>I don't think so, because arrays can contain duplicates.
I just add two element to the array. One for INITCOND value NULL, second
for first row value.
So Array size is always 2. So no duplicates.
>rhaas=# select coalesce(first(x.column1), 'wrong') from (values
>(null), ('correct')) x;
>coalesce
>----------
> wrong
>(1 row)
It works correct..
I didn't said it returns, first non-null value for a column from aggregate
window.
I said my implementation returns first row value for a column.
Here first row element is "null ", hence it returns null.
check this....
db=# select
db-# coalesce(first(x.column1),'null') as col1 ,
db-# coalesce(first(x.column2),'null') as col2,
db-# coalesce(first(x.column3),'null') as col3
db-# from (values (null,'abc',null), ('correct','wrong','notsure'),
('second','second1','second3')) x
db-# ;
col1 | col2 | col3
------+------+------
null | abc | null
(1 row)
Its work correct. It returns first row value for a column.
--Sudalai
-----
sudalai
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