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reader.go
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reader.go
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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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 (
"encoding/base64"
"encoding/csv"
"errors"
"fmt"
"io"
"strconv"
"strings"
"sync"
"sync/atomic"
"time"
"unicode/utf8"
"github.com/apache/arrow/go/v17/arrow"
"github.com/apache/arrow/go/v17/arrow/array"
"github.com/apache/arrow/go/v17/arrow/decimal128"
"github.com/apache/arrow/go/v17/arrow/decimal256"
"github.com/apache/arrow/go/v17/arrow/float16"
"github.com/apache/arrow/go/v17/arrow/internal/debug"
"github.com/apache/arrow/go/v17/arrow/memory"
)
// Reader wraps encoding/csv.Reader and creates array.Records from a schema.
type Reader struct {
r *csv.Reader
schema *arrow.Schema
refs int64
bld *array.RecordBuilder
cur arrow.Record
err error
chunk int
done bool
next func() bool
mem memory.Allocator
header bool
once sync.Once
fieldConverter []func(val string)
columnFilter []string
columnTypes map[string]arrow.DataType
conversions []conversionColumn
stringsCanBeNull bool
nulls []string
}
// NewInferringReader creates a CSV reader that attempts to infer the types
// and column names from the data in the first row of the CSV file.
//
// This can be further customized using the WithColumnTypes and
// WithIncludeColumns options.
// For BinaryType the reader will use base64 decoding with padding as per base64.StdDecoding.
func NewInferringReader(r io.Reader, opts ...Option) *Reader {
rr := &Reader{
r: csv.NewReader(r),
refs: 1,
chunk: 1,
stringsCanBeNull: false,
}
rr.r.ReuseRecord = true
for _, opt := range opts {
opt(rr)
}
if rr.mem == nil {
rr.mem = memory.DefaultAllocator
}
switch {
case rr.chunk < 0:
rr.next = rr.nextall
case rr.chunk > 1:
rr.next = rr.nextn
default:
rr.next = rr.next1
}
return rr
}
// NewReader returns a reader that reads from the CSV file and creates
// arrow.Records from the given schema.
//
// NewReader panics if the given schema contains fields that have types that are not
// primitive types.
func NewReader(r io.Reader, schema *arrow.Schema, opts ...Option) *Reader {
validate(schema)
rr := &Reader{
r: csv.NewReader(r),
schema: schema,
refs: 1,
chunk: 1,
stringsCanBeNull: false,
}
rr.r.ReuseRecord = true
for _, opt := range opts {
opt(rr)
}
if rr.mem == nil {
rr.mem = memory.DefaultAllocator
}
rr.bld = array.NewRecordBuilder(rr.mem, rr.schema)
switch {
case rr.chunk < 0:
rr.next = rr.nextall
case rr.chunk > 1:
rr.next = rr.nextn
default:
rr.next = rr.next1
}
return rr
}
func (r *Reader) readHeader() error {
// if we have an explicit schema and we want to skip the header
// then just return and do everything normally
if r.schema != nil && !r.header {
return nil
}
// either we need this first line for the header line
// or we are going to need this line to infer types
records, err := r.r.Read()
if err != nil {
return fmt.Errorf("arrow/csv: could not read header from file: %w", err)
}
// if we have an explicit schema, then r.header must be true otherwise
// we would have skipped this via the first line of this func
if r.schema != nil {
if len(records) != len(r.schema.Fields()) {
return ErrMismatchFields
}
fields := make([]arrow.Field, len(records))
for idx, name := range records {
fields[idx] = r.schema.Field(idx)
fields[idx].Name = name
}
meta := r.schema.Metadata()
r.schema = arrow.NewSchema(fields, &meta)
r.bld = array.NewRecordBuilder(r.mem, r.schema)
return nil
}
// we're going to need to infer some column types
r.conversions = make([]conversionColumn, 0, len(records))
if len(r.columnFilter) == 0 {
for i, rec := range records {
// if we are skipping the header, autogenerate field names
// using "f<n>" e.g. f0, f1, ....
