This commit ensures that any orphaned series (series that are to be
removed and no longer are referenced anywhere in the database) are
removed from the `inmem` index when a shard is dropped.
it's slightly slower, but the safety is worth it i think.
```
name old time/op new time/op delta
Next-8 30.0ns ± 2% 31.0ns ± 3% +3.56% (p=0.002 n=7+8)
NextParallel-8 79.4ns ± 1% 92.5ns ± 1% +16.58% (p=0.000 n=8+8)
```
use atomics rather than mutexes to synchronize state between calls.
```
name old time/op new time/op delta
Next-8 244ns ± 0% 30ns ± 2% -87.70% (p=0.000 n=8+7)
NextParallel-8 215µs ±60% 0µs ± 1% -99.96% (p=0.000 n=8+8)
```
The results for NextParallel are around ~80ns/op, but that doesn't
show up in the benchstat output.
Since all tag sets are materialised to strings before this method
returns, a large number of allocations can be avoided by carefully
resuing buffers and containers.
This commit reduces allocations by about 75%, which can be very
significant for high cardinality workloads.
The benchmark results shown below are for a benchmark that asks for all
series keys matching `tag5=value0'.
name old time/op new time/op delta
Index_ConcurrentWriteQuery/inmem/queries_100000-8 5.66s ± 4% 5.70s ± 5% ~ (p=0.739 n=10+10)
Index_ConcurrentWriteQuery/tsi1/queries_100000-8 26.5s ± 8% 26.8s ±12% ~ (p=0.579 n=10+10)
IndexSet_TagSets/1M_series/inmem-8 11.9ms ±18% 10.4ms ± 2% -12.81% (p=0.000 n=10+10)
IndexSet_TagSets/1M_series/tsi1-8 23.4ms ± 5% 18.9ms ± 1% -19.07% (p=0.000 n=10+9)
name old alloc/op new alloc/op delta
Index_ConcurrentWriteQuery/inmem/queries_100000-8 2.50GB ± 0% 2.50GB ± 0% ~ (p=0.315 n=10+10)
Index_ConcurrentWriteQuery/tsi1/queries_100000-8 32.6GB ± 0% 32.6GB ± 0% ~ (p=0.247 n=10+10)
IndexSet_TagSets/1M_series/inmem-8 3.56MB ± 0% 3.56MB ± 0% ~ (all equal)
IndexSet_TagSets/1M_series/tsi1-8 12.7MB ± 0% 5.2MB ± 0% -59.02% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
Index_ConcurrentWriteQuery/inmem/queries_100000-8 24.0M ± 0% 24.0M ± 0% ~ (p=0.353 n=10+10)
Index_ConcurrentWriteQuery/tsi1/queries_100000-8 96.6M ± 0% 96.7M ± 0% ~ (p=0.579 n=10+10)
IndexSet_TagSets/1M_series/inmem-8 51.0 ± 0% 51.0 ± 0% ~ (all equal)
IndexSet_TagSets/1M_series/tsi1-8 80.4k ± 0% 20.4k ± 0% -74.65% (p=0.000 n=10+10)
The internals of `newSeriesCursor` returned a struct pointer that
implicitly got turned into the interface. Unfortunately, Go treats this
type of interface conversion as a nil pointer to the struct rather than
as just nil so if you attempted to compare the returned cursor to nil,
they would not be equal and it would think it was non-nil and attempt to
use the cursor.
Edd Robinson
tmgordeeva
liukun
Ben Johnson
Jeff Wendling
Jeff Wendling
Tim Brooks
Hercules Mango Churchill
Jonathan A. Sternberg
David Norton
Stuart Carnie
Jacob Marble
Zach Goldstein