How to customise mutableColumns to read-only generated columns in PostgreSQL?

[rangzen]

Hello,
We use generated columns with PostgreSQL, see Generated Columns.
We would like to exclude these columns from the generated mutableColumns list.
Can we use something like Generator customization?
Is this possible without adding fields to metadata.Table or metadata.Column? Without changing DefaultTableModel(tableMetaData metadata.Table) TableModel to an interface to reimplement (t table) MutableColumns() []Column?
Thank you!

[go-jet]

Hi @rangzen,

Currently it is not possible to exclude columns from AllColumns or MutableColumns lists.
Workaround is to create new ColumnLists and use those instead. For instance:

var PeopleAllColumns     = People.AllColumns.Except(People.HeightIn)
var PeopleMutableColumns = People.MutableColumns.Except(People.HeightIn)

In terms of implementation, I suppose adding a new `Skip' flag would be enough to signal that the column should not appear in table sql builder struct.

[mlaflamm]

I just want to clarify that Postgres generated columns are read only. The goal would be to keep them in AllColumns and the table struct but to exclude them from MutableColumns.

[go-jet]

Aha, I see. In that case implementation can be simplified. We can retrieve additional column is_generated from information_schema.columns and then in MutableColumns() []Column filter out primary key and generated columns.

The only concern is this might affect existing users. But I think it should be fine, because generated columns can't be used in either insert or update statements, so existing users are probably already excluding generated columns.

[rangzen]

@go-jet PR and data pushed. Not sure how you deal with the submodule.

[rangzen]

Yep, CircleCI need first the link to the data submodule
panic: open ./testdata/init/cockroach/test_generated.sql: no such file or directory

[go-jet]

Yeah, when jet-test-data PR is merged, jet PR build will be fixed. For local development you can use makefile command - make checkout-testdata, in tests directory, to pull latest submodule master commit.