if !r.header {
rec = fmt.Sprintf("f%d", i)
}
var dt arrow.DataType
if len(r.columnTypes) > 0 {
dt = r.columnTypes[rec]
}
r.conversions = append(r.conversions, conversionColumn{name: rec, index: i, typ: dt})
}
} else {
// include columns from columnFilter (in that order)
// compute the indices of columns in the csv file
colIndices := make(map[string]int)
for i, n := range records {
// if we are skipping the header, autogenerate field names
// using "f<n>" e.g. f0, f1, ....
if !r.header {
n = fmt.Sprintf("f%d", i)
}
colIndices[n] = i
}
for _, n := range r.columnFilter {
idx, ok := colIndices[n]
if !ok {
return fmt.Errorf("%w: column '%s' in included columns, but doesn't exist in CSV file",
ErrMismatchFields, n)
}
var dt arrow.DataType
if len(r.columnTypes) > 0 {
dt = r.columnTypes[n]
}
r.conversions = append(r.conversions, conversionColumn{name: n, index: idx, typ: dt})
}
r.columnFilter = nil
}
r.columnTypes = nil
return nil
}
// Err returns the last error encountered during the iteration over the
// underlying CSV file.
func (r *Reader) Err() error { return r.err }
func (r *Reader) Schema() *arrow.Schema { return r.schema }
// Record returns the current record that has been extracted from the
// underlying CSV file.
// It is valid until the next call to Next.
func (r *Reader) Record() arrow.Record { return r.cur }
// Next returns whether a Record could be extracted from the underlying CSV file.
//
// Next panics if the number of records extracted from a CSV row does not match
// the number of fields of the associated schema. If a parse failure occurs, Next
// will return true and the Record will contain nulls where failures occurred.
// Subsequent calls to Next will return false - The user should check Err() after
// each call to Next to check if an error took place.
func (r *Reader) Next() bool {
r.once.Do(func() {
r.err = r.readHeader()
if r.err == nil && r.schema != nil {
// Create a table of functions that will parse columns. This optimization
// allows us to specialize the implementation of each column's decoding
// and hoist type-based branches outside the inner loop.
r.fieldConverter = make([]func(string), len(r.schema.Fields()))
for idx := range r.schema.Fields() {
r.fieldConverter[idx] = r.initFieldConverter(r.bld.Field(idx))
}
}
})
if r.cur != nil {
r.cur.Release()
r.cur = nil
}
if r.err != nil || r.done {
return false
}
return r.next()
}
// next1 reads one row from the CSV file and creates a single Record
// from that row.
func (r *Reader) next1() bool {
var recs []string
recs, r.err = r.r.Read()
if r.err != nil {
r.done = true
if errors.Is(r.err, io.EOF) {
r.err = nil
}
return false
}
r.validate(recs)
r.read(recs)
r.cur = r.bld.NewRecord()
return true
}
// nextall reads the whole CSV file into memory and creates one single
// Record from all the CSV rows.
func (r *Reader) nextall() bool {
defer func() {
r.done = true
}()
var (
recs [][]string
)
recs, r.err = r.r.ReadAll()
if r.err != nil {
return false
}
for _, rec := range recs {
r.validate(rec)
r.read(rec)
}
r.cur = r.bld.NewRecord()
return true
}
// nextn reads n rows from the CSV file, where n is the chunk size, and creates
// a Record from these rows.
