apache/cassandra · error · InvalidRequestException

Duplicate column ' ' declaration for table

Error message

Duplicate column '%s' declaration for table '%s'

What it means

The same column name appears more than once in the CREATE TABLE column list. The raw builder stores columns in a map keyed by ColumnIdentifier; if put() returns a previous value, the column was declared twice and the statement is rejected.

Solutions

1. Remove the duplicate column declaration, keeping only one type per name
2. Rename one of the colliding columns
3. If identifiers are quoted, ensure casing does not collapse two names into the same identifier

Example fix

// before
CREATE TABLE t (a int, a text, PRIMARY KEY (a));
// after
CREATE TABLE t (a int, b text, PRIMARY KEY (a));

const names = cols.map(c => c.name.toLowerCase());
const dup = names.find((n, i) => names.indexOf(n) !== i);
if (dup) throw new Error(`Duplicate column: ${dup}`);

try { session.execute(ddl); } catch (e) { if (/Duplicate column/.test(e.message)) { /* de-duplicate the column list and retry */ } else throw e; }

When it happens

Trigger: CREATE TABLE t (a int, a text); — the second addColumn call for an already-declared identifier throws.

Common situations: Copy-pasted column definitions; generated DDL concatenating column lists from multiple sources; case-insensitive collisions if quoting differs (e.g. A and "A" resolve to the same identifier).

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• ACCESS TO DATACENTERS operations not supported by…
• Aggregate ' ' already exists
• Argument ' ' cannot be frozen; remove frozen<> modifier from
• Can not alter a keyspace to use MetaReplicationStrategy
• Cannot add a column ' ' of type , incompatible with…

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/31ec95f05a9a7190. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/cql3/statements/schema/CreateTableStatement.java:626

            name.setKeyspace(keyspace, true);
            return this;
        }

        public Raw table(String table)
        {
            name.setName(table, true);
            return this;
        }

        public String table()
        {
            return name.getName();
        }

        public void addColumn(ColumnIdentifier column, CQL3Type.Raw type, boolean isStatic, boolean isNotNull, ColumnMask.Raw mask, ColumnConstraints.Raw constraints)
        {
            if (null != rawColumns.put(column, new ColumnProperties.Raw(type, mask)))
                throw ire("Duplicate column '%s' declaration for table '%s'", column, name);

            if (isStatic)
                staticColumns.add(column);

            ColumnConstraints preparedConstraints = constraints == null ? ColumnConstraints.NO_OP : constraints.prepare(column);

            if (isNotNull)
            {
                 if (preparedConstraints.containsNotNullConstraint())
                     throw ire("Duplicate definition of NOT NULL constraint");

                List<ColumnConstraint<?>> checkConstraints = new ArrayList<>(preparedConstraints.getConstraints());
                checkConstraints.add(new UnaryFunctionColumnConstraint(new NotNullConstraint()));
                preparedConstraints = new ColumnConstraints(checkConstraints);
                preparedConstraints.setColumnName(column);
            }

            columnConstraints.put(column, preparedConstraints);

View on GitHub (pinned to 88fd0f6a0e)