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sidebar_label	sidebar_position	slug	toc_max_heading_level
Format Settings	52	/en/operations/settings/formats	2

Format settings

format_display_secrets_in_show_and_select

Enables or disables showing secrets in SHOW and SELECT queries for tables, databases, table functions, and dictionaries.

User wishing to see secrets must also have display_secrets_in_show_and_select server setting turned on and a displaySecretsInShowAndSelect privilege.

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 0.

input_format_skip_unknown_fields

Enables or disables skipping insertion of extra data.

When writing data, ClickHouse throws an exception if input data contain columns that do not exist in the target table. If skipping is enabled, ClickHouse does not insert extra data and does not throw an exception.

Supported formats:

JSONEachRow (and other JSON formats)
BSONEachRow (and other JSON formats)
TSKV
All formats with suffixes WithNames/WithNamesAndTypes
MySQLDump
Native

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 1.

input_format_with_names_use_header

Enables or disables checking the column order when inserting data.

To improve insert performance, we recommend disabling this check if you are sure that the column order of the input data is the same as in the target table.

Supported formats:

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 1.

input_format_with_types_use_header

Controls whether format parser should check if data types from the input data match data types from the target table.

Supported formats:

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 1.

input_format_defaults_for_omitted_fields

When performing INSERT queries, replace omitted input column values with default values of the respective columns. This option applies to JSONEachRow (and other JSON formats), CSV, TabSeparated, TSKV, Parquet, Arrow, Avro, ORC, Native formats and formats with WithNames/WithNamesAndTypes suffixes.

:::note When this option is enabled, extended table metadata are sent from server to client. It consumes additional computing resources on the server and can reduce performance. :::

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 1.

input_format_null_as_default

Enables or disables the initialization of NULL fields with default values, if data type of these fields is not nullable. If column type is not nullable and this setting is disabled, then inserting NULL causes an exception. If column type is nullable, then NULL values are inserted as is, regardless of this setting.

This setting is applicable for most input formats.

For complex default expressions input_format_defaults_for_omitted_fields must be enabled too.

Possible values:

0 — Inserting NULL into a not nullable column causes an exception.
1 — NULL fields are initialized with default column values.

Default value: 1.

input_format_allow_seeks

Allow seeks while reading in ORC/Parquet/Arrow input formats.

Enabled by default.

input_format_max_rows_to_read_for_schema_inference

The maximum rows of data to read for automatic schema inference.

Default value: 25'000.

input_format_max_bytes_to_read_for_schema_inference

The maximum amount of data in bytes to read for automatic schema inference.

Default value: 33554432 (32 Mb).

column_names_for_schema_inference

The list of column names to use in schema inference for formats without column names. The format: 'column1,column2,column3,...'

schema_inference_hints

The list of column names and types to use as hints in schema inference for formats without schema.

Example:

Query:

desc format(JSONEachRow, '{"x" : 1, "y" : "String", "z" : "0.0.0.0" }') settings schema_inference_hints='x UInt8, z IPv4';

Result:

x	UInt8
y	Nullable(String)
z	IPv4

:::note If the schema_inference_hints is not formated properly, or if there is a typo or a wrong datatype, etc... the whole schema_inference_hints will be ignored. :::

schema_inference_make_columns_nullable

Controls making inferred types Nullable in schema inference for formats without information about nullability. If the setting is enabled, the inferred type will be Nullable only if column contains NULL in a sample that is parsed during schema inference.

Default value: true.

input_format_try_infer_integers

If enabled, ClickHouse will try to infer integers instead of floats in schema inference for text formats. If all numbers in the column from input data are integers, the result type will be Int64, if at least one number is float, the result type will be Float64.

Enabled by default.

input_format_try_infer_dates

If enabled, ClickHouse will try to infer type Date from string fields in schema inference for text formats. If all fields from a column in input data were successfully parsed as dates, the result type will be Date, if at least one field was not parsed as date, the result type will be String.

Enabled by default.

input_format_try_infer_datetimes

If enabled, ClickHouse will try to infer type DateTime64 from string fields in schema inference for text formats. If all fields from a column in input data were successfully parsed as datetimes, the result type will be DateTime64, if at least one field was not parsed as datetime, the result type will be String.

Enabled by default.

date_time_input_format

Allows choosing a parser of the text representation of date and time.

The setting does not apply to date and time functions.

Possible values:

'best_effort' — Enables extended parsing.

ClickHouse can parse the basic YYYY-MM-DD HH:MM:SS format and all ISO 8601 date and time formats. For example, '2018-06-08T01:02:03.000Z'.
'basic' — Use basic parser.

ClickHouse can parse only the basic YYYY-MM-DD HH:MM:SS or YYYY-MM-DD format. For example, 2019-08-20 10:18:56 or 2019-08-20.

Default value: 'basic'.

Cloud default value: 'best_effort'.

See also:

date_time_output_format

Allows choosing different output formats of the text representation of date and time.

Possible values:

simple - Simple output format.

ClickHouse output date and time YYYY-MM-DD hh:mm:ss format. For example, 2019-08-20 10:18:56. The calculation is performed according to the data type's time zone (if present) or server time zone.
iso - ISO output format.

ClickHouse output date and time in ISO 8601 YYYY-MM-DDThh:mm:ssZ format. For example, 2019-08-20T10:18:56Z. Note that output is in UTC (Z means UTC).
unix_timestamp - Unix timestamp output format.

ClickHouse output date and time in Unix timestamp format. For example 1566285536.

Default value: simple.

See also:

interval_output_format

Allows choosing different output formats of the text representation of interval types.

Possible values:

kusto - KQL-style output format.

ClickHouse outputs intervals in KQL format. For example, toIntervalDay(2) would be formatted as 2.00:00:00. Please note that for interval types of varying length (ie. IntervalMonth and IntervalYear) the average number of seconds per interval is taken into account.
numeric - Numeric output format.

ClickHouse outputs intervals as their underlying numeric representation. For example, toIntervalDay(2) would be formatted as 2.

Default value: numeric.

See also:

Interval

input_format_ipv4_default_on_conversion_error

Deserialization of IPv4 will use default values instead of throwing exception on conversion error.

