Thread: Range contains element filter not using index of the element column

27.11.2019, 16:32, "Lauri Kajan" <lauri.kajan@gmail.com>:
> Hi all,
> I'm wondering if there are anything to do to utilize a index when doing a range contains element  query. I have
testedthis with 9.6 and 12.0.
 
>
> I have a table with a timestamp column that has a btree index.
> I would like to do a query:
> SELECT * FROM table WHERE ts <@ tsrange($1, $2, '(]');
> The index is not used and a seq scan is done instead.
>
> To use the index correctly I have to do the query like this:
> SELECT * FROM table WHERE  ($1 IS null OR $1 < ts) AND ($2 IS null OR ts <= $2);
> I like the <@ syntax more. Is there something I can do differently? Maybe a different type of index instead?
>
> Thanks,
>
> -Lauri

Hi!
Do you use GIST index?
According to https://www.postgresql.org/docs/12/rangetypes.html#RANGETYPES-INDEXING <@ operator is supported:
> A GiST or SP-GiST index can accelerate queries involving these range operators: =, &&, <@, @>, <<, >>, -|-, &<, and
&>

On 11/27/19 6:33 AM, Lauri Kajan wrote:
> On Wed, Nov 27, 2019 at 1:05 PM Игорь Выскорко <vyskorko.igor@yandex.ru
> <mailto:vyskorko.igor@yandex.ru>> wrote:
>
>     Hi!
>     Do you use GIST index?
>     According to
>     https://www.postgresql.org/docs/12/rangetypes.html#RANGETYPES-INDEXING
>     <@ operator is supported:
>     > A GiST or SP-GiST index can accelerate queries involving these
>     range operators: =, &&, <@, @>, <<, >>, -|-, &<, and &>
>
>
> Hi,
>
> I have understood that gist indexes can be used if the column is range
> type but my column is just plain timestamp.
> I tried actually to add gist index for the timestamp column. That was
> not possible without installing the btree_gist extension. But that
> didn't work.


Try this:

create table tstest(id int, ts timestamptz);
insert into tstest
  select
   g.i,
   now() - (g.i::text || ' days')::interval
  from generate_series(1, 100000) as g(i);

create index tstest_gin
 on tstest using gist((tstzrange(ts,ts,'[]')));

explain analyze
 select * from tstest
 where
  tstzrange(ts,ts,'[]') <@
  tstzrange(now()- '9 days'::interval,
            now()-'7 days'::interval,'(]');
                QUERY PLAN

--------------------------------------------------------
 Bitmap Heap Scan on tstest  (cost=24.17..590.16 rows=500 width=12)
(actual time=0.069..0.070 rows=2 loops=1)
   Recheck Cond: (tstzrange(ts, ts, '[]'::text) <@ tstzrange((now() - '9
days'::interval), (now() - '7 days'::interval), '(]'::text))
   Heap Blocks: exact=1
   ->  Bitmap Index Scan on tstest_gin  (cost=0.00..24.04 rows=500
width=0) (actual time=0.063..0.063 rows=2 loops=1)
         Index Cond: (tstzrange(ts, ts, '[]'::text) <@ tstzrange((now()
- '9 days'::interval), (now() - '7 days'::interval), '(]'::text))
 Planning Time: 20.920 ms
 Execution Time: 0.115 ms
(7 rows)

HTH,

Joe

--
Crunchy Data - http://crunchydata.com
PostgreSQL Support for Secure Enterprises
Consulting, Training, & Open Source Development

Lauri Kajan <lauri.kajan@gmail.com> writes:
> I have a table with a timestamp column that has a btree index.
> I would like to do a query:
> SELECT * FROM table WHERE ts <@ tsrange($1, $2, '(]');
> The index is not used and a seq scan is done instead.
> To use the index correctly I have to do the query like this:
> SELECT * FROM table WHERE  ($1 IS null OR $1 < ts) AND ($2 IS null OR ts <=
> $2);
> I like the <@ syntax more. Is there something I can do differently? Maybe a
> different type of index instead?

As others mentioned, a gist index on a tsrange expression could be
used for this, but another idea is to build some syntactic sugar
using a custom operator.  Light testing suggests that this works:

create function expand_range_contain(anyelement, anyrange)
returns bool language sql parallel safe as
$$ select
case when lower_inf($2) then true
     when lower_inc($2) then $1 >= lower($2)
     else $1 > lower($2) end
and
case when upper_inf($2) then true
     when upper_inc($2) then $1 <= upper($2)
     else $1 < upper($2) end
$$;

create operator <<@ (
  function = expand_range_contain,
  leftarg = anyelement,
  rightarg = anyrange
);

select * from table where ts <<@ tsrange($1, $2, '(]');

An important caveat though is that the range operand *must* reduce
to a constant.  If the planner fails to const-simplify those CASE
expressions, you'll not only not get an indexscan, but you'll be worse
off than with the native <@ operator.  So this isn't an all-purpose
fix --- but it might cover your needs and be nicer than maintaining a
second index on the column.

            regards, tom lane

> On 27 Nov 2019, at 10:32, Lauri Kajan <lauri.kajan@gmail.com> wrote:
>
> Hi all,
> I'm wondering if there are anything to do to utilize a index when doing a range contains element  query. I have
testedthis with 9.6 and 12.0. 
>
> I have a table with a timestamp column that has a btree index.
> I would like to do a query:
> SELECT * FROM table WHERE ts <@ tsrange($1, $2, '(]');
> The index is not used and a seq scan is done instead.
>
> To use the index correctly I have to do the query like this:
> SELECT * FROM table WHERE  ($1 IS null OR $1 < ts) AND ($2 IS null OR ts <= $2);
> I like the <@ syntax more. Is there something I can do differently? Maybe a different type of index instead?

Does it help to use timestamps -infinity and infinity instead of nulls in your case?

=> select t, t < current_timestamp, current_timestamp <= t from (values ('-infinity'::timestamp),
('infinity'::timestamp))x(t);                            
     t     | ?column? | ?column?
-----------+----------+----------
 -infinity | t        | f
 infinity  | f        | t
(2 rows)

Regards,

Alban Hertroys
--
If you can't see the forest for the trees,
cut the trees and you'll find there is no forest.