The `exists` operator now gets pushed down to storage correctly. If
`exists` is used on a tag, then it will be rewritten to `tag != ""`
which is how storage defines if a tag exists. If `not exists` is used,
then it will use `tag == ""` which is how you would query storage for
only if a tag doesn't exist.
The `tag == ""` and `tag != ""` are different. For `tag == ""`, the
predicate is impossible for the storage layer to return true with.
Ideally, we would just rewrite this to return nothing and we wouldn't
bother with even querying storage. Instead, we just do not rewrite this
predicate because it cannot be rewritten to make sense with storage. If
we see `tag != ""`, it is the only one that can be passed through as-is
because `tag != ""` returns the same values as `exists tag`. It will
return true for every non-null value.
If we handle the flux errors in the query controller, it makes it so we
are handling the errors in the location where the happen rather than at
a layer further up the stack.
This should simplify it so the errors are handled in this single
location instead.
In the QueueSize test, it was possible that after the `done` channel was
closed, one of the queries from the queue would begin executing. If all
three began executing before the shutdown was done, the third would
block on attempting to send a value to the `executing` channel and it
would never finish so the controller would report that shutdown failed.
This increases the queue size to a combination of the concurrency quota
and the queue size so all of the started queries will never block when
sending a signal to the executing channel.
The storage table reader will now work correctly when there are multiple
outputs. The table interface now implements the new table and column
reader interfaces and works properly with `execute.CopyTable`. The
source uses `execute.CopyTable` to buffer the table in memory when there
are multiple output transformations.
The controller implementation is primarily used by influxdb so it
shouldn't be part of the flux repository. This copies the code from flux
to influxdb so it can be removed from the next flux release.
The `databases()` function was moved into the `influxdata/influxdb/v1`
package and so it wouldn't work anymore. The `percentile()` call was
changed to `quantile()` and the argument was changed to `q`. This also
updates `median()` to use `median()` since we now produce AST's and not
the spec so we can use the `median()` definition instead.
Stuart Carnie
Lorenzo Affetti
j. Emrys Landivar (docmerlin)
Christopher M. Wolff
Jonathan A. Sternberg
George
Nathaniel Cook
Adam
roshie548
Adam
jlapacik