Why doesn't the reviewtasks table contain records for close reviews before July 10th, 2012

Question

Due to reasons only known to hichris123 the close vote queue graph went dark.

As it was one of the ways to keep close voters motivated I tried to recreate that graph a little bit by using this query resulting in this graph:

I do know this data is flawed due the absence of now deleted posts but more disturbingly there are no rows in the reviewtasks table for reviewtasktypeid = 2 before July 10th, 2012. I tried to re-invent that data by bringing the rows for votetypeid = 6 in the Votes table in my dataset. That still shows a giant jump, because close votes expired after 4 days. The posthistory table for posthistorytypeid = 10 isn't of much help either.

Am I missing something in my reasoning and therefor in my query? Where did those 47,641 review tasks at the start of recording in the reviewtasks table came from?

Answer 1

As you probably know, there's no data for review items before that date simply because that's when the queue was first created.

Likewise, the close votes for the period you were trying to recreate the data are only reflective of active close votes. Close votes that would be considered expired under the four-day rule are not included, even if the closure was successful. The majority of close votes are "expired" and therefore not available in Data Explorer.

The close review queue also contains posts flagged for closure, for which I don't think there's any way to get historical data for either. Additionally accounting for the existence of deleted posts, there's a lot of data points missing.

So there's nothing particularly wrong with your query other than that you simply just don't have the data to recreate the close votes and flags that informed the review tasks at that point in time.