On Wed, Jun 8, 2016 at 7:13 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> It appears that the new <-> operator has been made to have exactly the
> same grammatical precedence as the existing & (AND) operator. Thus,
> for example, 'a & b <-> c'::tsquery means something different from
> 'b <-> c & a'::tsquery:
>
> regression=# select 'a & b <-> c'::tsquery;
> tsquery
> -----------------------------------
> ( 'a' <-> 'c' ) & ( 'b' <-> 'c' )
> (1 row)
>
> regression=# select 'b <-> c & a'::tsquery;
> tsquery
> -----------------------
> ( 'b' <-> 'c' ) & 'a'
> (1 row)
>
> I find this surprising. My intuitive feeling is that <-> ought to
> bind tighter than & (and therefore also tighter than |). What's
> the reasoning for making it act like this?
I don't remember, but it looks like a bug. I found another issue with that
If some dictionary returns two infinitives, like:
select * from to_tsquery('en','leavings'); to_tsquery
----------------------'leavings' | 'leave'
(1 row)
then following query looks like a bug
select to_tsquery('en', 'aa & leavings <-> tut'); to_tsquery
-------------------------------------------------------------------( 'aa' <-> 'tut' ) & ( 'leavings' <-> 'tut' |
'leave'<-> 'tut' )
(1 row)
It should be definitely
select to_tsquery('en', 'aa & leavings <-> tut'); to_tsquery
------------------------------------------------------------------- 'aa' & ( 'leavings' <-> 'tut' | 'leave' <-> 'tut'
)
(1 row)
so, yes, <-> should be more tight than &.
>
> regards, tom lane
