[Stats Refresh] Period queries being cancelled

[ScoutHarris]

A while back, a cancelQueries method was added to StatsPeriodStore to force cancel queries because they were being re-run when they weren't needed. I.e. overview queries were being re-run when Post Stats was displayed, and vice versa.

However, with the ongoing improvements/changes, I think this is causing some issues.

1. When stats is accessed for the first time, the overview chart is frequently blank.

When this happens, there are a slew of cancelled query messages in the logs. Example:

2019-05-21 14:41:00:166 WordPress[58418:31284690] Error fetching search terms: Optional("cancelled")
2019-05-21 14:41:00:166 WordPress[58418:31284690] Stats: Finished fetching search terms.
2019-05-21 14:41:00:167 WordPress[58418:31284690] Error fetching referrers: Optional("cancelled")
2019-05-21 14:41:00:167 WordPress[58418:31284690] Stats: Finished fetching referrers.
2019-05-21 14:41:00:167 WordPress[58418:31284690] Error fetching posts: Optional("cancelled")
....

2. When accessing a details view (via View more), then return to Period overview, several stats frequently show No data for this period even though there was data displayed before accessing the details view.

[ScoutHarris]

I was finally able to reproduce the issue where the error view shows upon first launch. I'm not sure this is a real world scenario, but this is how I trigger it.

• The last view selected is a Period (so when the app launches and stats is first accessed, it's on the Period view).
• From a new branch, run the app in the same simulator.
• When the app launches, it goes directly to stats Period.
• I see this view:

This is in the logs:

2019-05-22 12:00:56:938 WordPress[58245:35145890] Error fetching posts: Optional("cancelled")
2019-05-22 12:00:56:938 WordPress[58245:35145890] Stats: Finished fetching posts.
2019-05-22 12:00:56:938 WordPress[58245:35145890] Error fetching referrers: Optional("cancelled")
2019-05-22 12:00:56:938 WordPress[58245:35145890] Stats: Finished fetching referrers.
2019-05-22 12:00:56:939 WordPress[58245:35145890] Error fetching authors: Optional("cancelled")
2019-05-22 12:00:56:939 WordPress[58245:35145890] Stats: Finished fetching authors.
2019-05-22 12:00:56:939 WordPress[58245:35145890] Error fetching clicks: Optional("cancelled")
2019-05-22 12:00:56:939 WordPress[58245:35145890] Stats: Finished fetching clicks.
2019-05-22 12:00:56:939 WordPress[58245:35145890] Error fetching search terms: Optional("cancelled")
2019-05-22 12:00:56:939 WordPress[58245:35145890] Stats: Finished fetching search terms.
2019-05-22 12:00:56:939 WordPress[58245:35145890] Error fetching countries: Optional("cancelled")
2019-05-22 12:00:56:939 WordPress[58245:35145890] Stats: Finished fetching countries.
2019-05-22 12:00:56:940 WordPress[58245:35145890] Error fetching Post Stats: Optional("cancelled")
2019-05-22 12:00:56:940 WordPress[58245:35145890] Stats: Finished fetching post stats.
2019-05-22 12:00:56:940 WordPress[58245:35145890] Error fetching videos: Optional("cancelled")
2019-05-22 12:00:56:940 WordPress[58245:35145890] Stats: Finished fetching videos.
2019-05-22 12:00:56:940 WordPress[58245:35145890] Stats: All fetching operations finished.
2019-05-22 12:00:56:955 WordPress[58245:35145890] Error fetching Post Stats: Optional("cancelled")
2019-05-22 12:00:56:955 WordPress[58245:35145890] Stats: Finished fetching post stats.
2019-05-22 12:00:56:955 WordPress[58245:35145890] Stats: All fetching operations finished.
2019-05-22 12:00:56:958 WordPress[58245:35145890] Error fetching Post Stats: Optional("cancelled")
2019-05-22 12:00:56:958 WordPress[58245:35145890] Stats: Finished fetching post stats.
2019-05-22 12:00:56:959 WordPress[58245:35145890] Stats: All fetching operations finished.
2019-05-22 12:00:56:969 WordPress[58245:35145890] Stats: Finished loading data from Core Data.
2019-05-22 12:00:56:969 WordPress[58245:35145890] Stats: Finished setting data to store from Core Data.
2019-05-22 12:00:56:980 WordPress[58245:35145890] Stats: Finished loading data from Core Data.
2019-05-22 12:00:56:980 WordPress[58245:35145890] Stats: Finished setting data to store from Core Data.