apache/cassandra · error · InvalidRequestException

Cannot drop a table when materialized views still depend on…

Error message

Cannot drop a table when materialized views still depend on it (%s)

What it means

DROP TABLE was attempted on a base table that has materialized views defined over it. Cassandra requires views to be dropped first because a table cannot be removed while dependent views reference it.

Solutions

List the dependent views from the error message and run DROP MATERIALIZED VIEW for each
Then reissue DROP TABLE
Use system_schema.views to discover all views on the base table before dropping

Example fix

// before
DROP TABLE ks.metrics;
// after
DROP MATERIALIZED VIEW ks.metrics_by_day;
DROP TABLE ks.metrics;

Defensive patterns

Strategy: validation

Validate before calling

var views = session.execute("SELECT view_name FROM system_schema.views WHERE keyspace_name=? AND base_table_name=?", ks, table);
for (var v : views) session.execute("DROP MATERIALIZED VIEW IF EXISTS " + ks + "." + v.getString("view_name"));

Try / catch

try { dropTable(); } catch (InvalidRequest e) { if (e.getMessage().contains("materialized views still depend")) dropDependentViewsThenRetry(); else throw e; }

Prevention

Query system_schema.views for base_table_name before dropping any table
Document view dependencies alongside table schemas
Generate drop scripts in dependency order (views first, base tables last)

When it happens

Trigger: Running DROP TABLE on a keyspace table that still has at least one ViewMetadata in keyspace.views forTable(table.id).

Common situations: Developers forgetting which materialized views were created on a base table; migrations that create views but later drop the base table first; inherited schemas with undocumented views.

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

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/2947f683a38a1cf1. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/cql3/statements/schema/DropTableStatement.java:111

        if (null == table)
        {
            if (ifExists)
                return schema;

            throw ire("Table '%s.%s' doesn't exist", keyspaceName, tableName);
        }

        if (table.isView())
            throw ire("Cannot use DROP TABLE on a materialized view. Please use DROP MATERIALIZED VIEW instead.");

        if (table.requiresAccordSupport() && table.params.pendingDrop)
            throw ire("Table '%s.%s' is already being dropped", keyspaceName, tableName);

        Iterable<ViewMetadata> views = keyspace.views.forTable(table.id);
        if (!isEmpty(views))
        {
            throw ire("Cannot drop a table when materialized views still depend on it (%s)",
                      keyspaceName,
                      join(", ", transform(views, ViewMetadata::name)));
        }

        return schema.withAddedOrUpdated(keyspace.withSwapped(keyspace.tables.without(table)));
    }

    SchemaChange schemaChangeEvent(KeyspacesDiff diff)
    {
        return new SchemaChange(Change.DROPPED, Target.TABLE, keyspaceName, tableName);
    }

    public void authorize(ClientState client)
    {
        client.ensureTablePermission(keyspaceName, tableName, Permission.DROP);
    }

    @Override

View on GitHub (pinned to 88fd0f6a0e)