Re: [tarantool-patches] [PATCH v3 7/7] Add merger for tuple streams (Lua part)

[Konstantin Osipov <kostja.osipov@gmail.com>]

* Alexander Turenko <alexander.turenko@tarantool.org> [19/04/25 15:57]:
> > The api is generally LGTM, one comment below:
> > 
> > > A merger is a special kind of a source, which is created from a key_def
> > > object and a set of sources. It performs a kind of the merge sort:
> > > chooses a source with a minimal / maximal tuple on each step, consumes
> > > a tuple from this source and repeats. The API to create a merger is the
> > > following:
> > > 
> > > ```lua
> > > local ctx = merger.context.new(key_def.new(<...>))
> > > local sources = {<...>}
> > > local merger_inst = merger.new(ctx, sources, {
> > 
> >     Why do you need a separate object used only to construct a
> >     merger? Why not pass all parameters into merger.new?
> 
> A user may want to cache key_def + format creation when a schema changes
> rarely. The original merger allows it:
> https://github.com/tarantool/shard/blob/180948e99148973e89f75f8e4784315e183e3fa2/shard/init.lua#L1215-L1224
> 
> Even if one doesn't cache a merger context, but runs several merges over
> one data stream (see the multiplexed cases in examples) and a schema is
> the same, it worth to reuse the context.

I wouldn't bother with it.


-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov