Re: phrase search

I looked at query operators for tsquery and here are some of the new
query operators for position based queries. I am just proposing some
changes and the questions I have.

1. What is the meaning of such a query operator?

foo #5 bar -> true if the document has word "foo" followed by "bar" at
5th position.

foo #<5 bar -> true if document has word "foo" followed by "bar" with in
5 positions

foo #>5 bar -> true if document has word "foo" followed by "bar" after 5
positions

then some other ways it can be used are
!(foo #<5 bar) -> true if document never has any "foo" followed by bar
with in 5 positions.

etc .....

2. How to implement such query operators?

Should we modify QueryItem to include additional distance information or
is there any other way to accomplish it?

Is the following list sufficient to accomplish this?
a. Modify to_tsquery
b. Modify TS_execute in tsvector_op.c to check new operator

Is there anything needed in rewrite subsystem?

3. Are these valid uses of the operators and if yes what would they
mean?

foo #5 (bar & cup)

If no then should the operator be applied to only two QI_VAL's?

4. If the operator only applies to two query items can we create an
index such that (foo, bar)-> documents[min distance, max distance]
How difficult it is to implement an index like this?

Thanks,
-Sushant.

On Thu, 2008-06-05 at 19:37 +0400, Teodor Sigaev wrote:
> > I can add index support and support for arbitrary distance between
> > lexeme.
> > It appears to me that supporting arbitrary boolean expression will be
> > complicated. Can we pull out something from TSQuery?
>
> I don't very like an idea to have separated interface for phrase search. Your
> patch may be a module and used by people who really wants to have a phrase search.
>
> Introducing new operator in tsquery allows to use already existing
> infrastructure of tsquery such as concatenations (&&, ||, !!), rewrite subsystem
> etc. But new operation/types specially designed for phrase search makes needing
> to make that work again.
>