In response to Satish Burnwal (sburnwal) :
> I have a ques - say I have a table that has 10 columns. But in a simple
> select query from that table, I use just 3 columns. I want to know
> whether even for fetching 3 columns, read happens for all the 10 columns
> and out of that the required 3 columns are returned ? ie Does the
> complete row with all the 10 columns are fetched even though I need just
> 3 columns ? OR only 3 columns are fetched ?
Depends, large columns (TEXT, BYTA) are TOASTed¹, that means, the content
of this columns stored in a other table. So it is always a good idea to
specify all rows you needed and don't use select *.
¹ http://www.postgresql.org/docs/8.4/interactive/storage-toast.html
Regards, Andreas
--
Andreas Kretschmer
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