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)
Edd Robinson