COPY FROM

COPY ... FROM is a statement that allows reading data from a file into a table.

This is the recommended method for bulk loading CSV files into SQream DB.

In general, COPY moves data between file-system files and SQream DB tables.

Note

Permissions

The role must have the INSERT permission to the destination table.

Syntax

copy_from_stmt ::= COPY ( [schema name.]table_name ) FROM 'filepath_spec'
     [ [ WITH ] copy_opt [ ...] ]
;

schema_name ::= identifier

table_name ::= identifier

copy_opt ::=
   | OFFSET N
   | LIMIT N
   | DELIMITER '{ delimiter }'
   | RECORD DELIMITER '{ record delimiter }'
   | ERROR_LOG 'local filepath'
   | ERROR_VERBOSITY { 0 | 1 }
   | STOP AFTER N ERRORS
   | PARSERS { '[column_name=parser_format, ...]' }
   | AWS_ID '{ AWS ID }'
   | AWS_SECRET '{ AWS secret }'

filepath_spec ::=
   filename
   | directory path
   | S3 URI
   | HDFS URI

N ::= positive integer

Elements

Parameter Default value Description
[schema_name.]table_name None Table to copy data into
filepath_spec None A path on the local filesystem, S3, or HDFS URI. For example, /tmp/foo.csv, s3://my-bucket/foo.csv, or hdfs://my-namenode:8020/foo.csv. The local path must be an absolute path that SQream DB can access. Wildcards are premitted in this field
OFFSET 1 The row number to start with. The first row is 1.
LIMIT Unlimited When specified, tells SQream DB to stop loading after the specified number of rows.
DELIMITER ',' Specifies the field terminator - the character or characters that separates fields or columns columns within each row of the file
RECORD DELIMITER \n (UNIX style newline) Specifies the row terminator - the character that separates lines or rows, also known as a new line separator.
ERROR_LOG Disabled When used, the COPY process will ignore rows that can’t be parsed. Errors will be written to the file specified by the ERROR_LOG parameter.
ERROR_VERBOSITY 1 Controls the verbosity of the ERROR_LOG. When set to 0, only the rejected rows are saved to the ERROR_LOG file. When set to 1 the error message is logged for every rejected row.
STOP AFTER N ERRORS 1000000 Specifies the threshold of rejected rows. When used with ERROR_LOG, the COPY FROM command will roll back the transaction if the threshold N is reached.
PARSERS DEFAULT for every column Allows specifying a non-default date formats for specific columns
AWS_ID, AWS_SECRET None Specifies the authentication details for secured S3 buckets

Supported date formats

Supported date parsers
Name Pattern Examples
ISO8601, DEFAULT YYYY-MM-DD [hh:mm:ss[.SSS]] 2017-12-31 11:12:13.456, 2018-11-02 11:05:00, 2019-04-04
ISO8601C YYYY-MM-DD [hh:mm:ss[:SSS]] 2017-12-31 11:12:13:456
DMY DD/MM/YYYY [hh:mm:ss[.SSS]] 31/12/2017 11:12:13.123
YMD YYYY/MM/DD [hh:mm:ss[.SSS]] 2017/12/31 11:12:13.678
MDY MM/DD/YYYY [hh:mm:ss[.SSS]] 12/31/2017 11:12:13.456
YYYYMMDD YYYYMMDD[hh[mm[ss[SSS]]]] 20171231111213456
YYYY-M-D YYYY-M-D[ h:m[:s[.S]]] 2017-9-10 10:7:21.1 (optional leading zeroes)
YYYY/M/D YYYY/M/D[ h:m[:s[.S]]] 2017/9/10 10:7:21.1 (optional leading zeroes)
DD-mon-YYYY DD-mon-YYYY[ hh:mm[:ss[.SSS]]] 31-Dec-2017 11:12:13.456
YYYY-mon-DD YYYY-mon-DD[ hh:mm[:ss[.SSS]]] 2017-Dec-31 11:12:13.456
Pattern Description
YYYY four digit year representation (0000-9999)
MM two digit month representation (01-12)
DD two digit day of month representation (01-31)
m short month representation (Jan-Dec)
a short day of week representation (Sun-Sat).
hh two digit 24 hour representation (00-23)
h two digit 12 hour representation (00-12)
P uppercase AM/PM representation
mm two digit minute representation (00-59)
ss two digit seconds representation (00-59)
SSS 3 digits fraction representation for milliseconds (000-999)

Note

These date patterns are not the same as date parts used in the DATEPART function.

Supported field delimiters

Field delimiters can be one or more characters.

Multi-character delimiters

SQream DB supports multi-character field delimiters, sometimes found in non-standard files.

A multi-character delimiter can be specified. For example, DELIMITER '%%', DELIMITER '{~}', etc.

Printable characters

Any printable ASCII character (or characters) can be used as a delimiter without special syntax. The default CSV field delimiter is a comma (,).

A printable character is any ASCII character in the range 32 - 126.

Literal quoting rules apply with delimiters. For example, to use ' as a field delimiter, use DELIMITER ''''

Non-printable characters

A non-printable character (1 - 31, 127) can be used in its octal form.

A tab can be specified by escaping it, for example \t. Other non-printable characters can be specified using their octal representations, by using the E'\000' format, where 000 is the octal value of the character.

