Package oracle.nosql.driver.ops

Class QueryRequest

java.lang.Object
oracle.nosql.driver.ops.Request
oracle.nosql.driver.ops.DurableRequest
oracle.nosql.driver.ops.QueryRequest
All Implemented Interfaces:
AutoCloseable
public class QueryRequest extends DurableRequest implements AutoCloseable
A request that represents a query. A query may be specified as either a textual SQL statement (a String) or a prepared query (an instance of PreparedStatement), which may include bind variables.

For performance reasons prepared queries are preferred for queries that may be reused. This is because prepared queries bypass query compilation. They also allow for parameterized queries using bind variables.

There are two ways to get the results of a query: using an iterator or loop through partial results.

Iterator

Use NoSQLHandle.queryIterable(QueryRequest) to get an iterable that contains all the results. Usage example: 

    NoSQLHandle handle = ...;

    try (
        QueryRequest qreq = new QueryRequest().setStatement("select * from foo");
        QueryIterableResult qir = handle.queryIterable(qreq)) {
        for( MapValue row : qir) {
            // do something with row
        }
    }

Partial results

To compute and retrieve the full result set of a query, the same QueryRequest instance will, in general, have to be executed multiple times (via NoSQLHandle.query(oracle.nosql.driver.ops.QueryRequest). Each execution returns a QueryResult, which contains a subset of the result set. The following code snipet illustrates a typical query execution: 

 NoSQLHandle handle = ...;

 QueryRequest qreq = new QueryRequest().setStatement("select * from foo");

 do {
   QueryResult qres = handle.query(qreq);
   List<MapValue> results = qres.getResults();
   // do something with the results
 } while (!qreq.isDone())
Notice that a batch of results returned by a QueryRequest execution may be empty. This is because during each execution the query is allowed to read or write a maximum number of bytes. If this maximum is reached, execution stops. This can happen before any result was generated (for example, if none of the rows read satisfied the query conditions).

If an application wishes to terminate query execution before retrieving all the query results, it should call close() in order to release any local resources held by the query. This also allows the application to reuse the QueryRequest instance to run the same query from the beginning or a different query.

QueryRequest instances are not thread-safe. That is, if two or more application threads need to run the same query concurrently, they must create and use their own QueryRequest instances.

See Also:

  • Constructor Details

    • QueryRequest

      public QueryRequest()
      Default constructor for QueryRequest

  • Method Details

    • setCompartment

      public QueryRequest setCompartment(String compartment)
      Cloud service only.

      Sets the name or id of a compartment to be used for this operation.

      The compartment may be specified as either a name (or path for nested compartments) or as an id (OCID). A name (vs id) can only be used when authenticated using a specific user identity. It is not available if authenticated as an Instance Principal which can be done when calling the service from a compute instance in the Oracle Cloud Infrastructure. See SignatureProvider.createWithInstancePrincipal()

      Parameters:
      compartment - the name or id. If using a nested compartment, specify the full compartment path compartmentA.compartmentB, but exclude the name of the root compartment (tenant).
      Returns:
      this

    • getLimit

      public int getLimit()
      Returns the limit on number of items returned by the operation. If not set by the application this value will be 0 which means no limit set.
      Returns:
      the limit, or 0 if not set

    • setLimit

      public QueryRequest setLimit(int limit)
      Sets the limit on number of items returned by the operation. This allows an operation to return less than the default amount of data.
      Parameters:
      limit - the limit in terms of number of items returned
      Returns:
      this
      Throws:
      IllegalArgumentException - if the limit value is less than 0.

    • getMaxReadKB

      public int getMaxReadKB()
      Returns the limit on the total data read during this operation, in KB. If not set by the application this value will be 0 which means no application-defined limit.
      Returns:
      the limit, or 0 if not set

    • setMaxReadKB

      public QueryRequest setMaxReadKB(int maxReadKB)
      Sets the limit on the total data read during this operation, in KB. This value can only reduce the system defined limit. This limit is independent of read units consumed by the operation. It is recommended that for tables with relatively low provisioned read throughput that this limit be reduced to less than or equal to one half of the provisioned throughput in order to avoid or reduce throttling exceptions.
      Parameters:
      maxReadKB - the limit in terms of number of KB read during this operation.
      Returns:
      this
      Throws:
      IllegalArgumentException - if the maxReadKB value is less than 0

    • getMaxWriteKB

      public int getMaxWriteKB()
      Returns the limit on the total data written during this operation, in KB. If not set by the application this value will be 0 which means no application-defined limit.
      Returns:
      the limit, or 0 if not set

    • setMaxWriteKB

      public QueryRequest setMaxWriteKB(int maxWriteKB)
      Sets the limit on the total data written during this operation, in KB. This limit is independent of write units consumed by the operation.
      Parameters:
      maxWriteKB - the limit in terms of number of KB written during this operation.
      Returns:
      this
      Throws:
      IllegalArgumentException - if the maxWriteKB value is less than 0

    • setMaxMemoryConsumption

      public QueryRequest setMaxMemoryConsumption(long maxBytes)
      Sets the maximum number of memory bytes that may be consumed by the statement at the driver for operations such as duplicate elimination (which may be required due to the use of an index on an array or map) and sorting. Such operations may consume a lot of memory as they need to cache the full result set or a large subset of it at the client memory. If the maximum amount of memory is exceeded, a exception will be throw.