func (r *Reader) nextn() bool {
var (
recs []string
n = 0
err error
)
for i := 0; i < r.chunk && !r.done; i++ {
recs, err = r.r.Read()
if err != nil {
if !errors.Is(err, io.EOF) {
r.err = err
}
r.done = true
break
}
r.validate(recs)
r.read(recs)
n++
}
if r.err != nil {
r.done = true
}
r.cur = r.bld.NewRecord()
return n > 0
}
func (r *Reader) validate(recs []string) {
if r.err != nil {
return
}
if r.bld == nil {
// initialize the record builder in the case where we're inferring a schema
r.fieldConverter = make([]func(val string), len(recs))
fieldList := make([]arrow.Field, len(r.conversions))
for idx, cc := range r.conversions {
fieldList[idx].Name = cc.name
fieldList[idx].Nullable = true
fieldList[idx].Type = cc.inferType(recs[cc.index])
}
r.schema = arrow.NewSchema(fieldList, nil)
r.bld = array.NewRecordBuilder(r.mem, r.schema)
for idx, cc := range r.conversions {
r.fieldConverter[cc.index] = r.initFieldConverter(r.bld.Field(idx))
}
for idx, fc := range r.fieldConverter {
if fc == nil {
r.fieldConverter[idx] = func(string) {}
}
}
}
if len(recs) != len(r.fieldConverter) {
r.err = ErrMismatchFields
return
}
}
func (r *Reader) isNull(val string) bool {
for _, v := range r.nulls {
if v == val {
return true
}
}
return false
}
func (r *Reader) read(recs []string) {
for i, str := range recs {
r.fieldConverter[i](str)
}
}
func (r *Reader) initFieldConverter(bldr array.Builder) func(string) {
switch dt := bldr.Type().(type) {
case *arrow.BooleanType:
return func(str string) {
r.parseBool(bldr, str)
}
case *arrow.Int8Type:
return func(str string) {
r.parseInt8(bldr, str)
}
case *arrow.Int16Type:
return func(str string) {
r.parseInt16(bldr, str)
}
case *arrow.Int32Type:
return func(str string) {
r.parseInt32(bldr, str)
}
case *arrow.Int64Type:
return func(str string) {
r.parseInt64(bldr, str)
}
case *arrow.Uint8Type:
return func(str string) {
r.parseUint8(bldr, str)
}
case *arrow.Uint16Type:
return func(str string) {
r.parseUint16(bldr, str)
}
case *arrow.Uint32Type:
return func(str string) {
r.parseUint32(bldr, str)
}
case *arrow.Uint64Type:
return func(str string) {
r.parseUint64(bldr, str)
}
case *arrow.Float16Type:
return func(str string) {
r.parseFloat16(bldr, str)
}
case *arrow.Float32Type:
return func(str string) {
r.parseFloat32(bldr, str)
}
case *arrow.Float64Type:
return func(str string) {
r.parseFloat64(bldr, str)
}
case *arrow.StringType:
// specialize the implementation when we know we cannot have nulls
if r.stringsCanBeNull {
return func(str string) {
if r.isNull(str) {
bldr.AppendNull()
} else {
bldr.(*array.StringBuilder).Append(str)
}
}
} else {
return func(str string) {
bldr.(*array.StringBuilder).Append(str)
}
}
case *arrow.LargeStringType:
// specialize the implementation when we know we cannot have nulls
if r.stringsCanBeNull {
return func(str string) {
if r.isNull(str) {
bldr.AppendNull()
} else {
bldr.(*array.LargeStringBuilder).Append(str)
}
}
} else {
return func(str string) {
bldr.(*array.LargeStringBuilder).Append(str)
}
}
case *arrow.TimestampType:
return func(str string) {
r.parseTimestamp(bldr, str, dt.Unit)
}
case *arrow.Date32Type:
return func(str string) {
r.parseDate32(bldr, str)
}
case *arrow.Date64Type:
return func(str string) {
r.parseDate64(bldr, str)
}
case *arrow.Time32Type:
return func(str string) {
r.parseTime32(bldr, str, dt.Unit)
}
case *arrow.Decimal128Type:
return func(str string) {
r.parseDecimal128(bldr, str, dt.Precision, dt.Scale)
}
case *arrow.Decimal256Type:
return func(str string) {
r.parseDecimal256(bldr, str, dt.Precision, dt.Scale)
}
case *arrow.FixedSizeListType:
return func(s string) {
r.parseFixedSizeList(bldr.(*array.FixedSizeListBuilder), s, int(dt.Len()))
}
case arrow.ListLikeType:
return func(s string) {
r.parseListLike(bldr.(array.ListLikeBuilder), s)
}
case *arrow.BinaryType:
return func(s string) {
r.parseBinaryType(bldr, s)
}
case *arrow.LargeBinaryType:
return func(s string) {
r.parseLargeBinaryType(bldr, s)
}
case *arrow.FixedSizeBinaryType:
return func(s string) {
r.parseFixedSizeBinaryType(bldr, s, dt.Bytes())
}
case arrow.ExtensionType:
return func(s string) {
r.parseExtension(bldr, s)
}
default:
panic(fmt.Errorf("arrow/csv: unhandled field type %T", bldr.Type()))
}
}
func (r *Reader) parseBool(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseBool(str)
if err != nil {
