Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_20613292_1 (production_code VARCHAR, directed_by VARCHAR)

### Question ###
How many different production codes does the episode directed by Dominic Polcino have?

### Accurate SQL ###

SELECT COUNT(production_code) FROM table_20613292_1 WHERE directed_by = "Dominic Polcino"