| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | sud <suds1434(at)gmail(dot)com> |
| Cc: | "pgsql-general(at)lists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org>, "Peter J(dot) Holzer" <hjp-pgsql(at)hjp(dot)at> |
| Subject: | Re: Dropping column from big table |
| Date: | 2024-07-16 04:52:41 |
| Message-ID: | CAKFQuwZL8jWOX35fSRsMp2tjfGpqsnUgG=cCKuVBen5PC8Jddg@mail.gmail.com |
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| Lists: | pgsql-general |
On Monday, July 15, 2024, sud <suds1434(at)gmail(dot)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.
David J.
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