EXPORT TO DELIMITED

Exports a table, columns from a table, or query results to delimited files.

Exports a table, columns from a table, or query results to delimited files. The files can be read back in using DELIMITED (parser). Several exporter parameters have corresponding parser parameters, allowing you to change delimiters, null indicators, and other formatting.

There are some limitations on the queries you can use in an export statement. See Query Restrictions.

You can export data stored in Vertica in ROS format and data from external tables.

This statement returns the number of rows written and logs information about exported files in a system table. See Monitoring exports.

During an export to HDFS or an NFS mount point, Vertica writes files to a temporary directory in the same location as the destination and renames the directory when the export is complete. Do not attempt to use the files in the temporary directory. During an export to S3, GCS, or Azure, Vertica writes files directly to the destination path, so you must wait for the export to finish before reading the files. For more information, see Exporting to object stores.

Syntax


EXPORT [ /*+LABEL (label-string)*/ ] TO DELIMITED ( directory=path[, param=value [,...] ]
   [ OVER (over-clause ) ] AS SELECT query-expression

Parameters

LABEL

Assigns a label to a statement to identify it for profiling and debugging.

directory

The destination directory for the output files. The directory must not exist, and the current user must have permission to write it. The destination can be on any of the following file systems:

HDFS file system
S3 object store
Google Cloud Storage (GCS) object store
Azure Blob Storage object store
Linux file system, either an NFS mount or local storage on each node

filename

If specified, all output is written to a single file of this name in the location specified by directory. While the query can be processed by multiple nodes, only a single node generates the output data. The fileSizeMB parameter is ignored, and the query cannot use partitioning in the OVER() clause.

addHeader

Boolean, specifies whether to add a header row to the beginning of each file.

Default: false

delimiter

Column delimiter character. To produce CSV in accordance with RFC 4180, set the delimiter character to , (comma).

Default: | (vertical bar)

recordTerminator

Character that marks the record end.

Default: \n

enclosedBy

Character to use to enclose string and date/time data. If you omit this parameter, no character encloses these data types.

Default: '' (empty string)

escapeAs

Character to use to escape values in exported data that must be escaped, including the enclosedBy value.

Default: \ (backslash)

nullAs

String to represent null values in the data. If this parameter is included, the exporter exports all null values as this value. Otherwise, the exporter exports null values as zero-length strings.

binaryTypesFormat

Format for exported binary data type (BINARY, VARBINARY, and LONG VARBINARY) values, one of the following:

Default: Printable ASCII characters where possible and escaped octal representations of the non-printable bytes. The DELIMITED parser reads this format.
Hex: Base 16 (hexadecimal) representation; value is preceded by '0x' and bytes are not escaped.
Octal: Base 8 (octal) representation, without escaping.
Bitstring: Binary representation, without escaping.

For example, the value a\000b\001c can be exported as follows:

Default (assuming an escape character of \): a\\000b\\001c
Hex: 0x6100620163
Octal: 141000142001143
Bitstring: 0110000100000000011000100000000101100011

compression

Compression type, one of:

Uncompressed
BZip
GZip

Default: Uncompressed

fileExtension

Output file extension. If using compression, a compression-specific extension such as .bz2 is appended.

Default: csv

fileSizeMB

The maximum file size of a single output file. This value is a hint, not a hard limit. A value of 0 specifies no limit. If filename is also specified, fileSizeMB is ignored.

This value affects the size of individual output files, not the total output size. For smaller values, Vertica divides the output into more files; all data is still exported.

Default: 10GB

fileMode

For writes to HDFS only, permission to apply to all exported files. You can specify the value in Unix octal format (such as 665) or user-group-other format—for example, rwxr-xr-x. The value must be formatted as a string even if using the octal format.

Valid octal values range between 0 and 1777, inclusive. See HDFS Permissions in the Apache Hadoop documentation.

When writing files to any destination other than HDFS, this parameter has no effect.

Default: 660, regardless of the value of fs.permissions.umask-mode in hdfs-site.xml.

dirMode

For writes to HDFS only, permission to apply to all exported directories. Values follow the same rules as those for fileMode. Further, you must give the Vertica HDFS user full permission, at least rwx------ or 700.

When writing files to any destination other than HDFS, this parameter has no effect.

Default: 755, regardless of the value of fs.permissions.umask-mode in hdfs-site.xml.

Arguments

over-clause

Specifies how to partition table data using PARTITION BY. Within partitions you can sort using ORDER BY. See SQL analytics. This clause may contain column references but not expressions.

If you partition data, Vertica creates a Hive-style partition directory structure, transforming column names to lowercase. See Using partition columns for a description of the directory structure. If you use the fileName parameter, you cannot use partitioning. Not all parsers can read partition columns as columns.

If you omit this clause, Vertica optimizes for maximum parallelism.

query-expression

Specifies the data to export. See Query Restrictions for important limitations.

Privileges

Non-superusers:

Source table: SELECT
Source table schema: USAGE
Destination directory: Write

Query restrictions

The following requirements and restrictions apply:

You must provide an alias column label for selected column targets that are expressions.

The query can contain only a single outer SELECT statement. For example, you cannot use UNION:

=> EXPORT TO DELIMITED(directory = '/mnt/shared_nfs/accounts/rm')
   OVER(PARTITION BY hash)
   AS
   SELECT 1 as account_id, '{}' as json, 0 hash
   UNION ALL
   SELECT 2 as account_id, '{}' as json, 1 hash;
ERROR 8975:  Only a single outer SELECT statement is supported
HINT:  Please use a subquery for multiple outer SELECT statements

Instead, rewrite the query to use a subquery:

=> EXPORT TO DELIMITED(directory = '/mnt/shared_nfs/accounts/rm')
   OVER(PARTITION BY hash)
   AS
   SELECT
    account_id,
    json
   FROM
   (
     SELECT 1 as account_id, '{}' as json, 0 hash
     UNION ALL
     SELECT 2 as account_id, '{}' as json, 1 hash
   ) a;
 Rows Exported
---------------
             2
(1 row)

To use composite statements such as UNION, INTERSECT, and EXCEPT, rewrite them as subqueries.

Data types

This operation exports raw Flex columns as binary data.

Output

The export operation always creates an output directory, even if all output is written to a single file or the query produces zero rows.

Output file names follow the pattern: [8-character-hash]-[nodename]-[thread-id].fileExtension.

Column names in partition directories are lowercase.

Files exported to a local file system by any Vertica user are owned by the Vertica superuser. Files exported to HDFS or object stores are owned by the Vertica user who exported the data.

The following requirements and restrictions apply:

Avoid concurrent exports to the same output destination. Doing so is an error on any file system and can produce incorrect results.
Use a shared file location for output. If you use a directory in the local file system, it must be an NFS-mounted directory.
For output to the local file system, you must have a USER storage location.
When exporting to the local file system, the permission mode is 700 for directories and 600 for files. You cannot override these values.

For restrictions specific to object stores (S3, GCS, or Azure), see Exporting to object stores.

Examples

The following example exports uncompressed comma-separated values (CSV) with a header row in each file:

=> EXPORT TO DELIMITED(directory='webhdfs:///user1/data', delimiter=',', addHeader='true')
  AS SELECT * FROM public.sales;