Word-level bigrams/trigrams in tsvector

<div dir="ltr">I'm wondering how I can store word-level bigrams/trigrams in a tsvector that I can query against. I was
expectingthe final query to match "the air" and return the one tuple to me.<div style="style"><br /></div><div
style="style">Forinstance:</div><div style="style"><br /></div><blockquote style="margin:0px 0px 0px
40px;border:none;padding:0px"><divstyle="style">postgres=# create table docs (a tsvector);</div><div style="style"><div
style="style">CREATETABLE</div></div><div style="style"><div style="style"><div style="style"><div
style="style">postgres=#insert into docs (a) values (strip('''the air'' smells ''sea water'''::tsvector));</div><div
style="style">INSERT0 1</div><div style="style"> postgres=# select * from docs;</div><div style="style">             
 a               </div><div style="style">--------------------------------</div><div style="style"> 'sea water'
'smells''the air'</div><div style="style">(1 row)</div><div style="style"><br /></div><div style="style">postgres=#
select* from docs where a @@ to_tsquery('''the air''');</div><div style="style"> a </div><div
style="style">---</div><divstyle="style">(0 rows)</div><div style="style"><br
/></div></div></div></div></blockquote>Thanks,Alan</div>