Data points in charts with more than 1 dimension along x-axis attributed incorrectly when implicit 0-value data points exist

[mhobe]

Issue description

When

• a chart (be it a bar chart or a line chart, probably others too) has more than one dimension along its x-axis (e.g. time + category) and one dimension (e.g. count) along its y-axis,

then

• data points are not attributed to their correct position along the x-axis when they come after data points with an implicit value of 0

Steps to reproduce

1. Use the following query to have a data set:

   SELECT 1 AS COUNT,
      'Apple' AS fruit,
      'Monday' AS day
   UNION ALL SELECT 3 AS COUNT,
      'Apple' AS fruit,
      'Tuesday' AS day
   UNION ALL SELECT 3 AS COUNT,
      'Orange' AS fruit,
      'Tuesday' AS day

2. Create a bar chart for this data set with

   • day and fruit on its x-axis
   • count on its y-axis

Expected results

The expectation is clear: There should be

• 1 bar for Monday for Apple with a height of 1
• 2 bars for Tuesday for Apple and Orange with a height of 3 each

Actual results

There are:

• 2 bars for Monday
  • one for Apple with a height of 1 ✅
  • one for Orange with a height of 3 ❌ This is Tuesday's data
• 1 bar for Tuesday for Apple with a height of 3 ✅

It seems that the framework just starts painting the data points starting at the earliest opportunity possible

Workaround

This issue can be worked around by adjusting the query to artificially introduce data points with value 0 in all places where there is an implicit 0 value, where possible. This however makes queries more complex and may not work in all cases.

For the example above this means:

SELECT 1 AS COUNT,
       'Apple' AS fruit,
       'Monday' AS day
UNION ALL SELECT 0 AS COUNT,
       'Orange' AS fruit,
       'Monday' AS day
UNION ALL SELECT 3 AS COUNT,
       'Apple' AS fruit,
       'Tuesday' AS day
UNION ALL SELECT 3 AS COUNT,
       'Orange' AS fruit,
       'Tuesday' AS day

would not exhibit the issue: