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chore: reduce string allocations in TSI series cache #27255

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Merged
davidby-influx merged 2 commits into from
Feb 27, 2026
+21 −16
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chore: reduce string allocations in TSI series cache #27255

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7e001d9
chore: eliminate string allocations in TSI series cache
davidby-influx Feb 26, 2026
00096c5
chore: eliminate more string allocations
davidby-influx Feb 26, 2026
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26 changes: 16 additions & 10 deletions tsdb/index/tsi1/cache.go
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Original file line number Diff line number Diff line change
Expand Up @@ -109,34 +109,40 @@ func (c *TagValueSeriesIDCache) Put(name, key, value []byte, ss *tsdb.SeriesIDSe
ss = ss.Clone()
}

// Convert once; the same string backing array is shared between
// the cache element (used during eviction) and the map keys.
nameStr := string(name)
keyStr := string(key)
valueStr := string(value)
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Copilot AI Feb 26, 2026

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Put now reuses nameStr/keyStr/valueStr for insertion, but it still calls c.exists(name, key, value) beforehand, which converts the same []byte values to string again and allocates. To realize the allocation reduction described in the PR, consider performing the existence check using these already-converted strings (e.g., inline the lookup in Put or add an existsString(nameStr, keyStr, valueStr) helper) so each []byte→string conversion happens only once per Put.

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// Create list item, and add to the front of the eviction list.
listElement := c.evictor.PushFront(&seriesIDCacheElement{
name: string(name),
key: string(key),
value: string(value),
name: nameStr,
key: keyStr,
value: valueStr,
SeriesIDSet: ss,
})

// Add the listElement to the set of items.
if mmap, ok := c.cache[string(name)]; ok {
if tkmap, ok := mmap[string(key)]; ok {
if _, ok := tkmap[string(value)]; ok {
if mmap, ok := c.cache[nameStr]; ok {
if tkmap, ok := mmap[keyStr]; ok {
if _, ok := tkmap[valueStr]; ok {
goto EVICT
}

// Add the set to the map
tkmap[string(value)] = listElement
tkmap[valueStr] = listElement
goto EVICT
}

// No series set map for the tag key - first tag value for the tag key.
mmap[string(key)] = map[string]*list.Element{string(value): listElement}
mmap[keyStr] = map[string]*list.Element{valueStr: listElement}
goto EVICT
}

// No map for the measurement - first tag key for the measurment.
c.cache[string(name)] = map[string]map[string]*list.Element{
string(key): map[string]*list.Element{string(value): listElement},
c.cache[nameStr] = map[string]map[string]*list.Element{
keyStr: map[string]*list.Element{valueStr: listElement},
}

EVICT:
Expand Down