I was looking for code that can show all table sizes in postgres and got here.

when query executed it shows that field_data_body is consuming around 32mb space and it's external size is 22mb.I don't understand why it is consuming any space although body field of all nodes(~90K) are empty.

Comments

Even though the field is empty, there is still one record per node (more if you have revisions enabled). If you are not using the body field for the content type(s) you can delete it for that content type.