SQL supports hidden columns: columns that are only included in a projection if explicitly requested. An example of this is the rowid column that is created on tables without explicitly primary keys.

Currently, there is no way to get a hidden column on a user-defined table: it's only possible if you manually set the hidden boolean in the table descriptor, by editing the CockroachDB source code.

It could conceivably be useful for users to define hidden columns on their own tables. This issue tracks adding that functionality. It should be pretty straightforward, and reasonably suitable for a new contributor.

• Add an NOT VISIBLE keyword to pkg/sql/parser/sql.y as an optional modifier to columns for creation and modification. e.g. CREATE TABLE a (a INT NOT VISIBLE), ALTER TABLE a ALTER COLUMN a SET [NOT] VISIBLE sql: support NOT VISIBLE in CREATE TABLE for user-defined hidden columns #58923
• Add a NOT VISIBLE attribute to ColumnTableDef in pkg/sql/sem/tree/create.go sql: support NOT VISIBLE in CREATE TABLE for user-defined hidden columns #58923
• Update MakeColumnDefDescs in pkg/sql/catalog/tabledesc/table.go to set Hidden on the column descriptor if the attribute above is set sql: support NOT VISIBLE in CREATE TABLE for user-defined hidden columns #58923
• Add AlterTableSetHidden AST nodes to pkg/sql/sem/tree/alter_table.go
• Add cases for those AST nodes in pkg/sql/alter_table.go
• Add logic tests that verify that hidden columns work as expected. A good place for these would be in pkg/sql/logictest/testdata/logic_test/hidden. sql: support NOT VISIBLE in CREATE TABLE for user-defined hidden columns #58923