On 4 March 2018 at 14:58, Pavel Stehule <pavel.steh...@gmail.com> wrote: > > > 2018-03-04 3:09 GMT+01:00 Craig Ringer <cr...@2ndquadrant.com>: > >> On 3 March 2018 at 17:56, Fabien COELHO <coe...@cri.ensmp.fr> wrote: >> >>> >>> The (trivial) big picture is to allow client-side expressions in psql >>> (which as a \if:-) by reusing pgbench expression engine, so that one could >>> write things like >>> >>> \let i :j + 12 * :k >>> >>> or >>> >>> \if :VERSION_NUM < 140000 >>> >>> >> I still haven't really grasped why this isn't done by embedding a >> client-side scripting language interpreter, giving us vastly greater >> capabilities with only the maintenance of the glue instead of writing our >> own ad-hoc scripting tool. Something confine-able like JavaScript or Lua. >> > > I am primary a psql user, so I'll talk about psql. I don't need there more > functionality, than has C macros. Not more. So \if :VERSION_NUM < x is good > enough. && || operators are nice to have > > For this I don't to join any VM. It is overkill. What scripting > functionality we can do in psql now, and probably in long future > > a) setting prompt > b) some deployment - version checks > c) implementation of some simple regress scenarios > > Can be different if we start new rich TUI client based on ncurses, new > features - but it is different story. > > More - implementation of simple expression evaluation in psql doesn't > break later integration of some VM. Maybe it prepare a way for it. > > I can imagine the psql command \lua anylua expression, with possibility to > call any lua function with possibility to iterate over SQL result, show any > result, and read, write from psql variables - prefer Lua against > JavaScript, but same can be done there too. > > But this not against to this patch. This patch is not too big, too > complex, too hard to maintain - and some simple today issues can be done > simple > > Fine by me so long as it remains a manageable scope, rather than incrementally turning into some horror scripting language.
-- Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
