StatementWrapper (DataStax Java Driver for Apache Cassandra

java.lang.Object
- com.datastax.driver.core.Statement
- - com.datastax.driver.core.StatementWrapper

public abstract class StatementWrapper
extends Statement

Base class for custom Statement implementations that wrap another statement.

This is intended for use with a custom RetryPolicy, LoadBalancingPolicy or SpeculativeExecutionPolicy. The client code can wrap a statement to "mark" it, or add information that will lead to special handling in the policy.

Example:

 
 // Define your own subclass
 public class MyCustomStatement extends StatementWrapper {
     public MyCustomStatement(Statement wrapped) {
         super(wrapped);
     }
 }

 // In your load balancing policy, add a special case for that new type
 public class MyLoadBalancingPolicy implements LoadBalancingPolicy {
     public Iterator<Host> newQueryPlan(String loggedKeyspace, Statement statement) {
         if (statement instanceof MyCustomStatement) {
             // return specially crafted plan
         } else {
             // return default plan
         }
     }
 }

 // The client wraps whenever it wants to trigger the special plan
 Statement s = new SimpleStatement("...");
 session.execute(s);                         // will use default plan
 session.execute(new MyCustomStatement(s));  // will use special plan

Field Summary
- Fields inherited from class com.datastax.driver.core.Statement
  idempotent

Constructor Summary

Constructors
Modifier Constructor and Description

protected StatementWrapper(Statement wrapped)
Builds a new instance.

Constructors
Modifier	Constructor and Description
`protected`	`StatementWrapper(Statement wrapped)` Builds a new instance.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`Statement`	`disableTracing()` Disables tracing for this query.
`Statement`	`enableTracing()` Enables tracing for this query.
`ConsistencyLevel`	`getConsistencyLevel()` The consistency level for this query.
`int`	`getFetchSize()` The fetch size for this query.
`String`	`getKeyspace()` Returns the keyspace this query operates on.
`ByteBuffer`	`getPagingState()`
`RetryPolicy`	`getRetryPolicy()` Returns the retry policy sets for this query, if any.
`ByteBuffer`	`getRoutingKey()` Returns the routing key (in binary raw form) to use for token aware routing of this query.
`ConsistencyLevel`	`getSerialConsistencyLevel()` The serial consistency level for this query.
`boolean`	`isTracing()` Returns whether tracing is enabled for this query or not.
`Statement`	`setConsistencyLevel(ConsistencyLevel consistency)` Sets the consistency level for the query.
`Statement`	`setFetchSize(int fetchSize)` Sets the query fetch size.
`Statement`	`setPagingState(PagingState pagingState)` Sets the paging state.
`Statement`	`setRetryPolicy(RetryPolicy policy)` Sets the retry policy to use for this query.
`Statement`	`setSerialConsistencyLevel(ConsistencyLevel serialConsistency)` Sets the serial consistency level for the query.

Methods inherited from class com.datastax.driver.core.Statement
isIdempotent, setIdempotent, setPagingStateUnsafe

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - StatementWrapper
```
protected StatementWrapper(Statement wrapped)
```
    Builds a new instance.
    
    Parameters:
    
    wrapped - the wrapped statement.
- Method Detail
  - setConsistencyLevel
```
public Statement setConsistencyLevel(ConsistencyLevel consistency)
```
    Description copied from class: Statement
    
    Sets the consistency level for the query.
    
    Overrides:
    
    setConsistencyLevel in class Statement
    
    Parameters:
    
    consistency - the consistency level to set.
    
    Returns:
    
    this Statement object.
  - disableTracing
```
public Statement disableTracing()
```
    Description copied from class: Statement
    
    Disables tracing for this query.
    
    Overrides:
    
    disableTracing in class Statement
    
    Returns:
    
    this Statement object.
  - setSerialConsistencyLevel
```
public Statement setSerialConsistencyLevel(ConsistencyLevel serialConsistency)
```
    Description copied from class: Statement
    
    Sets the serial consistency level for the query. The serial consistency level is only used by conditional updates (so INSERT, UPDATE and DELETE with an IF condition). For those, the serial consistency level defines the consistency level of the serial phase (or "paxos" phase) while the normal consistency level defines the consistency for the "learn" phase, i.e. what type of reads will be guaranteed to see the update right away. For instance, if a conditional write has a regular consistency of QUORUM (and is successful), then a QUORUM read is guaranteed to see that write. But if the regular consistency of that write is ANY, then only a read with a consistency of SERIAL is guaranteed to see it (even a read with consistency ALL is not guaranteed to be enough).
    The serial consistency can only be one of ConsistencyLevel.SERIAL or ConsistencyLevel.LOCAL_SERIAL. While ConsistencyLevel.SERIAL guarantees full linearizability (with other SERIAL updates), ConsistencyLevel.LOCAL_SERIAL only guarantees it in the local data center.
    The serial consistency level is ignored for any query that is not a conditional update (serial reads should use the regular consistency level for instance).
    
