PostgreSQL - Document Collection Foreign Data Wrapper (dc_fdw)

This PostgreSQL extension implements a Foreign Data Wrapper (FDW) for the document collection on local disk.

More information can be found in the wiki page

###Building

No external library is needed.

###Limitations

Only these 4 types of quals and their boolean combinations can be pushed down:

1. id = <integer>
2. content @@ <term>
3. to_tsquery ( <tsquery text> )
4. plainto_tsquery ( <free text> )

Otherwise, a sequential scan on all the documents in the collection is expected.

###Usage

The following parameters can be set on a document collection foreign table:

data_dir      [where the files in a document collection are located]
index_dir     [where the index files are located: postings file, dictionary file]
index_method  [either In-memory(IM) Indexing or Single-pass in-memory(SPIM) indexing]
buffer_size   [when using SPIM indexing, this is the limit of memory available]
id_col        [the column name for mapping doc id]
text_col      [the column name for mapping doc content]

###Example

CREATE EXTENSION dc_fdw;

CREATE SERVER dc_server 
	FOREIGN DATA WRAPPER dc_fdw;

CREATE FOREIGN TABLE dc_table (id int, content text) 
	SERVER dc_server
	OPTIONS (
	    data_dir '/pgsql/postgres/contrib/dc_fdw/data/reuters/training', 
    	index_dir '/pgsql/postgres/contrib/dc_fdw/data/reuters/index',
    	index_method 'SPIM',
    	buffer_size '10',
    	id_col 'id',
    	text_col 'content'
    );

-- Zheng Yang
zhengyang4k@gmail.com