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Format Settings

These settings are autogenerated from source.

bool_false_representation​

Type: String

Default value: false

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

bool_true_representation​

Type: String

Default value: true

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

column_names_for_schema_inference​

Type: String

Default value:

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

cross_to_inner_join_rewrite​

Type: UInt64

Default value: 1

Use inner join instead of comma/cross join if there are joining expressions in the WHERE section. Values: 0 - no rewrite, 1 - apply if possible for comma/cross, 2 - force rewrite all comma joins, cross - if possible

date_time_64_output_format_cut_trailing_zeros_align_to_groups_of_thousands​

Type: Bool

Default value: 0

Dynamically trim the trailing zeros of datetime64 values to adjust the output scale to [0, 3, 6], corresponding to 'seconds', 'milliseconds', and 'microseconds'

date_time_input_format​

Type: DateTimeInputFormat

Default value: basic

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.

Cloud default value: 'best_effort'.

See also:

date_time_output_format​

Type: DateTimeOutputFormat

Default value: simple

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.

See also:

date_time_overflow_behavior​

Type: DateTimeOverflowBehavior

Default value: ignore

Overflow mode for Date, Date32, DateTime, DateTime64 types. Possible values: 'ignore', 'throw', 'saturate'.

dictionary_use_async_executor​

Type: Bool

Default value: 0

Execute a pipeline for reading dictionary source in several threads. It's supported only by dictionaries with local CLICKHOUSE source.

errors_output_format​

Type: String

Default value: CSV

Method to write Errors to text output.

exact_rows_before_limit​

Type: Bool

Default value: 0

When enabled, ClickHouse will provide exact value for rows_before_limit_at_least statistic, but with the cost that the data before limit will have to be read completely

format_avro_schema_registry_url​

Type: URI

Default value:

For AvroConfluent format: Confluent Schema Registry URL.

format_binary_max_array_size​

Type: UInt64

Default value: 1073741824

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

format_binary_max_string_size​

Type: UInt64

Default value: 1073741824

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

format_capn_proto_enum_comparising_mode​

Type: CapnProtoEnumComparingMode

Default value: by_values

How to map ClickHouse Enum and CapnProto Enum

format_capn_proto_use_autogenerated_schema​

Type: Bool

Default value: 1

Use autogenerated CapnProto schema when format_schema is not set

format_csv_allow_double_quotes​

Type: Bool

Default value: 1

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

format_csv_allow_single_quotes​

Type: Bool

Default value: 0

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

format_csv_delimiter​

Type: Char

Default value: ,

The character to be considered as a delimiter in CSV data. If setting with a string, a string has to have a length of 1.

format_csv_null_representation​

Type: String

Default value: \N

Custom NULL representation in CSV format

format_custom_escaping_rule​

Type: EscapingRule

Default value: Escaped

Field escaping rule (for CustomSeparated format)

format_custom_field_delimiter​

Type: String

Default value:

Delimiter between fields (for CustomSeparated format)

format_custom_result_after_delimiter​

Type: String

Default value:

Suffix after result set (for CustomSeparated format)

format_custom_result_before_delimiter​

Type: String

Default value:

Prefix before result set (for CustomSeparated format)

format_custom_row_after_delimiter​

Type: String

Default value:

Delimiter after field of the last column (for CustomSeparated format)

format_custom_row_before_delimiter​

Type: String

Default value:

Delimiter before field of the first column (for CustomSeparated format)

format_custom_row_between_delimiter​

Type: String

Default value:

Delimiter between rows (for CustomSeparated format)

format_display_secrets_in_show_and_select​

Type: Bool

Default value: 0

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.

format_json_object_each_row_column_for_object_name​

Type: String

Default value:

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.

