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

: 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:

password: The password to authenticate to the CouchDB server with. Default:

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 [email protected]