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stats: refine estimate in buckets #4601
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a567621
stats: refine estimate in buckets
9d6d88c
tiny change
ee6172c
address comment
b27ef49
fix test
d23ccb9
remove useless variable
087e3c4
check inf
540be22
optimize code
737f9f0
address comment
98d8818
address comment
3558f2c
Merge branch 'master' into xhb/est
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,115 @@ | ||
| // Copyright 2017 PingCAP, Inc. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package statistics | ||
|
|
||
| import ( | ||
| "encoding/binary" | ||
| "math" | ||
|
|
||
| "github.com/pingcap/tidb/util/types" | ||
| ) | ||
|
|
||
| // calcFraction is used to calculate the fraction of the interval [lower, upper] that lies within the [lower, value] | ||
| // using the continuous-value assumption. | ||
| func calcFraction(lower, upper, value *types.Datum) float64 { | ||
| lowerScalar, upperScalar, valueScalar := convertToScalar(lower, upper, value) | ||
| if upperScalar <= lowerScalar { | ||
| return 0.5 | ||
| } | ||
| if valueScalar <= lowerScalar { | ||
| return 0 | ||
| } | ||
| if valueScalar >= upperScalar { | ||
| return 1 | ||
| } | ||
| frac := (valueScalar - lowerScalar) / (upperScalar - lowerScalar) | ||
| if math.IsNaN(frac) || math.IsInf(frac, 0) || frac < 0 || frac > 1 { | ||
| return 0.5 | ||
| } | ||
| return frac | ||
| } | ||
|
|
||
| // convertToScalar converts the datum to scalar values. | ||
| // TODO: We may cache results for some types. | ||
| func convertToScalar(lower, upper, value *types.Datum) (float64, float64, float64) { | ||
| switch value.Kind() { | ||
| case types.KindFloat32: | ||
| return float64(lower.GetFloat32()), float64(upper.GetFloat32()), float64(value.GetFloat32()) | ||
| case types.KindFloat64: | ||
| return lower.GetFloat64(), upper.GetFloat64(), value.GetFloat64() | ||
| case types.KindInt64: | ||
| return float64(lower.GetInt64()), float64(upper.GetInt64()), float64(value.GetInt64()) | ||
| case types.KindUint64: | ||
| return float64(lower.GetUint64()), float64(upper.GetUint64()), float64(value.GetUint64()) | ||
| case types.KindMysqlDecimal: | ||
| return convertDecimalToScalar(lower, upper, value) | ||
| case types.KindMysqlDuration: | ||
| return float64(lower.GetMysqlDuration().Duration), float64(upper.GetMysqlDuration().Duration), float64(value.GetMysqlDuration().Duration) | ||
| case types.KindMysqlTime: | ||
| lowerTime := lower.GetMysqlTime() | ||
| upperTime := upper.GetMysqlTime() | ||
| valueTime := value.GetMysqlTime() | ||
| return 0, float64(upperTime.Sub(&lowerTime).Duration), float64(valueTime.Sub(&lowerTime).Duration) | ||
| case types.KindString, types.KindBytes: | ||
| return convertBytesToScalar(lower.GetBytes(), upper.GetBytes(), value.GetBytes()) | ||
| default: | ||
| // do not know how to convert | ||
| return 0, 0, 0 | ||
| } | ||
| } | ||
|
|
||
| // Decimal types are simply converted to their equivalent float64 values. | ||
| func convertDecimalToScalar(lower, upper, value *types.Datum) (float64, float64, float64) { | ||
| lowerScalar, err := lower.GetMysqlDecimal().ToFloat64() | ||
| if err != nil { | ||
| return 0, 0, 0 | ||
| } | ||
| upperScalar, err := upper.GetMysqlDecimal().ToFloat64() | ||
| if err != nil { | ||
| return 0, 0, 0 | ||
| } | ||
| valueScalar, err := value.GetMysqlDecimal().ToFloat64() | ||
| if err != nil { | ||
| return 0, 0, 0 | ||
| } | ||
| return lowerScalar, upperScalar, valueScalar | ||
| } | ||
|
|
||
| // Bytes type is viewed as a base-256 value. | ||
| func convertBytesToScalar(lower, upper, value []byte) (float64, float64, float64) { | ||
| minLen := len(lower) | ||
| if len(upper) < minLen { | ||
| minLen = len(upper) | ||
| } | ||
| if len(value) < minLen { | ||
| minLen = len(value) | ||
| } | ||
| // remove their common prefix | ||
| common := 0 | ||
| for common < minLen { | ||
| if lower[common] == upper[common] && lower[common] == value[common] { | ||
| common++ | ||
| } else { | ||
| break | ||
