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PostgreSQL SQL/MED FDW for CouchDB

branch: master
README
CouchDB FDW (beta) for PostgreSQL 9.1+
======================================

This PostgreSQL extension implements a Foreign Data Wrapper (FDW) for
the CouchDB document-oriented database: http://couchdb.apache.org/

IMPORTANT: There're bugs in the existing version. I'm working on it and will
be releasing another version very soon.


Building
--------

To build the code, you need the yajl(Yet Another JSON Library) and libcurl installed 
on your system. 

You can checkout the yajl from GitHub:
https://github.com/lloyd/yajl
OR
download from:
http://lloyd.github.com/yajl/

libcurl C interface can be found here:
http://curl.haxx.se/libcurl/c/

Once that's done, the extension can be built with:

PATH=/usr/local/pgsql91/bin/:$PATH make USE_PGXS=1 make
sudo PATH=/usr/local/pgsql91/bin/:$PATH make USE_PGXS=1 install

(assuming you have PostgreSQL 9.1 in /usr/local/pgsql91).

I've tested on Mac OS X 10.6 only, but other *nix's should also work.
I haven't tested on Windows, but the code should be good on MinGW.

Limitations
-----------

- If there is no quals to pushdown, we get a list of '_id's to begin with,
  and then fetch whatever records still exist as we build the tuples.

- We can only pushdown '_id' (with or without '_rev') to CouchDB, which must use 
  the TEXTEQ operator.

- The top-level-attributes of a document can be mapped to columns in a
  foreign table.
  
- In case you want the map a column to the entire JOSN doc, use 
	columnname '_doc'
  in foreign table options (which means your remote couchdb shouldn't have
  a top-level-attribute called '_doc', otherwise there will be conficts).

Usage
-----

The following parameters can be set on a CouchDB foreign server:

address:	The address or hostname of the CouchDB server.
	 	Default: 127.0.0.1

port:		The port number on which the CouchDB server is listening.
     		Default: 5984

The following parameter can be set on a CouchDB foreign table:

database:	The name of the CouchDB database to query.
	  	Default: test

<column name>:	The column mapping to remote JSON attributes.
		If there is no column mapping specified, default is the origninal column name.
		Please note that '_doc' is reserved for mapping the entire JSON document.

The following parameter can be set on a user mapping for a CouchDB
foreign server:

username:	The username to authenticate to the CouchDB server with.
		Default: <none>
		
password:	The password to authenticate to the CouchDB server with.
		Default: <none>

Example
-------

CREATE SERVER couchdb_server 
	FOREIGN DATA WRAPPER couchdb_fdw 
	OPTIONS (address '127.0.0.1', port '5984');

CREATE FOREIGN TABLE couchdb_table (key text, value text) 
	SERVER couchdb_server
	OPTIONS (database 'testdb', key '_id', value '_doc');

CREATE USER MAPPING FOR PUBLIC
	SERVER couchdb_server
	OPTIONS (username 'testuser', password 'secret');

-- 
Zheng Yang
zhengyang4k@gmail.com
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