ORDER BY time DESC probably returns the wrong results sometimes

[jsternberg]

Bug report

System info: InfluxDB 1.2.0

Steps to reproduce:

> CREATE DATABASE db0
> USE db0
> INSERT cpu,host=server01 value=2 1000000000
> INSERT cpu,host=server01 value=3 2000000000
> INSERT cpu,host=server02 value=4 1000000000
> INSERT cpu,host=server02 value=5 2000000000
> SELECT value, host FROM cpu ORDER BY time DESC
name: cpu
time                value host
----                ----- ----
2000000000          3     server01
2000000000          5     server02
1000000000          2     server01
1000000000          4     server02

The order should be server02 before server01. There is also an error in the Emitter which causes this one:

> CREATE DATABASE db0
> USE db0
> INSERT mem,host=server01 free=1 1000000000
> INSERT mem,host=server01 free=2 2000000000
> INSERT mem,host=server02 used=3 1000000000
> INSERT mem,host=server02 used=4 2000000000
> SELECT first("used") AS "used", first("free") AS "free" FROM "mem" WHERE time >= '1970-01-01T00:00:01Z' AND time <= '1970-01-01T00:00:02Z' GROUP BY host, time(1s) FILL(none) ORDER BY time DESC
name: mem
tags: host=server01
time       used free
----       ---- ----
2000000000      2
1000000000      1

name: mem
tags: host=server02
time       used free
----       ---- ----
2000000000 4
1000000000 3

server02 is supposed to be before server01.

Additional info:

This section of code seems wrong and an earlier version of the code seems to do something different:

        // Update range values if lower and emitter is in time ascending order.
        if e.ascending {
            if (itrName < name) || (itrName == name && itrTags.ID() < tags.ID()) || (itrName == name && itrTags.ID() == tags.ID() && itrTime < t) {
                t, name, tags = itrTime, itrName, itrTags
            }
            continue
        }

        // Update range values if higher and emitter is in time descending order.
        if (itrName < name) || (itrName == name && itrTags.ID() < tags.ID()) || (itrName == name && itrTags.ID() == tags.ID() && itrTime < t) {
            t, name, tags = itrTime, itrName, itrTags
        }

It seems like the second statement there have the conditions in the wrong direction.

[jsternberg]

Fixed via #7907.