Обсуждение: UPDATE works on a view?
Err, sorry if this is back to basics, but I was very confused by someone being able to UPDATE myview SET col = 1 and the underlying table actually being updated properly.
Wells Oliver <wells.oliver@gmail.com> writes: > Err, sorry if this is back to basics, but I was very confused by someone > being able to *UPDATE myview SET col = 1* and the underlying table actually > being updated properly. > Is this recent? When did we become able to UPDATE on views? Depends on your definition of "recent" ... Author: Tom Lane <tgl@sss.pgh.pa.us> Branch: master Release: REL9_3_BR [a99c42f29] 2012-12-08 18:26:21 -0500 Support automatically-updatable views. This patch makes "simple" views automatically updatable, without the need to create either INSTEAD OF triggers or INSTEAD rules. "Simple" views are those classified as updatable according to SQL-92 rules. The rewriter transforms INSERT/UPDATE/DELETE commands on such views directly into an equivalent command on the underlying table, which will generally have noticeably better performance than is possible with either triggers or user-written rules. A view that has INSTEAD OF triggers or INSTEAD rules continues to operate the same as before. For the moment, security_barrier views are not considered simple. Also, we do not support WITH CHECK OPTION. These features may be added in future. Dean Rasheed, reviewed by Amit Kapila regards, tom lane
Wild. Dead simple, had no idea, works. Learn something new every day.
Part of me thinks it's better for stuff to be explicit in what it is updating and views abstract that a little, but it's nice.
Thanks Tom!
On Wed, Aug 5, 2020 at 11:42 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
Wells Oliver <wells.oliver@gmail.com> writes:
> Err, sorry if this is back to basics, but I was very confused by someone
> being able to *UPDATE myview SET col = 1* and the underlying table actually
> being updated properly.
> Is this recent? When did we become able to UPDATE on views?
Depends on your definition of "recent" ...
Author: Tom Lane <tgl@sss.pgh.pa.us>
Branch: master Release: REL9_3_BR [a99c42f29] 2012-12-08 18:26:21 -0500
Support automatically-updatable views.
This patch makes "simple" views automatically updatable, without the need
to create either INSTEAD OF triggers or INSTEAD rules. "Simple" views
are those classified as updatable according to SQL-92 rules. The rewriter
transforms INSERT/UPDATE/DELETE commands on such views directly into an
equivalent command on the underlying table, which will generally have
noticeably better performance than is possible with either triggers or
user-written rules. A view that has INSTEAD OF triggers or INSTEAD rules
continues to operate the same as before.
For the moment, security_barrier views are not considered simple.
Also, we do not support WITH CHECK OPTION. These features may be
added in future.
Dean Rasheed, reviewed by Amit Kapila
regards, tom lane
Wells Oliver
wells.oliver@gmail.com
wells.oliver@gmail.com
Hi Oliver, > On 05. Aug, 2020, at 20:30, Wells Oliver <wells.oliver@gmail.com> wrote: > > Err, sorry if this is back to basics, but I was very confused by someone being able to UPDATE myview SET col = 1 and theunderlying table actually being updated properly. > > Is this recent? When did we become able to UPDATE on views? yes, this is possible: postgres=# create table t(i int); CREATE TABLE postgres=# create view v(i) as select i from t; CREATE VIEW postgres=# insert into v(i) values (0); INSERT 0 1 postgres=# select * from v; i --- 0 (1 row) postgres=# update v set i=3; UPDATE 1 postgres=# select * from v; i --- 3 (1 row) But I don't know since which PostgreSQL version views can up updated. Cheers, Paul
On Thu, Aug 6, 2020 at 7:56 AM Paul Förster <paul.foerster@gmail.com> wrote:
Hi Oliver,
> On 05. Aug, 2020, at 20:30, Wells Oliver <wells.oliver@gmail.com> wrote:
>
> Err, sorry if this is back to basics, but I was very confused by someone being able to UPDATE myview SET col = 1 and the underlying table actually being updated properly.
>
> Is this recent? When did we become able to UPDATE on views?
yes, this is possible:
postgres=# create table t(i int);
CREATE TABLE
postgres=# create view v(i) as select i from t;
CREATE VIEW
postgres=# insert into v(i) values (0);
INSERT 0 1
postgres=# select * from v;
i
---
0
(1 row)
postgres=# update v set i=3;
UPDATE 1
postgres=# select * from v;
i
---
3
(1 row)
But I don't know since which PostgreSQL version views can up updated.
For this type of high level features, the Feature Matrix is a pretty good way to find out these things (https://www.postgresql.org/about/featurematrix/#views-materialized-views).
Updatetable views was 9.3, WITH CHECK was 9.4.
Hi Magnus, > On 06. Aug, 2020, at 12:20, Magnus Hagander <magnus@hagander.net> wrote: > For this type of high level features, the Feature Matrix is a pretty good way to find out these things (https://www.postgresql.org/about/featurematrix/#views-materialized-views). I didn't know that. Many thanks. :-) Cheers, Paul