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318 lines
6.9 KiB
318 lines
6.9 KiB
/*
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* Minio Cloud Storage, (C) 2019 Minio, 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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*/
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package sql
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import (
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"errors"
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"fmt"
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)
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// Aggregation Function name constants
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const (
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aggFnAvg FuncName = "AVG"
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aggFnCount FuncName = "COUNT"
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aggFnMax FuncName = "MAX"
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aggFnMin FuncName = "MIN"
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aggFnSum FuncName = "SUM"
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)
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var (
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errNonNumericArg = func(fnStr FuncName) error {
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return fmt.Errorf("%s() requires a numeric argument", fnStr)
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}
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errInvalidAggregation = errors.New("Invalid aggregation seen")
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)
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type aggVal struct {
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runningSum *Value
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runningCount int64
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runningMax, runningMin *Value
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// Stores if at least one record has been seen
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seen bool
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}
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func newAggVal(fn FuncName) *aggVal {
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switch fn {
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case aggFnAvg, aggFnSum:
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return &aggVal{runningSum: FromInt(0)}
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case aggFnMin:
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return &aggVal{runningMin: FromInt(0)}
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case aggFnMax:
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return &aggVal{runningMax: FromInt(0)}
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default:
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return &aggVal{}
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}
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}
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// evalAggregationNode - performs partial computation using the
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// current row and stores the result.
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//
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// On success, it returns (nil, nil).
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func (e *FuncExpr) evalAggregationNode(r Record) error {
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// It is assumed that this function is called only when
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// `e` is an aggregation function.
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var val *Value
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var err error
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funcName := e.getFunctionName()
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if aggFnCount == funcName {
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if e.Count.StarArg {
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// Handle COUNT(*)
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e.aggregate.runningCount++
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return nil
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}
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val, err = e.Count.ExprArg.evalNode(r)
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if err != nil {
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return err
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}
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} else {
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// Evaluate the (only) argument
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val, err = e.SFunc.ArgsList[0].evalNode(r)
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if err != nil {
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return err
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}
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}
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if val.IsNull() {
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// E.g. the column or field does not exist in the
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// record - in all such cases the aggregation is not
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// updated.
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return nil
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}
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argVal := val
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if funcName != aggFnCount {
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// All aggregation functions, except COUNT require a
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// numeric argument.
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// Here, we diverge from Amazon S3 behavior by
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// inferring untyped values are numbers.
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if i, ok := argVal.bytesToInt(); ok {
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argVal.setInt(i)
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} else if f, ok := argVal.bytesToFloat(); ok {
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argVal.setFloat(f)
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} else {
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return errNonNumericArg(funcName)
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}
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}
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// Mark that we have seen one non-null value.
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isFirstRow := false
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if !e.aggregate.seen {
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e.aggregate.seen = true
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isFirstRow = true
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}
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switch funcName {
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case aggFnCount:
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// For all non-null values, the count is incremented.
