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Troubleshooting

Unrecognized and Unsupported Data Types

Not all data types present in a source database have a matching equivalent in Exasol. Also software updates on the source database can introduce new data type that the Virtual schema does not recognize.

There are a few important things you need to know about those data types.

  1. Columns of an unrecognized / unsupported data type are not mapped in a Virtual Schema. From Exasol's perspective those columns do not exist on a table. This is done so that tables containing those columns can still be mapped and do not have to be rejected as a whole.
  2. You can't query columns of an unrecognized / unsupported data type. If the source table contains them, you have to explicitly exclude them from the query. You can for example not use the asterisk (*) on a table that contains one ore more of those columns. This will result in an error issued by the Virtual schema.
  3. If you want to query all columns except unsupported, add 1 to the columns list. Otherwise you will see the same error as if you query with the asterisk (*). For example, a table contains 3 columns: bool_column BOOLEAN, timestamp_column TIMESTAMP, blob_column BLOB. The column BLOB is not supported. If you want to query two other columns, use: SELECT "bool_column", "timestamp_column", 1 FROM table_name; .
  4. You can't use functions that result in an unsupported / unknown data type.

Setting the Right IP Addresses for Database Connections

Keep in mind that the adapter script is deployed in the Exasol database. If you want it to be able to make connections to other databases, you need to make sure that the IP addresses or host names are the ones that the database sees, not your local machine. This is easily forgotten in case of automated integration tests since it feels like they run on your machine -- which is only partially true.

So a common source of error would be to specify localhost or 127.0.0.1 as address of the remote database in case you have it running in Docker or a VM on your local machine. But the Exasol Database cannot reach the other database there unless it is running on the same machine directly (i.e. not behind a virtual network device).