Re: Bug：Create a table with 1600 fields (reaching the upper limit), then drop several fields and create new ones, but the addition failed.

On Thu, May 4, 2023 at 9:09 AM BO ST <1599224321(at)qq(dot)com> wrote:

> *Create a table with 1600 fields (reaching the upper limit), then drop
> several fields and create new ones, but the addition failed.*
>
> test=# alter table t1 add column co1599 int;
> ALTER TABLE
> test=# alter table t1 add column co1600 int;
> ALTER TABLE
> test=# alter table t1 add column co1601 int;
> psql: ERROR: table can have at most 1600 columns
>
> *then, I drop column co1600 and add it again, failed:*
>
> test=# alter table t1 drop column co1600;
> ALTER TABLE
> test=# alter table t1 add column co1600 int;
> psql: ERROR: table can have at most 1600 columns
>
> *then, I drop column co1600 again:*
>
> test=# alter table t1 drop column co1600;
> psql: ERROR: column "co1600" of relation "t1" dose not exist
>

Implementation details - not all columns that are present on a table are
user-visible. In particular, dropped columns remain but are inaccessible
in order to avoid rewriting the table.

David J.