Disabled by default.

input_format_ipv6_default_on_conversion_error

Deserialization of IPV6 will use default values instead of throwing exception on conversion error.

Disabled by default.

bool_true_representation

Text to represent true bool value in TSV/CSV/Vertical/Pretty formats.

Default value: true

bool_false_representation

Text to represent false bool value in TSV/CSV/Vertical/Pretty formats.

Default value: false

output_format_decimal_trailing_zeros

Output trailing zeros when printing Decimal values. E.g. 1.230000 instead of 1.23.

Disabled by default.

input_format_allow_errors_num

Sets the maximum number of acceptable errors when reading from text formats (CSV, TSV, etc.).

The default value is 0.

Always pair it with input_format_allow_errors_ratio.

If an error occurred while reading rows but the error counter is still less than input_format_allow_errors_num, ClickHouse ignores the row and moves on to the next one.

If both input_format_allow_errors_num and input_format_allow_errors_ratio are exceeded, ClickHouse throws an exception.

input_format_allow_errors_ratio

Sets the maximum percentage of errors allowed when reading from text formats (CSV, TSV, etc.). The percentage of errors is set as a floating-point number between 0 and 1.

The default value is 0.

Always pair it with input_format_allow_errors_num.

If an error occurred while reading rows but the error counter is still less than input_format_allow_errors_ratio, ClickHouse ignores the row and moves on to the next one.

If both input_format_allow_errors_num and input_format_allow_errors_ratio are exceeded, ClickHouse throws an exception.

format_schema

This parameter is useful when you are using formats that require a schema definition, such as Cap’n Proto or Protobuf. The value depends on the format.

output_format_schema

The path to the file where the automatically generated schema will be saved in Cap’n Proto or Protobuf formats.

output_format_enable_streaming

Enable streaming in output formats that support it.

Disabled by default.

output_format_write_statistics

Write statistics about read rows, bytes, time elapsed in suitable output formats.

Enabled by default

insert_distributed_one_random_shard

Enables or disables random shard insertion into a Distributed table when there is no distributed key.

By default, when inserting data into a Distributed table with more than one shard, the ClickHouse server will reject any insertion request if there is no distributed key. When insert_distributed_one_random_shard = 1, insertions are allowed and data is forwarded randomly among all shards.

Possible values:

0 — Insertion is rejected if there are multiple shards and no distributed key is given.
1 — Insertion is done randomly among all available shards when no distributed key is given.

Default value: 0.

JSON formats settings

input_format_import_nested_json

Enables or disables the insertion of JSON data with nested objects.

Supported formats:

JSONEachRow

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 0.

See also:

Usage of Nested Structures with the JSONEachRow format.

input_format_json_read_bools_as_numbers

Allow parsing bools as numbers in JSON input formats.

Enabled by default.

input_format_json_read_bools_as_strings

Allow parsing bools as strings in JSON input formats.

Enabled by default.

input_format_json_read_numbers_as_strings

Allow parsing numbers as strings in JSON input formats.

Enabled by default.

input_format_json_try_infer_numbers_from_strings

If enabled, during schema inference ClickHouse will try to infer numbers from string fields. It can be useful if JSON data contains quoted UInt64 numbers.

Disabled by default.

input_format_json_read_objects_as_strings

Allow parsing JSON objects as strings in JSON input formats.

Example:

SET input_format_json_read_objects_as_strings = 1;
CREATE TABLE test (id UInt64, obj String, date Date) ENGINE=Memory();
INSERT INTO test FORMAT JSONEachRow {"id" : 1, "obj" : {"a" : 1, "b" : "Hello"}, "date" : "2020-01-01"};
SELECT * FROM test;

Result:

┌─id─┬─obj──────────────────────┬───────date─┐
│  1 │ {"a" : 1, "b" : "Hello"} │ 2020-01-01 │
└────┴──────────────────────────┴────────────┘

Enabled by default.

input_format_json_try_infer_named_tuples_from_objects

If enabled, during schema inference ClickHouse will try to infer named Tuple from JSON objects. The resulting named Tuple will contain all elements from all corresponding JSON objects from sample data.

Example:

SET input_format_json_try_infer_named_tuples_from_objects = 1;
DESC format(JSONEachRow, '{"obj" : {"a" : 42, "b" : "Hello"}}, {"obj" : {"a" : 43, "c" : [1, 2, 3]}}, {"obj" : {"d" : {"e" : 42}}}')

Result:

┌─name─┬─type───────────────────────────────────────────────────────────────────────────────────────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┐
│ obj  │ Tuple(a Nullable(Int64), b Nullable(String), c Array(Nullable(Int64)), d Tuple(e Nullable(Int64))) │              │                    │         │                  │                │
└──────┴────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┘

Enabled by default.

input_format_json_read_arrays_as_strings

Allow parsing JSON arrays as strings in JSON input formats.

Example:

SET input_format_json_read_arrays_as_strings = 1;
SELECT arr, toTypeName(arr), JSONExtractArrayRaw(arr)[3] from format(JSONEachRow, 'arr String', '{"arr" : [1, "Hello", [1,2,3]]}');

Result:

┌─arr───────────────────┬─toTypeName(arr)─┬─arrayElement(JSONExtractArrayRaw(arr), 3)─┐
│ [1, "Hello", [1,2,3]] │ String          │ [1,2,3]                                   │
└───────────────────────┴─────────────────┴───────────────────────────────────────────┘

Enabled by default.

input_format_json_infer_incomplete_types_as_strings

Allow to use String type for JSON keys that contain only Null/{}/[] in data sample during schema inference. In JSON formats any value can be read as String, and we can avoid errors like Cannot determine type for column 'column_name' by first 25000 rows of data, most likely this column contains only Nulls or empty Arrays/Maps during schema inference by using String type for keys with unknown types.

