On Fri, Feb 8, 2019 at 12:18 PM Ashutosh Sharma <ashu.coe...@gmail.com> wrote:
> Hi All, > > When "ON SELECT" rule is created on a table without columns, it > successfully converts a table into the view. However, when the same is > done using CREATE VIEW command, it fails with an error saying: "view > must have at least one column". Here is what I'm trying to say: > > -- create table t1 without columns > create table t1(); > > -- create table t2 without columns > create table t2(); > > -- create ON SELECT rule on t1 - this would convert t1 from table to view > create rule "_RETURN" as on select to t1 do instead select * from t2; > > -- now check the definition of t1 > \d t1 > > postgres=# \d+ t1 > View "public.t1" > Column | Type | Collation | Nullable | Default | Storage | Description > --------+------+-----------+----------+---------+---------+------------- > View definition: > SELECT > FROM t2; > > The output of "\d+ t1" shows the definition of converted view t1 which > doesn't have any columns in the select query. > > Now, when i try creating another view with the same definition using > CREATE VIEW command, it fails with the error -> ERROR: view must have > at least one column. See below > > postgres=# create view v1 as select from t2; > ERROR: view must have at least one column > > OR, > > postgres=# create view v1 as select * from t2; > ERROR: view must have at least one column > > Isn't that a bug in create rule command or am i missing something here ? > Yes, it's looks like a bug to me. > > If it is a bug, then, attached is the patch that fixes it. > I had quick glance to the patch - here are few commits: 1) + if (event_relation->rd_rel->relnatts == 0) Can't use direct relnatts - as need to consider attisdropped. 2) I think you may like to change the error message to be in-line with the other error message in the similar code area. May be something like: "could not convert table \"%s\" to a view because table does not have any column" Regards, Rushabh Lathia www.EnterpriseDB.com
