Skipscan(Distinct On) takes forever but the explain plan indicates that index scan is being used!

TimescaleDB and PostgreSQL Installation, Configuration, and Errors
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1

I am trying to find the distinct values of a column from a table. According to the article from blog-post by timescale, skipscan is the way to go for these type of queries because they are much more optimized. However, the query takes forever to run on our db and eventually times out.

Table details:

Table "ts_data"
 ts        :    timestamp with time zone, not null
 sensor_id :  uuid, not null
 value  : numeric 
Indexes:
    "ts_data_pkey" PRIMARY KEY, btree (sensor_id, ts)
    "ts_data_sensor_id" btree (sensor_id)
    "ts_data_ts_idx" btree (ts DESC)
Triggers:
    ts_insert_blocker BEFORE INSERT ON ts_data FOR EACH ROW EXECUTE PROCEDURE _timescaledb_internal.insert_blocker()
Number of child tables: 448

Query being used: select distinct on (sensor_id) * from ts_data;
Query Explain details: Explain-depesz
Postgres version: PostgreSQL 11.12
Timescale version: 2.3.1

2

What is the exact error you are getting when the query times out? A query by itself should never time out unless you have configured statement_timeout. I do see you have quite a few chunks so it will probably speed up the query a lot if you can limit the time range it has to consider.