Re: Performance issue with castings args of the function

Thanks all for explain!

On Mon, Jan 2, 2017 at 9:36 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> =?UTF-8?B?0JDQvdC00YDQtdC5INCl0L7Qt9C+0LI=?= <avkhozov(at)gmail(dot)com> writes:
> > create table t1 (id serial, str char(32));
>
> > create function f1(line text) returns void as $$
> > begin
> > perform * from t1 where str = line;
> > end;
> > $$ language plpgsql;
>
> This query is specifying a text comparison (text = text operator).
> Since the table column isn't text, a char-to-text conversion must
> happen at each line.
>
> > create function f2(line char) returns void as $$
> > begin
> > perform * from t1 where str = line;
> > end;
> > $$ language plpgsql;
>
> This query is specifying a char(n) comparison (char = char operator).
> No type conversion step needed, so it's faster.
>
> regards, tom lane
>

--
​Andrey Khozov