Exporting data

Output format

tt export exports data in the following formats:

• tt export and tt crud export: CSV
• tt tdg2 export: JSON lines

Limitations

Exporting isn’t supported for the interval field type.

Exporting with default settings

The command below exports data of the customers space to the customers.csv file:

$ tt crud export localhost:3301 customers:customers.csv

If the customers space has five fields (id, bucket_id, firstname, lastname, and age), the file with exported data might look like this:

1,477,Andrew,Fuller,38
2,401,Michael,Suyama,46
3,2804,Robert,King,33
# ...

If a tuple contains a null value, for example, [1, 477, 'Andrew', null, 38], it is exported as an empty value:

1,477,Andrew,,38

Exporting headers

To export data with a space’s field names in the first row of the CSV file, use the --header option:

$ tt crud export localhost:3301 customers:customers.csv  \
                 --header

In this case, field values start from the second row, for example:

id,bucket_id,firstname,lastname,age
1,477,Andrew,Fuller,38
2,401,Michael,Suyama,46
3,2804,Robert,King,33
# ...

Exporting compound data

In the CSV format, tt exports empty values by default for fields containing compound data such as arrays or maps. To export compound values in a specific format, use the --compound-value-format option. For example, the command below exports compound values to CSV serialized in JSON:

$ tt crud export localhost:3301 customers:customers.csv  \
                 --compound-value-format json

Exporting from Tarantool Data Grid 2

The command below exports data of the customers type from a TDG2 cluster to the customers.jsonl file:

$ tt tdg2 export localhost:3301 customers:customers.jsonl

If the customers type has four fields (id, firstname, lastname, and age), the file with exported data might look like this:

{"age":30,"first_name":"Samantha","id":1,"second_name":"Carter"}
{"age":41,"first_name":"Fay","id":2,"second_name":"Rivers"}
{"age":74,"first_name":"Milo","id":4,"second_name":"Walters"}

If an object contains a null value in a field, this field skipped:

{"age":13,"first_name":"Zachariah","id":3}

Object fields that contain maps with non-string keys are converted to maps with string keys.

TDG2 sets a limit on the number of objects transferred from each storage during a query execution (the hard-limits.returned TDG2 configuration parameter). If an export batch size (--batch-size parameter) is greater than this limit, it is possible that more than hard-limits.returned objects will be requested from one storage and export will fail. To make sure that hard-limits.returned is never exceeded during an export operation, set the export batch size less or equal to this limit.

For example, if your TDG2 cluster has a 1000 objects hard-limits.returned limit:

# tdg2 config.yaml
# ...
hard-limits.returned: 1000

Set the tt tdg2 export batch size less or equal to 1000:

$ tt tdg2 export localhost:3301 customers:customers.jsonl --batch-size=1000

Options

--batch-queue-size INT¶

The maximum number of tuple batches in a queue between a fetch and write threads (the default is 32).

tt exports data using two threads:

• A fetch thread makes requests and receives data from a Tarantool instance.
• A write thread encodes received data and writes it to the output.

The fetch thread uses a queue to pass received tuple batches to the write thread. If a queue is full, the fetch thread waits until the write thread takes a batch from the queue.

--batch-size INT¶

The number of tuples to transfer per request. The default is:

• 10000 for tt export and tt crud export.
• 100 for tt tdg2 export.

Важно

When using tt tdg2 export, make sure that the batch size does not exceed the hard-limits.returned TDG2 parameter value set on the cluster.

--compound-value-format STRING¶

Applicable to: tt export, tt crud export

A format used to export compound values like arrays or maps. By default, tt exports empty values for fields containing such values.

Supported formats: json.

See also: Exporting compound data.

--header¶

Applicable to: tt export, tt crud export

Add field names in the first row.

See also: Exporting headers.

--password STRING¶

A password used to connect to the instance.

--readview¶

Applicable to: tt export, tt crud export

Export data using a read view.

--username STRING¶

A username for connecting to the instance.