There is an index has many docs, recently add some new fields and full update the index, yesterday cat the index

health status index               uuid                   pri rep docs.count docs.deleted store.size pri.store.size
green  open   company             KTngnM6ASD-_KdU0FFAWRA   1   0   95889387     63357813     67.4gb         67.4gb

but today cat it again

health status index               uuid                   pri rep docs.count docs.deleted store.size pri.store.size
green  open   company             KTngnM6ASD-_KdU0FFAWRA   1   0   95891965      3368035     29.8gb         29.8gb

why store.size is reduced so many (merge and compression)? and why docs.deleted is also become smaller(63357813 ==> 3368035)?

CodePudding user response：

The deleted documents ratio was already pretty high before your update operation and a merge operation was about to be triggered.

By updating your index in place, you increased even more the deleted documents ratio, probably beyond a certain threshold that actually triggered a merge operation which expunged the deleted documents from your index and reduced the number of segments in the process.

What would have been interested to see is the results of _cat/segments before and after your update.