forked from pingcap/tidb
/
aggregation.go
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/
aggregation.go
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// Copyright 2016 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 aggregation
import (
"bytes"
"encoding/json"
"fmt"
"strings"
"github.com/juju/errors"
"github.com/pingcap/tidb/ast"
"github.com/pingcap/tidb/context"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/sessionctx/variable"
"github.com/pingcap/tidb/util/types"
tipb "github.com/pingcap/tipb/go-tipb"
)
// Aggregation stands for aggregate functions.
type Aggregation interface {
fmt.Stringer
json.Marshaler
// Update during executing.
Update(ctx *AggEvaluateContext, sc *variable.StatementContext, row []types.Datum) error
// GetPartialResult will called by coprocessor to get partial results. For avg function, partial results will return
// sum and count values at the same time.
GetPartialResult(ctx *AggEvaluateContext) []types.Datum
// SetMode sets aggFunctionMode for aggregate function.
SetMode(mode AggFunctionMode)
// GetMode gets aggFunctionMode from aggregate function.
GetMode() AggFunctionMode
// GetResult will be called when all data have been processed.
GetResult(ctx *AggEvaluateContext) types.Datum
// GetArgs stands for getting all arguments.
GetArgs() []expression.Expression
// GetName gets the aggregation function name.
GetName() string
// SetArgs sets argument by index.
SetArgs(args []expression.Expression)
// Create a new AggEvaluateContext for the aggregation function.
CreateContext() *AggEvaluateContext
// IsDistinct indicates if the aggregate function contains distinct attribute.
IsDistinct() bool
// Equal checks whether two aggregation functions are equal.
Equal(agg Aggregation, ctx context.Context) bool
// Clone copies an aggregate function totally.
Clone() Aggregation
// GetType gets field type of aggregate function.
GetType() *types.FieldType
// CalculateDefaultValue gets the default value when the aggregate function's input is null.
// The input stands for the schema of Aggregation's child. If the function can't produce a default value, the second
// return value will be false.
CalculateDefaultValue(schema *expression.Schema, ctx context.Context) (types.Datum, bool)
}
// NewAggFunction creates a new Aggregation.
func NewAggFunction(funcType string, funcArgs []expression.Expression, distinct bool) Aggregation {
switch tp := strings.ToLower(funcType); tp {
case ast.AggFuncSum:
return &sumFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
case ast.AggFuncCount:
return &countFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
case ast.AggFuncAvg:
return &avgFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
case ast.AggFuncGroupConcat:
return &concatFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
case ast.AggFuncMax:
return &maxMinFunction{aggFunction: newAggFunc(tp, funcArgs, distinct), isMax: true}
case ast.AggFuncMin:
return &maxMinFunction{aggFunction: newAggFunc(tp, funcArgs, distinct), isMax: false}
case ast.AggFuncFirstRow:
return &firstRowFunction{aggFunction: newAggFunc(tp, funcArgs, distinct)}
}
return nil
}
// NewDistAggFunc creates new Aggregate function for mock tikv.
func NewDistAggFunc(expr *tipb.Expr, fieldTps []*types.FieldType, sc *variable.StatementContext) (Aggregation, error) {
args := make([]expression.Expression, 0, len(expr.Children))
for _, child := range expr.Children {
arg, err := expression.PBToExpr(child, fieldTps, sc)
if err != nil {
return nil, errors.Trace(err)
}
args = append(args, arg)
}
switch expr.Tp {
case tipb.ExprType_Sum:
return &sumFunction{aggFunction: newAggFunc(ast.AggFuncSum, args, false)}, nil
case tipb.ExprType_Count:
return &countFunction{aggFunction: newAggFunc(ast.AggFuncCount, args, false)}, nil
case tipb.ExprType_Avg:
return &avgFunction{aggFunction: newAggFunc(ast.AggFuncAvg, args, false)}, nil
case tipb.ExprType_GroupConcat:
return &concatFunction{aggFunction: newAggFunc(ast.AggFuncGroupConcat, args, false)}, nil
case tipb.ExprType_Max:
return &maxMinFunction{aggFunction: newAggFunc(ast.AggFuncMax, args, false), isMax: true}, nil
case tipb.ExprType_Min:
return &maxMinFunction{aggFunction: newAggFunc(ast.AggFuncMin, args, false)}, nil
case tipb.ExprType_First:
return &firstRowFunction{aggFunction: newAggFunc(ast.AggFuncFirstRow, args, false)}, nil
}
return nil, errors.Errorf("Unknown aggregate function type %v", expr.Tp)
}
// AggEvaluateContext is used to store intermediate result when calculating aggregate functions.
