# CSV

This command instructs pgloader to load data from a CSV file. Because of the complexity of guessing the parameters of a CSV file, it’s simpler to instruct pgloader with how to parse the data in there, using the full pgloader command syntax and CSV specifications as in the following example.

## Using advanced options and a load command file

The command then would be:

    $ pgloader csv.load

And the contents of the `csv.load` file could be inspired from the following:

    LOAD CSV
       FROM 'GeoLiteCity-Blocks.csv' WITH ENCODING iso-646-us
            HAVING FIELDS
            (
               startIpNum, endIpNum, locId
            )
       INTO postgresql://user@localhost:54393/dbname
            TARGET TABLE geolite.blocks
            TARGET COLUMNS
            (
               iprange ip4r using (ip-range startIpNum endIpNum),
               locId
            )
       WITH truncate,
            skip header = 2,
            fields optionally enclosed by '"',
            fields escaped by backslash-quote,
            fields terminated by '\t'

        SET work_mem to '32 MB', maintenance_work_mem to '64 MB';

## Common Clauses

Please refer to Command Clauses for documentation about common clauses.

## CSV Source Specification: FROM

Filename where to load the data from. Accepts an ENCODING option. Use the –list-encodings option to know which encoding names are supported.

The filename may be enclosed by single quotes, and could be one of the following special values:

> - inline

>   The data is found after the end of the parsed commands. Any number of empty lines between the end of the commands and the beginning of the data is accepted.

> - stdin

>   Reads the data from the standard input stream.

> - FILENAME MATCHING

>   The whole matching clause must follow the following rule:

>       [ ALL FILENAMES | [ FIRST ] FILENAME ]
>       MATCHING regexp
>       [ IN DIRECTORY '...' ]

>   The matching clause applies given regular expression (see above for exact syntax, several options can be used here) to filenames. It’s then possible to load data from only the first match of all of them.

>   The optional IN DIRECTORY clause allows specifying which directory to walk for finding the data files, and can be either relative to where the command file is read from, or absolute. The given directory must exists.

## Fields Specifications

The FROM option also supports an optional comma separated list of field names describing what is expected in the CSV data file, optionally introduced by the clause HAVING FIELDS.

Each field name can be either only one name or a name following with specific reader options for that field, enclosed in square brackets and comma-separated. Supported per-field reader options are:

> - terminated by

>   > See the description of field terminated by below.

>   > The processing of this option is not currently implemented.

> - date format

>   When the field is expected of the date type, then this option allows to specify the date format used in the file.

>   Date format string are template strings modeled against the PostgreSQL to_char template strings support, limited to the following patterns:

>   > - YYYY, YYY, YY for the year part

>   > - MM for the numeric month part

>   > - DD for the numeric day part

>   > - HH, HH12, HH24 for the hour part

>   > - am, AM, a.m., A.M.

>   > - pm, PM, p.m., P.M.

>   > - MI for the minutes part

>   > - SS for the seconds part

>   > - MS for the milliseconds part (4 digits)

>   > - US for the microseconds part (6 digits)

>   > - unparsed punctuation signs: - . * # @ T / and space

>   Here’s an example of a date format specification:

>       column-name [date format 'YYYY-MM-DD HH24-MI-SS.US']

> - null if

>   > This option takes an argument which is either the keyword blanks or a double-quoted string.

>   > When blanks is used and the field value that is read contains only space characters, then it’s automatically converted to an SQL NULL value.

>   > When a double-quoted string is used and that string is read as the field value, then the field value is automatically converted to an SQL NULL value.

> - trim both whitespace, trim left whitespace, trim right whitespace

>   This option allows to trim whitespaces in the read data, either from both sides of the data, or only the whitespace characters found on the left of the streaing, or only those on the right of the string.

## CSV Loading Options: WITH

When loading from a CSV file, the following options are supported:

> - truncate

>   > When this option is listed, pgloader issues a TRUNCATE command against the PostgreSQL target table before reading the data file.

> - drop indexes

>   When this option is listed, pgloader issues DROP INDEX commands against all the indexes defined on the target table before copying the data, then CREATE INDEX commands once the COPY is done.

>   In order to get the best performance possible, all the indexes are created in parallel and when done the primary keys are built again from the unique indexes just created. This two step process allows creating the primary key index in parallel with the other indexes, as only the ALTER TABLE command needs an access exclusive lock on the target table.

> - disable triggers

>   When this option is listed, pgloader issues an ALTER TABLE … DISABLE TRIGGER ALL command against the PostgreSQL target table before copying the data, then the command ALTER TABLE … ENABLE TRIGGER ALL once the COPY is done.

>   This option allows loading data into a pre-existing table ignoring the foreign key constraints and user defined triggers and may result in invalid foreign key constraints once the data is loaded. Use with care.

> - skip header

>   Takes a numeric value as argument. Instruct pgloader to skip that many lines at the beginning of the input file.

> - csv header

>   Use the first line read after skip header as the list of csv field names to be found in the CSV file, using the same CSV parameters as for the CSV data.

> - trim unquoted blanks

>   When reading unquoted values in the CSV file, remove the blanks found in between the separator and the value. That behaviour is the default.

> - keep unquoted blanks

>   When reading unquoted values in the CSV file, keep blanks found in between the separator and the value.

> - fields optionally enclosed by

>   Takes a single character as argument, which must be found inside single quotes, and might be given as the printable character itself, the special value t to denote a tabulation character, the special value ' to denote a single-quote, or 0x then an hexadecimal value read as the ASCII code for the character.

>   The following options specify the same enclosing character, a single quote:

>       fields optionally enclosed by '\''
>       fields optionally enclosed by '0x27'

>   This character is used as the quoting character in the CSV file, and defaults to double-quote.

> - fields not enclosed

>   By default, pgloader will use the double-quote character as the enclosing character. If you have a CSV file where fields are not enclosed and are using double-quote as an expected ordinary character, then use the option fields not enclosed for the CSV parser to accept those values.

> - fields escaped by

>   Takes either the special value backslash-quote or double-quote, or any value supported by the fields terminated by option (see below). This value is used to recognize escaped field separators when they are to be found within the data fields themselves. Defaults to double-quote.

> - csv escape mode

>   Takes either the special value quote (the default) or following and allows the CSV parser to parse either only escaped field separator or any character (including CSV data) when using the following value.

> - fields terminated by

>   Takes a single character as argument, which must be found inside single quotes, and might be given as the printable character itself, the special value t to denote a tabulation character, or 0x then an hexadecimal value read as the ASCII code for the character.

>   This character is used as the field separator when reading the CSV data.

> - lines terminated by

>   Takes a single character as argument, which must be found inside single quotes, and might be given as the printable character itself, the special value t to denote a tabulation character, or 0x then an hexadecimal value read as the ASCII code for the character.

>   This character is used to recognize end-of-line condition when reading the CSV data.