Refactor s3select to support parquet. (#7023)

Also handle pretty formatted JSON documents.

pkg/s3select/csv/record.go

@@ -0,0 +1,95 @@
+/*
+ * 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 csv
+
+import (
+	"bytes"
+	"encoding/csv"
+	"fmt"
+
+	"github.com/minio/minio/pkg/s3select/sql"
+	"github.com/tidwall/sjson"
+)
+
+// Record - is CSV record.
+type Record struct {
+	columnNames  []string
+	csvRecord    []string
+	nameIndexMap map[string]int64
+}
+
+// Get - gets the value for a column name.
+func (r *Record) Get(name string) (*sql.Value, error) {
+	index, found := r.nameIndexMap[name]
+	if !found {
+		return nil, fmt.Errorf("column %v not found", name)
+	}
+
+	if index >= int64(len(r.csvRecord)) {
+		// No value found for column 'name', hence return empty string for compatibility.
+		return sql.NewString(""), nil
+	}
+
+	return sql.NewString(r.csvRecord[index]), nil
+}
+
+// Set - sets the value for a column name.
+func (r *Record) Set(name string, value *sql.Value) error {
+	r.columnNames = append(r.columnNames, name)
+	r.csvRecord = append(r.csvRecord, value.CSVString())
+	return nil
+}
+
+// MarshalCSV - encodes to CSV data.
+func (r *Record) MarshalCSV(fieldDelimiter rune) ([]byte, error) {
+	buf := new(bytes.Buffer)
+	w := csv.NewWriter(buf)
+	w.Comma = fieldDelimiter
+	if err := w.Write(r.csvRecord); err != nil {
+		return nil, err
+	}
+	w.Flush()
+	if err := w.Error(); err != nil {
+		return nil, err
+	}
+
+	data := buf.Bytes()
+	return data[:len(data)-1], nil
+}
+
+// MarshalJSON - encodes to JSON data.
+func (r *Record) MarshalJSON() ([]byte, error) {
+	data := "{}"
+
+	var err error
+	for i := len(r.columnNames) - 1; i >= 0; i-- {
+		if i >= len(r.csvRecord) {
+			continue
+		}
+
+		if data, err = sjson.Set(data, r.columnNames[i], r.csvRecord[i]); err != nil {
+			return nil, err
+		}
+	}
+
+	return []byte(data), nil
+}
+
+// NewRecord - creates new CSV record.
+func NewRecord() *Record {
+	return &Record{}
+}