Re: View not allowing to drop column (Bug or Feature enhancement )

On Mon, May 16, 2016 at 8:49 AM, Shrikant Bhende
<shrikantbhende.net@gmail.com> wrote:
> While working on the view I came across an unusual behaviour of the view,
> PostgreSQL do not allows to drop a column from the view, whereas same
> pattern of Create and Replace view works while adding a column.

This is probably because you are using create or replace, which is
normally used to switch things in place and so it needs them to be
compatible with the old ones. A view with an extra column can be used
instead of the old one, but a view with less columns can not. I do not
see the 'not dropping' part as unusual, and the 'can add columns',
well, I see them as a little unusual on a create or replace but I see
the point in hallowing it, so just a little.

> Alter command do not have any option to drop column
> postgres=# alter view vi1
> ALTER COLUMN  OWNER TO      RENAME TO     SET SCHEMA

Well, it is a view, not a table. They are basically shorthands for
queries and places to attach triggers, so its normal they do not have
as much management options.

> If its not a bug and a limitation kindly guide me towards any documentation
> where it is mentioned.

Right at the top of create view? :

>>>>
Description

CREATE VIEW defines a view of a query. The view is not physically
materialized. Instead, the query is run every time the view is
referenced in a query.

CREATE OR REPLACE VIEW is similar, but if a view of the same name
already exists, it is replaced. The new query must generate the same
columns that were generated by the existing view query (that is, the
same column names in the same order and with the same data types), but
it may add additional columns to the end of the list. The calculations
giving rise to the output columns may be completely different.
<<<<<<

Francisco Olarte.

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