On Sun, Jun 10, 2018 at 11:32:56AM -0400, Tom Lane wrote: > Andrew Gierth <and...@tao11.riddles.org.uk> writes: > > I beat at the grammar a bit to see what it would take to fix it at least > > to the extent of allowing a_expr ColId in a select list after removing > > postfix ops. It looked like it was doable by making these keywords more > > reserved (all of which are already reserved words per spec): > > DOUBLE, DAY, FILTER, HOUR, MINUTE, MONTH, OVER, PRECISION, SECOND, > > VARYING, WITHIN, WITHOUT, YEAR > > Yeah, a side effect of allowing "a_expr ColId" is that we can expect, > going forward, that a lot of new keywords are going to have to become > fully reserved that otherwise wouldn't have to be. This is particularly > a problem because of the SQL committee's COBOL-hangover tendency to > invent new syntax that involves sequences of keywords; we usually > don't have a good way to deal with that short of making the first > keyword(s) reserved. > > It's arguable that going down that path will, in the long run, lead to > breaking more applications (via their table/column names suddenly becoming > reserved in some new version) than we rescue from having to quote their > SELECT aliases. At the very least we need to recognize that this is far > from cost-free. > > (wanders away wondering exactly what parsing technology the SQL committee > thinks implementations use...)
If you're wondering why people think specifications that don't include a reference implementation are a bad idea... Best, David. -- David Fetter <david(at)fetter(dot)org> http://fetter.org/ Phone: +1 415 235 3778 Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate
