You have tried to use a function which does not exist in the current database.
Check that the function is correct and the required arguments have been specified and that you are connected to the correct database.
- Has the function name been spelled correctly?
- Have the correct arguments been supplied?
- Are you connected to the correct database?
- Does the function need to be qualified with a schema?
- Search for the function in this knowledge base to get its arguments and which database to connect to
- Use SELECT current_database(); to discover which database you are currently connected to