Re: First Aggregate Funtion?

The above implementation of "first" aggregate returns the first non-NULL item
value.

To get *first row item value* for a column use the below implementation.

-- create a function that push at most two element on given array
-- push the first row value at second index of the array
CREATE OR REPLACE FUNCTION two_value_holder(anyarray, anyelement)
returns anyarray as $$
select case when array_length($1,1) < 2 then array_append($1,$2) else
$1 end ;
$$ language sql immutable;

-- create a function that returns second element of an array
CREATE OR replace FUNCTION second_element (ANYARRAY)
RETURNS ANYELEMENT AS $$ SELECT $1[2]; $$ LANGUAGE SQL;

-- create first aggregate function that return first_row item value
CREATE AGGREGATE first(anyelement)(
SFUNC=two_value_holder,
STYPE=ANYARRAY,
INITCOND='{NULL}',
FINALFUNC=second_element
);

I hope this work..
--
Sudalai

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sudalai
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