How to set consistency level in a Cassandra query?

@natalia 

In Cassandra, you can specify the consistency level for a query using the ConsistencyLevel enum in the org.apache.cassandra.consistency package. This enum defines the following values:

• ANY: The query will return a result as soon as it has received a response from any node in the cluster.
• ONE: The query will return a result as soon as it has received a response from at least one node in the cluster.
• TWO: The query will return a result as soon as it has received a response from at least two nodes in the cluster.
• THREE: The query will return a result as soon as it has received a response from at least three nodes in the cluster.
• QUORUM: The query will return a result as soon as it has received a response from a majority of nodes in the cluster (rounded up).
• ALL: The query will return a result only after it has received a response from all nodes in the cluster.
• LOCAL_QUORUM: The query will return a result as soon as it has received a response from a majority of nodes in the local datacenter (rounded up).
• EACH_QUORUM: The query will return a result as soon as it has received a response from a majority of nodes in each datacenter (rounded up).
• SERIAL: The query will return a result only after it has received a response from all nodes in the cluster, and the data has been written to the commit log and the memtable on all nodes.
• LOCAL_SERIAL: The query will return a result only after it has received a response from all nodes in the local datacenter, and the data has been written to the commit log and the memtable on all nodes in the local datacenter.
• LOCAL_ONE: The query will return a result as soon as it has received a response from at least one node in the local datacenter.

To set the consistency level for a query, you can use the withConsistency method of the Statement class. For example:

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import org.apache.cassandra.consistency.ConsistencyLevel;

// ...

Statement stmt = new SimpleStatement("SELECT * FROM my_table WHERE key = 'abc'");
 stmt.setConsistencyLevel(ConsistencyLevel.QUORUM);

Alternatively, you can also set the consistency level for a query by using the setConsistencyLevel method of the QueryOptions class, which you can pass as an argument to the execute method of a Session object. For example:

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import org.apache.cassandra.consistency.ConsistencyLevel;
import org.apache.cassandra.query.QueryOptions;

// ...

Statement stmt = new SimpleStatement("SELECT * FROM my_table WHERE key = 'abc'");
 QueryOptions options = QueryOptions.forConsistencyLevel(ConsistencyLevel.QUORUM);
 session.execute(stmt, options);

It's important to note that the consistency level you choose for a query can affect the performance and availability of your Cassandra cluster. For example, using a high consistency level like ALL or SERIAL can result in slower performance, as the query will not return until it has received a response from all nodes in the cluster