On Mon, 25 Oct 1999, Aaron J. Seigo wrote:

> hi...

> my experience has been that this:
> 
>    select date_time_field::date from table_name;
> 
> is much faster than:
> 
>   select date_trunc('day',date) from table_name;
> 

Yes, date_trunc() is comlicated routine, this func. must internal parse and 
search your 'day' - it is slowly. (.. instead of datetime_date() which make
date from full DateTime only.) 

                                                        Zakkr

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