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Memoize tagset cursor's key #3676

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Aug 15, 2015
Merged

Memoize tagset cursor's key #3676

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7e72a1a
Precompute cursor keys
otoolep Aug 15, 2015
0cf8247
Update CHANGELOG
otoolep Aug 15, 2015
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,7 @@ There are breaking changes in this release. Please see the *Features* section be
- [#3646](https://github.com/influxdb/influxdb/pull/3646): Fix nil FieldCodec panic.
- [#3672](https://github.com/influxdb/influxdb/pull/3672): Reduce in-memory index by 20%-30%
- [#3673](https://github.com/influxdb/influxdb/pull/3673): Improve query performance by removing unnecessary tagset sorting.
- [#3676](https://github.com/influxdb/influxdb/pull/3676): Improve query performance by memomizing mapper output keys.

## v0.9.2 [2015-07-24]

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5 changes: 3 additions & 2 deletions tsdb/executor.go
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Expand Up @@ -269,8 +269,9 @@ func (e *Executor) executeRaw(out chan *influxql.Row) {
// Add up to the index to the values
if chunkedOutput == nil {
chunkedOutput = &MapperOutput{
Name: m.bufferedChunk.Name,
Tags: m.bufferedChunk.Tags,
Name: m.bufferedChunk.Name,
Tags: m.bufferedChunk.Tags,
cursorKey: m.bufferedChunk.key(),
}
chunkedOutput.Values = m.bufferedChunk.Values[:ind]
} else {
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36 changes: 23 additions & 13 deletions tsdb/mapper.go
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Expand Up @@ -28,14 +28,15 @@ func (a MapperValues) Less(i, j int) bool { return a[i].Time < a[j].Time }
func (a MapperValues) Swap(i, j int) { a[i], a[j] = a[j], a[i] }

type MapperOutput struct {
Name string `json:"name,omitempty"`
Tags map[string]string `json:"tags,omitempty"`
Fields []string `json:"fields,omitempty"` // Field names of returned data.
Values []*MapperValue `json:"values,omitempty"` // For aggregates contains a single value at [0]
Name string `json:"name,omitempty"`
Tags map[string]string `json:"tags,omitempty"`
Fields []string `json:"fields,omitempty"` // Field names of returned data.
Values []*MapperValue `json:"values,omitempty"` // For aggregates contains a single value at [0]
cursorKey string // Tagset-based key for the source cursor. Cached for performance reasons.
}

func (mo *MapperOutput) key() string {
return formMeasurementTagSetKey(mo.Name, mo.Tags)
return mo.cursorKey
}

// LocalMapper is for retrieving data for a query, from a given shard.
Expand Down Expand Up @@ -287,9 +288,10 @@ func (lm *LocalMapper) nextChunkRaw() (*MapperOutput, error) {

if output == nil {
output = &MapperOutput{
Name: cursor.measurement,
Tags: cursor.tags,
Fields: lm.selectFields,
Name: cursor.measurement,
Tags: cursor.tags,
Fields: lm.selectFields,
cursorKey: cursor.key(),
}
}
value := &MapperValue{Time: k, Value: v, Tags: t}
Expand Down Expand Up @@ -325,10 +327,11 @@ func (lm *LocalMapper) nextChunkAgg() (*MapperOutput, error) {
// for a single tagset.
if output == nil {
output = &MapperOutput{
Name: tsc.measurement,
Tags: tsc.tags,
Fields: lm.selectFields,
Values: make([]*MapperValue, 1),
Name: tsc.measurement,
Tags: tsc.tags,
Fields: lm.selectFields,
Values: make([]*MapperValue, 1),
cursorKey: tsc.key(),
}
// Aggregate values only use the first entry in the Values field. Set the time
// to the start of the interval.
Expand Down Expand Up @@ -643,6 +646,10 @@ type tagSetCursor struct {
// Performance profiling shows that this lookahead needs to be part
// of the tagSetCursor type and not part of the the cursors type.
pointHeap *pointHeap

// Memomize the cursor's tagset-based key. Profiling shows that calculating this
// is significant CPU cost, and it only needs to be done once.
memokey string
}

// tagSetCursors represents a sortable slice of tagSetCursors.
Expand Down Expand Up @@ -675,7 +682,10 @@ func newTagSetCursor(m string, t map[string]string, c []*seriesCursor, d *FieldC
}

func (tsc *tagSetCursor) key() string {
return formMeasurementTagSetKey(tsc.measurement, tsc.tags)
if tsc.memokey == "" {
tsc.memokey = formMeasurementTagSetKey(tsc.measurement, tsc.tags)
}
return tsc.memokey
}

// Next returns the next matching series-key, timestamp byte slice and meta tags for the tagset. Filtering
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