From: Jochen Erwied <jochen@pgsql-performance.erwied.eu>
To: Reuven M. Lerner <reuven@lerner.co.il>
Cc: pgsql-performance@postgresql.org
Subject: Re: Speeding up loops in pl/pgsql function
Date: Thu, 26 May 2011 10:46:55 +0200
Message-ID: <589023449.20110526104655@erwied.eu> (raw)
In-Reply-To: <4DDD8209.4020208@lerner.co.il>
References: <4DDD358E.20307@lerner.co.il>
<BANLkTiko3haYX_CV4QKF8GMvsnq8-Uxs8Q@mail.gmail.com>
<4DDD8209.4020208@lerner.co.il>
Thursday, May 26, 2011, 12:26:17 AM you wrote:
> Here you go... it looked nicer before I started to make optimizations;
> I've gotten it to run about 2x as fast as the previous version, but now
> I'm sorta stuck, looking for further optimizations, including possible
> use of builtin functions.
I've got only a 9.0.4 to play with, and bytea's are passed as an
hexadecimal string, so I resorted to writing the function with TEXT as
parameters, but maybe the following helps a bit, avoiding a few IMHO
useless string/int-operations:
CREATE OR REPLACE FUNCTION translate_octals_into_decimals(bytea_string text) RETURNS text AS $$
DECLARE
bytea_string_length INTEGER := length(bytea_string);
translated_string_array BYTEA[];
output_number INTEGER := 0;
num1 INTEGER;
num2 INTEGER;
num3 INTEGER;
npos INTEGER;
nlen INTEGER;
BEGIN
RAISE NOTICE '[translate_octals_into_decimals] start at %, string of
length %', clock_timestamp(), pg_size_pretty(length(bytea_string));
npos := 1;
FOR i IN 1..bytea_string_length BY 3 LOOP
num1 := substring(bytea_string from i for 1);
num2 := substring(bytea_string from i+1 for 1);
num3 := substring(bytea_string from i+2 for 1);
output_number := 64*num1 + 8*num2 + num3;
IF output_number = 0 THEN
translated_string_array[npos] := E'\\000'::bytea;
ELSIF output_number = 92 THEN
translated_string_array[npos] := E'\\\\'::bytea;
ELSE
translated_string_array[npos] := chr(output_number)::bytea;
END IF;
npos := npos+1;
END LOOP;
RETURN array_to_string(translated_string_array, '');
END;
$$ LANGUAGE 'plpgsql';
--
Jochen Erwied | home: jochen@erwied.eu +49-208-38800-18, FAX: -19
Sauerbruchstr. 17 | work: joe@mbs-software.de +49-2151-7294-24, FAX: -50
D-45470 Muelheim | mobile: jochen.erwied@vodafone.de +49-173-5404164
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To: pgsql-performance@postgresql.org
Cc: jochen@pgsql-performance.erwied.eu, reuven@lerner.co.il
Subject: Re: Speeding up loops in pl/pgsql function
In-Reply-To: <589023449.20110526104655@erwied.eu>
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