/parquet-go

pure golang library for reading/writing parquet file

Primary LanguageGoApache License 2.0Apache-2.0

parquet-go

Travis Status for xitongsys/parquet-go godoc for xitongsys/parquet-go

parquet-go is a pure-go implementation of reading and writing the parquet format file.

  • Support Read/Write Nested/Flat Parquet File
  • Simple to use
  • High performance

Install

Add the parquet-go library to your $GOPATH/src and install dependencies:

go get github.com/xitongsys/parquet-go

Examples

The example/ directory contains several examples.

The local_flat.go example creates some data and writes it out to the example/output/flat.parquet file.

cd $GOPATH/src/github.com/xitongsys/parquet-go/example
go run local_flat.go

The local_flat.go code shows how it's easy to output structs from Go programs to Parquet files.

Type

There are two types in Parquet: Primitive Type and Logical Type. Logical types are stored as primitive types. The following list is the currently implemented data types:

Parquet Type Primitive Type Go Type
BOOLEAN BOOLEAN bool
INT32 INT32 int32
INT64 INT64 int64
INT96 INT96 string
FLOAT FLOAT float32
DOUBLE DOUBLE float64
BYTE_ARRAY BYTE_ARRAY string
FIXED_LEN_BYTE_ARRAY FIXED_LEN_BYTE_ARRAY string
UTF8 BYTE_ARRAY string
INT_8 INT32 int8
INT_16 INT32 int16
INT_32 INT32 int32
INT_64 INT64 int64
UINT_8 INT32 uint8
UINT_16 INT32 uint16
UINT_32 INT32 uint32
UINT_64 INT64 uint64
DATE INT32 int32
TIME_MILLIS INT32 int32
TIME_MICROS INT64 int64
TIMESTAMP_MILLIS INT64 int64
TIMESTAMP_MICROS INT64 int64
INTERVAL FIXED_LEN_BYTE_ARRAY string
DECIMAL INT32,INT64,FIXED_LEN_BYTE_ARRAY,BYTE_ARRAY int32,int64,string,string
LIST slice
MAP map

Tips

  • Although DECIMAL can be stored as INT32,INT64,FIXED_LEN_BYTE_ARRAY,BYTE_ARRAY, Currently I suggest to use FIXED_LEN_BYTE_ARRAY.

Encoding

PLAIN:

All types

PLAIN_DICTIONARY:

All types

DELTA_BINARY_PACKED:

INT32, INT64, INT_8, INT_16, INT_32, INT_64, UINT_8, UINT_16, UINT_32, UINT_64, TIME_MILLIS, TIME_MICROS, TIMESTAMP_MILLIS, TIMESTAMP_MICROS

DELTA_BYTE_ARRAY:

BYTE_ARRAY, UTF8

DELTA_LENGTH_BYTE_ARRAY:

BYTE_ARRAY, UTF8

Tips

  • Some platforms don't support all kinds of encodings. If you are not sure, just use PLAIN and PLAIN_DICTIONARY.
  • If the fields have many different values, please don't use PLAIN_DICTIONARY encoding. Because it will record all the different values in a map which will use a lot of memory.

Repetition Type

There are three repetition types in Parquet: REQUIRED, OPTIONAL, REPEATED.

Repetition Type Example Description
REQUIRED V1 int32 `parquet:"name=v1, type=INT32"` No extra description
OPTIONAL V1 *int32 `parquet:"name=v1, type=INT32"` Declare as pointer
REPEATED V1 []int32 `parquet:"name=v1, type=INT32, repetitontype=REPEATED"` Add 'repetitiontype=REPEATED' in tags

Tips

  • The difference between a List and a REPEATED variable is the 'repetitiontype' in tags. Although both of them are stored as slice in go, they are different in parquet. You can find the detail of List in parquet at here. I suggest just use a List.
  • For LIST and MAP, some existed parquet files use some nonstandard formats(see here). For standard format, parquet-go will convert them to go slice and go map. For nonstandard formats, parquet-go will convert them to corresponding structs.

