LAST function in subquery

[nordewal]

First of all, I love the great new subquery feature - it helps me in many cases where a specific function etc. is not (yet) available.

But I see an issue when using the LAST function in combination with subqueries:

Using the TOP function I get a correct count of the values in the database:

> SELECT count(*) FROM (SELECT top("value", 1) FROM "consul_value" GROUP BY *)
name: consul_value
time                 count_top
----                 ---------
1970-01-01T00:00:00Z 439

But using the LAST function, I get a way too long number:

> SELECT count(*) FROM (SELECT last("value") FROM "consul_value" GROUP BY *)
name: consul_value
time                 count_last
----                 ----------
1970-01-01T00:00:00Z 2

It seems that somehow only two values make it from the subquery to the outer query when using the LAST function:

SELECT last FROM (SELECT last("value") FROM "consul_value" GROUP BY *)
name: consul_value
time                           last
----                           ----
2017-01-25T17:14:26.65126633Z  0
2017-01-25T17:14:26.651284406Z 0

SELECT top FROM (SELECT top("value", 1) FROM "consul_value" GROUP BY *)
name: consul_value
time                           top
----                           ---
2017-01-25T13:30:44.401091Z    0
2017-01-25T13:30:44.401105Z    1
2017-01-25T13:30:44.401116Z    0
2017-01-25T13:30:44.401128Z    0
2017-01-25T13:30:44.40314Z     1
2017-01-25T13:30:44.403162Z    0
2017-01-25T13:30:44.403181Z    0
2017-01-25T13:30:44.403195Z    1
2017-01-25T13:30:44.403211Z    0
2017-01-25T13:30:44.403225Z    0
2017-01-25T13:30:44.403244Z    1
2017-01-25T13:30:44.403257Z    0
2017-01-25T13:30:44.403297Z    0
2017-01-25T13:30:46.631056Z    0
(...)

[jsternberg]

I think I've tracked this down. It's due to an optimization in how both first() and last() work that is conflicting with some of the subquery code. I'm looking at it and will hopefully have a fix soon.

[jsternberg]

@rkuchan this issue will also probably be reproducible in any situation where the inner query has a limit and the outermost query has a different GROUP BY than the inner query. In situations where the GROUP BY matches exactly, I don't think there will be an issue.

[jsternberg]

I think this also affects SLIMIT and SOFFSET for the same reasons.

[clarkj]

@jsternberg just confirming your suspicion about reproducibility-even without a limit on the inner query, if the inner query has a GROUP BY tag and the outer query has a GROUP BY time(), the query seems to return odd values. I can paste in some examples if that would be helpful, but it seems to be just an extension of the problem above. Thanks!