`Option::unwrap()` error in t-digest `rollup()`

[kvc0]

Relevant system information:

• OS: Ubuntu 22.04.1 LTS
• PostgreSQL version: PostgreSQL 14.6 (Ubuntu 14.6-1.pgdg22.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0, 64-bit
• TimescaleDB Toolkit version: 1.13.0
• Installation method: sudo apt install timescaledb-2-postgresql-14

Describe the bug

metrics=> select
  time_bucket('1s', time),
  rollup(time_100)
from demo
group by 1
order by 1;
ERROR:  called `Option::unwrap()` on a `None` value
CONTEXT:  parallel worker

To Reproduce I don't know how. I tried:

create table f(a tdigest);
insert into f(a) values ('(version:1,buckets:1,max_buckets:1,count:1,sum:1,min:1,max:1,centroids:[(mean:1,weight:1)])'), (null);
select rollup(a) from f; -- it worked
delete from f;

insert into f(a) values (null), ('(version:1,buckets:1,max_buckets:1,count:1,sum:1,min:1,max:1,centroids:[(mean:1,weight:1)])');
select rollup(a) from f; -- it worked
delete from f;

insert into f(a) values (null), ('(version:1,buckets:1,max_buckets:1,count:1,sum:1,min:1,max:1,centroids:[(mean:1,weight:1)])'), (null);
select rollup(a) from f; -- it worked
delete from f;

Here's my table:

metrics=> \d demo
                           Table "public.demo"
   Column    |           Type           | Collation | Nullable | Default
-------------+--------------------------+-----------+----------+---------
 time        | timestamp with time zone |           | not null |
 application | text                     |           |          |
 time_100    | tdigest                  |           |          |
Indexes:
    "demo_time_idx" btree ("time" DESC)
Triggers:
    ts_insert_blocker BEFORE INSERT ON demo FOR EACH ROW EXECUTE FUNCTION _timescaledb_internal.insert_blocker()
Number of child tables: 3 (Use \d+ to list them.)

The column is sparse:

metrics=> select count(*) filter (where time_100 is not null) present, count(*) filter (where time_100 is null) absent from demo;
 present | absent
---------+--------
   18760 |   9712

Expected behavior rollup() function should work.

Actual behavior rollup() function attempted to call unwrap() on a Rust Option, which results in a panic!().

[epgts]

We agree about unwrap and have been removing them over time and trying to avoid adding them (though some slip through; we ain't perfect :). I'll have a look at this one in particular, and at your pull request.

Thanks!

[kvc0]

@epgts I am glad to hear it! I used unwrap all the time at first until I got a little more understanding. I think a lot of this is also from the 3rd party library you sourced from GitHub :-) I'll fix the lint thing when I get a minute. I think my clippy or ktlint is stale.