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import-db

Experimental

This is an experimental command, and is subject to breaking changes.

Snapshot a table or a SQL query results from a database into CSV/JSON format.

Description

With import-db, you can snapshot your ETL/database to a file to use in your data pipelines. This commands supports importing your table or a SQL query results into different file formats. To do so, you have to set connection strings to connect to a database, which can be setup in config as db.<name>. Check Database Connections for more information.

At the moment, import-db supports two different output format:

  • JSON records
  • CSV (with header, and no index)

An import .dvc file is created in the same location e.g. customers.txt.dvc. This makes it possible to update the import later, if the data source has changed (see dvc update).

You can dvc push and dvc pull data imported from the databases to/from remote storage normally.

Database Connections

To connect to a database, DVC needs a database connection string URI. This has to be configured in the db section.

$ dvc config db.pgsql.url postgresql://user@hostname:port/database
$ dvc config --local db.pgsql.password password

Security Alert

Configure password with --local option so they are written to a Git-ignored config file.

Security Alert

Use an user account with limited access to databases with read-only privileges, as --sql can run arbitrary queries. Different databases have different approaches to this. Refer to their documentation for more details.

You need to specify the name of database connection to use, when using import-db.

$ dvc import-db --table customers_table --conn pgsql

In addition to a connection string, DVC needs a driver to connect to the database. Check Installing database drivers for connection string format and necessary driver for your specific database.

Installing database drivers

DVC does not come preinstalled with all the drivers for databases, you’ll need to install the required packages for the database you want to use.

Some of the recommended packages are shown below, with their expected connection strings:

DatabasePyPI packageConnection String
Amazon Redshiftsqlalchemy-redshiftredshift+psycopg2://{username}:{password}@{aws_endpoint}:5439/{database_name}
Big Querypip install sqlalchemy-bigquerybigquery://{project_id}
Databricksdatabricks-sql-connectordatabricks://token:{token}@{hostname}:{port}/{database}?http_path={http_path}
MySQLmysqlclientmysql://{username}:{password}@{hostname}/{database_name}
Oraclecx_Oracleoracle://{username}:{password}@{hostname}/{database_name}
PostgreSQLpsycopg2postgresql://{username}:{password}@{hostname}/{database_name}
Snowflakesnowflake-sqlalchemysnowflake://{user}:{password}@{account}.{region}/{database}?role={role}&amp;warehouse={warehouse}
SQLite-sqlite://path/to/file.db
SQL Serverpyodbcmssql+pyodbc://{username}:{password}@{hostname}:{port}/{database_name}
Trinotrinotrino://{username}:{password}@{hostname}:{port}/{catalog}

DVC uses sqlalchemy internally. So DVC should support any SQL databases that provide dialects for SQLAlchemy. Refer to their documentation for more details.

Options

  • -o <path>, --out <path> - specify a path to the desired location in the workspace to place the file. If not specified, the filename will be generated using the arguments from --output-format and --table, or for --sql, it starts with "results" by default.

  • --table <table> - table to snapshot.

  • --sql <query> - execute SQL query and snapshot its result.

  • --output-format - type of format to materialize into. csv (default) and json is supported.

  • --conn connection - name of the database connection to use. The connection has to be set in the config.

  • -f, --force - when using --out to specify a local target file or directory, the operation will fail if those paths already exist. this flag will force the operation causing local files/dirs to be overwritten by the command.

  • -h, --help - prints the usage/help message, and exit.

  • -q, --quiet - do not write anything to standard output. Exit with 0 if no problems arise, otherwise 1.

  • -v, --verbose - displays detailed tracing information.

Examples

Downloading a table

To import a table from a database using a db config set:

$ dvc import-db --table "customers_table" --conn pgsql
...

dvc import-db will snapshot the complete table, and save to a file named customers_table.csv. It will also create a customers_table.csv.dvc file with the following contents:

md5: ddd4654188815dcae6ce4d4a37f83bde
frozen: true
deps:
  - db:
      file_format: csv
      connection: pgsql
      table: customers_table
outs:
  - md5: 131543a828b297ce0a5925800bd88810
    size: 15084226
    hash: md5
    path: customers_table.csv

You can use dvc update to update the snapshot.

Downloading SQL query result

Similarly, you can also snapshot a SQL query result as follows:

$ dvc import-db --sql "select * from customers" --conn pgsql
...

dvc import-db will snapshot the query results, and save to a file named results.csv. Similarly, it will also create a results.csv.dvc file, which can be used to dvc update later.

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