On Thu, Nov 12, 2020 at 9:32 AM Andrew Dunstan <and...@dunslane.net> wrote:
> > On 11/12/20 11:12 AM, David G. Johnston wrote: > > On Thu, Nov 12, 2020 at 8:59 AM Andrew Dunstan <and...@dunslane.net > > <mailto:and...@dunslane.net>> wrote: > > > > > > > > So if we then say: > > > > > > select x, j->>x from mytable; > > > > > > you want both result columns named x? That seems like a recipe for > > serious confusion. I really don't think this proposal has been > > properly > > thought through. > > > > > > IMO It no worse than today's: > > > > select count(*), count(*) from (values (1), (2)) vals (v); > > count | count > > 2 | 2 > > > > > I guess the difference here is that there's an extra level of > indirection. So > > > select x, j->>'x', j->>x from mytable > > > would have 3 result columns all named x. > > I totally missed the variable reference there - only two of those become "x", the variable reference stays un-rewritten and thus results in "?column?", similar to today: select count(*), count(*) +1 from (values (1), (2)) vals (v); count | ?column? 2 | 2 The query rewriter would only rewrite these expressions and provide an expression-related explicit alias clause if the expression is a single operator (same as single function today) and the right-hand side of the operator is a constant (meaning the constant is a reasonable representation of every output value that is going to appear in the result column). If the RHS is a variable then there is no good name that is known to cover all output values and thus ?column? (i.e., do not rewrite/provide an alias clause) is an appropriate choice. My concerns in this area involve stored views and ruleutils, dump/reload by extension. Greenfield, this would have been nice, and worth the minimal complexity given its usefulness in the common case, but is it useful enough to introduce a whole new default naming mechanism and dealing with dump/restore concerns? David J.