Example:

SET input_format_json_infer_incomplete_types_as_strings = 1, input_format_json_try_infer_named_tuples_from_objects = 1;
DESCRIBE format(JSONEachRow, '{"obj" : {"a" : [1,2,3], "b" : "hello", "c" : null, "d" : {}, "e" : []}}');
SELECT * FROM format(JSONEachRow, '{"obj" : {"a" : [1,2,3], "b" : "hello", "c" : null, "d" : {}, "e" : []}}');

Result:

┌─name─┬─type───────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬─default_type─┬─default_expression─┬─comment─┬─codec_expression─┬─ttl_expression─┐
│ obj  │ Tuple(a Array(Nullable(Int64)), b Nullable(String), c Nullable(String), d Nullable(String), e Array(Nullable(String))) │              │                    │         │                  │                │
└──────┴────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────────────┴────────────────────┴─────────┴──────────────────┴────────────────┘

┌─obj────────────────────────────┐
│ ([1,2,3],'hello',NULL,'{}',[]) │
└────────────────────────────────┘

Enabled by default.

input_format_json_validate_types_from_metadata

For JSON/JSONCompact/JSONColumnsWithMetadata input formats, if this setting is set to 1, the types from metadata in input data will be compared with the types of the corresponding columns from the table.

Enabled by default.

output_format_json_quote_64bit_integers

Controls quoting of 64-bit or bigger integers (like UInt64 or Int128) when they are output in a JSON format. Such integers are enclosed in quotes by default. This behavior is compatible with most JavaScript implementations.

Possible values:

0 — Integers are output without quotes.
1 — Integers are enclosed in quotes.

Default value: 1.

output_format_json_quote_64bit_floats

Controls quoting of 64-bit floats when they are output in JSON* formats.

Disabled by default.

output_format_json_quote_denormals

Enables +nan, -nan, +inf, -inf outputs in JSON output format.

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 0.

Example

Consider the following table account_orders:

┌─id─┬─name───┬─duration─┬─period─┬─area─┐
│  1 │ Andrew │       20 │      0 │  400 │
│  2 │ John   │       40 │      0 │    0 │
│  3 │ Bob    │       15 │      0 │ -100 │
└────┴────────┴──────────┴────────┴──────┘

When output_format_json_quote_denormals = 0, the query returns null values in output:

SELECT area/period FROM account_orders FORMAT JSON;

{
        "meta":
        [
                {
                        "name": "divide(area, period)",
                        "type": "Float64"
                }
        ],

        "data":
        [
                {
                        "divide(area, period)": null
                },
                {
                        "divide(area, period)": null
                },
                {
                        "divide(area, period)": null
                }
        ],

        "rows": 3,

        "statistics":
        {
                "elapsed": 0.003648093,
                "rows_read": 3,
                "bytes_read": 24
        }
}

When output_format_json_quote_denormals = 1, the query returns:

{
        "meta":
        [
                {
                        "name": "divide(area, period)",
                        "type": "Float64"
                }
        ],

        "data":
        [
                {
                        "divide(area, period)": "inf"
                },
                {
                        "divide(area, period)": "-nan"
                },
                {
                        "divide(area, period)": "-inf"
                }
        ],

        "rows": 3,

        "statistics":
        {
                "elapsed": 0.000070241,
                "rows_read": 3,
                "bytes_read": 24
        }
}

output_format_json_quote_decimals

Controls quoting of decimals in JSON output formats.

Disabled by default.

output_format_json_escape_forward_slashes

Controls escaping forward slashes for string outputs in JSON output format. This is intended for compatibility with JavaScript. Don't confuse with backslashes that are always escaped.

Enabled by default.

output_format_json_named_tuples_as_objects

Serialize named tuple columns as JSON objects.

Enabled by default.

input_format_json_named_tuples_as_objects

Parse named tuple columns as JSON objects.

Enabled by default.

input_format_json_ignore_unknown_keys_in_named_tuple

Ignore unknown keys in json object for named tuples.

Enabled by default.

input_format_json_defaults_for_missing_elements_in_named_tuple

Insert default values for missing elements in JSON object while parsing named tuple. This setting works only when setting input_format_json_named_tuples_as_objects is enabled.

Enabled by default.

input_format_json_throw_on_bad_escape_sequence

Throw an exception if JSON string contains bad escape sequence in JSON input formats. If disabled, bad escape sequences will remain as is in the data.

Enabled by default.

output_format_json_array_of_rows

Enables the ability to output all rows as a JSON array in the JSONEachRow format.

Possible values:

1 — ClickHouse outputs all rows as an array, each row in the JSONEachRow format.
0 — ClickHouse outputs each row separately in the JSONEachRow format.

Default value: 0.

Example of a query with the enabled setting

Query:

SET output_format_json_array_of_rows = 1;
SELECT number FROM numbers(3) FORMAT JSONEachRow;

Result:

[
{"number":"0"},
{"number":"1"},
{"number":"2"}
]

Example of a query with the disabled setting

Query:

SET output_format_json_array_of_rows = 0;
SELECT number FROM numbers(3) FORMAT JSONEachRow;

Result:

{"number":"0"}
{"number":"1"}
{"number":"2"}

output_format_json_validate_utf8

Controls validation of UTF-8 sequences in JSON output formats, doesn't impact formats JSON/JSONCompact/JSONColumnsWithMetadata, they always validate UTF-8.

Disabled by default.

format_json_object_each_row_column_for_object_name

The name of column that will be used for storing/writing object names in JSONObjectEachRow format. Column type should be String. If value is empty, default names row_{i}will be used for object names.

Default value: ''.

input_format_json_compact_allow_variable_number_of_columns

Allow variable number of columns in rows in JSONCompact/JSONCompactEachRow input formats. Ignore extra columns in rows with more columns than expected and treat missing columns as default values.

Disabled by default.

output_format_markdown_escape_special_characters

When enabled, escape special characters in Markdown.

Common Mark defines the following special characters that can be escaped by :

! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~

Possible values:

0 — Disable.
1 — Enable.

Default value: 0.

TSV format settings

input_format_tsv_empty_as_default

When enabled, replace empty input fields in TSV with default values. For complex default expressions input_format_defaults_for_omitted_fields must be enabled too.

Disabled by default.

input_format_tsv_enum_as_number

When enabled, always treat enum values as enum ids for TSV input format. It's recommended to enable this setting if data contains only enum ids to optimize enum parsing.

Possible values:

0 — Enum values are parsed as values or as enum IDs.
1 — Enum values are parsed only as enum IDs.

