Re: [GENERAL] Custom shuffle function stopped working in 9.6 - Mailing list pgsql-general

From Pavel Stehule
Subject Re: [GENERAL] Custom shuffle function stopped working in 9.6
Date
Msg-id CAFj8pRAbcVUrkQM_5zsOLj=szKtQUuG3J0t=nAEsNuWhfxTOVQ@mail.gmail.com
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In response to [GENERAL] Custom shuffle function stopped working in 9.6  (Alexander Farber <alexander.farber@gmail.com>)
Responses Re: [GENERAL] Custom shuffle function stopped working in 9.6  (Alexander Farber <alexander.farber@gmail.com>)
List pgsql-general
Hi

2017-02-11 17:37 GMT+01:00 Alexander Farber <alexander.farber@gmail.com>:
Good evening,

after switching to 9.6.2 from 9.5.3 the following custom function has stopped working:

CREATE OR REPLACE FUNCTION words_shuffle(in_array varchar[])
        RETURNS varchar[] AS
$func$
        SELECT array_agg(letters.x) FROM 
        (SELECT UNNEST(in_array) x ORDER BY RANDOM()) letters;
$func$ LANGUAGE sql STABLE;

In 9.5.3 it was shuffling characters:

words=> select words_shuffle(ARRAY['a','b','c','d','e','f']);
 words_shuffle 
---------------
 {c,d,b,a,e,f}
(1 row)

But in 9.6.2 it has stopped doing so:
words=> select words_shuffle(ARRAY['a','b','c','d','e','f']);
 words_shuffle 
---------------
 {a,b,c,d,e,f}
(1 row)

Any suggestions for a better shuffling function please?

CREATE OR REPLACE FUNCTION words_shuffle(in_array varchar[])
        RETURNS varchar[] AS
$func$
        SELECT array_agg(letters.x) FROM 
        (SELECT x FROM UNNEST(in_array) x ORDER BY RANDOM()) letters;
$func$ LANGUAGE sql STABLE;

there was some optimisations for faster expression evaluation - probably this is one effect of this optimisation.

generally SRF function should not be used in target list - now when we have LATERAL join, it is not necessary

Regards

Pavel

 

Regards
Alex


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