Incorrect results when select uses measurement regex without field regex

[dmitrios]

Bug report

System info: [1.1.2, MacOs, 10.12.3]

Steps to reproduce:

Two measurements, M1 and M2 with same fields: A and B. These are fields, not tags.

1. select "A","B" from /M1|M2/ =>empty
2. select A,/B/ from /M1|M2/ => correct result for B
3. select /A/,/B/ from /M1|M2/ =>correct result A,B

Expected behavior: [the value of the fields "A" and "B" are correctly selected in all queries]

Actual behavior: [it appears that regex in field expressions TRIGGERS parsing regex in measurement expression]

Additional info: [the query 1 works fine with influx 1.1.0-1 on Windows and MacOs] This new behavior in influxdb 1.2.0-1 will break Grafana.

[e-dard]

Version 1.1.0:

>
> create database "db"
> insert m1 a=1,b=2
> insert m2 a=1,b=2
>
>
> select "a","b" from /m1|m2/
name: m1
time                a b
----                - -
1485354751060183470 1 2

name: m2
time                a b
----                - -
1485354752738582585 1 2

>
>
>
> select a,/b/ from /m1|m2/
name: m1
time                a b
----                - -
1485354751060183470 1 2

name: m2
time                a b
----                - -
1485354752738582585 1 2

>
>
> select /a/,/b/ from /m1|m2/
name: m1
time                a b
----                - -
1485354751060183470 1 2

name: m2
time                a b
----                - -
1485354752738582585 1 2

>

Version 1.2.0:

> create database "db"
> insert m1 a=1,b=2
> insert m2 a=1,b=2
>
> select "a","b" from /m1|m2/
>
>
>
> select a,/b/ from /m1|m2/
name: m1
time                a b
----                - -
1485354644496814831   2

name: m2
time                a b
----                - -
1485354651667789584   2

>
>
> select /a/,/b/ from /m1|m2/
name: m1
time                a b
----                - -
1485354644496814831 1 2

name: m2
time                a b
----                - -
1485354651667789584 1 2

>

In the case of query number (2), notice that the field a shows up for 1.2.0 but it's not populated.

[e-dard]

A cursory glance of statement_executor.go changes indicates that it probably has something to do with this change: d7c8c7c#diff-084cb29c383c1c0fffae2fac08113ad5L547 introduced in #7646.

[jsternberg]

I think I know what this issue might be. I think what's happening is the part of the code that maps types isn't working with regexes. But when you do /a/ for a field, it retrieves the type as part of expanding the field regex so it doesn't happen when you use that.

I'll confirm and fix it.

[jsternberg]

Fixed via #7881.