pgadmin, sql, function inputday by table name
<p>I made a function im pgadmin</p>

<hr>

<pre><code>create or replace function get_source2(a text)

returns integer as

$$
declare

    a text;

    geom geometry;

begin

    select get_source(geom) 

    from a;


end

$$

language plpgsql;
</code></pre>

<hr>

<p>I want input a by table name
How can I do?
I try to like this</p>

<p>select get_source2('postgis.center')
but
ERROR:  relation "a" does not exist
LINE 2:  from a
help me</p>