Default value: 0.

Example

Consider the table:

CREATE TABLE table_with_enum_column_for_tsv_insert (Id Int32,Value Enum('first' = 1, 'second' = 2)) ENGINE=Memory();

When the input_format_tsv_enum_as_number setting is enabled:

Query:

SET input_format_tsv_enum_as_number = 1;
INSERT INTO table_with_enum_column_for_tsv_insert FORMAT TSV 102	2;
SELECT * FROM table_with_enum_column_for_tsv_insert;

Result:

┌──Id─┬─Value──┐
│ 102 │ second │
└─────┴────────┘

Query:

SET input_format_tsv_enum_as_number = 1;
INSERT INTO table_with_enum_column_for_tsv_insert FORMAT TSV 103	'first';

throws an exception.

When the input_format_tsv_enum_as_number setting is disabled:

Query:

SET input_format_tsv_enum_as_number = 0;
INSERT INTO table_with_enum_column_for_tsv_insert FORMAT TSV 102	2;
INSERT INTO table_with_enum_column_for_tsv_insert FORMAT TSV 103	'first';
SELECT * FROM table_with_enum_column_for_tsv_insert;

Result:

┌──Id─┬─Value──┐
│ 102 │ second │
└─────┴────────┘
┌──Id─┬─Value──┐
│ 103 │ first  │
└─────┴────────┘

input_format_tsv_use_best_effort_in_schema_inference

Use some tweaks and heuristics to infer schema in TSV format. If disabled, all fields will be treated as String.

Enabled by default.

input_format_tsv_skip_first_lines

The number of lines to skip at the beginning of data in TSV input format.

Default value: 0.

output_format_tsv_crlf_end_of_line

Use DOS/Windows-style line separator (CRLF) in TSV instead of Unix style (LF).

Disabled by default.

input_format_tsv_crlf_end_of_line

Use DOS/Windows-style line separator (CRLF) for TSV input files instead of Unix style (LF).

Disabled by default.

format_tsv_null_representation

Defines the representation of NULL for TSV output and input formats. User can set any string as a value, for example, My NULL.

Default value: \N.

Examples

Query

SELECT * FROM tsv_custom_null FORMAT TSV;

Result

788
\N
\N

Query

SET format_tsv_null_representation = 'My NULL';
SELECT * FROM tsv_custom_null FORMAT TSV;

Result

788
My NULL
My NULL

input_format_tsv_skip_trailing_empty_lines {input_format_tsv_skip_trailing_empty_lines}

When enabled, trailing empty lines at the end of TSV file will be skipped.

Disabled by default.

input_format_tsv_allow_variable_number_of_columns

Allow variable number of columns in rows in TSV input format. Ignore extra columns in rows with more columns than expected and treat missing columns as default values.

Disabled by default.

CSV format settings

format_csv_delimiter

The character is interpreted as a delimiter in the CSV data.

Default value: ,.

format_csv_allow_single_quotes

If it is set to true, allow strings in single quotes.

Disabled by default.

format_csv_allow_double_quotes

If it is set to true, allow strings in double quotes.

Enabled by default.

output_format_csv_crlf_end_of_line

Use DOS/Windows-style line separator (CRLF) in CSV instead of Unix style (LF).

Disabled by default.

input_format_csv_allow_cr_end_of_line

If it is set true, CR(\r) will be allowed at end of line not followed by LF(\n)

Disabled by default.

input_format_csv_enum_as_number

When enabled, always treat enum values as enum ids for CSV input format. It's recommended to enable this setting if data contains only enum ids to optimize enum parsing.

Possible values:

0 — Enum values are parsed as values or as enum IDs.
1 — Enum values are parsed only as enum IDs.

Default value: 0.

Examples

Consider the table:

CREATE TABLE table_with_enum_column_for_csv_insert (Id Int32,Value Enum('first' = 1, 'second' = 2)) ENGINE=Memory();

When the input_format_csv_enum_as_number setting is enabled:

Query:

SET input_format_csv_enum_as_number = 1;
INSERT INTO table_with_enum_column_for_csv_insert FORMAT CSV 102,2

Result:

┌──Id─┬─Value──┐
│ 102 │ second │
└─────┴────────┘

Query:

SET input_format_csv_enum_as_number = 1;
INSERT INTO table_with_enum_column_for_csv_insert FORMAT CSV 103,'first'

throws an exception.

When the input_format_csv_enum_as_number setting is disabled:

Query:

SET input_format_csv_enum_as_number = 0;
INSERT INTO table_with_enum_column_for_csv_insert FORMAT CSV 102,2
INSERT INTO table_with_enum_column_for_csv_insert FORMAT CSV 103,'first'
SELECT * FROM table_with_enum_column_for_csv_insert;

Result:

┌──Id─┬─Value──┐
│ 102 │ second │
└─────┴────────┘
┌──Id─┬─Value─┐
│ 103 │ first │
└─────┴───────┘

input_format_csv_arrays_as_nested_csv

When reading Array from CSV, expect that its elements were serialized in nested CSV and then put into string. Example: "[""Hello"", ""world"", ""42"""" TV""]". Braces around array can be omitted.

Disabled by default.

input_format_csv_empty_as_default

When enabled, replace empty input fields in CSV with default values. For complex default expressions input_format_defaults_for_omitted_fields must be enabled too.

Enabled by default.

input_format_csv_use_best_effort_in_schema_inference

Use some tweaks and heuristics to infer schema in CSV format. If disabled, all fields will be treated as String.

Enabled by default.

input_format_csv_skip_first_lines

The number of lines to skip at the beginning of data in CSV input format.

Default value: 0.

format_csv_null_representation

Defines the representation of NULL for CSV output and input formats. User can set any string as a value, for example, My NULL.

Default value: \N.

Examples

Query

SELECT * from csv_custom_null FORMAT CSV;

Result

788
\N
\N

Query

SET format_csv_null_representation = 'My NULL';
SELECT * FROM csv_custom_null FORMAT CSV;

Result

788
My NULL
My NULL

input_format_csv_skip_trailing_empty_lines {input_format_csv_skip_trailing_empty_lines}

When enabled, trailing empty lines at the end of CSV file will be skipped.