For example, ASCII character 15, known as “shift in”, can be specified using E'\017'.

Capturing rejected rows

Prior to the column process and storage, the COPY command parses the data. Whenever the data can’t be parsed because it is improperly formatted or doesn’t match the data structure, the entire record (or row) will be rejected.

../../../../_images/copy_from_rejected_rows.png
  1. When ERROR_LOG is not used, the COPY command will stop and roll back the transaction upon the first error.
  2. When ERROR_LOG is set and ERROR_VERBOSITY is set to 1 (default), all errors and rejected rows are saved to the file path specified.
  3. When ERROR_LOG is set and ERROR_VERBOSITY is set to 0, rejected rows are saved to the file path specified, but errors are not logged. This is useful for replaying the file later.

CSV support

By default, SQream DB’s CSV parser can handle RFC 4180 standard CSVs , but can also be modified to support non-standard CSVs (with multi-character delimiters, unquoted fields, etc).

All CSV files shoudl be prepared according to these recommendations:

  • Files are UTF-8 or ASCII encoded

  • Field delimiter is an ASCII character or characters

  • Record delimiter, also known as a new line separator, is a Unix-style newline (\n), DOS-style newline (\r\n), or Mac style newline (\r).

  • Fields are optionally enclosed by double-quotes, or mandatory quoted if they contain one of the following characters:

    • The record delimiter or field delimiter
    • A double quote character
    • A newline
  • If a field is quoted, any double quote that appears must be double-quoted (similar to the string literals quoting rules. For example, to encode What are "birds"?, the field should appear as "What are ""birds""?".

    Other modes of escaping are not supported (e.g. 1,"What are \"birds\"?" is not a valid way of escaping CSV values).

Null markers

NULL values can be marked in two ways in the CSV:

  • An explicit null marker. For example, col1,\N,col3
  • An empty field delimited by the field delimiter. For example, col1,,col3

Note

If a text field is quoted but contains no content ("") it is considered an empty text field. It is not considered NULL.

Examples

Loading a standard CSV file

COPY table_name FROM 'file.csv';

Loading a PSV (pipe separated value) file

COPY table_name FROM 'file.psv' WITH DELIMITER '|';

Loading a TSV (tab separated value) file

COPY table_name FROM 'file.tsv' WITH DELIMITER '\t';

Loading a text file with non-printable delimiter

In the file below, the separator is DC1, which is represented by ASCII 17 decimal or 021 octal.

COPY table_name FROM 'file.txt' WITH DELIMITER E'\021';

Loading a text file with multi-character delimiters

In the file below, the separator is ^|.

COPY table_name FROM 'file.txt' WITH DELIMITER '^|';

In the file below, the separator is '|. The quote character has to be repeated, as per the literal quoting rules.

COPY table_name FROM 'file.txt' WITH DELIMITER ''''|';

Loading files with a header row

Use OFFSET to skip rows.

Note

When loading multiple files (e.g. with wildcards), this setting affects each file separately.

COPY  table_name FROM 'filename.psv' WITH DELIMITER '|' OFFSET  2;

Loading files formatted for Windows (\r\n)

COPY table_name FROM 'filename.psv' WITH DELIMITER '|' RECORD DELIMITER '\r\n';

Loading a file from a public S3 bucket

Note

The bucket must be publicly available and objects can be listed

COPY nba FROM 's3://sqream-demo-data/nba.csv' WITH OFFSET 2 RECORD DELIMITER '\r\n';

Loading files from an authenticated S3 bucket

COPY nba FROM 's3://secret-bucket/*.csv' WITH OFFSET 2 RECORD DELIMITER '\r\n' AWS_ID '12345678' AWS_SECRET 'super_secretive_secret';

Saving rejected rows to a file

Note

When loading multiple files (e.g. with wildcards), this error threshold is for the entire transaction.

COPY table_name FROM 'filename.psv' WITH DELIMITER '|'
                                      ERROR_LOG  '/temp/load_error.log' -- Save error log
                                      ERROR_VERBOSITY 0; -- Only save rejected rows
COPY  table_name  FROM  'filename.csv'  WITH  delimiter  '|'
                                         ERROR_LOG  '/temp/load_err.log' -- Save error log
                                         OFFSET 2 -- skip header row
                                         LIMIT  100 -- Only load 100 rows
                                         STOP AFTER 5 ERRORS; -- Stop the load if 5 errors reached

Load CSV files from a set of directories

COPY  table_name  from  '/path/to/files/2019_08_*/*.csv';

Rearrange destination columns

When the source of the files does not match the table structure, tell the COPY command what the order of columns should be

COPY table_name (fifth, first, third) FROM '/path/to/files/*.csv';

Note

Any column not specified will revert to its default value or NULL value if nullable

Loading non-standard dates

If files contain dates not formatted as ISO8601, tell COPY how to parse the column. After parsing, the date will appear as ISO8601 inside SQream DB.

These are called date parsers. You can find the supported dates in the ‘Supported date parsers’ table above

In this example, date_col1 and date_col2 in the table are non-standard. date_col3 is mentioned explicitly, but can be left out. Any column that is not specified is assumed to be ISO8601.

COPY table_name FROM '/path/to/files/*.csv' WITH PARSERS 'date_col1=YMD,date_col2=MDY,date_col3=default';