I am using "Cardinality Aggregation" on "Date Histogram".
And I found one weird result.
I already know that "Counts are approximate", so the precision is not 100% accurate.
But when I draw the "Date Histogram" only one particular date (ex. September 11th) is very inaccurate compared to other dates.
I've tried computing the exact unique count.
Other dates except that one date are accurate enough. Weird...
- Doc counts are almost similar each date.
- Docs are in the same index (3 shards, 1 replica).
- Docs are inserted in datetime order.
Now, I wonder about the inaccuracy behind the scene.
Could anyone explain this?