statistics: add bucket structure. #2993
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coocood
reviewed
Apr 5, 2017
statistics/builder.go
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| col.Numbers[bucketIdx] = i * sampleFactor | ||
| col.Repeats[bucketIdx] += sampleFactor | ||
| col.Buckets[bucketIdx].Count = (i + 1) * sampleFactor | ||
| col.Buckets[bucketIdx].Repeats += sampleFactor | ||
| } else if i*sampleFactor-lastNumber <= valuesPerBucket { |
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This should be (i+1)*sampleFactor-lastNumber).
coocood
reviewed
Apr 5, 2017
statistics/builder.go
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| col.Repeats[bucketIdx] = 0 | ||
| col.Buckets[bucketIdx].Count = (i + 1) * sampleFactor | ||
| col.Buckets[bucketIdx].Value = samples[i] | ||
| col.Buckets[bucketIdx].Repeats = sampleFactor |
alivxxx
reviewed
Apr 5, 2017
statistics/column.go
Outdated
| c.Repeats[curBuck] = c.Repeats[i+1] | ||
| c.Buckets[curBuck].Count = c.Buckets[i+1].Count | ||
| c.Buckets[curBuck].Value = c.Buckets[i+1].Value | ||
| c.Buckets[curBuck].Repeats = c.Buckets[i+1].Repeats |
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Why not directly copy the whole bucket?
statistics/column.go
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| return greaterThanBucketValueCount, nil | ||
| } | ||
| return (nextNumber + greaterThanBucketValueCount) / 2, nil | ||
| return c.totalRowCount() - lessCount, nil |
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Greater count should be total count minus less or equal count.
coocood
reviewed
Apr 5, 2017
statistics/column.go
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| c.Numbers[curBuck] = c.Numbers[i+1] | ||
| c.Values[curBuck] = c.Values[i+1] | ||
| c.Repeats[curBuck] = c.Repeats[i+1] | ||
| c.Buckets[curBuck].Count = c.Buckets[i+1].Count |
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c.Bucket[curBuck] = Bucket{
...
}
alivxxx
reviewed
Apr 5, 2017
statistics/builder.go
Outdated
| } else { | ||
| // The bucket is full, store the item in the next bucket. | ||
| lastNumber = col.Numbers[bucketIdx] |
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it's use less, count is calculate by (i+1) * sampleFactor
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If you delete this, then when you test if this bucket is full, it will always false, which will lead to too many buckets.
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I think we need a test to make sure that the number of buckets do not exceed the predefined bucket count.
alivxxx
reviewed
Apr 5, 2017
statistics/builder.go
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| } | ||
| valuesPerBucket := t.Count/bucketCount + 1 | ||
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| // As we use samples to build the histogram, the bucket number and repeat should multiply a factor. | ||
| sampleFactor := t.Count / int64(len(samples)) | ||
| ndvFactor := t.Count / ndv | ||
| log.Warnf("sample %d ndv %d ndvFact %d", sampleFactor, ndv, ndvFactor) |
|
LGTM |
zimulala
reviewed
Apr 5, 2017
statistics/column.go
Outdated
|
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| // bucket is an element of histogram. | ||
| // | ||
| // A bucket number is the number of items stored in all previous buckets and the current bucket. |
zimulala
reviewed
Apr 5, 2017
statistics/builder.go
Outdated
| col.Numbers[bucketIdx] = i * sampleFactor | ||
| col.Repeats[bucketIdx] += sampleFactor | ||
| } else if i*sampleFactor-lastNumber <= valuesPerBucket { | ||
| col.Buckets[bucketIdx].Count = (i + 1) * sampleFactor |
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Define a variable for i+1. Many places use it.
|
LGTM |
zimulala
approved these changes
Apr 5, 2017
zimulala
added
status/LGT2
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add Buctket structure and adjust the way of estimating.
@shenli @coocood @zimulala @lamxTyler PTAL