CODEWITHSUNDEEP
cassandracql3
Eric Urban
Eric Urban

Reputation: 3820

How can I use CQL in Cassandra 3 to determine if a table uses compact storage?

If I use the cqlsh tool that comes with Cassandra 3, it can tell me if a table was created WITH COMPACT STORAGE. All I have to do is describe table_name; and it shows me the CQL used to create the table.

The describe functionality is a feature of cqlsh, not of the CQL language. I need to determine if a table uses compact storage using just CQL. What do I need to query in the system_schema to determine if a table is using compact storage?

Upvotes: 1

Views: 673

Answers (1)

Eric Urban
Eric Urban

Reputation: 3820

From the definition of the TableMetadataV3 class in the cassandra driver for python, the logic for determining compact storage is as follows

 flags = row.get('flags', set())
            if flags:
                compact_static = False
                table_meta.is_compact_storage = 'dense' in flags or 'super' in flags or 'compound' not in flags
                is_dense = 'dense' in flags
            else:
                compact_static = True
                table_meta.is_compact_storage = True
                is_dense = False

The row object is a dictionary that is the result of the query "SELECT * FROM system_schema.tables"

So to determine if a table uses compact storage, the following steps are necessary.

  1. Use CQL to query Select flags from system_schema.tables where keyspace_name=? and table_name=?. Substitute the keyspace and table in as parameters
  2. If flags is empty, then the table uses compact storage.
  3. If flags is present with 'dense' or 'super' as members of the set then the table uses compact storage.
  4. If 'compound' is not in the set then the table uses compact storage.
  5. Otherwise the table does not use compact storage.

Upvotes: 1

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