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tsdb: Update comment about a possible space optimization (#11303)

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See also #11195 for the detailed reasoning.

Signed-off-by: beorn7 <beorn@grafana.com>

Signed-off-by: beorn7 <beorn@grafana.com>
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Björn Rabenstein 2022-09-15 09:41:57 +02:00 committed by GitHub
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13
tsdb/chunkenc/varbit.go
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@ -23,11 +23,14 @@ import (
// optimized for the dod's observed in histogram buckets, plus a few additional
// buckets for large numbers.
//
// TODO(Dieterbe): We could improve this further: Each branch doesn't need to
// support any values of any of the prior branches. So we can expand the range
// of each branch. Do more with fewer bits. It comes at the price of more
// expensive encoding and decoding (cutting out and later adding back that
// center-piece we skip).
// For optimal space utilization, each branch didn't need to support any values
// of any of the prior branches. So we could expand the range of each branch. Do
// more with fewer bits. It would come at the price of more expensive encoding
// and decoding (cutting out and later adding back that center-piece we
// skip). With the distributions of values we see in practice, we would reduce
// the size by around 1%. A more detailed study would be needed for precise
// values, but it's appears quite certain that we would end up far below 10%,
// which would maybe convince us to invest the increased coding/decoding cost.
func putVarbitInt(b *bstream, val int64) {
switch {
case val == 0: // Precisely 0, needs 1 bit.