From: Tom Lane <tgl@sss.pgh.pa.us>
To: Андрей Хозов <avkhozov@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Performance issue with castings args of the function
Date: Mon, 02 Jan 2017 11:36:20 -0500
Message-ID: <18071.1483374980@sss.pgh.pa.us> (raw)
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=?UTF-8?B?0JDQvdC00YDQtdC5INCl0L7Qt9C+0LI=?= <avkhozov@gmail.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
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, avkhozov@gmail.com
Subject: Re: Performance issue with castings args of the function
In-Reply-To: <18071.1483374980@sss.pgh.pa.us>
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