TiDB Lightning supports reading CSV (comma-separated values) data source, as well as other delimited format such as TSV (tab-separated values).
A CSV file representing a whole table must be named as
db_name.table_name.csv. This will be restored as a table
table_name inside the database
If a table spans multiple CSV files, they should be named like
The file extension must be
*.csv, even if the content is not separated by commas.
CSV files are schema-less. To import them into TiDB, a table schema must be provided. This could be done either by:
- Providing a file named
CREATE TABLEDDL statement
- Creating the empty tables directly in TiDB in the first place, and then setting
[mydumper] no-schema = truein
The CSV format can be configured in
tidb-lightning.toml under the
[mydumper.csv] section. Most settings have a corresponding option in the MySQL
LOAD DATA statement.
[mydumper.csv] # Separator between fields, should be an ASCII character. separator = ',' # Quoting delimiter, can either be an ASCII character or empty string. delimiter = '"' # Whether the CSV files contain a header. # If `header` is true, the first line will be skipped. header = true # Whether the CSV contains any NULL value. # If `not-null` is true, all columns from CSV cannot be NULL. not-null = false # When `not-null` is false (that is, CSV can contain NULL), # fields equal to this value will be treated as NULL. null = '\N' # Whether to interpret backslash escapes inside fields. backslash-escape = true # If a line ends with a separator, remove it. trim-last-separator = false
Defines the field separator.
Must be a single ASCII character.
Corresponds to the
FIELDS TERMINATED BYoption in the LOAD DATA statement.
Defines the delimiter used for quoting.
delimiteris empty, all fields are unquoted.
'"'quote fields with double-quote, same as RFC 4180
Corresponds to the
FIELDS ENCLOSED BYoption in the
- Whether all CSV files contain a header row.
headeris true, the first row will be used as the column names. If
headeris false, the first row is not special and treated as an ordinary data row.
not-nullsetting controls whether all fields are non-nullable.
not-nullis false, the string specified by
nullwill be transformed to the SQL NULL instead of a concrete value.
Quoting will not affect whether a field is null.
For example, with the CSV file:A,B,C \N,"\N",
In the default settings (
not-null = false; null = '\N'), the columns
Bare both converted to NULL after importing to TiDB. The column
Cis simply the empty string
''but not NULL.
Whether to interpret backslash escapes inside fields.
backslash-escapeis true, the following sequences are recognized and transformed:
Sequence Converted to
Null character (U+0000)
Line feed (U+000A)
Carriage return (U+000D)
Windows EOF (U+001A)
In all other cases (for example,
\") the backslash is simply stripped, leaving the next character (
") in the field. The character left has no special roles (for example, delimiters) and is just an ordinary character.
Quoting will not affect whether backslash escapes are interpreted.
Corresponds to the
FIELDS ESCAPED BY '\'option in the
Treats the field
separatoras a terminator, and removes all trailing separators.
For example, with the CSV file:A,,B,,
trim-last-separator = false, this is interpreted as a row of 5 fields
('A', '', 'B', '', '').
trim-last-separator = true, this is interpreted as a row of 3 fields
('A', '', 'B').
TiDB Lightning does not support every option supported by the
LOAD DATA statement. Some examples:
- The line terminator must only be CR (
\r), LF (
\n) or CRLF (
\r\n), which means
LINES TERMINATED BYis not customizable.
- There cannot be line prefixes (
LINES STARTING BY).
- The header cannot be simply skipped (
IGNORE n LINES), it must be valid column names if present.
- Delimiters and separators can only be a single ASCII character.
The default setting is already tuned for CSV following RFC 4180.
[mydumper.csv] separator = ',' delimiter = '"' header = true not-null = false null = '\N' backslash-escape = true trim-last-separator = false
ID,Region,Count 1,"East",32 2,"South",\N 3,"West",10 4,"North",39
[mydumper.csv] separator = "\t" delimiter = '' header = true not-null = false null = 'NULL' backslash-escape = false trim-last-separator = false
ID Region Count 1 East 32 2 South NULL 3 West 10 4 North 39
[mydumper.csv] separator = '|' delimiter = '' header = false not-null = true backslash-escape = false trim-last-separator = true
1|East|32| 2|South|0| 3|West|10| 4|North|39|