      The default value is 1GB.

      Parameters:
      maxBytes - the amount of memory to use, in bytes
      Returns:
      this

    • getMaxMemoryConsumption

      public long getMaxMemoryConsumption()
      Returns the maximum number of memory bytes that may be consumed by the statement at the driver for operations such as duplicate elimination (which may be required due to the use of an index on an array or map) and sorting (sorting by distance when a query contains a geo_near() function). Such operations may consume a lot of memory as they need to cache the full result set at the client memory.

      The default value is 1GB.

      Returns:
      the maximum number of memory bytes

    • getMathContext

      public MathContext getMathContext()
      Returns the MathContext used for BigDecimal operations. MathContext.DECIMAL32 is used by default.
      Returns:
      the MathContext to use for the query

    • setMathContext

      public QueryRequest setMathContext(MathContext mathContext)
      Sets the MathContext used for BigDecimal operations. MathContext.DECIMAL32 is used by default.
      Parameters:
      mathContext - the MathContext to use for the query
      Returns:
      this

    • getStatement

      public String getStatement()
      Returns the query statement
      Returns:
      the statement, or null if it has not been set

    • setStatement

      public QueryRequest setStatement(String statement)
      Sets the query statement.
      Parameters:
      statement - the query statement
      Returns:
      this

    • getPreparedStatement

      public PreparedStatement getPreparedStatement()
      Returns the prepared query statement
      Returns:
      the statement, or null if it has not been set

    • setPreparedStatement

      public QueryRequest setPreparedStatement(PreparedStatement preparedStatement)
      Sets the prepared query statement.
      Parameters:
      preparedStatement - the prepared query statement
      Returns:
      this

    • setPreparedStatement

      public QueryRequest setPreparedStatement(PrepareResult prepareResult)
      A convenience method to set the prepared query statement from a PrepareResult
      Parameters:
      prepareResult - the result of a prepare request
      Returns:
      this

    • getContinuationKey

      @Deprecated public byte[] getContinuationKey()
      Deprecated.
      Returns the continuation key if set
      Returns:
      the key

    • setContinuationKey

      @Deprecated public QueryRequest setContinuationKey(byte[] continuationKey)
      Deprecated.
      There is no reason to use this method anymore, because setting the continuation key is now done internally.
      Sets the continuation key. This is used to continue an operation that returned this key in its QueryResult.
      Parameters:
      continuationKey - the key which should have been obtained from QueryResult.getContinuationKey()
      Returns:
      this;

    • isDone

      public boolean isDone()
      Returns true if the query execution is finished, i.e., there are no more query results to be generated. Otherwise false.
      Returns:
      whether the query is execution is finished or not

    • close

      public void close()
      Terminates the query execution and releases any memory consumed by the query at the driver. An application should use this method if it wishes to terminate query execution before retrieving all of the query results.
      Specified by:
      close in interface AutoCloseable

    • setConsistency

      public QueryRequest setConsistency(Consistency consistency)
      Sets the Consistency to use for the operation
      Parameters:
      consistency - the Consistency
      Returns:
      this

    • setDurability

      public QueryRequest setDurability(Durability durability)
      Sets the durability to use for the operation. On-premises only. This setting only applies if the query modifies a row using an INSERT, UPSERT, or DELETE statement. If the query is read-only it is ignored.
      Parameters:
      durability - the durability value. Set to null for the default durability setting on the server.
      Returns:
      this
      Since:
      5.4.0

    • getConsistency

      public Consistency getConsistency()
      Returns the consistency set for this request, or null if not set.
      Returns:
      the consistency

    • setTimeout

      public QueryRequest setTimeout(int timeoutMs)
      Sets the request timeout value, in milliseconds. This overrides any default value set with NoSQLHandleConfig.setRequestTimeout(int). The value must be positive.
      Parameters:
      timeoutMs - the timeout value, in milliseconds
      Returns:
      this
      Throws:
      IllegalArgumentException - if the timeout value is less than or equal to 0

    • setNamespace

      public QueryRequest setNamespace(String namespace)
      Sets the optional namespace. On-premises only. This overrides any default value set with NoSQLHandleConfig.setDefaultNamespace(java.lang.String). Note: if a namespace is specified in the table name in the SQL statement (using the namespace:tablename format), that value will override this setting.
      Parameters:
      namespace - the namespace to use for the operation
      Returns:
      this
      Since:
      5.4.10

    • getTimeout

      public int getTimeout()
      Returns the timeout to use for the operation, in milliseconds. A value of 0 indicates that the timeout has not been set.
      Returns:
      the value

    • getTypeName

      public String getTypeName()
      Description copied from class: Request
      Returns the type name of the request. This is used for stats.
      Specified by:
      getTypeName in class Request
      Returns:
      the type name of the request