CREATE UNIQUE INDEX IF NOT EXISTS in postgreSQL

Question

Plese I would like to do in PostgreSQL something like

CREATE UNIQUE INDEX IF NOT EXISTS

Any idea?

Answer 1

I have wrapped a_horse_with_no_name's code with PLSQL function for more convenient usage. I hope somebody will find it useful.

CREATE OR REPLACE FUNCTION create_index(table_name text, index_name text, column_name text) RETURNS void AS $$ 
declare 
   l_count integer;
begin
  select count(*)
     into l_count
  from pg_indexes
  where schemaname = 'public'
    and tablename = lower(table_name)
    and indexname = lower(index_name);

  if l_count = 0 then 
     execute 'create index ' || index_name || ' on ' || table_name || '(' || column_name || ')';
  end if;
end;
$$ LANGUAGE plpgsql;

usage: select create_index('my_table', 'my_index_name', 'id');