Does dropping index on column A affect queries on column B?
Since none of the updated columns are in indexes or constraints, you could conceivably do a 'HOT' (Heap-Only-Tuple) update, which doesn't need to maintain the indexes. But for that to work you have to have room in each table block to hold both the old and the new data at the same time. Once it needs to migrate rows to different blocks (because there is no room in the current block) then it needs to maintain all the indexes to point to the new block. Since you are updating every row in the table in a single transaction, this is unlikely to be practical as space for the old tuples cannot be recycled that quickly. You could help promote the HOT updates by setting the table fillfactor to a low value (&lt;50) before loading the table data, but this unlikely to be an optimal solution.  Better to just drop the index and constraints, or to delay creating them in the first place, as discussed in your related question.