The percolator has been redesigned and because of this the dedicated
_percolator index is no longer used by the percolator,
but instead the percolator works with a dedicated
.percolator type. Read the redesigned percolator
blog post for the reasons why the percolator has been redesigned.
Elasticsearch will not delete the
_percolator index when upgrading, only the percolate api will not use the queries
stored in the
_percolator index. In order to use the already stored queries, you can just re-index the queries from the
_percolator index into any index under the reserved
.percolator type. The format in which the percolate queries
were stored has not been changed. So a simple script that does a scan search to retrieve all the percolator queries
and then does a bulk request into another index should be sufficient.