How to use Logical Operators in Fulltext Search?

Hi All,

I am doing a fulltext search something like this:

SELECT doc_id FROM docs WHERE tsv_title($$'magnetic induction'$$) OR
tsv_body($$'magnetic induction'$$) OR tsv_abstract($$'abstract'$$)

It is taking approximately 100 secs to execute.

But running the query on individual column something like below is taking
just few milliseconds

1) SELECT doc_id FROM docs WHERE tsv_title($$'magnetic induction'$$)

2) SELECT doc_id FROM docs WHERE tsv_body($$'magnetic induction'$$)

3) SELECT doc_id FROM docs WHERE tsv_abstract($$'magnetic induction'$$)

All the above queries are taking just few milliseconds, whereas the bigining
one taking around 100 secs.

Does anyone know, what could be wrong in this? Is this not the way to
specify logical operators like *AND, OR, NOT ?*