What?

Grist is a set of tools for managing spatial data non-relationally. A Grist database is a collection of features of the form:

{
    "geom": 'POINT (0.0 0.0)',
    "attr": {

    },
    "_rev": "1-4c1cee11d99c19cbc6d762b11f1b5b21"
}

...where "geom" is the Well-Known Text geometry, "attr" is the attribute data (or document), and "_rev" is the revision (modeled after the CouchDB style of ordinal+md5hash and used for conflict resolution, etc.).

Dependencies

The gristmgr program requires libgeos, libtokyocabinet, and libmozjs185.

Usage

The gristmgr tool provides management facilities for grist databases. Usage is as follows:

gristmgr v0.01
usage: gristmgr cmd [options...] path [params...]
    init path
    stat path
    list [-pv] path
    put path [key] wkt-geom json-object
    get path [-wb|-js|-gj|-wt] key
    del path key
    eval path key script
    map path script
    mkview path view [-lu|-js] script
    rmview path view
    vget path view key
    version
    help

Creating a Database

>gristmgr init mydatabase.grist

Database Info

>gristmgr stat mydatabase.grist

List Keys

>gristmgr list mydatabase.grist

Add a Feature

>gristmgr put mydatabase.grist myfeature 'POINT (-71.0617 42.3578)' '{"name": "Boston", "nicknames": ["Beantown","St. Botolph\'s Town"]}'

Get a Feature

>gristmgr get mydatabase.grist myfeature

Delete a Feature

>gristmgr del mydatabase.grist myfeature

Evaluate a Javascript Function Against a Feature

>gristmgr eval mydatabase.grist myfeature myjavascript.js

Map a Javascript Function Against All Features

>gristmgr map mydatabase.grist myjavascript.js

Implementation Details

Grist files consist of features and metadata. A feature is a geometry (libgeos) and a "document" (json-serialized object). Database files are Tokyo Cabinet key-value stores. Javascript functions may be evaluated against individual keys or against all features in the database:

>gristmgr eval mygristdb.grist mykey mymapfunction.js
>gristmgr map mygristdb mymapfunction.js

Coming Soon

• View generation
• Multiple output formats for map and eval functions(including geojson)
• RESTful server (gristd)