WordPress Popular Posts Table Is Getting Big

I uninstalled WordPress Popular Posts plugin because it is getting slow lately. By digging to my database, I found that the table wp_popularpostsdatacache which is part of WordPress Popular Posts plugin is betting big. Currently it has 3,501,405 rows with 160.7 MiB used space.

I am thinking that this cache was not purge because I am using nginx instead of apache. This happens to me on my Drupal site also. But I cannot confirm this. So, do you think this is because of nginx? If not, why it is getting bigger and bigger? It seems that the record there is not deleted.

I am using using “Last 24 hours” option in Time Range option of this plugin. So I think a record of yesterday will be deleted automatically. But this is not the case.

Any idea about this?