How to resolve the “PostgreSQL relation doesn’t exist” error?
I am a database manager for a particular e-commerce company by uses Postgresql as the backend for its product catalog. A recent update was pushed to the production environment, however soon after, the users started reporting a particular error that stated that “PostgreSQL relation doesn’t exist” when they tried to access a certain page of the website. How can I troubleshoot and resolve this particular issue?
In the context of SQL, Here are the troubleshooting steps given:-
Verify the relation's existence
You should check if the relation exists in the database or not.
Checking schemas
You should try to ensure that you are referencing the right schema. If your particular table is in a specific schema, you should prefix the schema name.
Case sensitivity
If the table was created with the help of quoted identifiers, then you would need to use the exact name including the quotes and case.
Here are the probable reasons for this particular error:-
Typographical error
It is very much possible that this error is occurring due to the misspelling of the name of the relation.
Schema issues
The relation which exists in different schemas is not correct.
Case sensitivity
By default, the PostgreSQL folds unquited identifiers to the lowercase. If the table or even other relation name was created by using the quoted identifiers with uppercase letters then you would need to be referenced exactly as created, including also quotes and case.
Here is a combined structure is given which would demonstrate how you can check for the existence of the table, handle schema issues, and address case sensitivity. The script would demonstrate how you can troubleshoot and resolve this particular issue:-
Replace these variables with your actual schema and table names
DO $$
DECLARE
Schema_name TEXT := ‘your_schema’; -- e.g., ‘public’
Table_name TEXT := ‘your_table_name’; -- e.g., ‘your_table’
Quoted_table_name TEXT := ‘”YourTableName”’; -- if the table was created with quoted identifiers
Relation_exists BOOLEAN;
BEGIN
Check if the relation exists without considering case sensitivity
SELECT EXISTS ( SELECT 1
FROM information_schema.tables
WHERE table_schema = schema_name
AND table_name = table_name
) INTO relation_exists;
IF relation_exists THEN
RAISE NOTICE ‘Relation %.% exists.’, schema_name, table_name;
Select from the table
EXECUTE format(‘SELECT * FROM %I.%I’, schema_name, table_name);
ELSE
Check if the relation exists considering case sensitivity (quoted identifiers)
SELECT EXISTS (
SELECT 1
FROM information_schema.tables
WHERE table_schema = schema_name
AND table_name = quoted_table_name
) INTO relation_exists;
IF relation_exists THEN
RAISE NOTICE ‘Relation %.% exists (case-sensitive).’, schema_name, quoted_table_name;
Select from the table with quoted identifiers
EXECUTE format(‘SELECT * FROM %I.%s’, schema_name, quoted_table_name);
ELSE
RAISE EXCEPTION ‘Relation %.% does not exist.’, schema_name, table_name;
END IF;
END IF;
END $$;Here is also the java structure given of how you can handle this particular issue by checking if a table existing in a PostgreSQL database. This particular example uses the JDBC for the database connection and Interaction:-
Import java.sql.Connection;
Import java.sql.DriverManager;
Import java.sql.PreparedStatement;
Import java.sql.ResultSet;
Import java.sql.SQLException;Public class PostgresTableCheck {
Private static final String URL = “jdbc:postgresql://localhost:5432/your_database”;
Private static final String USER = “your_user”;
Private static final String PASSWORD = “your_password”;
Public static void main(String[] args) {
String schemaName = “public”;
String tableName = “your_table”;
Try (Connection conn = DriverManager.getConnection(URL, USER, PASSWORD)) {
If (tableExists(conn, schemaName, tableName)) {
System.out.println(“Table “ + schemaName + “.” + tableName + “ exists.”);
} else {
System.out.println(“Table “ + schemaName + “.” + tableName + “ does not exist.”);
}
} catch (SQLException e) {
e.printStackTrace();
}
}
Private static boolean tableExists(Connection conn, String schema, String table) throws SQLException {
String query = “SELECT EXISTS (SELECT 1 FROM information_schema.tables WHERE table_schema = ? AND table_name = ?)”;
Try (PreparedStatement pstmt = conn.prepareStatement(query)) {
Pstmt.setString(1, schema);
Pstmt.setString(2, table);
Try (ResultSet rs = pstmt.executeQuery()) {
If (rs.next()) {
Return rs.getBoolean(1);
}
}
}
Return false;
}
}This above java example would check for the existence of a table and handle the potential SQL exception gracefully.