Add JSON Path expression evaluation support (#7315)

- Includes support for FROM clause JSON path

pkg/s3select/sql/jsonpath_test.go

@@ -0,0 +1,96 @@
+/*
+ * 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 (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+
+	"github.com/alecthomas/participle"
+	"github.com/bcicen/jstream"
+)
+
+func getJSONStructs(b []byte) ([]interface{}, error) {
+	dec := jstream.NewDecoder(bytes.NewBuffer(b), 0).ObjectAsKVS()
+	var result []interface{}
+	for parsedVal := range dec.Stream() {
+		result = append(result, parsedVal.Value)
+	}
+	if err := dec.Err(); err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+func TestJsonpathEval(t *testing.T) {
+	f, err := os.Open(filepath.Join("jsondata", "books.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	b, err := ioutil.ReadAll(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	p := participle.MustBuild(
+		&JSONPath{},
+		participle.Lexer(sqlLexer),
+		participle.CaseInsensitive("Keyword"),
+	)
+	cases := []struct {
+		str string
+		res []interface{}
+	}{
+		{"s.title", []interface{}{"Murder on the Orient Express", "The Robots of Dawn", "Pigs Have Wings"}},
+		{"s.authorInfo.yearRange", []interface{}{[]interface{}{1890.0, 1976.0}, []interface{}{1920.0, 1992.0}, []interface{}{1881.0, 1975.0}}},
+		{"s.authorInfo.name", []interface{}{"Agatha Christie", "Isaac Asimov", "P. G. Wodehouse"}},
+		{"s.authorInfo.yearRange[0]", []interface{}{1890.0, 1920.0, 1881.0}},
+		{"s.publicationHistory[0].pages", []interface{}{256.0, 336.0, nil}},
+	}
+	for i, tc := range cases {
+		jp := JSONPath{}
+		err := p.ParseString(tc.str, &jp)
+		// fmt.Println(jp)
+		if err != nil {
+			t.Fatalf("parse failed!: %d %v %s", i, err, tc)
+		}
+
+		// Read only the first json object from the file
+		recs, err := getJSONStructs(b)
+		if err != nil || len(recs) != 3 {
+			t.Fatalf("%v or length was not 3", err)
+		}
+
+		for j, rec := range recs {
+			// fmt.Println(rec)
+			r, err := jsonpathEval(jp.PathExpr, rec)
+			if err != nil {
+				t.Errorf("Error: %d %d %v", i, j, err)
+			}
+			if !reflect.DeepEqual(r, tc.res[j]) {
+				fmt.Printf("%#v (%v) != %v (%v)\n", r, reflect.TypeOf(r), tc.res[j], reflect.TypeOf(tc.res[j]))
+				t.Errorf("case: %d %d failed", i, j)
+			}
+		}
+	}
+}