On Monday, July 15, 2024, sud <suds1...@gmail.com> wrote:

>
> However even with "vacuum full", the old rows will be removed completely
> from the storage , but the new rows will always be there with the 'dropped'
> column still existing under the hood along with the table storage,  with
> just carrying "null" values in it. […] Is this understanding correct?
>

No.  The table rewrite process involves creating new tuples that exactly
conform to the current row specification.  The potentially non-null data
present in live tuples for columns that have been dropped are not copied
into the newly constructed tuples.

https://github.com/postgres/postgres/blob/d2b74882cab84b9f4fdce0f2f32e892ba9164f5c/src/backend/access/heap/heapam_handler.c#L2499

David J.

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