COPY TO

You can use the COPY TO statement to export table data to a file.

See also

Data manipulation: Import and export

SQL syntax: COPY FROM

Synopsis

  1. COPY table_ident [ PARTITION ( partition_column = value [ , ... ] ) ]
  2.                  [ ( column [ , ...] ) ]
  3.                  [ WHERE condition ]
  4.                  TO DIRECTORY output_uri
  5.                  [ WITH ( copy_parameter [= value] [, ... ] ) ]

Description

The COPY TO command exports the contents of a table to one or more files into a given directory with unique filenames. Each node with at least one shard of the table will export its contents onto their local disk.

The created files are JSON formatted and contain one table row per line and, due to the distributed nature of CrateDB, will remain on the same nodes where the shards are.

Here’s an example:

  1. cr> COPY quotes TO DIRECTORY '/tmp/' with (compression='gzip');
  2. COPY OK, 3 rows affected ...

Note

Currently only user tables can be exported. System tables like sys.nodes and blob tables don’t work with the COPY TO statement.

Parameters

table_ident

The name (optionally schema-qualified) of the table to be exported.

column

(optional) A list of column expressions that should be exported.

Note

When declaring columns, this changes the output to JSON list format, which is currently not supported by the COPY FROM statement.

Clauses

PARTITION

If the table is partitioned, the optional PARTITION clause can be used to export data from a one partition exclusively.

  1. [ PARTITION ( partition_column = value [ , ... ] ) ]

partition_column

One of the column names used for table partitioning.

value

The respective column value.

All partition columns (specified by the PARTITIONED BY clause) must be listed inside the parentheses along with their respective values using the partition_column = value syntax (separated by commas).

Because each partition corresponds to a unique set of partition column row values, this clause uniquely identifies a single partition to export.

Tip

The SHOW CREATE TABLE statement will show you the complete list of partition columns specified by the PARTITIONED BY clause.

Caution

The exported data doesn’t contain the partition columns or the corresponding values because they are not part of the partitioned tables.

If COPY TO is used on a partitioned table without the PARTITION clause, the partition columns and values will be included in the rows of the exported files. If a partition column is a generated column, it will not be included even if the PARTITION clause is missing.

WHERE

The WHERE clauses use the same syntax as SELECT statements, allowing partial exports. (see WHERE clause for more information).

TO

The TO clause allows you to specify an output location.

  1. TO DIRECTORY output_uri

Parameters

output_uri

An expression must evaluate to a string literal that is a well-formed URI. URIs must use one of the supported URI schemes.

Note

If the URI scheme is missing, CrateDB assumes the value is a pathname and will prepend the file URI scheme (i.e., file://). So, for example, CrateDB will convert /tmp/file.json to file:///tmp/file.json.

URI schemes

CrateDB supports the following URI schemes:

file

You can use the file:// scheme to specify an absolute path to a file on the local file system.

For example:

  1. file:///path/to/dir

Tip

If you are running CrateDB inside a container, the file must be inside the container. If you are using Docker, you may have to configure a Docker volume to accomplish this.

Tip

If you are using Microsoft Windows, you must include the drive letter in the file URI.

For example:

  1. file://C:\/tmp/import_data/quotes.json

Consult the Windows documentation for more information.

s3

You can use the s3:// scheme to access buckets on the Amazon Simple Storage Service (Amazon S3).

For example:

  1. s3://[<accesskey>:<secretkey>@]<bucketname>/<path>

Tip

A secretkey provided by Amazon Web Services can contain characters such as ‘/’, ‘+’ or ‘=’. These characters must be URL encoded. For a detailed explanation read the official AWS documentation.

To escape a secret key, you can use a snippet like this:

  1. sh$ python -c "from getpass import getpass; from urllib.parse import quote_plus; print(quote_plus(getpass('secret_key: ')))"

This will prompt for the secret key and print the encoded variant.

Additionally, versions prior to 0.51.x use HTTP for connections to S3. Since 0.51.x these connections are using the HTTPS protocol. Please make sure you update your firewall rules to allow outgoing connections on port 443.

WITH

You can use the optional WITH clause to specify copy parameter values.

  1. [ WITH ( copy_parameter [= value] [, ... ] ) ]

The WITH clause supports the following copy parameters:

compression

Define if and how the exported data should be compressed.

By default the output is not compressed.

Possible values for the compression setting are:

gzip

Use gzip to compress the data output.

format

Optional parameter to override default output behavior.

Possible values for the format settings are:

json_object

Each row in the result set is serialized as JSON object and written to an output file where one line contains one object. This is the default behavior if no columns are defined. Use this format to import with COPY FROM.

json_array

Each row in the result set is serialized as JSON array, storing one array per line in an output file. This is the default behavior if columns are defined.