Improve performance of recordsets API

The performance of /v2/recordsets API was found slow when
filtering on large amount of recordsets. The patch proposes
the following ways to improve the performance,
and was tested with 1M recordsets.

1. To explicitly mention a correct table index in sql queries
for different sort keys and filtering keys.
We found mysql optimizer is not able to choose the most suitable index;

2. Introduce a new header 'OpenStack-DNS-Hide-Counts' to give operators
the flexibility of showing total_count or not, because we found that
the count query does not scale well on a large amount of records.

Performance results are at: https://gist.github.com/jamesyli/2eb9fb474a493477a9beb42fe122180f

DB migration
Change-Id: I7f3a09ce2c7396ff6ad02d3b5d562d186f66ed30

0 files changed, 0 insertions, 0 deletions