r.err = fmt.Errorf("%w: unrecognized boolean: %s", err, str)
field.AppendNull()
return
}
field.(*array.BooleanBuilder).Append(v)
}
func (r *Reader) parseInt8(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseInt(str, 10, 8)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Int8Builder).Append(int8(v))
}
func (r *Reader) parseInt16(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseInt(str, 10, 16)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Int16Builder).Append(int16(v))
}
func (r *Reader) parseInt32(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseInt(str, 10, 32)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Int32Builder).Append(int32(v))
}
func (r *Reader) parseInt64(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseInt(str, 10, 64)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Int64Builder).Append(v)
}
func (r *Reader) parseUint8(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseUint(str, 10, 8)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Uint8Builder).Append(uint8(v))
}
func (r *Reader) parseUint16(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseUint(str, 10, 16)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Uint16Builder).Append(uint16(v))
}
func (r *Reader) parseUint32(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseUint(str, 10, 32)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Uint32Builder).Append(uint32(v))
}
func (r *Reader) parseUint64(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseUint(str, 10, 64)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Uint64Builder).Append(v)
}
func (r *Reader) parseFloat16(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseFloat(str, 32)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Float16Builder).Append(float16.New(float32(v)))
}
func (r *Reader) parseFloat32(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseFloat(str, 32)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Float32Builder).Append(float32(v))
}
func (r *Reader) parseFloat64(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := strconv.ParseFloat(str, 64)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Float64Builder).Append(v)
}
// parses timestamps using millisecond precision
func (r *Reader) parseTimestamp(field array.Builder, str string, unit arrow.TimeUnit) {
if r.isNull(str) {
field.AppendNull()
return
}
v, err := arrow.TimestampFromString(str, unit)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.TimestampBuilder).Append(v)
}
func (r *Reader) parseDate32(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
tm, err := time.Parse("2006-01-02", str)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Date32Builder).Append(arrow.Date32FromTime(tm))
}
func (r *Reader) parseDate64(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
tm, err := time.Parse("2006-01-02", str)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Date64Builder).Append(arrow.Date64FromTime(tm))
}
func (r *Reader) parseTime32(field array.Builder, str string, unit arrow.TimeUnit) {
if r.isNull(str) {
field.AppendNull()
return
}
val, err := arrow.Time32FromString(str, unit)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Time32Builder).Append(val)
}
func (r *Reader) parseDecimal128(field array.Builder, str string, prec, scale int32) {
if r.isNull(str) {
field.AppendNull()
return
}
val, err := decimal128.FromString(str, prec, scale)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Decimal128Builder).Append(val)
}
func (r *Reader) parseDecimal256(field array.Builder, str string, prec, scale int32) {
if r.isNull(str) {
field.AppendNull()
return
}
val, err := decimal256.FromString(str, prec, scale)
if err != nil && r.err == nil {
r.err = err
field.AppendNull()
return
}
field.(*array.Decimal256Builder).Append(val)
}
func (r *Reader) parseListLike(field array.ListLikeBuilder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
if !(strings.HasPrefix(str, "{") && strings.HasSuffix(str, "}")) {
r.err = errors.New("invalid list format. should start with '{' and end with '}'")
return
}
str = strings.Trim(str, "{}")
field.Append(true)
if len(str) == 0 {
// we don't want to create the csv reader if we already know the
// string is empty
return
}
valueBldr := field.ValueBuilder()
reader := csv.NewReader(strings.NewReader(str))
items, err := reader.Read()
if err != nil {
