In Piwik there is the possibility for users to delete old log data:

• Manage DB size tools
• Deleting old data faq

When a user has setup Piwik to delete old log data, it may happen during normal use of Piwik, that a user requests a report for a very long date range.

Problems

• When a user requests a report with old dates where the data has been deleted for these dates, Piwik creates a report that is actually wrong and incomplete!
• the user is not notified and does not know that the report data is incomplete... causing issues such as Visits are count differently between segmentation and visits - devices #10261 which are hard to troubleshoot.

Solutions

Not sure the best way to solve this...

• when the Log Data deletion is active,
• when the Date range for this request overlaps with some of the deleted data,
• maybe we could not show any data in the UI (and not process any report data at all), and display an "error / warning" notification to the user, to indicate You have requested a report going as far back as YYYY-MM-DD. Unfortunately, your Piwik is configured to delete any log data older than N days. The earliest date range you can request is the following: &date=YYYY-MM-DD,YYYY-MM-DD (eg. see findOlderDateWithLogs)

Thoughts?
Follows up #10261 (comment)