Disabled by default.

input_format_csv_trim_whitespaces

Trims spaces and tabs in non-quoted CSV strings.

Default value: true.

Examples

Query

echo '  string  ' | ./clickhouse local -q  "select * from table FORMAT CSV" --input-format="CSV" --input_format_csv_trim_whitespaces=true

Result

"string"

Query

echo '  string  ' | ./clickhouse local -q  "select * from table FORMAT CSV" --input-format="CSV" --input_format_csv_trim_whitespaces=false

Result

"  string  "

input_format_csv_allow_variable_number_of_columns

Allow variable number of columns in rows in CSV input format. Ignore extra columns in rows with more columns than expected and treat missing columns as default values.

Disabled by default.

input_format_csv_allow_whitespace_or_tab_as_delimiter

Allow to use whitespace or tab as field delimiter in CSV strings.

Default value: false.

Examples

Query

echo 'a b' | ./clickhouse local -q  "select * from table FORMAT CSV" --input-format="CSV" --input_format_csv_allow_whitespace_or_tab_as_delimiter=true --format_csv_delimiter=' '

Result

a  b

Query

echo 'a         b' | ./clickhouse local -q  "select * from table FORMAT CSV" --input-format="CSV" --input_format_csv_allow_whitespace_or_tab_as_delimiter=true --format_csv_delimiter='\t'

Result

a  b

input_format_csv_use_default_on_bad_values

Allow to set default value to column when CSV field deserialization failed on bad value

Default value: false.

Examples

Query

./clickhouse local -q "create table test_tbl (x String, y UInt32, z Date) engine=MergeTree order by x"
echo 'a,b,c' | ./clickhouse local -q  "INSERT INTO test_tbl SETTINGS input_format_csv_use_default_on_bad_values=true FORMAT CSV"
./clickhouse local -q "select * from test_tbl"

Result

a  0  1971-01-01

input_format_csv_try_infer_numbers_from_strings

If enabled, during schema inference ClickHouse will try to infer numbers from string fields. It can be useful if CSV data contains quoted UInt64 numbers.

Disabled by default.

Values format settings

input_format_values_interpret_expressions

Enables or disables the full SQL parser if the fast stream parser can’t parse the data. This setting is used only for the Values format at the data insertion. For more information about syntax parsing, see the Syntax section.

Possible values:

0 — Disabled.

In this case, you must provide formatted data. See the Formats section.
1 — Enabled.

In this case, you can use an SQL expression as a value, but data insertion is much slower this way. If you insert only formatted data, then ClickHouse behaves as if the setting value is 0.

Default value: 1.

Example of Use

Insert the DateTime type value with the different settings.

SET input_format_values_interpret_expressions = 0;
INSERT INTO datetime_t VALUES (now())

Exception on client:
Code: 27. DB::Exception: Cannot parse input: expected ) before: now()): (at row 1)

SET input_format_values_interpret_expressions = 1;
INSERT INTO datetime_t VALUES (now())

Ok.

The last query is equivalent to the following:

SET input_format_values_interpret_expressions = 0;
INSERT INTO datetime_t SELECT now()

Ok.

input_format_values_deduce_templates_of_expressions

Enables or disables template deduction for SQL expressions in Values format. It allows parsing and interpreting expressions in Values much faster if expressions in consecutive rows have the same structure. ClickHouse tries to deduce the template of an expression, parse the following rows using this template and evaluate the expression on a batch of successfully parsed rows.

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 1.

For the following query:

INSERT INTO test VALUES (lower('Hello')), (lower('world')), (lower('INSERT')), (upper('Values')), ...

If input_format_values_interpret_expressions=1 and format_values_deduce_templates_of_expressions=0, expressions are interpreted separately for each row (this is very slow for large number of rows).
If input_format_values_interpret_expressions=0 and format_values_deduce_templates_of_expressions=1, expressions in the first, second and third rows are parsed using template lower(String) and interpreted together, expression in the forth row is parsed with another template (upper(String)).
If input_format_values_interpret_expressions=1 and format_values_deduce_templates_of_expressions=1, the same as in previous case, but also allows fallback to interpreting expressions separately if it’s not possible to deduce template.

input_format_values_accurate_types_of_literals

This setting is used only when input_format_values_deduce_templates_of_expressions = 1. Expressions for some column may have the same structure, but contain numeric literals of different types, e.g.

(..., abs(0), ...),             -- UInt64 literal
(..., abs(3.141592654), ...),   -- Float64 literal
(..., abs(-1), ...),            -- Int64 literal

Possible values:

0 — Disabled.

In this case, ClickHouse may use a more general type for some literals (e.g., Float64 or Int64 instead of UInt64 for 42), but it may cause overflow and precision issues.
1 — Enabled.

In this case, ClickHouse checks the actual type of literal and uses an expression template of the corresponding type. In some cases, it may significantly slow down expression evaluation in Values.

Default value: 1.

Arrow format settings

input_format_arrow_case_insensitive_column_matching

Ignore case when matching Arrow column names with ClickHouse column names.

Disabled by default.

input_format_arrow_allow_missing_columns

While importing data, when column is not found in schema default value will be used instead of error.

Disabled by default.

input_format_arrow_skip_columns_with_unsupported_types_in_schema_inference

Allow skipping columns with unsupported types while schema inference for format Arrow.

Disabled by default.

output_format_arrow_low_cardinality_as_dictionary

Allows to convert the LowCardinality type to the DICTIONARY type of the Arrow format for SELECT queries.

Possible values:

0 — The LowCardinality type is not converted to the DICTIONARY type.
1 — The LowCardinality type is converted to the DICTIONARY type.

Default value: 0.

output_format_arrow_use_signed_indexes_for_dictionary

Use signed integer types instead of unsigned in DICTIONARY type of the Arrow format during LowCardinality output when output_format_arrow_low_cardinality_as_dictionary is enabled.

Possible values:

0 — Unsigned integer types are used for indexes in DICTIONARY type.
1 — Signed integer types are used for indexes in DICTIONARY type.

Default value: 1.

output_format_arrow_use_64_bit_indexes_for_dictionary

Use 64-bit integer type in DICTIONARY type of the Arrow format during LowCardinality output when output_format_arrow_low_cardinality_as_dictionary is enabled.

