With pointerdb listing objects operation was optimized to skip
objects from prefixes for non recursive listing. This change it
adopting this optimiaztion from old code.
Main change is to drop current page results if we detect a prefix
that needs to be skipped and jump with next listing query after this
prefix by setting cursor to "some-prefix(byte('/')+1) which is
effectively "some-prefix0".
Benchmark:
name old time/op new time/op delta
NonRecursiveListing/Postgres/listing_no_prefix-8 960µs ±11% 257µs ±12% -73.19% (p=0.008 n=5+5)
NonRecursiveListing/Postgres/listing_with_prefix-8 945µs ±11% 671µs ±12% -28.97% (p=0.008 n=5+5)
NonRecursiveListing/Cockroach/listing_no_prefix-8 4.31ms ± 8% 1.19ms ± 7% -72.44% (p=0.008 n=5+5)
NonRecursiveListing/Cockroach/listing_with_prefix-8 4.97ms ± 8% 3.35ms ±15% -32.67% (p=0.008 n=5+5)
Fixes https://github.com/storj/team-metainfo/issues/115
Change-Id: Iafdf3600d058abbaf441f792d32a7fc17cc08696
7390f389cd