| } | ||
| } | ||
| return convertOneBytesToScalar(lower[common:]), convertOneBytesToScalar(upper[common:]), convertOneBytesToScalar(value[common:]) | ||
| } | ||
|
|
||
| func convertOneBytesToScalar(value []byte) float64 { | ||
| // Since the base is 256, we only consider at most 8 bytes. | ||
| var buf [8]byte | ||
| copy(buf[:], value) | ||
| return float64(binary.BigEndian.Uint64(buf[:])) | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,131 @@ | ||
| // Copyright 2017 PingCAP, Inc. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package statistics | ||
|
|
||
| import ( | ||
| "math" | ||
|
|
||
| . "github.com/pingcap/check" | ||
| "github.com/pingcap/tidb/mysql" | ||
| "github.com/pingcap/tidb/util/types" | ||
| ) | ||
|
|
||
| const eps = 1e-9 | ||
|
|
||
| func getDecimal(value float64) *types.MyDecimal { | ||
| dec := &types.MyDecimal{} | ||
| dec.FromFloat64(value) | ||
| return dec | ||
| } | ||
|
|
||
| func getDuration(value string) types.Duration { | ||
| dur, _ := types.ParseDuration(value, 0) | ||
| return dur | ||
| } | ||
|
|
||
| func getTime(value string) types.Time { | ||
| t, _ := types.ParseTime(value, mysql.TypeDate, 0) | ||
| return t | ||
| } | ||
|
|
||
| func getBinaryLiteral(value string) types.BinaryLiteral { | ||
| b, _ := types.ParseBitStr(value) | ||
| return b | ||
| } | ||
|
|
||
| func (t *testStatisticsSuite) TestCalcFraction(c *C) { | ||
| tests := []struct { | ||
| lower types.Datum | ||
| upper types.Datum | ||
| value types.Datum | ||
| fraction float64 | ||
| }{ | ||
| { | ||
| lower: types.NewIntDatum(0), | ||
| upper: types.NewIntDatum(4), | ||
| value: types.NewIntDatum(1), | ||
| fraction: 0.25, | ||
| }, | ||
| { | ||
| lower: types.NewIntDatum(0), | ||
| upper: types.NewIntDatum(4), | ||
| value: types.NewIntDatum(4), | ||
| fraction: 1, | ||
| }, | ||
| { | ||
| lower: types.NewIntDatum(0), | ||
| upper: types.NewIntDatum(4), | ||
| value: types.NewIntDatum(-1), | ||
| fraction: 0, | ||
| }, | ||
| { | ||
| lower: types.NewUintDatum(0), | ||
| upper: types.NewUintDatum(4), | ||
| value: types.NewUintDatum(1), | ||
| fraction: 0.25, | ||
| }, | ||
| { | ||
| lower: types.NewFloat64Datum(0), | ||
| upper: types.NewFloat64Datum(4), | ||
| value: types.NewFloat64Datum(1), | ||
| fraction: 0.25, | ||
| }, | ||
| { | ||
| lower: types.NewFloat32Datum(0), | ||
| upper: types.NewFloat32Datum(4), | ||
| value: types.NewFloat32Datum(1), | ||
| fraction: 0.25, | ||
| }, | ||
| { | ||
| lower: types.NewDecimalDatum(getDecimal(0)), | ||
| upper: types.NewDecimalDatum(getDecimal(4)), | ||
| value: types.NewDecimalDatum(getDecimal(1)), | ||
| fraction: 0.25, | ||
| }, | ||
| { | ||
| lower: types.NewMysqlBitDatum(getBinaryLiteral("0b0")), | ||
| upper: types.NewMysqlBitDatum(getBinaryLiteral("0b100")), | ||
| value: types.NewMysqlBitDatum(getBinaryLiteral("0b1")), | ||
| fraction: 0.5, | ||
| }, | ||
| { | ||
| lower: types.NewDurationDatum(getDuration("0:00:00")), | ||
| upper: types.NewDurationDatum(getDuration("4:00:00")), | ||
| value: types.NewDurationDatum(getDuration("1:00:00")), | ||
| fraction: 0.25, | ||
| }, | ||
| { | ||
| lower: types.NewTimeDatum(getTime("2017-01-01")), | ||
| upper: types.NewTimeDatum(getTime("2017-04-01")), | ||
| value: types.NewTimeDatum(getTime("2017-02-01")), | ||
| fraction: 0.34444444444444444, | ||
| }, | ||
| { | ||
| lower: types.NewStringDatum("aasad"), | ||
| upper: types.NewStringDatum("addad"), | ||
| value: types.NewStringDatum("abfsd"), | ||
| fraction: 0.32280253984063745, | ||
| }, | ||
| { | ||
| lower: types.NewBytesDatum([]byte("aasad")), | ||
| upper: types.NewBytesDatum([]byte("asdff")), | ||
| value: types.NewBytesDatum([]byte("abfsd")), | ||
| fraction: 0.0529216802217269, | ||
| }, | ||
| } | ||
| for _, test := range tests { | ||
| fraction := calcFraction(&test.lower, &test.upper, &test.value) | ||
| c.Check(math.Abs(fraction-test.fraction) < eps, IsTrue) | ||
| } | ||
| } |
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This function is complex, how about using
BigEndian.Uint64?