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.

input_format_json_empty_as_default​

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

Possible values:

  • 0 — Disable.
  • 1 — Enable.

format_protobuf_use_autogenerated_schema​

Type: Bool

Default value: 1

Use autogenerated Protobuf when format_schema is not set

format_regexp​

Type: String

Default value:

Regular expression (for Regexp format)

format_regexp_escaping_rule​

Type: EscapingRule

Default value: Raw

Field escaping rule (for Regexp format)

format_regexp_skip_unmatched​

Type: Bool

Default value: 0

Skip lines unmatched by regular expression (for Regexp format)

format_schema​

Type: String

Default value:

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.

format_template_resultset​

Type: String

Default value:

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

format_template_resultset_format​

Type: String

Default value:

Format string for result set (for Template format)

format_template_row​

Type: String

Default value:

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

format_template_row_format​

Type: String

Default value:

Format string for rows (for Template format)

format_template_rows_between_delimiter​

Type: String

Default value:

Delimiter between rows (for Template format)

format_tsv_null_representation​

Type: String

Default value: \N

Custom NULL representation in TSV format

input_format_allow_errors_num​

Type: UInt64

Default value: 0

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​

Type: Float

Default value: 0

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.

input_format_allow_seeks​

Type: Bool

Default value: 1

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

Enabled by default.

input_format_arrow_allow_missing_columns​

Type: Bool

Default value: 1

Allow missing columns while reading Arrow input formats

input_format_arrow_case_insensitive_column_matching​

Type: Bool

Default value: 0

Ignore case when matching Arrow columns with CH columns.

input_format_arrow_skip_columns_with_unsupported_types_in_schema_inference​

Type: Bool

Default value: 0

Skip columns with unsupported types while schema inference for format Arrow

input_format_avro_allow_missing_fields​

Type: Bool

Default value: 0

For Avro/AvroConfluent format: when field is not found in schema use default value instead of error

input_format_avro_null_as_default​

Type: Bool

Default value: 0

For Avro/AvroConfluent format: insert default in case of null and non Nullable column

input_format_binary_decode_types_in_binary_format​

Type: Bool

Default value: 0

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

input_format_binary_read_json_as_string​

Type: Bool

Default value: 0

Read values of JSON data type as JSON String values in RowBinary input format.

input_format_bson_skip_fields_with_unsupported_types_in_schema_inference​

Type: Bool

Default value: 0

Skip fields with unsupported types while schema inference for format BSON.

input_format_capn_proto_skip_fields_with_unsupported_types_in_schema_inference​

Type: Bool

Default value: 0

Skip columns with unsupported types while schema inference for format CapnProto

input_format_csv_allow_cr_end_of_line​

Type: Bool

Default value: 0

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

input_format_csv_allow_variable_number_of_columns​

Type: Bool

Default value: 0

Ignore extra columns in CSV input (if file has more columns than expected) and treat missing fields in CSV input as default values

input_format_csv_allow_whitespace_or_tab_as_delimiter​

Type: Bool

Default value: 0

Allow to use spaces and tabs(\t) as field delimiter in the CSV strings

input_format_csv_arrays_as_nested_csv​

Type: Bool

Default value: 0

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.

input_format_csv_deserialize_separate_columns_into_tuple​

Type: Bool

Default value: 1

If it set to true, then separate columns written in CSV format can be deserialized to Tuple column.

input_format_csv_detect_header​

Type: Bool

Default value: 1

Automatically detect header with names and types in CSV format

input_format_csv_empty_as_default​

Type: Bool

Default value: 1

Treat empty fields in CSV input as default values.

input_format_csv_enum_as_number​

Type: Bool

Default value: 0

Treat inserted enum values in CSV formats as enum indices

input_format_csv_skip_first_lines​

Type: UInt64

Default value: 0

Skip specified number of lines at the beginning of data in CSV format

input_format_csv_skip_trailing_empty_lines​

Type: Bool

Default value: 0

Skip trailing empty lines in CSV format

input_format_csv_trim_whitespaces​

Type: Bool

Default value: 1

Trims spaces and tabs (\t) characters at the beginning and end in CSV strings

input_format_csv_try_infer_numbers_from_strings​

Type: Bool

Default value: 0

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.

input_format_csv_try_infer_strings_from_quoted_tuples​

Type: Bool

Default value: 1

Interpret quoted tuples in the input data as a value of type String.

input_format_csv_use_best_effort_in_schema_inference​

Type: Bool

Default value: 1

Use some tweaks and heuristics to infer schema in CSV format

input_format_csv_use_default_on_bad_values​

Type: Bool

Default value: 0

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

input_format_custom_allow_variable_number_of_columns​

Type: Bool

Default value: 0

Ignore extra columns in CustomSeparated input (if file has more columns than expected) and treat missing fields in CustomSeparated input as default values

input_format_custom_detect_header​

Type: Bool

Default value: 1

Automatically detect header with names and types in CustomSeparated format

input_format_custom_skip_trailing_empty_lines​

Type: Bool

Default value: 0

Skip trailing empty lines in CustomSeparated format

input_format_defaults_for_omitted_fields​

Type: Bool

Default value: 1

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.

