SQLSTATE[42703]: Undefined column: ### ERROR: column t.word does not exist at character ###.

Tested on Postgres 8.4

Steps to reproduce

1. Create full text index on any field.
2. Create view with exposed filter on this field. Enter 2 or more words.
3. You will get provided error.

More details

Module generates the following SQL:

SELECT COUNT(*) AS expression
FROM (
	SELECT 1 AS expression
	FROM search_api_db_entity_search_api_language t
	WHERE t.item_id IN  (
		SELECT t.item_id AS item_id
		FROM (
			SELECT t.item_id AS item_id
			FROM search_api_db_entity_field t
			WHERE ( (word = 'first') OR (word = 'second') )
		) t
		GROUP BY t.item_id
		HAVING  (COUNT(DISTINCT t.word) >= '2') 
	) 
) subquery

The problem is in HAVING (COUNT(DISTINCT t.word) >= '2') line, because of missing t.word field in the SELECT clause.

Proper SQL query:

SELECT COUNT(*) AS expression
FROM (
	SELECT 1 AS expression
	FROM search_api_db_entity_search_api_language t
	WHERE t.item_id IN  (
		SELECT t.item_id AS item_id
		FROM (
			SELECT t.item_id AS item_id, t.word AS word
			FROM search_api_db_entity_field t
			WHERE ( (word = 'first') OR (word = 'second') )
		) t
		GROUP BY t.item_id
		HAVING  (COUNT(DISTINCT t.word) >= '2') 
	) 
) subquery