    Overrides:
    
    setSerialConsistencyLevel in class Statement
    
    Parameters:
    
    serialConsistency - the serial consistency level to set.
    
    Returns:
    
    this Statement object.
  - enableTracing
```
public Statement enableTracing()
```
    Description copied from class: Statement
    
    Enables tracing for this query. By default (that is unless you call this method), tracing is not enabled.
    
    Overrides:
    
    enableTracing in class Statement
    
    Returns:
    
    this Statement object.
  - getPagingState
```
public ByteBuffer getPagingState()
```
  - isTracing
```
public boolean isTracing()
```
    Description copied from class: Statement
    
    Returns whether tracing is enabled for this query or not.
    
    Overrides:
    
    isTracing in class Statement
    
    Returns:
    
    true if this query has tracing enabled, false otherwise.
  - getRetryPolicy
```
public RetryPolicy getRetryPolicy()
```
    Description copied from class: Statement
    
    Returns the retry policy sets for this query, if any.
    
    Overrides:
    
    getRetryPolicy in class Statement
    
    Returns:
    
    the retry policy sets specifically for this query or null if no query specific retry policy has been set through Statement.setRetryPolicy(com.datastax.driver.core.policies.RetryPolicy) (in which case the Cluster retry policy will apply if necessary).
  - getRoutingKey
```
public ByteBuffer getRoutingKey()
```
    Description copied from class: Statement
    
    Returns the routing key (in binary raw form) to use for token aware routing of this query.
    The routing key is optional in that implementers are free to return null. The routing key is an hint used for token-aware routing (see TokenAwarePolicy), and if provided should correspond to the binary value for the query partition key. However, not providing a routing key never causes a query to fail and if the load balancing policy used is not token aware, then the routing key can be safely ignored.
    
    Specified by:
    
    getRoutingKey in class Statement
    
    Returns:
    
    the routing key for this query or null.
  - setRetryPolicy
```
public Statement setRetryPolicy(RetryPolicy policy)
```
    Description copied from class: Statement
    
    Sets the retry policy to use for this query.
    The default retry policy, if this method is not called, is the one returned by Policies.getRetryPolicy() in the cluster configuration. This method is thus only useful in case you want to punctually override the default policy for this request.
    
    Overrides:
    
    setRetryPolicy in class Statement
    
    Parameters:
    
    policy - the retry policy to use for this query.
    
    Returns:
    
    this Statement object.
  - getConsistencyLevel
```
public ConsistencyLevel getConsistencyLevel()
```
    Description copied from class: Statement
    
    The consistency level for this query.
    
    Overrides:
    
    getConsistencyLevel in class Statement
    
    Returns:
    
    the consistency level for this query, or null if no consistency level has been specified (through setConsistencyLevel). In the latter case, the default consistency level will be used.
  - setPagingState
```
public Statement setPagingState(PagingState pagingState)
```
    Description copied from class: Statement
    Sets the paging state.
    This will cause the next execution of this statement to fetch results from a given page, rather than restarting from the beginning.
    You get the paging state from a previous execution of the statement (see ExecutionInfo.getPagingState(). This is typically used to iterate in a "stateless" manner (e.g. across HTTP requests):
```
 
 Statement st = new SimpleStatement("your query");
 ResultSet rs = session.execute(st.setFetchSize(20));
 int available = rs.getAvailableWithoutFetching();
 for (int i = 0; i < available; i++) {
     Row row = rs.one();
     // Do something with row (e.g. display it to the user...)
 }
 // Get state and serialize as string or byte[] to store it for the next execution
 // (e.g. pass it as a parameter in the "next page" URI)
 PagingState pagingState = rs.getExecutionInfo().getPagingState();
 String savedState = pagingState.toString();

 // Next execution:
 // Get serialized state back (e.g. get URI parameter)
 String savedState = ...
 Statement st = new SimpleStatement("your query");
 st.setPagingState(PagingState.fromString(savedState));
 ResultSet rs = session.execute(st.setFetchSize(20));
 int available = rs.getAvailableWithoutFetching();
 for (int i = 0; i < available; i++) {
     ...
 }
 
 
```
    The paging state can only be reused between perfectly identical statements (same query string, same bound parameters). Altering the contents of the paging state or trying to set it on a different statement will cause this method to fail.
    Note that, due to internal implementation details, the paging state is not portable across native protocol versions (see the online documentation for more explanations about the native protocol). This means that PagingState instances generated with an old version won't work with a higher version. If that is a problem for you, consider using the "unsafe" API (see Statement.setPagingStateUnsafe(byte[])).
    Overrides:
    
