PL/SQL block error

Hello,
I am very new to the postgres sql, i am trying to execute below pl/sql
block in postgres but i am getting error *'ERROR: syntax error at or
near "integer" '*, Could some one help me in this regard

declare
v_count integer;
begin
select count(1) into v_count from pg_index inx where inx.indexrelid in
(select oid from pg_class where relname='action_pk' and relowner in
(select oid from pg_authid where rolname='postgres_ref'))
and inx.indrelid in
(select oid from pg_class where relname='action' and relowner in
(select oid from pg_authid where rolname='postgres_ref'));

if v_count = 0 then
execute immediate 'create unique index action_pk
on action(acn_id)';
end if;
end

*Sivannarayanareddy Nusum****| **System Analyst(Moneta GDO)*

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