input_format_force_null_for_omitted_fields​

Type: Bool

Default value: 0

Force initialize omitted fields with null values

input_format_hive_text_allow_variable_number_of_columns​

Type: Bool

Default value: 1

Ignore extra columns in Hive Text input (if file has more columns than expected) and treat missing fields in Hive Text input as default values

input_format_hive_text_collection_items_delimiter​

Type: Char

Default value: 

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

input_format_hive_text_fields_delimiter​

Type: Char

Default value: 

Delimiter between fields in Hive Text File

input_format_hive_text_map_keys_delimiter​

Type: Char

Default value: 

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

input_format_import_nested_json​

Type: Bool

Default value: 0

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

Supported formats:

Possible values:

  • 0 — Disabled.
  • 1 — Enabled.

See also:

input_format_ipv4_default_on_conversion_error​

Type: Bool

Default value: 0

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

Disabled by default.

input_format_ipv6_default_on_conversion_error​

Type: Bool

Default value: 0

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

Disabled by default.

input_format_json_compact_allow_variable_number_of_columns​

Type: Bool

Default value: 0

Ignore extra columns in JSONCompact(EachRow) input (if file has more columns than expected) and treat missing fields in JSONCompact(EachRow) input as default values

input_format_json_defaults_for_missing_elements_in_named_tuple​

Type: Bool

Default value: 1

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_empty_as_default​

Type: Bool

Default value: 0

Treat empty fields in JSON input as default values.

input_format_json_ignore_unknown_keys_in_named_tuple​

Type: Bool

Default value: 1

Ignore unknown keys in json object for named tuples.

Enabled by default.

input_format_json_ignore_unnecessary_fields​

Type: Bool

Default value: 1

Ignore unnecessary fields and not parse them. Enabling this may not throw exceptions on json strings of invalid format or with duplicated fields

input_format_json_infer_incomplete_types_as_strings​

Type: Bool

Default value: 1

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_max_depth​

Type: UInt64

Default value: 1000

Maximum depth of a field in JSON. This is not a strict limit, it does not have to be applied precisely.

input_format_json_named_tuples_as_objects​

Type: Bool

Default value: 1

Parse named tuple columns as JSON objects.

Enabled by default.

input_format_json_read_arrays_as_strings​

Type: Bool

Default value: 1

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_read_bools_as_numbers​

Type: Bool

Default value: 1

Allow parsing bools as numbers in JSON input formats.

Enabled by default.

input_format_json_read_bools_as_strings​

Type: Bool

Default value: 1

Allow parsing bools as strings in JSON input formats.

Enabled by default.

input_format_json_read_numbers_as_strings​

Type: Bool

Default value: 1

Allow parsing numbers as strings in JSON input formats.

Enabled by default.

input_format_json_read_objects_as_strings​

Type: Bool

Default value: 1

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_throw_on_bad_escape_sequence​

Type: Bool

Default value: 1

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.

input_format_json_try_infer_named_tuples_from_objects​

Type: Bool

Default value: 1

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_try_infer_numbers_from_strings​

Type: Bool

Default value: 0

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_use_string_type_for_ambiguous_paths_in_named_tuples_inference_from_objects​

Type: Bool

Default value: 0

Use String type instead of an exception in case of ambiguous paths in JSON objects during named tuples inference

input_format_json_validate_types_from_metadata​

Type: Bool

Default value: 1

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.

input_format_max_bytes_to_read_for_schema_inference​

Type: UInt64

Default value: 33554432

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

input_format_max_rows_to_read_for_schema_inference​

Type: UInt64

Default value: 25000

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

input_format_msgpack_number_of_columns​

Type: UInt64

Default value: 0

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

input_format_mysql_dump_map_column_names​

Type: Bool

Default value: 1

Match columns from table in MySQL dump and columns from ClickHouse table by names

input_format_mysql_dump_table_name​

Type: String

Default value:

Name of the table in MySQL dump from which to read data

input_format_native_allow_types_conversion​

Type: Bool

Default value: 1

Allow data types conversion in Native input format

input_format_native_decode_types_in_binary_format​

Type: Bool

Default value: 0

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

input_format_null_as_default​

Type: Bool

Default value: 1

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.