    setPagingState in class Statement
    
    Parameters:
    
    pagingState - the paging state to set, or null to remove any state that was previously set on this statement.
    
    Returns:
    
    this Statement object.
  - getSerialConsistencyLevel
```
public ConsistencyLevel getSerialConsistencyLevel()
```
    Description copied from class: Statement
    
    The serial consistency level for this query.
    See Statement.setSerialConsistencyLevel(com.datastax.driver.core.ConsistencyLevel) for more detail on the serial consistency level.
    
    Overrides:
    
    getSerialConsistencyLevel in class Statement
    
    Returns:
    
    the consistency level for this query, or null if no serial consistency level has been specified (through setSerialConsistencyLevel). In the latter case, the default serial consistency level will be used.
  - getKeyspace
```
public String getKeyspace()
```
    Description copied from class: Statement
    
    Returns the keyspace this query operates on.
    Note that not all query specify on which keyspace they operate on, and so this method can always return null. Firstly, some queries do not operate inside a keyspace: keyspace creation, USE queries, user creation, etc. Secondly, even query that operate within a keyspace do not have to specify said keyspace directly, in which case the currently logged in keyspace (the one set through a USE query (or through the use of Cluster.connect(String))). Lastly, as for the routing key, this keyspace information is only a hint for token-aware routing (since replica placement depend on the replication strategy in use which is a per-keyspace property) and having this method return null (or even a bogus keyspace name) will never cause the query to fail.
    
    Specified by:
    
    getKeyspace in class Statement
    
    Returns:
    
    the keyspace this query operate on if relevant or null.
  - getFetchSize
```
public int getFetchSize()
```
    Description copied from class: Statement
    
    The fetch size for this query.
    
    Overrides:
    
    getFetchSize in class Statement
    
    Returns:
    
    the fetch size for this query. If that value is less or equal to 0 (the default unless Statement.setFetchSize(int) is used), the default fetch size will be used.
  - setFetchSize
```
public Statement setFetchSize(int fetchSize)
```
    Description copied from class: Statement
    
    Sets the query fetch size.
    The fetch size controls how much resulting rows will be retrieved simultaneously (the goal being to avoid loading too much results in memory for queries yielding large results). Please note that while value as low as 1 can be used, it is *highly* discouraged to use such a low value in practice as it will yield very poor performance. If in doubt, leaving the default is probably a good idea.
    Only SELECT queries only ever make use of that setting.
    Note: Paging is not supported with the native protocol version 1. If you call this method with fetchSize > 0 and fetchSize != Integer.MAX_VALUE and the protocol version is in use (i.e. if you've force version 1 through Cluster.Builder.withProtocolVersion(int) or you use Cassandra 1.2), you will get UnsupportedProtocolVersionException when submitting this statement for execution.
    
    Overrides:
    
    setFetchSize in class Statement
    
    Parameters:
    
    fetchSize - the fetch size to use. If fetchSize &lte; 0, the default fetch size will be used. To disable paging of the result set, use fetchSize == Integer.MAX_VALUE.
    
    Returns:
    
    this Statement object.

Class StatementWrapper

Field Summary

Fields inherited from class com.datastax.driver.core.Statement

Constructor Summary

Method Summary

Methods inherited from class com.datastax.driver.core.Statement

Methods inherited from class java.lang.Object

Constructor Detail

StatementWrapper

Method Detail

setConsistencyLevel

disableTracing

setSerialConsistencyLevel

enableTracing

getPagingState

isTracing

getRetryPolicy

getRoutingKey

setRetryPolicy

getConsistencyLevel

setPagingState

getSerialConsistencyLevel

getKeyspace

getFetchSize

setFetchSize