Example of Type and Encoding

Bool              bool    `parquet:"name=bool, type=BOOLEAN"`
Int32             int32   `parquet:"name=int32, type=INT32"`
Int64             int64   `parquet:"name=int64, type=INT64"`
Int96             string  `parquet:"name=int96, type=INT96"`
Float             float32 `parquet:"name=float, type=FLOAT"`
Double            float64 `parquet:"name=double, type=DOUBLE"`
ByteArray         string  `parquet:"name=bytearray, type=BYTE_ARRAY"`
FixedLenByteArray string  `parquet:"name=FixedLenByteArray, type=FIXED_LEN_BYTE_ARRAY, length=10"`

Utf8            string `parquet:"name=utf8, type=UTF8, encoding=PLAIN_DICTIONARY"`
Int_8           int8  `parquet:"name=int_8, type=INT_8"`
Int_16          int16  `parquet:"name=int_16, type=INT_16"`
Int_32          int32  `parquet:"name=int_32, type=INT_32"`
Int_64          int64  `parquet:"name=int_64, type=INT_64"`
Uint_8          uint8 `parquet:"name=uint_8, type=UINT_8"`
Uint_16         uint16 `parquet:"name=uint_16, type=UINT_16"`
Uint_32         uint32 `parquet:"name=uint_32, type=UINT_32"`
Uint_64         uint64 `parquet:"name=uint_64, type=UINT_64"`
Date            int32  `parquet:"name=date, type=DATE"`
TimeMillis      int32  `parquet:"name=timemillis, type=TIME_MILLIS"`
TimeMicros      int64  `parquet:"name=timemicros, type=TIME_MICROS"`
TimestampMillis int64  `parquet:"name=timestampmillis, type=TIMESTAMP_MILLIS"`
TimestampMicros int64  `parquet:"name=timestampmicros, type=TIMESTAMP_MICROS"`
Interval        string `parquet:"name=interval, type=INTERVAL"`

Decimal1 int32  `parquet:"name=decimal1, type=DECIMAL, scale=2, precision=9, basetype=INT32"`
Decimal2 int64  `parquet:"name=decimal2, type=DECIMAL, scale=2, precision=18, basetype=INT64"`
Decimal3 string `parquet:"name=decimal3, type=DECIMAL, scale=2, precision=10, basetype=FIXED_LEN_BYTE_ARRAY, length=12"`
Decimal4 string `parquet:"name=decimal4, type=DECIMAL, scale=2, precision=20, basetype=BYTE_ARRAY"`

Map      map[string]int32 `parquet:"name=map, type=MAP, keytype=UTF8, valuetype=INT32"`
List     []string         `parquet:"name=list, type=LIST, valuetype=UTF8"`
Repeated []int32          `parquet:"name=repeated, type=INT32, repetitiontype=REPEATED"`

Compression Type

Type Support
CompressionCodec_UNCOMPRESSED YES
CompressionCodec_SNAPPY YES
CompressionCodec_GZIP YES
CompressionCodec_LZO NO
CompressionCodec_BROTLI NO
CompressionCodec_LZ4 NO
CompressionCodec_ZSTD YES

ParquetFile

Read/Write a parquet file need a ParquetFile interface implemented

type ParquetFile interface {
	io.Seeker
	io.Reader
	io.Writer
	io.Closer
	Open(name string) (ParquetFile, error)
	Create(name string) (ParquetFile, error)
}

Using this interface, parquet-go can read/write parquet file on different platforms. All the file sources are at parquet-go-source. Now it supports(local/hdfs/s3/gcs/memory).

Writer

Three Writers are supported: ParquetWriter, JSONWriter, CSVWriter.

Reader

Two Readers are supported: ParquetReader, ColumnReader

  • ParquetReader is used to read predefined Golang structs Example of ParquetReader

  • ColumnReader is used to read raw column data. The read function return 3 slices([value], [RepetitionLevel], [DefinitionLevel]) of the records. Example of ColumnReader

Tips

  • If the parquet file is very big (even the size of parquet file is small, the uncompressed size may be very large), please don't read all rows at one time, which may induce the OOM. You can read a small portion of the data at a time like a stream-oriented file.

Schema

There are three methods to define the schema: go struct tags, Json, CSV metadata. Only items in schema will be written and others will be ignored.

