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ORC

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Input Output Alias
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Description

Apache ORC is a columnar storage format widely used in the Hadoop ecosystem.

Data types matching

The table below compares supported ORC data types and their corresponding ClickHouse data types in INSERT and SELECT queries.

ORC data type (INSERT) ClickHouse data type ORC data type (SELECT)
Boolean Bool Boolean
Tinyint Int8/UInt8/Enum8 Tinyint
Smallint Int16/UInt16/Enum16 Smallint
Int Int32/UInt32 Int
Bigint Int64/UInt64 Bigint
Float Float32 Float
Double Float64 Double
Decimal Decimal Decimal
Date Date32 Date
Timestamp DateTime64 Timestamp
String, Varchar, Binary String String
Char FixedString String
List Array List
Struct Tuple Struct
Map Map Map
Int IPv4 Int
Binary IPv6 Binary
Binary Int128/UInt128/Int256/UInt256 Binary
Binary Decimal256 Binary
Union Variant Union
  • Other types are not supported.
  • An ORC Union column is read as a Variant over the union’s branch types, and a Variant column is written as an ORC Union over its branch types. Note that Variant sorts its branch types, so the branch order may differ from the ORC file. Unions with duplicate branch types (e.g. uniontype<int,int>) are not supported.
  • Arrays can be nested and can have a value of the Nullable type as an argument. Tuple and Map types also can be nested.
  • The data types of ClickHouse table columns do not have to match the corresponding ORC data fields. When inserting data, ClickHouse interprets data types according to the table above and then casts the data to the data type set for the ClickHouse table column.

Example usage

Inserting data

Using an ORC file with the following data, named as football.orc:

    ┌───────date─┬─season─┬─home_team─────────────┬─away_team───────────┬─home_team_goals─┬─away_team_goals─┐
 1. │ 2022-04-30 │   2021 │ Sutton United         │ Bradford City       │               1 │               4 │
 2. │ 2022-04-30 │   2021 │ Swindon Town          │ Barrow              │               2 │               1 │
 3. │ 2022-04-30 │   2021 │ Tranmere Rovers       │ Oldham Athletic     │               2 │               0 │
 4. │ 2022-05-02 │   2021 │ Port Vale             │ Newport County      │               1 │               2 │
 5. │ 2022-05-02 │   2021 │ Salford City          │ Mansfield Town      │               2 │               2 │
 6. │ 2022-05-07 │   2021 │ Barrow                │ Northampton Town    │               1 │               3 │
 7. │ 2022-05-07 │   2021 │ Bradford City         │ Carlisle United     │               2 │               0 │
 8. │ 2022-05-07 │   2021 │ Bristol Rovers        │ Scunthorpe United   │               7 │               0 │
 9. │ 2022-05-07 │   2021 │ Exeter City           │ Port Vale           │               0 │               1 │
10. │ 2022-05-07 │   2021 │ Harrogate Town A.F.C. │ Sutton United       │               0 │               2 │
11. │ 2022-05-07 │   2021 │ Hartlepool United     │ Colchester United   │               0 │               2 │
12. │ 2022-05-07 │   2021 │ Leyton Orient         │ Tranmere Rovers     │               0 │               1 │
13. │ 2022-05-07 │   2021 │ Mansfield Town        │ Forest Green Rovers │               2 │               2 │
14. │ 2022-05-07 │   2021 │ Newport County        │ Rochdale            │               0 │               2 │
15. │ 2022-05-07 │   2021 │ Oldham Athletic       │ Crawley Town        │               3 │               3 │
16. │ 2022-05-07 │   2021 │ Stevenage Borough     │ Salford City        │               4 │               2 │
17. │ 2022-05-07 │   2021 │ Walsall               │ Swindon Town        │               0 │               3 │
    └────────────┴────────┴───────────────────────┴─────────────────────┴─────────────────┴─────────────────┘

Insert the data:

INSERT INTO football FROM INFILE 'football.orc' FORMAT ORC;

Reading data

Read data using the ORC format:

SELECT *
FROM football
INTO OUTFILE 'football.orc'
FORMAT ORC

Format settings

Setting Description Default
output_format_orc_string_as_string Use ORC String type instead of Binary for String columns. true
output_format_orc_compression_method Compression method used in output ORC format. Default value zstd
input_format_orc_case_insensitive_column_matching Ignore case when matching ORC columns with ClickHouse columns. false
input_format_orc_allow_missing_columns Allow missing columns while reading ORC data. true
input_format_orc_skip_columns_with_unsupported_types_in_schema_inference Allow skipping columns with unsupported types while schema inference for ORC format. false

To exchange data with Hadoop, you can use HDFS table engine.

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