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ClassDB

An open-source system to let students experiment with relational data

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Troubleshooting

Author: Andrew Figueroa

Although ClassDB is designed to be easy to use and cause minimal issues, some problems or concerns could occur during use. This page describes these issues and potential solutions.

Cannot connect to the database

Cause Solution
Username is not correct Ensure the user name is correct and that the user has been created. Keep in mind that user names are case-sensitive. See the Adding Users page and Postgres’ documentation for more information on identifier quoting and folding.
Password is not correct Use the correct password. If the password has been forgotten, it can be reset by an instructor or DB manager.
Connection information is not correct or the server is refusing connections. Ensure the server, port, and database information is correct and that it is being given to the client in the proper format. Also ensure that the PostgreSQL instance is running and has been configured to accept connections from the user’s computer.
User is a student and has too many connections open Close stray connections. If this becomes a recurring problem, consider raising the Connection Limit and/or using a different client.

Issues with queries

Cause Solution
Query is improperly formatted or too complex Fix issues with the query and/or reduce the complexity of the query.
User is a student and is executing a complex query The query may be timing out due to the statement timeout that is set on student users. Increase the timeout if necessary.
Connection to the database has been lost Reestablish the connection to the database.

Log files are too large

Cause Solution
Old log files are being maintained longer than necessary By default, ClassDB sets log files to be maintained for up to 1 year. If this is not necessary, they can be manually removed.
Too many users are using the Postgres instance Reduce the number of users, or implement other solutions to reduce the size of log files.
Log verbosity is set too high By default, Postgres may set the log verbosity to a value that is higher than necessary. See Managing Log Files or the Postgres documentation for more information.