Possible values:

0 — Type for indexes in DICTIONARY type is determined automatically.
1 — 64-bit integer type is used for indexes in DICTIONARY type.

Default value: 0.

output_format_arrow_string_as_string

Use Arrow String type instead of Binary for String columns.

Disabled by default.

output_format_arrow_fixed_string_as_fixed_byte_array (#output_format_arrow_fixed_string_as_fixed_byte_array)

Use Arrow FIXED_SIZE_BINARY type instead of Binary/String for FixedString columns.

Enabled by default.

output_format_arrow_compression_method

Compression method used in output Arrow format. Supported codecs: lz4_frame, zstd, none (uncompressed)

Default value: lz4_frame.

ORC format settings

input_format_orc_row_batch_size

Batch size when reading ORC stripes.

Default value: 100'000

input_format_orc_case_insensitive_column_matching

Ignore case when matching ORC column names with ClickHouse column names.

Disabled by default.

input_format_orc_allow_missing_columns

While importing data, when column is not found in schema default value will be used instead of error.

Disabled by default.

input_format_orc_skip_columns_with_unsupported_types_in_schema_inference

Allow skipping columns with unsupported types while schema inference for format Arrow.

Disabled by default.

output_format_orc_string_as_string

Use ORC String type instead of Binary for String columns.

Disabled by default.

output_format_orc_compression_method

Compression method used in output ORC format. Supported codecs: lz4, snappy, zlib, zstd, none (uncompressed)

Default value: none.

Parquet format settings

input_format_parquet_case_insensitive_column_matching

Ignore case when matching Parquet column names with ClickHouse column names.

Disabled by default.

output_format_parquet_row_group_size

Row group size in rows.

Default value: 1'000'000.

input_format_parquet_allow_missing_columns

While importing data, when column is not found in schema default value will be used instead of error.

Enabled by default.

input_format_parquet_skip_columns_with_unsupported_types_in_schema_inference

Allow skipping columns with unsupported types while schema inference for format Parquet.

Disabled by default.

input_format_parquet_local_file_min_bytes_for_seek

min bytes required for local read (file) to do seek, instead of read with ignore in Parquet input format.

Default value - 8192.

output_format_parquet_string_as_string

Use Parquet String type instead of Binary for String columns.

Disabled by default.

output_format_parquet_fixed_string_as_fixed_byte_array (#output_format_parquet_fixed_string_as_fixed_byte_array)

Use Parquet FIXED_LENGTH_BYTE_ARRAY type instead of Binary/String for FixedString columns.

Enabled by default.

output_format_parquet_version

The version of Parquet format used in output format. Supported versions: 1.0, 2.4, 2.6 and 2.latest.

Default value: 2.latest.

output_format_parquet_compression_method

Compression method used in output Parquet format. Supported codecs: snappy, lz4, brotli, zstd, gzip, none (uncompressed)

Default value: lz4.

input_format_parquet_max_block_size

Max block row size for parquet reader. By controlling the number of rows in each block, you can control the memory usage, and in some operators that cache blocks, you can improve the accuracy of the operator's memory control。

Default value: 65409.

input_format_parquet_prefer_block_bytes

Average block bytes output by parquet reader. Lowering the configuration in the case of reading some high compression parquet relieves the memory pressure.

Default value: 65409 * 256 = 16744704

output_format_parquet_write_page_index

Could add page index into parquet files. To enable this, need set output_format_parquet_use_custom_encoder=false and output_format_parquet_write_page_index=true.

Enable by default.

Hive format settings

input_format_hive_text_fields_delimiter

Delimiter between fields in Hive Text File.

Default value: \x01.

input_format_hive_text_collection_items_delimiter

Delimiter between collection(array or map) items in Hive Text File.

Default value: \x02.

input_format_hive_text_map_keys_delimiter

Delimiter between a pair of map key/values in Hive Text File.

Default value: \x03.

MsgPack format settings

input_format_msgpack_number_of_columns

The number of columns in inserted MsgPack data. Used for automatic schema inference from data.

Default value: 0.

output_format_msgpack_uuid_representation

The way how to output UUID in MsgPack format. Possible values:

bin - as 16-bytes binary.
str - as a string of 36 bytes.
ext - as extension with ExtType = 2.

Default value: ext.

Protobuf format settings

input_format_protobuf_flatten_google_wrappers

Enable Google wrappers for regular non-nested columns, e.g. google.protobuf.StringValue 'str' for String column 'str'. For Nullable columns empty wrappers are recognized as defaults, and missing as nulls.

Disabled by default.

output_format_protobuf_nullables_with_google_wrappers

When serializing Nullable columns with Google wrappers, serialize default values as empty wrappers. If turned off, default and null values are not serialized.

Disabled by default.

format_protobuf_use_autogenerated_schema

Use autogenerated Protobuf schema when format_schema is not set. The schema is generated from ClickHouse table structure using function structureToProtobufSchema

Avro format settings

input_format_avro_allow_missing_fields

Enables using fields that are not specified in Avro or AvroConfluent format schema. When a field is not found in the schema, ClickHouse uses the default value instead of throwing an exception.

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 0.

format_avro_schema_registry_url

Sets Confluent Schema Registry URL to use with AvroConfluent format.

Format:

http://[user:password@]machine[:port]"

Examples:

http://registry.example.com:8081
http://admin:secret@registry.example.com:8081

Default value: Empty.

output_format_avro_codec

Sets the compression codec used for output Avro file.

Type: string

Possible values:

null — No compression
deflate — Compress with Deflate (zlib)
snappy — Compress with Snappy

Default value: snappy (if available) or deflate.

output_format_avro_sync_interval

Sets minimum data size (in bytes) between synchronization markers for output Avro file.

Type: unsigned int

Possible values: 32 (32 bytes) - 1073741824 (1 GiB)

Default value: 32768 (32 KiB)

output_format_avro_string_column_pattern

Regexp of column names of type String to output as Avro string (default is bytes). RE2 syntax is supported.

Type: string

output_format_avro_rows_in_file

Max rows in a file (if permitted by storage).

Default value: 1.