type AggEvaluateContext struct {
DistinctChecker *distinctChecker
Count int64
Value types.Datum
Buffer *bytes.Buffer // Buffer is used for group_concat.
GotFirstRow bool // It will check if the agg has met the first row key.
}
// AggFunctionMode stands for the aggregation function's mode.
type AggFunctionMode int
const (
// CompleteMode function accepts origin data.
CompleteMode AggFunctionMode = iota
// FinalMode function accepts partial data.
FinalMode
)
type aggFunction struct {
name string
mode AggFunctionMode
Args []expression.Expression
Distinct bool
}
// Equal implements Aggregation interface.
func (af *aggFunction) Equal(b Aggregation, ctx context.Context) bool {
if af.GetName() != b.GetName() {
return false
}
if af.Distinct != b.IsDistinct() {
return false
}
if len(af.GetArgs()) != len(b.GetArgs()) {
return false
}
for i, argA := range af.GetArgs() {
if !argA.Equal(b.GetArgs()[i], ctx) {
return false
}
}
return true
}
// String implements fmt.Stringer interface.
func (af *aggFunction) String() string {
result := af.name + "("
for i, arg := range af.Args {
result += arg.String()
if i+1 != len(af.Args) {
result += ", "
}
}
result += ")"
return result
}
// MarshalJSON implements json.Marshaler interface.
func (af *aggFunction) MarshalJSON() ([]byte, error) {
buffer := bytes.NewBufferString(fmt.Sprintf("\"%s\"", af))
return buffer.Bytes(), nil
}
func newAggFunc(name string, args []expression.Expression, dist bool) aggFunction {
return aggFunction{
name: name,
Args: args,
Distinct: dist,
}
}
// CalculateDefaultValue implements Aggregation interface.
func (af *aggFunction) CalculateDefaultValue(schema *expression.Schema, ctx context.Context) (types.Datum, bool) {
return types.Datum{}, false
}
// IsDistinct implements Aggregation interface.
func (af *aggFunction) IsDistinct() bool {
return af.Distinct
}
// GetName implements Aggregation interface.
func (af *aggFunction) GetName() string {
return af.name
}
// SetMode implements Aggregation interface.
func (af *aggFunction) SetMode(mode AggFunctionMode) {
af.mode = mode
}
// GetMode implements Aggregation interface.
func (af *aggFunction) GetMode() AggFunctionMode {
return af.mode
}
// GetArgs implements Aggregation interface.
func (af *aggFunction) GetArgs() []expression.Expression {
return af.Args
}
// SetArgs implements Aggregation interface.
func (af *aggFunction) SetArgs(args []expression.Expression) {
af.Args = args
}
// CreateContext implements Aggregation interface.
func (af *aggFunction) CreateContext() *AggEvaluateContext {
ctx := &AggEvaluateContext{}
if af.Distinct {
ctx.DistinctChecker = createDistinctChecker()
}
return ctx
}
func (af *aggFunction) updateSum(ctx *AggEvaluateContext, sc *variable.StatementContext, row []types.Datum) error {
a := af.Args[0]
value, err := a.Eval(row)
if err != nil {
return errors.Trace(err)
}
if value.IsNull() {
return nil
}
if af.Distinct {
d, err1 := ctx.DistinctChecker.Check([]types.Datum{value})
if err1 != nil {
return errors.Trace(err1)
}
if !d {
return nil
}
}
ctx.Value, err = calculateSum(sc, ctx.Value, value)
if err != nil {
return errors.Trace(err)
}
ctx.Count++
return nil
}