Byte Sizes

Hello,

* On the size of arrays :

I did not find any info in the Docs on this.
How many bytes does an array take on disk ?

My bet would be 4 bytes for number of dimensions, 4 per dimension for the
length, and then the storage requirements of whatever's in the array.

If the array contains fixed size elements like integers, it'd be 4 bytes
per element.
However if it contains variable length elements like text, is there a
pointer table ? Or are the elements packed together ?

Is there any advantage in using a smallint[] over an integer[] ?

Does a smallint[] with 2 elements really take 12 bytes ?

* On Alignment :

The docs say fields are aligned on 4-bytes boundaries.
Does this mean that several consecutive smallint fields will take 4 bytes
each ?
What about seleral consecutive "char" fields ?

I ask this because I'll have a lot of columns with small values to store
in a table, and would like it to be small and to fit in the cache.

Thanks for any info.