input_format_orc_allow_missing_columns​

Type: Bool

Default value: 1

Allow missing columns while reading ORC input formats

input_format_orc_case_insensitive_column_matching​

Type: Bool

Default value: 0

Ignore case when matching ORC columns with CH columns.

input_format_orc_dictionary_as_low_cardinality​

Type: Bool

Default value: 1

Treat ORC dictionary encoded columns as LowCardinality columns while reading ORC files.

input_format_orc_filter_push_down​

Type: Bool

Default value: 1

When reading ORC files, skip whole stripes or row groups based on the WHERE/PREWHERE expressions, min/max statistics or bloom filter in the ORC metadata.

input_format_orc_reader_time_zone_name​

Type: String

Default value: GMT

The time zone name for ORC row reader, the default ORC row reader's time zone is GMT.

input_format_orc_row_batch_size​

Type: Int64

Default value: 100000

Batch size when reading ORC stripes.

input_format_orc_skip_columns_with_unsupported_types_in_schema_inference​

Type: Bool

Default value: 0

Skip columns with unsupported types while schema inference for format ORC

input_format_orc_use_fast_decoder​

Type: Bool

Default value: 1

Use a faster ORC decoder implementation.

input_format_parquet_allow_missing_columns​

Type: Bool

Default value: 1

Allow missing columns while reading Parquet input formats

input_format_parquet_bloom_filter_push_down​

Type: Bool

Default value: 0

When reading Parquet files, skip whole row groups based on the WHERE expressions and bloom filter in the Parquet metadata.

input_format_parquet_case_insensitive_column_matching​

Type: Bool

Default value: 0

Ignore case when matching Parquet columns with CH columns.

input_format_parquet_enable_row_group_prefetch​

Type: Bool

Default value: 1

Enable row group prefetching during parquet parsing. Currently, only single-threaded parsing can prefetch.

input_format_parquet_filter_push_down​

Type: Bool

Default value: 1

When reading Parquet files, skip whole row groups based on the WHERE/PREWHERE expressions and min/max statistics in the Parquet metadata.

input_format_parquet_local_file_min_bytes_for_seek​

Type: UInt64

Default value: 8192

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

input_format_parquet_max_block_size​

Type: UInt64

Default value: 65409

Max block size for parquet reader.

input_format_parquet_prefer_block_bytes​

Type: UInt64

Default value: 16744704

Average block bytes output by parquet reader

input_format_parquet_preserve_order​

Type: Bool

Default value: 0

Avoid reordering rows when reading from Parquet files. Usually makes it much slower.

input_format_parquet_skip_columns_with_unsupported_types_in_schema_inference​

Type: Bool

Default value: 0

Skip columns with unsupported types while schema inference for format Parquet

input_format_parquet_use_native_reader​

Type: Bool

Default value: 0

When reading Parquet files, to use native reader instead of arrow reader.

input_format_protobuf_flatten_google_wrappers​

Type: Bool

Default value: 0

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

input_format_protobuf_skip_fields_with_unsupported_types_in_schema_inference​

Type: Bool

Default value: 0

Skip fields with unsupported types while schema inference for format Protobuf

input_format_record_errors_file_path​

Type: String

Default value:

Path of the file used to record errors while reading text formats (CSV, TSV).

input_format_skip_unknown_fields​

Type: Bool

Default value: 1

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:

Possible values:

  • 0 — Disabled.
  • 1 — Enabled.

input_format_try_infer_dates​

Type: Bool

Default value: 1

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​

Type: Bool

Default value: 1

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.

input_format_try_infer_datetimes_only_datetime64​

Type: Bool

Default value: 0

When input_format_try_infer_datetimes is enabled, infer only DateTime64 but not DateTime types

input_format_try_infer_exponent_floats​

Type: Bool

Default value: 0

Try to infer floats in exponential notation while schema inference in text formats (except JSON, where exponent numbers are always inferred)

input_format_try_infer_integers​

Type: Bool

Default value: 1

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_variants​

Type: Bool

Default value: 0

If enabled, ClickHouse will try to infer type Variant in schema inference for text formats when there is more than one possible type for column/array elements.

