Description:

Suppose we have two extra log tables in a plugin: log_thing_event and log_thing. log_thing_event joins log_visit on idvisit, while log_thing joins log_thing_event on idlogthing.

If we try to use Segment to generate SQL that queries log_thing_event, it will automatically join on log_visit to get segmentation to work. BUT if we try to use it to generate SQL that queries log_thing, it will not be able to make segmentation work, even though it can be joined to log_visit through log_thing_event.

This PR fixes this case. When looking for joins, the existing code tries to join a table to one of the previously seen tables in the $from array. It will look to see if it is directly joinable to log_visit, otherwise it will look in the getWaysToJoinOtherTables() of the table to join. This doesn't work in our case where $from = ['log_thing', 'log_thing_event'], because 'log_thing_event' won't be in the getWaysToJoinOtherTables() of 'log_thing'. Instead, log_thing will be in the getWaysToJoinOtherTables() of log_thing_event. So this adds the reverse of the existing check to make this type of query work.

The use case here is that log_thing will have far less rows than log_thing_event and querying over it first instead of log_thing_event can in some cases be far more efficient.

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed