apache/cassandra · error · InvalidRequestException

Cannot rename column

Error message

Cannot rename column %s to %s in table '%s'; another column with that name already exists

What it means

A rename must produce a unique column name. renameColumn (AlterTableStatement.java:591) throws this InvalidRequest when table.getColumn(newName) already returns a column, because two columns cannot share a name in the table metadata.

Solutions

Choose a distinct newName that does not collide (check system_schema.columns first)
Drop the conflicting existing column if it is no longer needed before renaming
Reorder your migration so the rename happens before adding a column with the target name

Example fix

// before
ALTER TABLE users RENAME user_id TO id; // 'id' already exists
// after
ALTER TABLE users DROP id;
ALTER TABLE users RENAME user_id TO id;

Defensive patterns

Strategy: validation

Validate before calling

Set<String> names = session.execute("SELECT column_name FROM system_schema.columns WHERE keyspace_name=? AND table_name=?", ks, table).all().stream().map(r -> r.getString("column_name")).collect(Collectors.toSet()); if (names.contains(newName)) { /* choose a different target name or drop the conflict */ }

Try / catch

try { session.execute(renameStmt); } catch (InvalidRequestException e) { if (e.getMessage().contains("another column with that name already exists")) { /* resolve collision */ } else throw e; }

Prevention

Generate migrations from the live schema, not from a stale model
Order migration steps so renames precede column additions with the target name
Uniqueness-check target names programmatically before applying

When it happens

Trigger: ALTER TABLE t RENAME old TO new where new already exists as any column (key or regular) in the table.

Common situations: Renaming a key column to a name that collides with an existing regular column; running a migration that adds the target column first and then renames into it; copy-paste mistakes in migration scripts.

Understand the failure class

Background: "already exists" / EEXIST / FileAlreadyExistsException: what the 'file already exists' error means and how to fix it — this error's family across 37 libraries.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/8660e2cdca3e846b. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/cql3/statements/schema/AlterTableStatement.java:591

                                  ColumnIdentifier newName,
                                  boolean ifColumnsExists,
                                  TableMetadata.Builder tableBuilder,
                                  Views.Builder viewsBuilder)
        {
            ColumnMetadata column = table.getExistingColumn(oldName);
            if (null == column)
            {
                if (!ifColumnsExists)
                    throw ire("Column %s was not found in table %s", oldName, table);
                return;
            }

            if (!column.isPrimaryKeyColumn())
                throw ire("Cannot rename non PRIMARY KEY column %s", oldName);

            if (null != table.getColumn(newName))
            {
                throw ire("Cannot rename column %s to %s in table '%s'; another column with that name already exists",
                          oldName,
                          newName,
                          table);
            }

            if (!table.indexes.isEmpty())
                AlterTableStatement.validateIndexesForColumnModification(table, oldName, true);

            for (ViewMetadata view : keyspace.views.forTable(table.id))
            {
                if (view.includes(oldName))
                {
                    viewsBuilder.put(viewsBuilder.get(view.name()).withRenamedPrimaryKeyColumn(oldName, newName));
                }
            }

            tableBuilder.renamePrimaryKeyColumn(oldName, newName);
        }

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