Geodatabase attachments are not automatically included in the output of geoprocessing tools

Description

Geodatabase attachments are not automatically included in the output of geoprocessing tools. The instructions provided describe the steps to copy attachments from an input dataset to the output dataset.

Cause

Geodatabase attachments are stored as BLOBs in a table that is related to the feature class via a relationship class. This associated table and relationship class can be found in the same geodatabase as the feature class; they are named the same as the feature class, but with __ATTACH and __ATTACHREL suffixes. Geoprocessing operations do not copy datasets that are related to a feature class through a relationship class.

Workaround

1. Run the desired geoprocessing tool, such as the Project tool.
2. Right-click the output feature class and click create/enable Attachments.
   This creates an empty __ATTACH table and a relationship class relating that table to the output feature class.
3. Use the Append tool to append the original feature class' __ATTACH table into the output feature class' __ATTACH table. The __ATTACH table is where the attachments are actually stored (in a BLOB field), so appending these records is a key step:
   • Input Dataset = input__ATTACH
   • Target Dataset = output__ATTACH