r.err = err
return
}
for _, str := range items {
r.initFieldConverter(valueBldr)(str)
}
}
func (r *Reader) parseFixedSizeList(field *array.FixedSizeListBuilder, str string, n int) {
if r.isNull(str) {
field.AppendNull()
return
}
if !(strings.HasPrefix(str, "{") && strings.HasSuffix(str, "}")) {
r.err = errors.New("invalid list format. should start with '{' and end with '}'")
return
}
str = strings.Trim(str, "{}")
field.Append(true)
if len(str) == 0 {
// we don't want to create the csv reader if we already know the
// string is empty
return
}
valueBldr := field.ValueBuilder()
reader := csv.NewReader(strings.NewReader(str))
items, err := reader.Read()
if err != nil {
r.err = err
return
}
if len(items) == n {
for _, str := range items {
r.initFieldConverter(valueBldr)(str)
}
} else {
r.err = fmt.Errorf("%w: fixed size list items should match the fixed size list length, expected %d, got %d", arrow.ErrInvalid, n, len(items))
}
}
func (r *Reader) parseBinaryType(field array.Builder, str string) {
// specialize the implementation when we know we cannot have nulls
if r.isNull(str) {
field.AppendNull()
return
}
decodedVal, err := base64.StdEncoding.DecodeString(str)
if err != nil {
r.err = fmt.Errorf("cannot decode base64 string %s", str)
field.AppendNull()
return
}
field.(*array.BinaryBuilder).Append(decodedVal)
}
func (r *Reader) parseLargeBinaryType(field array.Builder, str string) {
// specialize the implementation when we know we cannot have nulls
if r.isNull(str) {
field.AppendNull()
return
}
decodedVal, err := base64.StdEncoding.DecodeString(str)
if err != nil {
r.err = fmt.Errorf("cannot decode base64 string %s", str)
field.AppendNull()
return
}
field.(*array.BinaryBuilder).Append(decodedVal)
}
func (r *Reader) parseFixedSizeBinaryType(field array.Builder, str string, byteWidth int) {
// specialize the implementation when we know we cannot have nulls
if r.isNull(str) {
field.AppendNull()
return
}
decodedVal, err := base64.StdEncoding.DecodeString(str)
if err != nil {
r.err = fmt.Errorf("cannot decode base64 string %s", str)
field.AppendNull()
return
}
if len(decodedVal) == byteWidth {
field.(*array.FixedSizeBinaryBuilder).Append(decodedVal)
} else {
r.err = fmt.Errorf("%w: the length of fixed size binary value should match the fixed size binary byte width, expected %d, got %d", arrow.ErrInvalid, byteWidth, len(decodedVal))
}
}
func (r *Reader) parseExtension(field array.Builder, str string) {
if r.isNull(str) {
field.AppendNull()
return
}
if err := field.AppendValueFromString(str); err != nil {
r.err = err
return
}
}
// Retain increases the reference count by 1.
// Retain may be called simultaneously from multiple goroutines.
func (r *Reader) Retain() {
atomic.AddInt64(&r.refs, 1)
}
// Release decreases the reference count by 1.
// When the reference count goes to zero, the memory is freed.
// Release may be called simultaneously from multiple goroutines.
func (r *Reader) Release() {
debug.Assert(atomic.LoadInt64(&r.refs) > 0, "too many releases")
if atomic.AddInt64(&r.refs, -1) == 0 {
if r.cur != nil {
r.cur.Release()
}
}
}
type conversionColumn struct {
name string
index int
typ arrow.DataType
}
func (c conversionColumn) inferType(v string) arrow.DataType {
if c.typ != nil {
return c.typ
}
var err error
c.typ = arrow.PrimitiveTypes.Int64
for {
// attempt to parse
if err = tryParse(v, c.typ); err == nil {
return c.typ
}
switch dt := c.typ.(type) {
case *arrow.Int64Type:
c.typ = arrow.FixedWidthTypes.Boolean
case *arrow.BooleanType:
c.typ = arrow.FixedWidthTypes.Date32
case *arrow.Date32Type:
c.typ = arrow.FixedWidthTypes.Time32s
case *arrow.Time32Type:
c.typ = &arrow.TimestampType{Unit: arrow.Second}
case *arrow.TimestampType:
if dt.TimeZone == "" {
if dt.Unit == arrow.Second {
c.typ = &arrow.TimestampType{Unit: arrow.Nanosecond}
} else {
c.typ = &arrow.TimestampType{Unit: arrow.Second, TimeZone: "UTC"}
}
} else {
if dt.Unit == arrow.Second {
c.typ = &arrow.TimestampType{Unit: arrow.Nanosecond, TimeZone: "UTC"}
} else {
c.typ = arrow.PrimitiveTypes.Float64
}
}
case *arrow.Float64Type:
c.typ = arrow.BinaryTypes.String
case *arrow.StringType:
// binary is the fallback type
return arrow.BinaryTypes.Binary
}
}
}
func tryParse(val string, dt arrow.DataType) error {
switch dt := dt.(type) {
case *arrow.Int64Type:
_, err := strconv.ParseInt(val, 10, 64)
return err