Possible values:

  • 0 — Disabled.
  • 1 — Enabled.

input_format_tsv_allow_variable_number_of_columns​

Type: Bool

Default value: 0

Ignore extra columns in TSV input (if file has more columns than expected) and treat missing fields in TSV input as default values

input_format_tsv_crlf_end_of_line​

Type: Bool

Default value: 0

If it is set true, file function will read TSV format with \r\n instead of \n.

input_format_tsv_detect_header​

Type: Bool

Default value: 1

Automatically detect header with names and types in TSV format

input_format_tsv_empty_as_default​

Type: Bool

Default value: 0

Treat empty fields in TSV input as default values.

input_format_tsv_enum_as_number​

Type: Bool

Default value: 0

Treat inserted enum values in TSV formats as enum indices.

input_format_tsv_skip_first_lines​

Type: UInt64

Default value: 0

Skip specified number of lines at the beginning of data in TSV format

input_format_tsv_skip_trailing_empty_lines​

Type: Bool

Default value: 0

Skip trailing empty lines in TSV format

input_format_tsv_use_best_effort_in_schema_inference​

Type: Bool

Default value: 1

Use some tweaks and heuristics to infer schema in TSV format

input_format_values_accurate_types_of_literals​

Type: Bool

Default value: 1

For Values format: when parsing and interpreting expressions using template, check actual type of literal to avoid possible overflow and precision issues.

input_format_values_deduce_templates_of_expressions​

Type: Bool

Default value: 1

For Values format: if the field could not be parsed by streaming parser, run SQL parser, deduce template of the SQL expression, try to parse all rows using template and then interpret expression for all rows.

input_format_values_interpret_expressions​

Type: Bool

Default value: 1

For Values format: if the field could not be parsed by streaming parser, run SQL parser and try to interpret it as SQL expression.

input_format_with_names_use_header​

Type: Bool

Default value: 1

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.

input_format_with_types_use_header​

Type: Bool

Default value: 1

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.

insert_distributed_one_random_shard​

Type: Bool

Default value: 0

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.

interval_output_format​

Type: IntervalOutputFormat

Default value: numeric

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.

See also:

output_format_arrow_compression_method​

Type: ArrowCompression

Default value: lz4_frame

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

output_format_arrow_fixed_string_as_fixed_byte_array​

Type: Bool

Default value: 1

Use Arrow FIXED_SIZE_BINARY type instead of Binary for FixedString columns.

output_format_arrow_low_cardinality_as_dictionary​

Type: Bool

Default value: 0

Enable output LowCardinality type as Dictionary Arrow type

output_format_arrow_string_as_string​

Type: Bool

Default value: 1

Use Arrow String type instead of Binary for String columns

output_format_arrow_use_64_bit_indexes_for_dictionary​

Type: Bool

Default value: 0

Always use 64 bit integers for dictionary indexes in Arrow format

output_format_arrow_use_signed_indexes_for_dictionary​

Type: Bool

Default value: 1

Use signed integers for dictionary indexes in Arrow format

output_format_avro_codec​

Type: String

Default value:

Compression codec used for output. Possible values: 'null', 'deflate', 'snappy', 'zstd'.

output_format_avro_rows_in_file​

Type: UInt64

Default value: 1

Max rows in a file (if permitted by storage)

output_format_avro_string_column_pattern​

Type: String

Default value:

For Avro format: regexp of String columns to select as AVRO string.

output_format_avro_sync_interval​

Type: UInt64

Default value: 16384

Sync interval in bytes.

output_format_binary_encode_types_in_binary_format​

Type: Bool

Default value: 0

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

output_format_binary_write_json_as_string​

Type: Bool

Default value: 0

Write values of JSON data type as JSON String values in RowBinary output format.

output_format_bson_string_as_string​

Type: Bool

Default value: 0

Use BSON String type instead of Binary for String columns.

output_format_csv_crlf_end_of_line​

Type: Bool

Default value: 0

If it is set true, end of line in CSV format will be \r\n instead of \n.

output_format_csv_serialize_tuple_into_separate_columns​

Type: Bool

Default value: 1

If it set to true, then Tuples in CSV format are serialized as separate columns (that is, their nesting in the tuple is lost)

output_format_decimal_trailing_zeros​

Type: Bool

Default value: 0

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

Disabled by default.

output_format_enable_streaming​

Type: Bool

Default value: 0

Enable streaming in output formats that support it.

