On Thu, Aug 29, 2024 at 8:15 PM Peter Eisentraut <pe...@eisentraut.org> wrote: > > > > drop table if exists comment_test cascade; > > CREATE TABLE comment_test ( > > id int, > > positive_col int GENERATED ALWAYS AS (22) CHECK (positive_col > 0), > > positive_col1 int GENERATED ALWAYS AS (22) stored CHECK (positive_col > > > 0) , > > indexed_col int, > > CONSTRAINT comment_test_pk PRIMARY KEY (id)); > > CREATE INDEX comment_test_index ON comment_test(indexed_col); > > ALTER TABLE comment_test ALTER COLUMN positive_col1 SET DATA TYPE text; > > ALTER TABLE comment_test ALTER COLUMN positive_col SET DATA TYPE text; > > the last query should work just fine? > > I played with this and I don't see anything wrong with the current > behavior. I noticed that in your test case > > > positive_col1 int GENERATED ALWAYS AS (22) stored CHECK > (positive_col > 0) , > > you have the wrong column name in the check constraint. I'm not sure if > that was intentional. >
That's my mistake. sorry for the noise. On Wed, Aug 21, 2024 at 6:52 PM Dean Rasheed <dean.a.rash...@gmail.com> wrote: > > > Another argument for doing it that way round is to not add too many > extra cycles to the processing of existing queries that don't > reference generated expressions. ISTM that this patch is potentially > adding quite a lot of additional overhead -- it looks like, for every > Var in the tree, it's calling get_attgenerated(), which involves a > syscache lookup to see if that column is a generated expression (which > most won't be). Ideally, we should be trying to do the minimum amount > of extra work in the common case where there are no generated > expressions. > > Regards, > Dean > > The new patch does some rebasing and contains various fixes to the > issues you presented. As I mentioned, I'll look into improving the > rewriting. based on your latest patch (v4-0001-Virtual-generated-columns.patch), I did some minor cosmetic code change and tried to address get_attgenerated overhead. basically in expand_generated_columns_in_query and expand_generated_columns_in_expr preliminary collect (reloid,attnum) that have generated_virtual flag into expand_generated_context. later in expand_generated_columns_mutator use the collected information. deal with wholerow within the expand_generated_columns_mutator seems tricky, will try later.
v4-0001-Virtual-generated-columns_minorchange.no-cfbot
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