Re: Custom shuffle function stopped working in 9.6

[Pavel Stehule <pavel.stehule@xxxxxxxxx>]

Hi

2017-02-11 17:37 GMT+01:00 Alexander Farber <alexander.farber@xxxxxxxxx>:

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