Re: [tarantool-patches] [PATCH v3 2/5] Synchronize lua schema update with space cache

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Wed, Mar 27, 2019 at 01:03:51PM +0300, Vladimir Davydov wrote:
> On Fri, Mar 22, 2019 at 03:06:07PM +0300, Georgy Kirichenko wrote:
> > Update lua schema as soon as space cache replace was done instead of
> > doing this while on_commit trigger executes. In opposite then case
> > schema changes would not be visible until commit was finished.
> > 
> > Needed for: #2798
> > ---
> >  src/box/alter.cc | 13 ++++++++-----
> >  1 file changed, 8 insertions(+), 5 deletions(-)
> > 
> > diff --git a/src/box/alter.cc b/src/box/alter.cc
> > index daaa9cd57..275e39dd5 100644
> > --- a/src/box/alter.cc
> > +++ b/src/box/alter.cc
> > @@ -750,8 +750,6 @@ alter_space_commit(struct trigger *trigger, void *event)
> >  		op->commit(alter, txn->signature);
> >  	}
> >  
> > -	trigger_run_xc(&on_alter_space, alter->new_space);
> > -
> >  	alter->new_space = NULL; /* for alter_space_delete(). */
> >  	/*
> >  	 * Delete the old version of the space, we are not
> > @@ -787,6 +785,8 @@ alter_space_rollback(struct trigger *trigger, void * /* event */)
> >  	space_swap_triggers(alter->new_space, alter->old_space);
> >  	space_swap_fk_constraints(alter->new_space, alter->old_space);
> >  	space_cache_replace(alter->new_space, alter->old_space);
> > +	trigger_run(&on_alter_space, alter->old_space);
> > +
> >  	alter_space_delete(alter);
> >  }
> >  
> > @@ -888,6 +888,7 @@ alter_space_do(struct txn *txn, struct alter_space *alter)
> >  	 * cache with it.
> >  	 */
> >  	space_cache_replace(alter->old_space, alter->new_space);
> > +	trigger_run_xc(&on_alter_space, alter->new_space);
> 
> The comment right above says that this function must not throw an
> exception here so I guess we should use _xc free variant. Not that it
> really matters, as on_alter_space trigger can only fail on OOM, which
> is hardly ever possible.

Guess we should simply fold trigger_run_xc in space_cache_replace and
panic on error.

BTW this is how things were before

commit 1f736583361f537c8e1fb4ea0df0b92ee8d50c6d
Author: Vladimir Davydov <vdavydov.dev@gmail.com>
Date:   Tue Sep 19 14:21:59 2017 +0300

    box: use trigger to push space data to Lua

    Currently, it is done by space_cache_replace/delete which violates
    incapsulation. Let's introduce a trigger that is fired after a change in
    a space definition is committed and use it to propagate changes to Lua.
    Patch by @kostja.