webread function

[b00m18]

Hey @EnricSala ,

first, thanks for sharing!

I have a question about the webread function you are using in your script. I am trying to use the query:

'SELECT mean("Tmp") FROM "weather" WHERE ("sensor_" = ''Temperature_1'') AND time >= 1607868000000ms and time <= 1607925600000ms GROUP BY time(1m) fill(null);SELECT mean("Tmp") FROM "weather" WHERE ("sensor" = ''Temperature_2'') AND time >= 1607868000000ms and time <= 1607925600000ms GROUP BY time(1m) fill(null)'

The query is generated in Grafana. I should get two Signals, but in the struct 'response' is only one of the two signals. Do you know this problem or can matlab only get one?

I am using Matlab 2020b.

Best regards

[EnricSala]

Hi @b00m18, thanks for reporting the issue!

Seems to be related to encoding the ; character that separates queries.

Looks like the same issue also affected the Java client: influxdata/influxdb-java#214

Will try to find some time to fix it this week.

[b00m18]

Thanks for the fast reply!

It seems like Matlab doesnt encode ; in webread. When I am using urlencode() its replacing it with %3B.

[b00m18]

I've received the following solution from the Mathwork support: Matlab ist using the RFC 3986 specs in this syntax with webread:
r = webread('http://myServer:8086/query','db','mydb','q','SELECT * FROM cpu_load_short;SELECT * FROM cpu_load_short');

So it won't replace the ; with %3B

But this syntax:
r = webread('http://myServer:8086/query?db=mydb&q=SELECT * FROM cpu_load_short;SELECT * FROM cpu_load_short');

replaces ; with %3B because it provides backwards compatibility with older versions of 'webread', which was not entirely following the RFC specs.

[EnricSala]

Thanks for looking into a solution! Filed a PR with the suggested approach in #11.

@b00m18 would you be able to take a look to verify it makes sense?

[EnricSala]

Closing this issue, fixed in #11.