CREATE OR REPLACE FUNCTION array_append_distinct(anyarray, anyelement)
RETURNS anyarray AS $$
SELECT ARRAY(SELECT unnest($1) union SELECT $2)
$$ LANGUAGE sql;
postgres=# select array_append_distinct(array[1,2,3,4],1);
array_append_distinct
-----------------------
{1,2,3,4}
(1 row)
postgres=# select array_append_distinct(array[1,2,3,4],7);
array_append_distinct
-----------------------
{1,2,3,4,7}
(1 row)
CREATE OR REPLACE FUNCTION array_erase(anyarray, anyelement)
RETURNS anyarray AS $$
SELECT ARRAY(SELECT v FROM unnest($1) g(v) WHERE v <> $2)
$$ LANGUAGE sql;
postgres=# select array_erase(array[1,2,3,2,5], 2);
array_erase
-------------
{1,3,5}
(1 row)
postgres=# select array_erase(array[1,2,3,2,5], 1);
array_erase
-------------
{2,3,2,5}
(1 row)
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Wednesday, April 21, 2010
two small functions for arrays
Hello,
If you miss some functions for arrays look here:
Hey, could You explain to me how should I interpret "unnest($1) g(v)" shouldnt there be an ',' ? Otherwise I've never seen sucha a construct in psql and I wonder how it works.
ReplyDeletethis is just alias with column names. The "unnest" is table function - it returns a table, so I can rename a returned table (by g like generator) and columns (by v like value).
ReplyDeleteit is same like
postgres=# create table a(b integer);
CREATE TABLE
Time: 173.711 ms
postgres=# select * from a g(x);
x
───
(0 rows)
Thank You, now it is all clear. Btw, great blog with very interesting posts. I hope You will keep it that way :)
ReplyDelete