USE databasename will work only for existing databases.

[pires]

• CHANGELOG.md updated
• Rebased/mergable
• Tests pass
• Sign CLA (if not already signed)

Fixes #5174

Unfortunately, I don't see a way of testing this without implementing some database behavior on cli_test.go, namely to return one existing database.

$ influx -host 192.168.99.100
Visit https://enterprise.influxdata.com to register for updates, InfluxDB server management, and monitoring.
Connected to http://192.168.99.100:8086 version 0.9.6.1
InfluxDB shell 0.9
> show databases
name: databases
---------------
name
_internal

> use pires
ERR: Database pires doesn't exist. Run SHOW DATABASES for a list of existing databases.
> use _internal
Using database _internal

[pires]

Also, I'd like to know why name shows up as a database when SHOW DATABASES runs. It sounds like a bug when formatting the response to output but I want this PR to be validated before looking into that issue - I'll open a new one though.

[beckettsean]

@pires name is not a database name, it's because the query response format is a recycled structure. If you do any SELECT or SHOW query, the first line of results are the column names. In this case, there's only one column returned, the list of database names, and the column title is name.

[pires]

@beckettsean indeed, thank you. Does this LGTY?

[beckettsean]

@pires again I can't qualify Go code, but it looks like the right approach. It might be a little weird to get error messages for a SHOW DATABASES query when I typed USE foo into the CLI. Perhaps the error code could prepend an explanation to the error message to make that clearer?

response, err := c.Client.Query(client.Query{Command: query})
    if err != nil {
        fmt.Printf("ERR:  Cannot fetch list of databases: %s\n", err)
        return
    }

if err := response.Error(); err != nil {
        fmt.Printf("ERR: Cannot fetch list of databases: %s\n", err)
        return
    }

[otoolep]

Very minor, but just shove SHOW DATABASES inside the call to Query. A new variable isn't really needed, don't you agree?

[pires]

Agreed.

[otoolep]

Works for me, some minor improvements suggested. +1

@corylanou

[corylanou]

+1.

[pires]

@beckettsean you may find issues with the database that are not related to the database not existing. Said verifications follow the same pattern as other queries. SHOW DATABASES is a query.

[pires]

@corylanou @otoolep comments addressed. Thank you!