TablePanel: Add support for Count calculation per column or per entire dataset

[mdvictor]

What is this feature?
The Count calculation in the table panel shows values per each column, and they are usually the same number since the count calculation takes in the data length itself. With this change, the calculation counts only non-null values and shows them per column.
An extra switch has been added in the options ui, available only for the count calculation, which allows the user to set the count calculation for the entire dataset, thus showing the count only on the first column of the table footer.

Why do we need this feature?
The count calculation could do more than it already does and by occupying less space. We don't need to see the same count value (aka the dataset length) across all columns in the table footer. At the same time, we might not want to see the dataset length at all, but only a counter of all valid (non-null) values

Who is this feature for?
Table panel users

Which issue(s) does this PR fix?:

Fixes #57799

Todo:

• Write some tests for this
• Add footerOptions to schema
• Refactor name and write description
• Docs

[grafanabot]

Drone build failed: https://drone.grafana.net/grafana/grafana-enterprise/40660

[grafanabot]

Drone build failed: https://drone.grafana.net/grafana/grafana-enterprise/40684

[joshhunt]

Can we properly narrow the type down, rather than just hoping for the best that the value is a string?

We want to avoid adding more exceptions to .betterer.results that we only have to go in and clean up later.

[joshhunt]

Alternatively, rename this file to .js and remove all typescript and be prepared to justify the decision 😅

[joshhunt]

Is the footerValues property really potentially an array of arrays (of an objects)? Or is the wrong type being used here?

At the moment it looks like if this function is called incorrectly it can lead to a runtime crash as react tries to render an object. I see maybe two approaches to fix this directly here:

Throw an exception directly if the input doesn't match our expectations. This is the current behaviour of the code, but it's being honest about it's potential to crash

  if (isCountAllSet) {
    const count = footerValues[index];
    if (typeof count !== 'string') {
      throw new Error("didn't except a string!");
    }

    return FooterCell({ value: [{ Count: count }] });
  }

Or, all .toString() on the value if it's not a string. This can still (silently) give you something undesirable like [object Object] being printed, but at least grafana doesn't crash.

  if (isCountAllSet) {
    const count = footerValues[index];
    if (!count) {
      return EmptyCell;
    }

    const value = typeof count === 'string' ? count : count?.toString();
    return FooterCell({ value: [{ Count: value }] });
  }

[grafanabot]

This pull request was removed from the 9.2.5 milestone because 9.2.5 is currently being released.

[grafanabot]

Hello @mdvictor!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!

[mdvictor]

@zoltanbedi Calculation functionality docs seem to be in a different page. Since this functionality is only for the table panel, it doesn't make sense to add it there, but since the table doc page doesn't describe calculations at all it kind of feels out of context to describe this feature in there. Not sure how to add this to the docs in a readable way. Any suggestions?

Tagging @grafana/docs-dev also for help on this, if possible.

[zoltanbedi]

Calculation functionality docs seem to be in a different page. Since this functionality is only for the table panel, it doesn't make sense to add it there, but since the table doc page doesn't describe calculations at all it kind of feels out of context to describe this feature in there. Not sure how to add this to the docs in a readable way. Any suggestions?

Yes this is a good opportunity to improve the doc for the table panel. Add a new section for Table footer options mention the calcs and how it works. Link it to the original article. Explain the feature that you just added.

[zoltanbedi]

Let's rather not modify the model in this pr. This is not going to be the same as the one we have down there and there aren't any TableFooterCalc interface in the mudball.

[zoltanbedi]

lgtm

[chri2547]

After you enable the table footer:

1. Select the Calculation.
2. Select the Fields you want to calculate.

The system applies the calculation to all numeric fields if you do not select a field.

[chri2547]

I think you can combine these two statements by saying:

Select the Count calculation when you want to show the number of rows in the dataset instead of the number of values in the selected fields.

[chri2547]

Docs reviewed post-merge.