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package mapr
import (
"errors"
"fmt"
"strings"
)
// AggregateOperation is to specify the aggregate operation type.
type AggregateOperation int
// Aggregate operation types
const (
UndefAggregateOperation AggregateOperation = iota
Count AggregateOperation = iota
Sum AggregateOperation = iota
Min AggregateOperation = iota
Max AggregateOperation = iota
Last AggregateOperation = iota
Avg AggregateOperation = iota
Len AggregateOperation = iota
)
// Represents a parsed "select" clause, used by mapr.Query.
type selectCondition struct {
Field string
FieldStorage string
Operation AggregateOperation
}
func (sc selectCondition) String() string {
return fmt.Sprintf("selectCondition(Field:%s,FieldStorage:%s,Operation:%v)",
sc.Field,
sc.FieldStorage,
sc.Operation)
}
func makeSelectConditions(tokens []token) ([]selectCondition, error) {
var sel []selectCondition
// Parse select aggregation, e.g. sum(foo)
parse := func(token token) (selectCondition, error) {
var sc selectCondition
tokenStr := token.str
if !strings.Contains(tokenStr, "(") && !strings.Contains(tokenStr, ")") {
sc.Field = tokenStr
sc.FieldStorage = tokenStr
sc.Operation = Last
return sc, nil
}
a := strings.Split(tokenStr, "(")
if len(a) != 2 {
return sc, errors.New(invalidQuery + "Can't parse 'select' aggregation: " +
token.str)
}
agg := a[0] // Aggregation, e.g. 'sum'
b := strings.Split(a[1], ")")
if len(b) != 2 {
return sc, errors.New(invalidQuery + "Can't parse 'select' field name " +
"from aggregation: " + token.str)
}
sc.Field = b[0] // Field name, e.g. 'foo'
sc.FieldStorage = tokenStr // e.g. 'sum(foo)'
switch agg {
case "count":
sc.Operation = Count
case "sum":
sc.Operation = Sum
case "min":
sc.Operation = Min
case "max":
sc.Operation = Max
case "last":
sc.Operation = Last
case "avg":
sc.Operation = Avg
case "len":
sc.Operation = Len
default:
return sc, errors.New(invalidQuery +
"Unknown aggregation in 'select' clause: " + agg)
}
return sc, nil
}
for _, token := range tokens {
sc, err := parse(token)
if err != nil {
return nil, err
}
sel = append(sel, sc)
}
return sel, nil
}
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