.created, pa.updated, >> pa.rule_id, pa.marketing_reply_id, pa.delivered_at, pa.reply_fragments, >> pa.status_fragment, pa.internal_meta, pa.interaction_id, >> pa.do_not_translate, pa.should_translate, pa.in_reply_to* > Not knowing the source code in this area at all... > I'm pretty sure its because it doesn't matter. It's actually intentional, to save a projection step within that plan node. We'll discard the extra columns once it matters, at some higher plan level. (There have been some debates on -hackers about whether this optimization is still worth anything, given all the executor improvements that have been made since it went in. But it was clearly a win at the time.) regards, tom lane
