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From "Adam Kocoloski (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-1118) Adding a NIF based JSON decoding/encoding module
Date Sun, 03 Apr 2011 20:14:05 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-1118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13015204#comment-13015204
] 

Adam Kocoloski commented on COUCHDB-1118:
-----------------------------------------

Hi Filipe, which version are you proposing to commit?

There must be some overhead associated with using a NIF.  I thought in at least one version
of Paul's work the overhead made the NIF version slower at decoding very small documents than
pure Erlang.  Is that no longer the case?  Also, has anyone studied the impact that working
with very large JSON bodies has on the soft real-time properties of the Erlang VM?  Do you
know what kind of throughput you see in terms of MB/sec? I guess if that number is large enough
then any reasonably-sized JSON body (even a very big batch of KV pairs returned from a map_docs
call) will be processed without mucking up the scheduling too much.

> Adding a NIF based JSON decoding/encoding module
> ------------------------------------------------
>
>                 Key: COUCHDB-1118
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-1118
>             Project: CouchDB
>          Issue Type: Improvement
>          Components: Database Core
>            Reporter: Filipe Manana
>             Fix For: 1.2
>
>
> Currently, all the Erlang based JSON encoders and decoders are very slow, and decoding
and encoding JSON is something that we do basically everywhere.
> Via IRC, it recently discussed about adding a JSON NIF encoder/decoder. Damien also started
a thread at the development mailing list about adding NIFs to trunk.
> The patch/branch at [1] adds such a JSON encoder/decoder. It is based on Paul Davis'
eep0018 project [2]. Damien made some modifications [3] to it mostly to add support for big
numbers (Paul's eep0018 limits the precision to 32/64 bits) and a few optimizations. I made
a few corrections and minor enhancements on top of Damien's fork as well [4]. Finally BenoƮt
identified some missing capabilities compared to mochijson2 (on encoding, allow atoms as strings
and strings as object properties).
> Also, the version added in the patch at [1] uses mochijson2 when the C NIF is not loaded.
Autotools configuration was adapted to compile the NIF only when we're using an OTP release
>= R13B04 (R13B03 NIF API is too limited and suffered many changes compared to R13B04 and
R14) - therefore it should work on any OTP release > R13B at least.
> I successfully tested this on R13B03, R13B04 and R14B02 in an Ubuntu environment.
> I'm not sure if it builds at all on Windows - would appreciate if someone could verify
it.
> Also, I'm far from being good with the autotools, so I probably missed something important
or I'm doing something in a not very standard way.
> This NIF encoder/decoder is about one order of magnitude faster compared to mochijson2
and other Erlang-only solutions such as jsx. A read and writes test with relaximation shows
this has a very positive impact, specially on reads (the EJSON encoding is more expensive
than JSON decoding) - http://graphs.mikeal.couchone.com/#/graph/698bf36b6c64dbd19aa2bef634052381
> @Paul, since this is based on your eep0018 effort, do you think any other missing files
should be added (README, etap tests, etc)? Also, should we put somewhere a note this is based
on your project?
> [1] - https://github.com/fdmanana/couchdb/compare/json_nif
> [2] - https://github.com/davisp/eep0018
> [3] - https://github.com/Damienkatz/eep0018/commits/master
> [4] - https://github.com/fdmanana/eep0018/commits/final_damien

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