wehub-resource-sync
135 lines
4.0 KiB
Go
135 lines
4.0 KiB
Go
// Copyright 2024 Dolthub, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package functions
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import (
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"math"
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"strings"
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"github.com/cockroachdb/apd/v3"
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"github.com/cockroachdb/errors"
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"github.com/dolthub/go-mysql-server/sql"
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"github.com/dolthub/doltgresql/server/functions/framework"
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pgtypes "github.com/dolthub/doltgresql/server/types"
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)
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// initLog registers the functions to the catalog.
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func initLog() {
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framework.RegisterFunction(log_float64)
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framework.RegisterFunction(log_numeric)
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framework.RegisterFunction(log_numeric_numeric)
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}
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// log_float64 represents the PostgreSQL function of the same name, taking the same parameters.
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var log_float64 = framework.Function1{
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Name: "log",
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Return: pgtypes.Float64,
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Parameters: [1]*pgtypes.DoltgresType{pgtypes.Float64},
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Strict: true,
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Callable: func(ctx *sql.Context, _ [2]*pgtypes.DoltgresType, val1Interface any) (any, error) {
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val1 := val1Interface.(float64)
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if val1 == 0 {
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return nil, errors.Errorf("cannot take logarithm of zero")
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} else if val1 < 0 {
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return nil, errors.Errorf("cannot take logarithm of a negative number")
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}
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return math.Log10(val1), nil
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},
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}
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// log_numeric represents the PostgreSQL function of the same name, taking the same parameters.
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var log_numeric = framework.Function1{
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Name: "log",
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Return: pgtypes.Numeric,
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Parameters: [1]*pgtypes.DoltgresType{pgtypes.Numeric},
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Strict: true,
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Callable: func(ctx *sql.Context, _ [2]*pgtypes.DoltgresType, val1 any) (any, error) {
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dec := val1.(*apd.Decimal)
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if dec.IsZero() {
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return nil, errors.Errorf("cannot take logarithm of zero")
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} else if dec.Sign() < 0 {
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return nil, errors.Errorf("cannot take logarithm of a negative number")
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}
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// calculate precision and scale
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p := uint32(17)
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if dec.Exponent < 0 {
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p += uint32(-dec.Exponent)
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}
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res := new(apd.Decimal)
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_, err := sql.DecimalCtx.WithPrecision(p).Log10(res, dec)
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if err != nil {
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return nil, err
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}
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return res, nil
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},
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}
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// log_numeric_numeric represents the PostgreSQL function of the same name, taking the same parameters.
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var log_numeric_numeric = framework.Function2{
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Name: "log",
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Return: pgtypes.Numeric,
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Parameters: [2]*pgtypes.DoltgresType{pgtypes.Numeric, pgtypes.Numeric},
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Strict: true,
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Callable: func(ctx *sql.Context, _ [3]*pgtypes.DoltgresType, val1 any, val2 any) (any, error) {
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base := val1.(*apd.Decimal)
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num := val2.(*apd.Decimal)
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if base.IsZero() || num.IsZero() {
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return nil, errors.Errorf("cannot take logarithm of zero")
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} else if base.Sign() < 0 || num.Sign() < 0 {
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return nil, errors.Errorf("cannot take logarithm of a negative number")
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}
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// TODO: calculate precision and scale accurately
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sNum := num.Text('f')
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sBase := base.Text('f')
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partsNum := strings.Split(sNum, ".")
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partsBase := strings.Split(sBase, ".")
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exp := int32(-16)
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if minExp := math.Min(float64(base.Exponent), float64(num.Exponent)); int32(minExp) < exp {
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exp = int32(minExp)
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}
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p := uint32(int32(math.Max(float64(len(partsNum[0])), float64(len(partsBase[0])))) + (-exp))
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c := sql.DecimalCtx.WithPrecision(p)
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lnBase := new(apd.Decimal)
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_, err := c.Ln(lnBase, base)
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if err != nil {
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return nil, err
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}
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if lnBase.IsZero() {
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return nil, errors.Errorf("division by zero")
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}
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lnNum := new(apd.Decimal)
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_, err = c.Ln(lnNum, num)
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if err != nil {
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return nil, err
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}
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if lnNum.IsZero() {
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return apd.New(0, -16), nil
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}
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res := new(apd.Decimal)
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_, err = c.Quo(res, lnNum, lnBase)
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if err != nil {
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return nil, err
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}
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return sql.DecimalRound(res, -exp)
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},
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}
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