Hashing a String to a Numeric Value in PostgreSQL

Question

I need to Convert Strings stored in my Database to a Numeric value. Result can be Integer (preferred) or Bigint. This conversion is to be done at Database side in a PL/pgSQL

Answer 1

This is an implementation of Java's String.hashCode():

CREATE OR REPLACE FUNCTION hashCode(_string text) RETURNS INTEGER AS $$
DECLARE
  val_ CHAR[];
  h_ INTEGER := 0;
  ascii_ INTEGER;
  c_ char;
BEGIN
  val_ = regexp_split_to_array(_string, '');

  FOR i in 1 .. array_length(val_, 1)
  LOOP
    c_ := (val_)[i];
    ascii_ := ascii(c_);
    h_ = 31 * h_ + ascii_;
    raise info '%: % = %', i, c_, h_;
  END LOOP;
RETURN h_;
END;
$$ LANGUAGE plpgsql;