Disabled by default.

output_format_json_array_of_rows​

Type: Bool

Default value: 0

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.

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_escape_forward_slashes​

Type: Bool

Default value: 1

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​

Type: Bool

Default value: 1

Serialize named tuple columns as JSON objects.

Enabled by default.

output_format_json_quote_64bit_floats​

Type: Bool

Default value: 0

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

Disabled by default.

output_format_json_quote_64bit_integers​

Type: Bool

Default value: 1

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.

output_format_json_quote_decimals​

Type: Bool

Default value: 0

Controls quoting of decimals in JSON output formats.

Disabled by default.

output_format_json_quote_denormals​

Type: Bool

Default value: 0

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

Possible values:

  • 0 — Disabled.
  • 1 — Enabled.

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_skip_null_value_in_named_tuples​

Type: Bool

Default value: 0

Skip key value pairs with null value when serialize named tuple columns as JSON objects. It is only valid when output_format_json_named_tuples_as_objects is true.

output_format_json_validate_utf8​

Type: Bool

Default value: 0

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.

output_format_markdown_escape_special_characters​

Type: Bool

Default value: 0

Escape special characters in Markdown

output_format_msgpack_uuid_representation​

Type: MsgPackUUIDRepresentation

Default value: ext

The way how to output UUID in MsgPack format.

output_format_native_encode_types_in_binary_format​

Type: Bool

Default value: 0

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

output_format_native_write_json_as_string​

Type: Bool

Default value: 0

Write data of JSON column as String column containing JSON strings instead of default native JSON serialization.

output_format_orc_compression_method​

Type: ORCCompression

Default value: zstd

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

output_format_orc_dictionary_key_size_threshold​

Type: Double

Default value: 0

For a string column in ORC output format, if the number of distinct values is greater than this fraction of the total number of non-null rows, turn off dictionary encoding. Otherwise dictionary encoding is enabled

output_format_orc_row_index_stride​

Type: UInt64

Default value: 10000

Target row index stride in ORC output format

output_format_orc_string_as_string​

Type: Bool

Default value: 1

Use ORC String type instead of Binary for String columns

output_format_parquet_batch_size​

Type: UInt64

Default value: 1024

Check page size every this many rows. Consider decreasing if you have columns with average values size above a few KBs.

output_format_parquet_compliant_nested_types​

Type: Bool

Default value: 1

In parquet file schema, use name 'element' instead of 'item' for list elements. This is a historical artifact of Arrow library implementation. Generally increases compatibility, except perhaps with some old versions of Arrow.

output_format_parquet_compression_method​

Type: ParquetCompression

Default value: zstd

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

output_format_parquet_data_page_size​

Type: UInt64

Default value: 1048576

Target page size in bytes, before compression.

output_format_parquet_fixed_string_as_fixed_byte_array​

Type: Bool

Default value: 1

Use Parquet FIXED_LENGTH_BYTE_ARRAY type instead of Binary for FixedString columns.

output_format_parquet_parallel_encoding​

Type: Bool

Default value: 1

Do Parquet encoding in multiple threads. Requires output_format_parquet_use_custom_encoder.

output_format_parquet_row_group_size​

Type: UInt64

Default value: 1000000

Target row group size in rows.

output_format_parquet_row_group_size_bytes​

Type: UInt64

Default value: 536870912

Target row group size in bytes, before compression.

output_format_parquet_string_as_string​

Type: Bool

Default value: 1

Use Parquet String type instead of Binary for String columns.

output_format_parquet_use_custom_encoder​

Type: Bool

Default value: 1

Use a faster Parquet encoder implementation.

output_format_parquet_version​

Type: ParquetVersion

Default value: 2.latest

Parquet format version for output format. Supported versions: 1.0, 2.4, 2.6 and 2.latest (default)

output_format_parquet_write_page_index​

Type: Bool

Default value: 1

Add a possibility to write page index into parquet files.

output_format_pretty_color​

Type: UInt64Auto

Default value: auto

Use ANSI escape sequences in Pretty formats. 0 - disabled, 1 - enabled, 'auto' - enabled if a terminal.

