I use PostgreSQL as a storage for JIRA data. Everything works fine except the case, when I try to enter any Unicode text (any national alphabet's characters) to the textarea column of my Grid - characters get corrupted.
Even latest version of JIRA (7.3.0) uses outdated PostgreSQL JDBC driver (postgresql-9.1-903.jdbc4-atlassian-hosted). There is a bug in this version of driver, it encodes clobs (data type to store huge text values) to ASCII encoding. This conversion corrupts the data. Unfortunately this cannot be fixed in the Table Grid Editor code because the problem lies in the PostgreSQL.
Change PostgreSQL JDBC driver in JIRA to newer version. Steps to change driver in JIRA:
Go to the 'lib' subdirectory of a 'JIRA Installation Directory'.
Paste newly downloaded driver into this directory.
Remove previous driver from this directory (name of driver could be different, it depends on version of JIRA, you should find a JAR file which name includes 'postgresql').
Start your JIRA server.
Use your JIRA database as a datasource in Grid configuration. Table Grid Editor uses fixed version of the PostgreSQL JDBC driver. If you define your JIRA database as external datasource - Table Grid Editor would handle storing data to database. How to create the datasource - described here