Information Schema¶
DataFusion supports showing metadata about the tables and views available. This information can be accessed using the
views of the ISO SQL information_schema schema or the DataFusion specific SHOW TABLES and SHOW COLUMNS commands.
To show tables in the DataFusion catalog, use the SHOW TABLES command or the information_schema.tables view:
> show tables;
or
> select * from information_schema.tables;
+---------------+--------------------+------------+------------+
| table_catalog | table_schema | table_name | table_type |
+---------------+--------------------+------------+------------+
| datafusion | public | t | BASE TABLE |
| datafusion | information_schema | tables | VIEW |
| datafusion | information_schema | views | VIEW |
| datafusion | information_schema | columns | VIEW |
+---------------+--------------------+------------+------------+
To show the schema of a table in DataFusion, use the SHOW COLUMNS command or the information_schema.columns view:
> show columns from t;
or
> select table_catalog, table_schema, table_name, column_name, data_type, is_nullable from information_schema.columns;
+---------------+--------------+------------+-------------+-----------+-------------+
| table_catalog | table_schema | table_name | column_name | data_type | is_nullable |
+---------------+--------------+------------+-------------+-----------+-------------+
| datafusion | public | t | Int64(1) | Int64 | NO |
+---------------+--------------+------------+-------------+-----------+-------------+
To show the current session configuration options, use the SHOW ALL command or the information_schema.df_settings view:
select * from information_schema.df_settings;
+-------------------------------------------------+---------+
| name | setting |
+-------------------------------------------------+---------+
| datafusion.execution.batch_size | 8192 |
| datafusion.execution.coalesce_batches | true |
| datafusion.execution.time_zone | UTC |
| datafusion.explain.logical_plan_only | false |
| datafusion.explain.physical_plan_only | false |
| datafusion.optimizer.filter_null_join_keys | false |
| datafusion.optimizer.skip_failed_rules | true |
+-------------------------------------------------+---------+