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+ id 1565C100637; Mon, 2 Jul 2012 15:29:16 +0300 (EEST)\r
+From: Tomi Ollila <tomi.ollila@iki.fi>\r
+To: Austin Clements <amdragon@MIT.EDU>,\r
+ Mark Walters <markwalters1009@gmail.com>, Peter Feigl <craven@gmx.net>\r
+Subject: Re: [PATCH] cli: notmuch-show with framing newlines between threads\r
+ in JSON.\r
+In-Reply-To: <20120702035241.GD6220@mit.edu>\r
+References: <1341041024-5342-1-git-send-email-markwalters1009@gmail.com>\r
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+ <20120702001215.GC6220@mit.edu> <20120702035241.GD6220@mit.edu>\r
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+Date: Mon, 02 Jul 2012 15:29:16 +0300\r
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+\r
+On Mon, Jul 02 2012, Austin Clements <amdragon@MIT.EDU> wrote:\r
+\r
+> Quoth myself on Jul 01 at 8:12 pm:\r
+>> Quoth Tomi Ollila on Jul 02 at 1:13 am:\r
+>> > On Sat, Jun 30 2012, Mark Walters <markwalters1009@gmail.com> wrote:\r
+>> > \r
+>> > > Add newlines between complete threads to make asynchronous parsing\r
+>> > > of the JSON easier.\r
+>> > > ---\r
+>> > >\r
+>> > > notmuch-pick uses the JSON output of notmuch show but, in many cases,\r
+>> > > for many threads. This can take quite a long time when displaying a\r
+>> > > large number of messages (say 20 seconds for the 10,000 messages in\r
+>> > > the notmuch archive). Thus it is desirable to display results\r
+>> > > incrementally in the same way that search currently does.\r
+>> > >\r
+>> > > To make this easier this patch adds newlines between each toplevel\r
+>> > > thread. So the ouput becomes\r
+>> > >\r
+>> > > [\r
+>> > > thread1\r
+>> > > , thread2\r
+>> > > , thread3\r
+>> > > ...\r
+>> > > , last_thread\r
+>> > > ]\r
+>> > >\r
+>> > > Thus the parser can easily tell if it has enough data to do some more\r
+>> > > parsing.\r
+>> > >\r
+>> > > Obviously, this changes the JSON output. This should not break any\r
+>> > > consumer as the JSON parsers should not mind. However, it does break\r
+>> > > several tests. Obviously, I will fix these but I wanted to check if\r
+>> > > people were basically happy with the change first.\r
+>> > \r
+>> > To provide this feature rather than relying on newlines the parser should\r
+>> > use it's state to notice when one thread ends. \r
+>> > \r
+>> > Such a change could be used (privately) for human consumption -- allowing \r
+>> > free change of whitespace during inspection (in a debugging session or so).\r
+>> > Computer software should not rely (or suffer) from any additional\r
+>> > (or lack thereof) whitespace there is...\r
+>> > \r
+>> > ... or at least a really convicing argument for the chance needs to\r
+>> > be presented (before "restricting" the json output notmuch spits out).\r
+>> \r
+>> Given a JSON parser that only knows how to parse complete JSON\r
+>> expressions, it's potentially very inefficient to keep attempting to\r
+>> parse something when you don't know if it's complete. The newlines\r
+>> provide an in-band framing so the consumer knows when there's a\r
+>> complete object to be parsed.\r
+>> \r
+>> In effect, this defines a super-protocol of JSON that's compatible\r
+>> with standard JSON, but easy to incrementally parse.\r
+>> \r
+>> That said, just this weekend I implemented JSON-based search with\r
+>> incremental JSON parsing and I took a slightly different approach. I\r
+>> still put framing into the newlines of the search results, but rather\r
+>> than rely on it for correctness, the consumer uses it as an\r
+>> optimization that only hints that a complete JSON expression is\r
+>> probably available. If the expression turns out to be incomplete,\r
+>> that's okay.\r
+>> \r
+>> I considered building a fully-incremental JSON parser that never\r
+>> backtracks by more than a token, which would eliminate even the cost\r
+>> of reparsing, but if we do move to S-expressions (which I think we\r
+>> should), we want to let Emacs' C implementation do as much of the\r
+>> parsing as possible, and the only thing we can do with that is read a\r
+>> complete expression.\r
+>\r
+> Actually, I take that back. While we can't do fast incremental\r
+> S-expression parsing, `parse-partial-sexp' can tell us incrementally\r
+> (and probably very quickly) *if* there's a complete expression ready\r
+> to parse, so we could avoid calling into the parser at all unless it\r
+> would succeed.\r
+>\r
+> I'll try this out in my incremental JSON parser and see how well it\r
+> works.\r
+\r
+I played a bit with parse-partial-sexp (and sexp-at-point) and it looks\r
+like this really could work. IMO the things to be done could be\r
+\r
+1) add --format=sexp support to notmuch cli\r
+2) add tests for that (I can do some tests)\r
+3) review those patches (I will definitely be one reviewer)\r
+4) convert emacs to use --format=sexp everywhere it now uses --format=json,\r
+ (is it then basically s/(json-read)/(sexp-at-point)/ ?) and adjust tests.\r
+5) review those patches (I will definitely be one reviewer)\r
+6) add support to commands lines like \r
+ 'notmuch search --output=sexp --sort=oldest-first tag:unread' ...\r
+ (even I can do that) (of course --output=json would work too as expected)\r
+7) review...\r
+8) convert emacs notmuch search to use that syntax and incrementally\r
+ display progress.\r
+9) review...\r
+\r
+This means that we would drop adding new features using json output in\r
+emacs mua and concentrate using sexps wherever applicable.\r
+\r
+(during this we should be able to determine whether those framing newlines\r
+ are needed or not)\r
+\r
+Tomi\r
+\r
+PS: A week ago I also did some experiments how notmuch cli could spit sexp\r
+output using current json formatters -- just naiively copying those and\r
+modifying would result like 99% of copy-paste and 1% of changes. I got some\r
+initial thoughts how thihgs could be done but luckily Peter & Austin are\r
+ahead of me -- I now just eagerly wait for patches to be reviewed :D\r
projects / notmuch-archives.git / commitdiff