apache/cassandra · error · InvalidRequestException

Cannot %s column %s because it has dependent secondary index

Error message

Cannot %s column %s because it has dependent secondary indexes (%s)

What it means

This InvalidRequestException is thrown when an ALTER TABLE DROP (or RENAME) targets a column that has secondary indexes defined on it. Cassandra refuses the schema change because dropping/renaming the column would leave the index metadata pointing at a non-existent or renamed column. The message lists every dependent index so the developer knows exactly which indexes to drop first.

Source

Thrown at src/java/org/apache/cassandra/cql3/statements/schema/AlterTableStatement.java:452

        {
            Optional<Pair<ColumnMetadata, IndexTarget.Type>> target = TargetParser.tryParse(table, index);
            if (target.isEmpty())
            {
                // The target column(s) of this index is not trivially discernible from its metadata.
                // This implies an external custom index implementation and without instantiating the
                // index itself we cannot be sure that the column metadata is safe to modify.
                dependentIndexes.add(index.name);
            }
            else if (target.get().left.equals(column))
            {
                // The index metadata declares an explicit dependency on the column being modified, so
                // the mutation must be rejected.
                dependentIndexes.add(index.name);
            }
        }
        if (!dependentIndexes.isEmpty())
        {
            throw ire("Cannot %s column %s because it has dependent secondary indexes (%s)",
                      isRename ? "rename" : "drop",
                      colId,
                      join(", ", dependentIndexes));
        }
    }

    /**
     * {@code ALTER TABLE [IF EXISTS] <table> DROP [IF EXISTS] <column>}
     * {@code ALTER TABLE [IF EXISTS] <table> DROP [IF EXISTS] ( <column>, <column1>, ... <columnn>)}
     */
    // TODO: swap UDT refs with expanded tuples on drop
    private static class DropColumns extends AlterTableStatement
    {
        private final Set<ColumnIdentifier> removedColumns;
        private final boolean ifColumnExists;
        private final Long timestamp;

        private DropColumns(String keyspaceName, String tableName, Set<ColumnIdentifier> removedColumns, boolean ifTableExists, boolean ifColumnExists, Long timestamp)

View on GitHub (pinned to 88fd0f6a0e)

Solutions

Drop the dependent secondary index first: `DROP INDEX <keyspace>.<index_name>`, then re-run the ALTER TABLE DROP/RENAME.
If the index is still needed, drop/re-add it around the change: DROP INDEX, ALTER TABLE DROP COLUMN, then re-create the index on a suitable column.
If using a custom index, consult its documentation; you may need to remove the custom index before modifying any column.
Query system_schema.indexes (or DESCRIBE TABLE) beforehand to identify indexes on the target column.

Example fix

// before
ALTER TABLE users DROP email; -- fails: dependent index users_email_idx
// after
DROP INDEX users_email_idx;
ALTER TABLE users DROP email;

Defensive patterns

Strategy: validation

Validate before calling

// CQL pre-check before ALTER TABLE DROP/RENAME
SELECT index_name, options FROM system_schema.indexes
WHERE keyspace_name = 'ks' AND table_name = 'tbl';
// If any row targets the column (or is a custom index), drop the index first.

Try / catch

// Driver (java)
try {
    session.execute("ALTER TABLE ks.tbl DROP col");
} catch (com.datastax.oss.driver.api.core.servererrors.InvalidQueryException e) {
    if (e.getMessage().contains("dependent secondary indexes")) {
        // parse index names from message and DROP INDEX before retrying
    } else throw e;
}

Prevention

Check system_schema.indexes for the column before any DROP/RENAME migration.
Make migrations idempotent with IF EXISTS and explicit DROP INDEX steps.
Avoid secondary indexes in favor of denormalized tables/query tables where possible.
Treat any custom index as blocking all column modifications.

When it happens

Trigger: Executing `ALTER TABLE ... DROP column` or `ALTER TABLE ... RENAME column` on a column that is the target of a secondary index (CREATE INDEX). Also triggered when a custom index implementation's target column cannot be discerned from metadata (TargetParser.tryParse returns empty), which is treated as a dependency conservatively.

Common situations: Developers added a secondary index during prototyping and later try to clean up the schema by dropping the indexed column; schema migration scripts that drop columns without first checking system_schema.indexes; tables using custom index implementations (e.g. Storage-Attached Indexes or third-party indexes) where all column changes are rejected.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/ed4025f3d090ad98. Report an issue: GitHub.