Fetching rows from million rows table(Optimization)

I have millions of rows in a table of Greenplum database out of which I have to fetch around 45k rows and store them in a python List. It's taking more than 2hrs to fetch the data. How can I optimize the time taken to fetch data? resultList = [] for(item in list): result = SELECT column_1, ... column_n from TABLE WHERE column = item resultList.append(result)