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From: Vladimir Davydov <vdavydov.dev@gmail.com>
To: Alexander Turenko <alexander.turenko@tarantool.org>
Cc: tarantool-patches@freelists.org
Subject: Re: [PATCH v2 2/6] Add functions to ease using Lua iterators from C
Date: Wed, 16 Jan 2019 15:20:38 +0300	[thread overview]
Message-ID: <20190116122038.udcbj4qbb5gung2c@esperanza> (raw)
In-Reply-To: <20190116114012.gxw4q3nxj7moopx6@tkn_work_nb>

On Wed, Jan 16, 2019 at 02:40:12PM +0300, Alexander Turenko wrote:
> > > > > +
> > > > > +/**
> > > > > + * Create a Lua iterator from {gen, param, state}.
> > > > 
> > > > May be, we could pass idx == 0 to create an iterator from
> > > > gen, param, state (without a table)? Would it be worthwhile?
> > > > 
> > > 
> > > I think it is good idea, because cases could be different. My thought
> > > was that we'll add another function for this case (if we'll need), but
> > > using idx == 0 is better. I created the similar API before for
> > > luaT_newtuple().
> > > 
> > > And I think the new merger API will require it.
> > 
> > The patch looks good to me now, but I'm still not sure the new merger
> > implementation will need to deal with Lua iterators in C at all, as one
> > can easily write a wrapper function in Lua turning an iterator to a
> > 'fetch' closure, which then can be passed to a source constructor.
> 
> This is not the thread about merger, but the idea looks weird for me.
> 'next' has one meaning (get one tuple), 'fetch' has another meaning (get
> next tuples batch). 'next' is written in C and predefined, 'fetch' is
> user-defined Lua function. When you'll try to express one over another
> you'll find rough edges, e. g. need of extra wrapping table.

Yep, why not wrap an iterator/table/whatever so that it works as fetch()
closure taken by one of available source constructors.

> 
> But my main objection is that it is hard to think what is going on
> when 'next' and 'fetch' are mixed.

I never mixed those.

'next' would be a C function returning C tuples. This would be a method
of a source. It would be used by a merger to get the next tuple to
merge. It would also be used by source:pairs() Lua function.

'fetch' would be a Lua function returning either Lua tuples or tuple
batches (represented by Lua tables or raw msgpack). What exactly it
returns depends on the source type.

  reply	other threads:[~2019-01-16 12:20 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09 20:20 [PATCH v2 0/6] Merger Alexander Turenko
2019-01-09 20:20 ` [PATCH v2 1/6] Add luaL_iscallable with support of cdata metatype Alexander Turenko
2019-01-10 12:21   ` Vladimir Davydov
2019-01-09 20:20 ` [PATCH v2 2/6] Add functions to ease using Lua iterators from C Alexander Turenko
2019-01-10 12:29   ` Vladimir Davydov
2019-01-15 23:26     ` Alexander Turenko
2019-01-16  8:18       ` Vladimir Davydov
2019-01-16 11:40         ` Alexander Turenko
2019-01-16 12:20           ` Vladimir Davydov [this message]
2019-01-17  1:20             ` Alexander Turenko
2019-01-28 18:17         ` Alexander Turenko
2019-03-01  4:04           ` Alexander Turenko
2019-01-09 20:20 ` [PATCH v2 3/6] lua: add luaT_newtuple() Alexander Turenko
2019-01-10 12:44   ` Vladimir Davydov
2019-01-18 21:58     ` Alexander Turenko
2019-01-23 16:12       ` Vladimir Davydov
2019-01-28 16:51         ` Alexander Turenko
2019-03-01  4:08           ` Alexander Turenko
2019-01-09 20:20 ` [PATCH v2 4/6] lua: add luaT_new_key_def() Alexander Turenko
2019-01-10 13:07   ` Vladimir Davydov
2019-01-29 18:52     ` Alexander Turenko
2019-01-30 10:58       ` Alexander Turenko
2019-03-01  4:10         ` Alexander Turenko
2019-01-09 20:20 ` [PATCH v2 5/6] net.box: add helpers to decode msgpack headers Alexander Turenko
2019-01-10 17:29   ` Vladimir Davydov
2019-02-01 15:11     ` Alexander Turenko
2019-03-05 12:00       ` Alexander Turenko
2019-01-09 20:20 ` [PATCH v2 6/6] Add merger for tuple streams Alexander Turenko

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