Re: array functions - request for opinions (was Re: [PATCHES]

Tom Lane wrote:
> You would also have to assume that the subscript lower bound is one,
> which doesn't bother me but is an additional bit of state that has to
> appear out of nowhere.  (In the assignment case you don't have to assume
> that, since the subscript tells you what to do.)

I've gotten this working for array concatenation and assignment.

Examples:

-- empty array concatenated with any element, return one element,
-- one-dimensional array, with lower bound set to 1
regression=# select '{}'::int4[] || 1; ?column?
---------- {1}
(1 row)

regression=# select 0 || '{}'::int4[]; ?column?
---------- {0}
(1 row)

regression=# select array_dims(0 || '{}'::int4[]); array_dims
------------ [1:1]
(1 row)

-- empty array concatenated with any non-empty, return the non-empty one
regression=# select '{}'::int4[] || array[[[1,2],[3,4]]];    ?column?
----------------- {{{1,2},{3,4}}}
(1 row)

-- concatenate two empty arrays, return empty array
regression=# select '{}'::int4[] || '{}'::int4[]; ?column?
---------- {}
(1 row)

-- assignment to empty array: determine number
-- of dimensions and array subscripts based on those
-- given in the assignment statement
regression=# create table t(f float8[]);
CREATE TABLE
regression=# insert into t values('{}');
INSERT 2011035 1
regression=# update t set f[-2:2] = array[1,2,3,4,5];
UPDATE 1
regression=# select * from t;      f
------------- {1,2,3,4,5}
(1 row)

regression=# select array_dims(f) from t; array_dims
------------ [-2:2]
(1 row)


One question, should this work to create an empty array:

regression=# select array[];
ERROR:  parser: parse error at or near "]" at character 14

or by analogy to '{}'::int4[]

regression=# select array[]::int4[];
ERROR:  parser: parse error at or near "]" at character 14

Or is the current '{}'::int4[] syntax all we want/need?

Joe