Type: UInt64

Default value: 1

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

Possible values:

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)─┘

Type: UInt64

Default value: 50

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.

output_format_pretty_grid_charset​

Type: String

Default value: UTF-8

Charset for printing grid borders. Available charsets: ASCII, UTF-8 (default one).

output_format_pretty_highlight_digit_groups​

Type: Bool

Default value: 1

If enabled and if output is a terminal, highlight every digit corresponding to the number of thousands, millions, etc. with underline.

output_format_pretty_max_column_pad_width​

Type: UInt64

Default value: 250

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

output_format_pretty_max_rows​

Type: UInt64

Default value: 10000

Rows limit for Pretty formats.

output_format_pretty_max_value_width​

Type: UInt64

Default value: 10000

Maximum width of value to display in Pretty formats. If greater - it will be cut.

output_format_pretty_max_value_width_apply_for_single_value​

Type: UInt64

Default value: 0

Only cut values (see the output_format_pretty_max_value_width setting) when it is not a single value in a block. Otherwise output it entirely, which is useful for the SHOW CREATE TABLE query.

output_format_pretty_row_numbers​

Type: Bool

Default value: 1

Add row numbers before each row for pretty output format

output_format_pretty_single_large_number_tip_threshold​

Type: UInt64

Default value: 1000000

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)

output_format_protobuf_nullables_with_google_wrappers​

Type: Bool

Default value: 0

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

output_format_schema​

Type: String

Default value:

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

output_format_sql_insert_include_column_names​

Type: Bool

Default value: 1

Include column names in INSERT query

output_format_sql_insert_max_batch_size​

Type: UInt64

Default value: 65409

The maximum number of rows in one INSERT statement.

output_format_sql_insert_quote_names​

Type: Bool

Default value: 1

Quote column names with '`' characters

output_format_sql_insert_table_name​

Type: String

Default value: table

The name of table in the output INSERT query

output_format_sql_insert_use_replace​

Type: Bool

Default value: 0

Use REPLACE statement instead of INSERT

output_format_tsv_crlf_end_of_line​

Type: Bool

Default value: 0

If it is set true, end of line in TSV format will be \r\n instead of \n.

output_format_values_escape_quote_with_quote​

Type: Bool

Default value: 0

If true escape ' with '', otherwise quoted with \'

output_format_write_statistics​

Type: Bool

Default value: 1

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

Enabled by default

precise_float_parsing​

Type: Bool

Default value: 0

Prefer more precise (but slower) float parsing algorithm

regexp_dict_allow_hyperscan​

Type: Bool

Default value: 1

Allow regexp_tree dictionary using Hyperscan library.

regexp_dict_flag_case_insensitive​

Type: Bool

Default value: 0

Use case-insensitive matching for a regexp_tree dictionary. Can be overridden in individual expressions with (?i) and (?-i).

regexp_dict_flag_dotall​

Type: Bool

Default value: 0

Allow '.' to match newline characters for a regexp_tree dictionary.

rows_before_aggregation​

Type: Bool

Default value: 0

When enabled, ClickHouse will provide exact value for rows_before_aggregation statistic, represents the number of rows read before aggregation

schema_inference_hints​

Type: String

Default value:

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 formatted 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​

Type: UInt64Auto

Default value: 1

Controls making inferred types Nullable in schema inference. If the setting is enabled, all inferred type will be Nullable, if disabled, the inferred type will never be Nullable, if set to auto, the inferred type will be Nullable only if the column contains NULL in a sample that is parsed during schema inference or file metadata contains information about column nullability.

schema_inference_mode​

Type: SchemaInferenceMode

Default value: default

Mode of schema inference. 'default' - assume that all files have the same schema and schema can be inferred from any file, 'union' - files can have different schemas and the resulting schema should be the a union of schemas of all files

show_create_query_identifier_quoting_rule​

Type: IdentifierQuotingRule

Default value: when_necessary

Set the quoting rule for identifiers in SHOW CREATE query

show_create_query_identifier_quoting_style​

Type: IdentifierQuotingStyle

Default value: Backticks

Set the quoting style for identifiers in SHOW CREATE query

type_json_skip_duplicated_paths​

Type: Bool

Default value: 0

When enabled, during parsing JSON object into JSON type duplicated paths will be ignored and only the first one will be inserted instead of an exception

validate_experimental_and_suspicious_types_inside_nested_types​

Type: Bool

Default value: 1

Validate usage of experimental and suspicious types inside nested types like Array/Map/Tuple