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Subject: Re: view server line protocol changes for _list
From: J Chris Anderson <jchris@gmail.com>
In-Reply-To: <AANLkTinZ8nkVHlj9ShDOOCnMXWIHuVsS3ciIJbfIVjzG@mail.gmail.com>
Date: Tue, 25 May 2010 16:42:31 -0700
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References: <AANLkTinZ8nkVHlj9ShDOOCnMXWIHuVsS3ciIJbfIVjzG@mail.gmail.com>
To: dev@couchdb.apache.org


On May 25, 2010, at 4:36 PM, Mikeal Rogers wrote:

> There is a fairly serious problem at the moment with using list
> functions in CouchDB.
>=20
> To recap, the view server line protocol for _list functions looks like =
this.
>=20
>>>> ["lists", "name", {request}]
> <<< ["start", ["chunks"], {"headers":{}, "code":200}]
>>>> ["list_row", {"key":"k","value":"v"}]
> <<< ["chunk", ["chunks"]]
>>>> ["list_end"]
> <<< ["end", ["tail chunks"]]
>=20
> The problem with this is that the response from the view server that
> contains the status code MUST come before any list_row calls have
> happened. This means that the view server can't return 404 for queries
> that don't have any results. In fact, the view can really only return
> 200 for anything but a HEAD request on list functions.
>=20
> I'd like to propose the following changes to the view server protocol
> for list functions.
>=20
>>>> ["lists", "name"]
> <<< ["getRow"]
>>>> ["list_row", {"key":"k","value":"v"}]
> <<< ["getRow"]
>>>> ["list_row", {"key":"k","value":"v"}]
> <<< ["start", "chunk", {"headers":{}, "code":200}]
> <<< ["send", "chunk"]
> <<< ["send", "chunk"]
> <<< ["getRow"]
>>>> ["list_row", {"key":"k","value":"v"}]
> <<< ["getRow"]
>>>> ["list_end"]
> <<< ["end", "tail chunk"]
>=20
> The big change is that there is no longer a strict request/response.
> The erlang side stays idle accepting chunks to send until it gets a
> ["getRow"] call.
>=20
> Also, all chunks sent in a single line to erlang get sent to the
> client in one chunk anyway so I changed the type from array to string
> since you can do multiple ["send"] calls between ["list_row"]
> responses anyway.
>=20
> Thoughts?

I think this sounds right to me. I'm not seeing any big issues off the =
top of my head.

Chris

>=20
> -Mikeal