On Thu, Oct 21, 2010 at 5:05 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Tim Uckun <timuckun@xxxxxxxxx> writes: >> I have a very simple update query. > >> update cu >> set screenshot_file_name = tu.screenshot_file_name, >> Â Â screenshot_content_type Â= tu.screenshot_content_type, >> Â Â screenshot_file_size = tu.screenshot_file_size, >> Â Â screenshot_status Â= tu.screenshot_status >> from Âcu >> inner join tu on tu.cu_id = cu.id > > That isn't actually the query you're issuing, because if it were > you would get an error "table name "cu" specified more than once". Sorry I shortened the names of the tables. > I suspect that the query you're actually issuing involves an > unconstrained cartesian product self-join between the target table > and another instance of itself. ÂPostgres doesn't consider that > the target table should be named again in FROM. ÂBut it's hard to > be sure about that when looking at a redacted query. I apologize for the redacted query. I was trying to make it easier to follow. Here is the actual query. update consolidated_urls set screenshot_file_name = tu.screenshot_file_name, screenshot_content_type = tu.screenshot_content_type, screenshot_file_size = tu.screenshot_file_size, screenshot_status = tu.screenshot_status from consolidated_urls cu inner join trending_urls tu on tu.consolidated_url_id = cu.id This is a simple inner join. select count(cu.id) from consolidated_urls cu inner join trending_urls tu on tu.consolidated_url_id = cu.id yields 3657 records. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
