COPY TO
Export table contents to files on CrateDB node machines.
Table of Contents
Synopsis
COPY table_ident [ PARTITION ( partition_column = value [ , ... ] ) ]
[ ( column [ , ...] ) ]
[ WHERE condition ]
TO DIRECTORY output_uri
[ 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.
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
Declaring columns changes the output to JSON list format, which is currently not supported by the COPY FROM statement.
Clauses
WHERE
WHERE
clauses use the same syntax as SELECT
statements, allowing partial exports. (see WHERE Clause for more information).
Output URI
The output_uri
can be any expression evaluating to a string.
The resulting string should be a valid URI of one of the supporting schemes:
file://
s3://[<accesskey>:<secretkey>@]<bucketname>/<path>
If no scheme is given (e.g.: ‘/path/to/dir’) the default uri-scheme file://
will be used.
Note
A secretkey
provided by Amazon Web Service can contain characters such as ‘/’, ‘+’ or ‘=’. Such characters must be URI encoded. The same encoding as in s3 applies.
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
.
Clauses
PARTITION
If the table is partitioned this clause can be used to only export data from a specific partition.
The exported data doesn’t contain the partition columns or values as they are not part of the partitioned tables.
[ PARTITION ( partition_column = value [ , ... ] ) ]
partition_column: | The name of the column by which the table is partitioned. All partition columns that were part of the PARTITIONED BY of the CREATE TABLE statement must be specified. |
---|---|
value: | The columns value. |
Note
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.
WITH
The optional WITH clause can specify parameters for the copy statement.
[ WITH ( copy_parameter [= value] [, ... ] ) ]
Possible copy_parameters are:
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. |