minio/pkg/s3select/sql/jsonpath.go
2020-02-13 14:03:52 -08:00

129 lines
3.3 KiB
Go

/*
* MinIO Cloud Storage, (C) 2019 MinIO, 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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package sql
import (
"errors"
"github.com/bcicen/jstream"
"github.com/minio/simdjson-go"
)
var (
errKeyLookup = errors.New("Cannot look up key in non-object value")
errIndexLookup = errors.New("Cannot look up array index in non-array value")
errWildcardObjectLookup = errors.New("Object wildcard used on non-object value")
errWildcardArrayLookup = errors.New("Array wildcard used on non-array value")
errWilcardObjectUsageInvalid = errors.New("Invalid usage of object wildcard")
)
// jsonpathEval evaluates a JSON path and returns the value at the path.
// If the value should be considered flat (from wildcards) any array returned should be considered individual values.
func jsonpathEval(p []*JSONPathElement, v interface{}) (r interface{}, flat bool, err error) {
// fmt.Printf("JPATHexpr: %v jsonobj: %v\n\n", p, v)
if len(p) == 0 || v == nil {
return v, false, nil
}
switch {
case p[0].Key != nil:
key := p[0].Key.keyString()
switch kvs := v.(type) {
case jstream.KVS:
for _, kv := range kvs {
if kv.Key == key {
return jsonpathEval(p[1:], kv.Value)
}
}
// Key not found - return nil result
return nil, false, nil
case simdjson.Object:
elem := kvs.FindKey(key, nil)
if elem == nil {
// Key not found - return nil result
return nil, false, nil
}
val, err := IterToValue(elem.Iter)
if err != nil {
return nil, false, err
}
return jsonpathEval(p[1:], val)
default:
return nil, false, errKeyLookup
}
case p[0].Index != nil:
idx := *p[0].Index
arr, ok := v.([]interface{})
if !ok {
return nil, false, errIndexLookup
}
if idx >= len(arr) {
return nil, false, nil
}
return jsonpathEval(p[1:], arr[idx])
case p[0].ObjectWildcard:
switch kvs := v.(type) {
case jstream.KVS:
if len(p[1:]) > 0 {
return nil, false, errWilcardObjectUsageInvalid
}
return kvs, false, nil
case simdjson.Object:
if len(p[1:]) > 0 {
return nil, false, errWilcardObjectUsageInvalid
}
return kvs, false, nil
default:
return nil, false, errWildcardObjectLookup
}
case p[0].ArrayWildcard:
arr, ok := v.([]interface{})
if !ok {
return nil, false, errWildcardArrayLookup
}
// Lookup remainder of path in each array element and
// make result array.
var result []interface{}
for _, a := range arr {
rval, flatten, err := jsonpathEval(p[1:], a)
if err != nil {
return nil, false, err
}
if flatten {
// Flatten if array.
if arr, ok := rval.([]interface{}); ok {
result = append(result, arr...)
continue
}
}
result = append(result, rval)
}
return result, true, nil
}
panic("cannot reach here")
}