The Issue:
If you are working with a MySQL Database, you might be getting Data too long for column 'BANDANAVALUE' at row 1 error while creating a baseline that contains 10K+ documents.
Details:
Baselines for Confluence saves its data in the Bandana table of your Confluence database. The datatypes for columns in Bandana table are different for different RDBMS systems and for MySQL, the datatype for bandanavalue column is MEDIUMTEXT which allow up to 16MBs of text.
A baselines with 10K+ documents may create a baselines that will not fit in this.
Workaround
You can manually change the datatype of your bandanavalue column to allow larger text with an SQL statement like below:
ALTER TABLE bandana MODIFY bandanavalue LONGTEXT;
Reference: https://jira.atlassian.com/browse/CONFSERVER-23298