Tag

type Student struct {
	Name   string  `parquet:"name=name, type=UTF8, encoding=PLAIN_DICTIONARY"`
	Age    int32   `parquet:"name=age, type=INT32"`
	Id     int64   `parquet:"name=id, type=INT64"`
	Weight float32 `parquet:"name=weight, type=FLOAT"`
	Sex    bool    `parquet:"name=sex, type=BOOLEAN"`
	Day    int32   `parquet:"name=day, type=DATE"`
}

Example of tags

JSON

JSON schema can be used to define some complicated schema, which can't be defined by tag.

type Student struct {
	Name    string
	Age     int32
	Id      int64
	Weight  float32
	Sex     bool
	Classes []string
	Scores  map[string][]float32

	Friends []struct {
		Name string
		Id   int64
	}
	Teachers []struct {
		Name string
		Id   int64
	}
}

var jsonSchema string = `
{
  "Tag": "name=parquet-go-root, repetitiontype=REQUIRED",
  "Fields": [
    {"Tag": "name=name, inname=Name, type=UTF8, repetitiontype=REQUIRED"},
    {"Tag": "name=age, inname=Age, type=INT32, repetitiontype=REQUIRED"},
    {"Tag": "name=id, inname=Id, type=INT64, repetitiontype=REQUIRED"},
    {"Tag": "name=weight, inname=Weight, type=FLOAT, repetitiontype=REQUIRED"},
    {"Tag": "name=sex, inname=Sex, type=BOOLEAN, repetitiontype=REQUIRED"},

    {"Tag": "name=classes, inname=Classes, type=LIST, repetitiontype=REQUIRED",
     "Fields": [{"Tag": "name=element, type=UTF8, repetitiontype=REQUIRED"}]
    },
    {
      "Tag": "name=scores, inname=Scores, type=MAP, repetitiontype=REQUIRED",
      "Fields": [
        {"Tag": "name=key, type=UTF8, repetitiontype=REQUIRED"},
        {"Tag": "name=value, type=LIST, repetitiontype=REQUIRED",
         "Fields": [{"Tag": "name=element, type=FLOAT, repetitiontype=REQUIRED"}]
        }
      ]
    },
    {
      "Tag": "name=friends, inname=Friends, type=LIST, repetitiontype=REQUIRED",
      "Fields": [
       {"Tag": "name=element, repetitiontype=REQUIRED",
        "Fields": [
         {"Tag": "name=name, inname=Name, type=UTF8, repetitiontype=REQUIRED"},
         {"Tag": "name=id, inname=Id, type=INT64, repetitiontype=REQUIRED"}
        ]}
      ]
    },
    {
      "Tag": "name=teachers, inname=Teachers, repetitiontype=REPEATED",
      "Fields": [
        {"Tag": "name=name, inname=Name, type=UTF8, repetitiontype=REQUIRED"},
        {"Tag": "name=id, inname=Id, type=INT64, repetitiontype=REQUIRED"}
      ]
    }
  ]
}
`

Example of JSON schema

CSV metadata

md := []string{
	"name=Name, type=UTF8, encoding=PLAIN_DICTIONARY",
	"name=Age, type=INT32",
	"name=Id, type=INT64",
	"name=Weight, type=FLOAT",
	"name=Sex, type=BOOLEAN",
}

Example of CSV metadata

Parallel

Read/Write initial functions have a parallel parameters np which is the number of goroutines in reading/writing.

func NewParquetReader(pFile ParquetFile.ParquetFile, obj interface{}, np int64) (*ParquetReader, error)
func NewParquetWriter(pFile ParquetFile.ParquetFile, obj interface{}, np int64) (*ParquetWriter, error)
func NewJSONWriter(jsonSchema string, pfile ParquetFile.ParquetFile, np int64) (*JSONWriter, error)
func NewCSVWriter(md []string, pfile ParquetFile.ParquetFile, np int64) (*CSVWriter, error)

Examples

Example file Descriptions
local_flat.go write/read parquet file with no nested struct
local_nested.go write/read parquet file with nested struct
read_partial.go read partial fields from a parquet file
read_partial2.go read sub-struct from a parquet file
read_without_schema_predefined.go read a parquet file and no struct/schema predefined needed
read_partial_without_schema_predefined.go read sub-struct from a parquet file and no struct/schema predefined needed
json_schema.go define schema using json string
json_write.go convert json to parquet
convert_to_json.go convert parquet to json
csv_write.go special csv writer
column_read.go read raw column data and return value,repetitionLevel,definitionLevel
type.go example for schema of types

Tool

  • parquet-tools: Command line tools that aid in the inspection of Parquet files

Please start to use it and give feedback or start it! Help is needed and anything is welcome.