Pretty formats settings

output_format_pretty_max_rows

Rows limit for Pretty formats.

Default value: 10'000.

output_format_pretty_max_column_pad_width

Maximum width to pad all values in a column in Pretty formats.

Default value: 250.

output_format_pretty_max_value_width

Limits the width of value displayed in Pretty formats. If the value width exceeds the limit, the value is cut.

Possible values:

Positive integer.
0 — The value is cut completely.

Default value: 10000 symbols.

Examples

Query:

SET output_format_pretty_max_value_width = 10;
SELECT range(number) FROM system.numbers LIMIT 10 FORMAT PrettyCompactNoEscapes;

Result:

┌─range(number)─┐
│ []            │
│ [0]           │
│ [0,1]         │
│ [0,1,2]       │
│ [0,1,2,3]     │
│ [0,1,2,3,4⋯   │
│ [0,1,2,3,4⋯   │
│ [0,1,2,3,4⋯   │
│ [0,1,2,3,4⋯   │
│ [0,1,2,3,4⋯   │
└───────────────┘

Query with zero width:

SET output_format_pretty_max_value_width = 0;
SELECT range(number) FROM system.numbers LIMIT 5 FORMAT PrettyCompactNoEscapes;

Result:

┌─range(number)─┐
│ ⋯             │
│ ⋯             │
│ ⋯             │
│ ⋯             │
│ ⋯             │
└───────────────┘

output_format_pretty_color

Use ANSI escape sequences to paint colors in Pretty formats.

possible values:

0 — Disabled. Pretty formats do not use ANSI escape sequences.
1 — Enabled. Pretty formats will use ANSI escape sequences except for NoEscapes formats.
auto - Enabled if stdout is a terminal except for NoEscapes formats.

Default value is auto.

output_format_pretty_grid_charset

Allows changing a charset which is used for printing grids borders. Available charsets are UTF-8, ASCII.

Example

SET output_format_pretty_grid_charset = 'UTF-8';
SELECT * FROM a;
┌─a─┐
│ 1 │
└───┘

SET output_format_pretty_grid_charset = 'ASCII';
SELECT * FROM a;
+-a-+
| 1 |
+---+

output_format_pretty_row_numbers

Adds row numbers to output in the Pretty format.

Possible values:

0 — Output without row numbers.
1 — Output with row numbers.

Default value: 1.

Example

Query:

SET output_format_pretty_row_numbers = 1;
SELECT TOP 3 name, value FROM system.settings;

Result:

   ┌─name────────────────────┬─value───┐
1. │ min_compress_block_size │ 65536   │
2. │ max_compress_block_size │ 1048576 │
3. │ max_block_size          │ 65505   │
   └─────────────────────────┴─────────┘

output_format_pretty_single_large_number_tip_threshold

Print a readable number tip on the right side of the table if the block consists of a single number which exceeds this value (except 0).

Possible values:

0 — The readable number tip will not be printed.
Positive integer — The readable number tip will be printed if the single number exceeds this value.

Default value: 1000000.

Example

Query:

SELECT 1000000000 as a;

Result:

┌──────────a─┐
│ 1000000000 │ -- 1.00 billion
└────────────┘

output_format_pretty_display_footer_column_names

Display column names in the footer if there are many table rows.

Possible values:

0 — No column names are displayed in the footer.
1 — Column names are displayed in the footer if row count is greater than or equal to the threshold value set by output_format_pretty_display_footer_column_names_min_rows (50 by default).

Default value: 1.

Example

Query:

SELECT *, toTypeName(*) FROM (SELECT * FROM system.numbers LIMIT 1000);

Result:

      ┌─number─┬─toTypeName(number)─┐
   1. │      0 │ UInt64             │
   2. │      1 │ UInt64             │
   3. │      2 │ UInt64             │
   ...
 999. │    998 │ UInt64             │
1000. │    999 │ UInt64             │
      └─number─┴─toTypeName(number)─┘

output_format_pretty_display_footer_column_names_min_rows

Sets the minimum number of rows for which a footer with column names will be displayed if setting output_format_pretty_display_footer_column_names is enabled.

Default value: 50.

Template format settings

format_template_resultset

Path to file which contains format string for result set (for Template format).

format_template_resultset_format

Format string for result set (for Template format)

format_template_row

Path to file which contains format string for rows (for Template format).

format_template_rows_between_delimiter

Delimiter between rows (for Template format).

format_template_row_format

Format string for rows (for Template format)

CustomSeparated format settings {custom-separated-format-settings}

format_custom_escaping_rule

Sets the field escaping rule for CustomSeparated data format.

Possible values:

'Escaped' — Similarly to TSV.
'Quoted' — Similarly to Values.
'CSV' — Similarly to CSV.
'JSON' — Similarly to JSONEachRow.
'XML' — Similarly to XML.
'Raw' — Extracts subpatterns as a whole, no escaping rules, similarly to TSVRaw.

Default value: 'Escaped'.

format_custom_field_delimiter

Sets the character that is interpreted as a delimiter between the fields for CustomSeparated data format.

Default value: '\t'.

format_custom_row_before_delimiter

Sets the character that is interpreted as a delimiter before the field of the first column for CustomSeparated data format.

Default value: ''.

format_custom_row_after_delimiter

Sets the character that is interpreted as a delimiter after the field of the last column for CustomSeparated data format.

Default value: '\n'.

format_custom_row_between_delimiter

Sets the character that is interpreted as a delimiter between the rows for CustomSeparated data format.

Default value: ''.

format_custom_result_before_delimiter

Sets the character that is interpreted as a prefix before the result set for CustomSeparated data format.

Default value: ''.

format_custom_result_after_delimiter

Sets the character that is interpreted as a suffix after the result set for CustomSeparated data format.

Default value: ''.

input_format_custom_skip_trailing_empty_lines {input_format_custom_skip_trailing_empty_lines}

When enabled, trailing empty lines at the end of file in CustomSeparated format will be skipped.

Disabled by default.

input_format_custom_allow_variable_number_of_columns

Allow variable number of columns in rows in CustomSeparated input format. Ignore extra columns in rows with more columns than expected and treat missing columns as default values.

Disabled by default.

