urgent help on function/trigger

hello,
i have a procedure and a trigger as below
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create function FUNCTEST () returns opaque
as
'begin
 delete from X where COLX in (select COLX from X
 where COLX not in (select COLY from Y ));
 return null;
 end;'
language 'plpgsql';

create trigger TRIGTEST after delete on Y for each row
execute procedure FUNCTEST();
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i need some tuples to be deleted from X while i delete some from Y.

the function and trigger are created without any problem.
when i delete a tuple from Y , i get the following error.
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ERROR:  fmgr_info: function 152480: cache lookup failed
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why this error is due to ? can anyone help me on this ?
thanx in advance.