Query Showing blank result

I have data in my bucket it’s also showing count.
but when I am firing query it’s showing the blank result. I already created primary index.
What are the possibilities? please help me out.

Check how many entries in the index. what is your query and sample document

How to check entry in index?
In dataset I have 15 document and 1 B records.

But its showing blank result in simple query.

Select * from data limit 1;

Check UI primary index stats.
OR drop and create primary index

When we are doing high data load then we are facing problem. That time are queries are failer.
What we can do at that time ?