Regexp format settings

format_regexp_escaping_rule

Field escaping rule.

Possible values:

'Escaped' — Similarly to TSV.
'Quoted' — Similarly to Values.
'CSV' — Similarly to CSV.
'JSON' — Similarly to JSONEachRow.
'XML' — Similarly to XML.
'Raw' — Extracts subpatterns as a whole, no escaping rules, similarly to TSVRaw.

Default value: Raw.

format_regexp_skip_unmatched

Skip lines unmatched by regular expression.

Disabled by default.

CapnProto format settings

format_capn_proto_enum_comparising_mode

Determines how to map ClickHouse Enum data type and CapnProto Enum data type from schema.

Possible values:

'by_values' — Values in enums should be the same, names can be different.
'by_names' — Names in enums should be the same, values can be different.
'by_name_case_insensitive' — Names in enums should be the same case-insensitive, values can be different.

Default value: 'by_values'.

format_capn_proto_use_autogenerated_schema

Use autogenerated CapnProto schema when format_schema is not set. The schema is generated from ClickHouse table structure using function structureToCapnProtoSchema

MySQLDump format settings

input_format_mysql_dump_table_name (#input_format_mysql_dump_table_name)

The name of the table from which to read data from in MySQLDump input format.

input_format_mysql_dump_map_columns (#input_format_mysql_dump_map_columns)

Enables matching columns from table in MySQL dump and columns from ClickHouse table by names in MySQLDump input format.

Possible values:

0 — Disabled.
1 — Enabled.

Default value: 1.

SQLInsert format settings

output_format_sql_insert_max_batch_size

The maximum number of rows in one INSERT statement.

Default value: 65505.

output_format_sql_insert_table_name

The name of table that will be used in the output INSERT statement.

Default value: table.

output_format_sql_insert_include_column_names

Include column names in INSERT statement.

Default value: true.

output_format_sql_insert_use_replace

Use REPLACE keyword instead of INSERT.

Default value: false.

output_format_sql_insert_quote_names

Quote column names with "`" characters

Default value: true.

BSONEachRow format settings

output_format_bson_string_as_string

Use BSON String type instead of Binary for String columns.

Disabled by default.

input_format_bson_skip_fields_with_unsupported_types_in_schema_inference

Allow skipping columns with unsupported types while schema inference for format BSONEachRow.

Disabled by default.

RowBinary format settings

format_binary_max_string_size

The maximum allowed size for String in RowBinary format. It prevents allocating large amount of memory in case of corrupted data. 0 means there is no limit.

Default value: 1GiB.

output_format_binary_encode_types_in_binary_format

Write data types in binary format instead of type names in RowBinaryWithNamesAndTypes output format.

Disabled by default.

input_format_binary_decode_types_in_binary_format

Read data types in binary format instead of type names in RowBinaryWithNamesAndTypes input format.

Disabled by default.

Native format settings

input_format_native_allow_types_conversion

Allow types conversion in Native input format between columns from input data and requested columns.

Enabled by default.

output_format_native_encode_types_in_binary_format

Write data types in binary format instead of type names in Native output format.

Disabled by default.

input_format_native_decode_types_in_binary_format

Read data types in binary format instead of type names in Native input format.

Disabled by default.

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Format settings

format_display_secrets_in_show_and_select

input_format_skip_unknown_fields

input_format_with_names_use_header

input_format_with_types_use_header

input_format_defaults_for_omitted_fields

input_format_null_as_default

input_format_allow_seeks

input_format_max_rows_to_read_for_schema_inference

input_format_max_bytes_to_read_for_schema_inference

column_names_for_schema_inference

schema_inference_hints

schema_inference_make_columns_nullable

input_format_try_infer_integers

input_format_try_infer_dates

input_format_try_infer_datetimes

date_time_input_format

date_time_output_format

interval_output_format

input_format_ipv4_default_on_conversion_error

input_format_ipv6_default_on_conversion_error

bool_true_representation

bool_false_representation

output_format_decimal_trailing_zeros

input_format_allow_errors_num

input_format_allow_errors_ratio

format_schema

output_format_schema

output_format_enable_streaming

output_format_write_statistics

insert_distributed_one_random_shard

JSON formats settings

input_format_import_nested_json

input_format_json_read_bools_as_numbers

input_format_json_read_bools_as_strings

input_format_json_read_numbers_as_strings

input_format_json_try_infer_numbers_from_strings

input_format_json_read_objects_as_strings

input_format_json_try_infer_named_tuples_from_objects

input_format_json_read_arrays_as_strings

input_format_json_infer_incomplete_types_as_strings

input_format_json_validate_types_from_metadata

output_format_json_quote_64bit_integers

output_format_json_quote_64bit_floats

output_format_json_quote_denormals

output_format_json_quote_decimals

output_format_json_escape_forward_slashes

output_format_json_named_tuples_as_objects

input_format_json_named_tuples_as_objects

input_format_json_ignore_unknown_keys_in_named_tuple

input_format_json_defaults_for_missing_elements_in_named_tuple

input_format_json_throw_on_bad_escape_sequence

output_format_json_array_of_rows

output_format_json_validate_utf8

format_json_object_each_row_column_for_object_name

input_format_json_compact_allow_variable_number_of_columns

output_format_markdown_escape_special_characters

TSV format settings

input_format_tsv_empty_as_default

input_format_tsv_enum_as_number

input_format_tsv_use_best_effort_in_schema_inference

input_format_tsv_skip_first_lines

output_format_tsv_crlf_end_of_line

input_format_tsv_crlf_end_of_line

format_tsv_null_representation

input_format_tsv_skip_trailing_empty_lines {input_format_tsv_skip_trailing_empty_lines}

input_format_tsv_allow_variable_number_of_columns

CSV format settings

format_csv_delimiter

format_csv_allow_single_quotes

format_csv_allow_double_quotes

output_format_csv_crlf_end_of_line

input_format_csv_allow_cr_end_of_line

input_format_csv_enum_as_number

input_format_csv_arrays_as_nested_csv

input_format_csv_empty_as_default

input_format_csv_use_best_effort_in_schema_inference

input_format_csv_skip_first_lines

format_csv_null_representation

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