When a dataset in a PostgreSQL database that is not registered with the geodatabase is published to ArcGIS Enterprise, opening the attribute table for the referenced feature layer in ArcGIS Pro and selecting the option to “show selected” records displays the following error message:
Failed to load data. ERROR: code:400, Unable to complete operation. Unable to perform query operation. Bad syntax in request.
When viewing the schema for the dataset, it is determined that the database-maintained, unique, not null column is defined as an identity or unique integer field, as shown in the following image.
For a PostgreSQL database, ArcGIS requires the unique ID field to be of type serial. The error can be resolved in two ways: