CSV

This guide covers ingesting data from CSV files into SQream DB using the COPY FROM method.

Foreign Data Wrapper Prerequisites 

Before proceeding, ensure the following Foreign Data Wrapper (FDW) prerequisites:

File Existence: Verify that the file you are ingesting data from exists at the specified path.
Path Accuracy: Confirm that all path elements are present and correctly spelled. Any inaccuracies may lead to data retrieval issues.
Bucket Access Permissions: Ensure that you have the necessary access permissions to the bucket from which you are ingesting data. Lack of permissions can hinder the data retrieval process.
Wildcard Accuracy: If using wildcards, double-check their spelling and configuration. Misconfigured wildcards may result in unintended data ingestion.

Prepare CSVs 

Prepare the source CSVs, with the following requirements:

Files should be a valid CSV. 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).
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 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.

Place CSVs where SQream DB workers can access 

During data load, the COPY FROM command can run on any worker (unless explicitly speficied with the Workload Manager). It is important that every node has the same view of the storage being used - meaning, every SQream DB worker should have access to the files.

For files hosted on NFS, ensure that the mount is accessible from all servers.
For HDFS, ensure that SQream DB servers can access the HDFS name node with the correct user-id. See our HDFS Environment guide for more information.
For S3, ensure network access to the S3 endpoint. See our Amazon Web Services guide for more information.

Figure out the table structure 

Prior to loading data, you will need to write out the table structure, so that it matches the file structure.

For example, to import the data from nba.csv, we will first look at the file:

nba.csv
Name	Team	Number	Position	Age	Height	Weight	College	Salary
Avery Bradley	Boston Celtics	0	PG	25	44714	180	Texas	7730337
Jae Crowder	Boston Celtics	99	SF	25	44718	235	Marquette	6796117
John Holland	Boston Celtics	30	SG	27	44717	205	Boston University
R.J. Hunter	Boston Celtics	28	SG	22	44717	185	Georgia State	1148640
Jonas Jerebko	Boston Celtics	8	PF	29	44722	231		5000000
Amir Johnson	Boston Celtics	90	PF	29	44721	240		12000000
Jordan Mickey	Boston Celtics	55	PF	21	44720	235	LSU	1170960
Kelly Olynyk	Boston Celtics	41	C	25	36708	238	Gonzaga	2165160
Terry Rozier	Boston Celtics	12	PG	22	44714	190	Louisville	1824360

The file format in this case is CSV, and it is stored as an S3 object.
The first row of the file is a header containing column names.
The record delimiter was a DOS newline (\r\n).
The file is stored on S3, at s3://sqream-demo-data/nba.csv.

We will make note of the file structure to create a matching CREATE TABLE statement.

CREATE TABLE
  nba (
        Name text(40),
        Team text(40),
        Number tinyint,
        Position text(2),
        Age tinyint,
        Height text(4),
        Weight real,
        College text(40),
        Salary float
  );

Bulk load the data with COPY FROM 

The CSV is a standard CSV, but with two differences from SQream DB defaults:

The record delimiter is not a Unix newline (\n), but a Windows newline (\r\n)
The first row of the file is a header containing column names, which we’ll want to skip.

COPY
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    RECORD_DELIMITER = '\r\n',
    OFFSET = 2;
);

Repeat steps 3 and 4 for every CSV file you want to import.

Loading a standard CSV File From a Local Filesystem

COPY
  table_name
FROM
WRAPPER
  csv_fdw
OPTIONS (LOCATION = '/home/rhendricks/file.csv');

Loading a PSV (pipe separated value) file

COPY
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    DELIMITER = '|'
);

Loading a TSV (tab separated value) file

COPY
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    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
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    DELIMITER = E'\021'
);

Loading a Text File With Multi-Character Delimiters

In the file below, the separator is '|.

COPY
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    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
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    DELIMITER = '|',
    OFFSET  2
);

Loading Files Formatted for Windows (`\r\n`)

COPY
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    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
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    OFFSET = 2,
    RECORD_DELIMITER = '\r\n'
);

Loading files from an authenticated S3 bucket

COPY
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    OFFSET = 2,
    RECORD_DELIMITER = '\r\n',
    AWS_ID = '12345678',
    AWS_SECRET = 'super_secretive_secret'
);

Loading files from an HDFS storage

COPY
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 'hdfs://hadoop-nn.piedpiper.com/rhendricks/*.csv',
    OFFSET = 2,
    RECORD DELIMITER = '\r\n'
);

Saving rejected rows to a file

See Unsupported Field Delimiters for more information about the error handling capabilities of COPY FROM.

COPY
  t
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = '/tmp/file.psv',
    DELIMITER = '|',
    CONTINUE_ON_ERROR = True,
    ERROR_LOG = '/temp/load_error.log' -- Save error log,
    REJECTED_DATA = '/temp/load_rejected.log' -- Only save rejected rows
  );

Stopping the load if a certain amount of rows were rejected

COPY
  table
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION =  'filename.csv',
    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

Use glob patterns (wildcards) to load multiple files to one table.

COPY
  table
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION =  '/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 (fifth, first, third)
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION =  '/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.

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
  nba
FROM
WRAPPER
  csv_fdw
OPTIONS
  (
    LOCATION = 's3://sqream-docs/nba.csv',
    DATETIME_FORMAT = 'date_col1=YMD,date_col2=MDY,date_col3=default'
);

Tip

The full list of supported date formats can be found under the Supported date formats section of the COPY FROM reference.

CSV

Foreign Data Wrapper Prerequisites

Prepare CSVs

Place CSVs where SQream DB workers can access

Figure out the table structure

Bulk load the data with COPY FROM

Loading a standard CSV File From a Local Filesystem

Loading a PSV (pipe separated value) file

Loading a TSV (tab separated value) file

Loading a text file with non-printable delimiter

Loading a Text File With Multi-Character Delimiters

Loading Files With a Header Row

Loading Files Formatted for Windows (\r\n)

Loading a File From a Public S3 Bucket

Loading files from an authenticated S3 bucket

Loading files from an HDFS storage

Saving rejected rows to a file

Stopping the load if a certain amount of rows were rejected

Load CSV files from a set of directories

Rearrange destination columns

Loading non-standard dates

Foreign Data Wrapper Prerequisites 

Prepare CSVs 

Place CSVs where SQream DB workers can access 

Figure out the table structure 

Bulk load the data with COPY FROM 

Loading Files Formatted for Windows (`\r\n`)