Parquet functions

QuestDB can read and query external Apache Parquet files using SQL.

To export data as Parquet, see Parquet Export.

:::info Apache Parquet support is in beta. Please report issues via email, Slack, or Discourse. :::

read_parquet

Reads a parquet file as a table.

read_parquet(parquet_file_path)

Usage

The file path must be within the configured root directory. It can be specified as a relative path (resolved under the root) or as an absolute path (which must still start with the root directory). Path traversal (../) is not allowed.

SELECT * FROM read_parquet('trades.parquet')
WHERE side = 'buy'
LIMIT 1;

SELECT * FROM read_parquet('/var/lib/questdb/import/trades.parquet');

SELECT t.symbol, t.price, r.label
FROM read_parquet('trades.parquet') t
JOIN ref_data r ON t.symbol = r.symbol;

Configuration

For security reasons, reading is only allowed from a configured directory. By default, this is the import directory inside the QuestDB root directory (e.g. /var/lib/questdb/import/). To change it, set cairo.sql.copy.root:

• In server.conf: cairo.sql.copy.root=/path/to/dir
• Or via the environment variable QDB_CAIRO_SQL_COPY_ROOT

Limitations

Parquet format supports a rich set of data types, including structural types. QuestDB can only read Parquet columns whose types map to QuestDB types:

• Boolean
• Byte
• Short
• Char
• Int
• Long
• Long128
• Long256
• Float
• Double
• Varchar (also reads Symbol columns as Varchar)
• Timestamp
• Date
• UUID
• IPv4
• GeoHash (Byte, Short, Int, Long)
• Binary
• Array (Double)

Parquet columns with unsupported data types are ignored.

Only a single file can be read per read_parquet call.