In Calcite we call that a "system column". I don't recall whether there's support in the validator to add system columns; if not, it could be added.
In Oracle only base tables can have system columns (not even views). But in Calcite any relational operator can have them. For instance, streaming join is able to add a rowtime system column. Hence the Join.getSystemFieldList() method. On Tue, Apr 18, 2017 at 8:39 AM, Jacques Nadeau <[email protected]> wrote: > James, thanks for the reminder on EXTENDS. And Julian, thanks for the > reminder of the _MAP, that must have been what I was remembering. I'm > actually looking for something slightly different: > > I want a column to exists for validation when explicitly requested but be > excluded from star expansion. Any other ideas on how to handle this? Think > ROWNUM in Oracle. I guess they call it a pseudocolumn. > > On Mon, Apr 17, 2017 at 11:49 PM, Julian Hyde <[email protected]> wrote: > >> There’s also the “_MAP” column returned by the MongoDB and Elasticsearch >> adapters. It contains a (key, value) pair for the top-level fields of each >> row. It DOES appear in SELECT *. >> >> We had the idea of rewriting >> >> SELECT empno FROM Emp >> >> to >> >> SELECT _MAP[‘empno’] FROM Emp >> >> if Emp had a particular row type but I don’t think we ever did it. >> >> Julian >> >> >> >> >> > On Apr 17, 2017, at 7:27 PM, James Taylor <[email protected]> >> wrote: >> > >> > Hey Jacques, >> > The EXTENDS (col1 type, col2 type) keyword can be used for this (and the >> > EXTENDS keyword is optional). Something like this in Phoenix: >> > >> > SELECT foo FROM bar (my_col VARCHAR) WHERE my_col = 'bas' >> > >> > Phoenix uses this for dynamic column support. >> > >> > Thanks, >> > James >> > >> > On Mon, Apr 17, 2017 at 7:17 PM, Jacques Nadeau <[email protected]> >> wrote: >> > >> >> Hey All, >> >> >> >> I remember there being a syntax in Calcite that allowed one to define an >> >> _EXTRA column or columns that could be referenced in Calcite but >> wouldn't >> >> be included in a select *. If I recall, the Splunk adapter used this at >> one >> >> point. Does this actually exist or have I lost my mind. I can't seem to >> >> find a reference to this anywhere. >> >> >> >> thanks! >> >> >> >>
