I think i figured out what is slowing down my insert statement:

In the source table, i have a field of type varchar(60), which i am
inserting in the destination table in a blob field.

The insert statement takes about 50 minutes when i try to transfer
this field, and about 5 seconds (!!) when i don't mention it.

So probably this incredible delay is a result of some conversion
from varchar to blob.

Is this expected?