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e.aggregate.runningCount++
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case aggFnAvg:
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e.aggregate.runningCount++
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err = e.aggregate.runningSum.arithOp(opPlus, argVal)
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case aggFnMin:
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err = e.aggregate.runningMin.minmax(argVal, false, isFirstRow)
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case aggFnMax:
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err = e.aggregate.runningMax.minmax(argVal, true, isFirstRow)
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case aggFnSum:
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err = e.aggregate.runningSum.arithOp(opPlus, argVal)
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default:
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err = errInvalidAggregation
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}
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return err
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}
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func (e *AliasedExpression) aggregateRow(r Record) error {
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return e.Expression.aggregateRow(r)
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}
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func (e *Expression) aggregateRow(r Record) error {
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for _, ex := range e.And {
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err := ex.aggregateRow(r)
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if err != nil {
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return err
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}
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}
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return nil
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}
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func (e *AndCondition) aggregateRow(r Record) error {
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for _, ex := range e.Condition {
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err := ex.aggregateRow(r)
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if err != nil {
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return err
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}
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}
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return nil
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}
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func (e *Condition) aggregateRow(r Record) error {
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if e.Operand != nil {
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return e.Operand.aggregateRow(r)
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}
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return e.Not.aggregateRow(r)
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}
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func (e *ConditionOperand) aggregateRow(r Record) error {
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err := e.Operand.aggregateRow(r)
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if err != nil {
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return err
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}
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if e.ConditionRHS == nil {
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return nil
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}
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switch {
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case e.ConditionRHS.Compare != nil:
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return e.ConditionRHS.Compare.Operand.aggregateRow(r)
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case e.ConditionRHS.Between != nil:
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err = e.ConditionRHS.Between.Start.aggregateRow(r)
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if err != nil {
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return err
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}
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return e.ConditionRHS.Between.End.aggregateRow(r)
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case e.ConditionRHS.In != nil:
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for _, elt := range e.ConditionRHS.In.Expressions {
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err = elt.aggregateRow(r)
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if err != nil {
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return err
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}
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}
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return nil
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case e.ConditionRHS.Like != nil:
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err = e.ConditionRHS.Like.Pattern.aggregateRow(r)
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if err != nil {
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return err
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}
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return e.ConditionRHS.Like.EscapeChar.aggregateRow(r)
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default:
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return errInvalidASTNode
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}
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}
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func (e *Operand) aggregateRow(r Record) error {
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err := e.Left.aggregateRow(r)
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if err != nil {
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return err
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}
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for _, rt := range e.Right {
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err = rt.Right.aggregateRow(r)
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if err != nil {
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return err
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}
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}
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return nil
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}
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func (e *MultOp) aggregateRow(r Record) error {
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err := e.Left.aggregateRow(r)
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if err != nil {
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return err
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}
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for _, rt := range e.Right {
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err = rt.Right.aggregateRow(r)
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if err != nil {
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return err
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}
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}
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return nil
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}
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func (e *UnaryTerm) aggregateRow(r Record) error {
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if e.Negated != nil {
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return e.Negated.Term.aggregateRow(r)
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}
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return e.Primary.aggregateRow(r)
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}
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func (e *PrimaryTerm) aggregateRow(r Record) error {
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switch {
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case e.SubExpression != nil:
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return e.SubExpression.aggregateRow(r)
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case e.FuncCall != nil:
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return e.FuncCall.aggregateRow(r)
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}
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return nil
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}
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func (e *FuncExpr) aggregateRow(r Record) error {
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switch e.getFunctionName() {
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case aggFnAvg, aggFnSum, aggFnMax, aggFnMin, aggFnCount:
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return e.evalAggregationNode(r)
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default:
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// TODO: traverse arguments and call aggregateRow on
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// them if they could be an ancestor of an
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// aggregation.
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}
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return nil
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}
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// getAggregate() implementation for each AST node follows. This is
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// called after calling aggregateRow() on each input row, to calculate
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// the final aggregate result.
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func (e *Expression) getAggregate() (*Value, error) {
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return e.evalNode(nil)
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}
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func (e *FuncExpr) getAggregate() (*Value, error) {
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switch e.getFunctionName() {
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case aggFnCount:
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return FromFloat(float64(e.aggregate.runningCount)), nil
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case aggFnAvg:
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if e.aggregate.runningCount == 0 {
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// No rows were seen by AVG.
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return FromNull(), nil
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}
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err := e.aggregate.runningSum.arithOp(opDivide, FromInt(e.aggregate.runningCount))
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return e.aggregate.runningSum, err
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case aggFnMin:
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if !e.aggregate.seen {
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// No rows were seen by MIN
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return FromNull(), nil
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}
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return e.aggregate.runningMin, nil
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case aggFnMax:
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if !e.aggregate.seen {
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// No rows were seen by MAX
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return FromNull(), nil
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}
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return e.aggregate.runningMax, nil
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case aggFnSum:
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// TODO: check if returning 0 when no rows were seen
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// by SUM is expected behavior.
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return e.aggregate.runningSum, nil
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default:
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// TODO:
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}
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return nil, errInvalidAggregation
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}
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