EXPORT TO DELIMITED

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.

You can use an OVER() clause to partition the data before export. You can partition data instead of or in addition to exporting the column data. Partitioning data can improve query performance by enabling partition pruning. See Improving Query Performance.

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

Arguments

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.

You cannot export data from an external table that contains external, non-native data types, such as ROW. See Complex Types. This restriction applies even if your SELECT statement does not include those columns.

Output

The export operation always creates an output directory, even if 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;