minio/internal/s3select/csv/record.go

// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package csv

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"strconv"
	"strings"

	"github.com/bcicen/jstream"
	csv "github.com/minio/csvparser"
	"github.com/minio/minio/internal/s3select/sql"
)

// Record - is a CSV record.
type Record struct {
	columnNames  []string
	csvRecord    []string
	nameIndexMap map[string]int64
}

// Get - gets the value for a column name. CSV fields do not have any
// defined type (other than the default string). So this function
// always returns fields using sql.FromBytes so that the type
// specified/implied by the query can be used, or can be automatically
// converted based on the query.
func (r *Record) Get(name string) (*sql.Value, error) {
	index, found := r.nameIndexMap[name]
	if !found {
		// Check if index.
		if strings.HasPrefix(name, "_") {
			idx, err := strconv.Atoi(strings.TrimPrefix(name, "_"))
			if err != nil {
				return nil, fmt.Errorf("column %v not found", name)
			}
			// The position count starts at 1.
			idx--
			if idx >= len(r.csvRecord) || idx < 0 {
				// If field index > number of columns, return null
				return sql.FromNull(), nil
			}
			return sql.FromBytes([]byte(r.csvRecord[idx])), nil
		}
		return nil, fmt.Errorf("column %v not found", name)
	}

	if index >= int64(len(r.csvRecord)) {
		// No value found for column 'name', hence return null
		// value
		return sql.FromNull(), nil
	}

	return sql.FromBytes([]byte(r.csvRecord[index])), nil
}

// Set - sets the value for a column name.
func (r *Record) Set(name string, value *sql.Value) (sql.Record, error) {
	r.columnNames = append(r.columnNames, name)
	r.csvRecord = append(r.csvRecord, value.CSVString())
	return r, nil
}

// Reset data in record.
func (r *Record) Reset() {
	if len(r.columnNames) > 0 {
		r.columnNames = r.columnNames[:0]
	}
	if len(r.csvRecord) > 0 {
		r.csvRecord = r.csvRecord[:0]
	}
	for k := range r.nameIndexMap {
		delete(r.nameIndexMap, k)
	}
}

// Clone the record.
func (r *Record) Clone(dst sql.Record) sql.Record {
	other, ok := dst.(*Record)
	if !ok {
		other = &Record{}
	}
	if len(other.columnNames) > 0 {
		other.columnNames = other.columnNames[:0]
	}
	if len(other.csvRecord) > 0 {
		other.csvRecord = other.csvRecord[:0]
	}
	other.columnNames = append(other.columnNames, r.columnNames...)
	other.csvRecord = append(other.csvRecord, r.csvRecord...)
	return other
}

// WriteCSV - encodes to CSV data.
func (r *Record) WriteCSV(writer io.Writer, opts sql.WriteCSVOpts) error {
	w := csv.NewWriter(writer)
	w.Comma = opts.FieldDelimiter
	w.AlwaysQuote = opts.AlwaysQuote
	w.Quote = opts.Quote
	w.QuoteEscape = opts.QuoteEscape
	if err := w.Write(r.csvRecord); err != nil {
		return err
	}
	w.Flush()
	return w.Error()
}

// WriteJSON - encodes to JSON data.
func (r *Record) WriteJSON(writer io.Writer) error {
	var kvs jstream.KVS = make([]jstream.KV, len(r.columnNames))
	for i := 0; i < len(r.columnNames); i++ {
		kvs[i] = jstream.KV{Key: r.columnNames[i], Value: r.csvRecord[i]}
	}
	return json.NewEncoder(writer).Encode(kvs)
}

// Raw - returns the underlying data with format info.
func (r *Record) Raw() (sql.SelectObjectFormat, interface{}) {
	return sql.SelectFmtCSV, r
}

// Replace - is not supported for CSV
func (r *Record) Replace(_ interface{}) error {
	return errors.New("Replace is not supported for CSV")
}

// NewRecord - creates new CSV record.
func NewRecord() *Record {
	return &Record{}
}