Group by incorrectly creating large number of groups

[phemmer]

Bug report

System info: [Include InfluxDB version, operating system name, and other relevant details]
influxdb-1.1.0~n201610280800-0.x86_64
CentOS/7

Steps to reproduce:

insert test,t=a x=1i 1000
insert test,t=b y=1i 1000
insert test,t=a x=2i 2000
insert test,t=b y=2i 2000
insert test,t=a x=3i 3000
insert test,t=b y=3i 3000
select mean("x") as "x", mean("y") as "y" from test where time > 0u and time < 4u group by t, time(1u)

Expected behavior: [What you expected to happen]

name: test
tags: t=a
time	x	y
----	-	-
0		
1000	1	
2000	2	
3000	3	

name: test
tags: t=b
time	x	y
----	-	-
0		
1000		1
2000		2
3000		3

Actual behavior: [What actually happened]

name: test
tags: t=a
time	x	y
----	-	-
0		

name: test
tags: t=b
time	x	y
----	-	-
0		

name: test
tags: t=a
time	x	y
----	-	-
1000	1	

name: test
tags: t=b
time	x	y
----	-	-
1000		1

name: test
tags: t=a
time	x	y
----	-	-
2000	2	

name: test
tags: t=b
time	x	y
----	-	-
2000		2

name: test
tags: t=a
time	x	y
----	-	-
3000	3	

name: test
tags: t=b
time	x	y
----	-	-
3000		3

[jsternberg]

Good catch! This has been around for awhile. I think I know where it's coming from. It's also present in 1.0 and I think 0.13.