Vertica::IterativeSourceFactory Class Reference

Source factory that works with a SourceIterator to produce UDSources. More...

Inheritance diagram for Vertica::IterativeSourceFactory:

Collaboration diagram for Vertica::IterativeSourceFactory:

Public Member Functions
virtual ssize_t	getDesiredThreads (ServerInterface &srvInterface, ExecutorPlanContext &planCtxt)
UDXFactory::UDXType	getUDXFactoryType () __override__
virtual bool	isSourceApportionable ()
virtual void	plan (ServerInterface &srvInterface, NodeSpecifyingPlanContext &planCtxt)
virtual SourceIterator *	prepare (ServerInterface &srvInterface, NodeSpecifyingPlanContext &planCtxt)
virtual SourceIterator *	prepareExecutor (ServerInterface &srvInterface, ExecutorPlanContext &planCtxt)

Detailed Description

Source factory that works with a SourceIterator to produce UDSources.

Usually it is easier to subclass SourceFactory and have its prepareUDSources() method return a vector of UDSource objects. Behind the scenes, Vertica uses a built-in iterator to pull sources from that vector. However, if you need to be able to control source management at this level, you can instead write your own SourceIterator and use it with an IterativeSourceFactory.

This class performs initial validation and planning of a query, before it is distributed over the network. It also instantiates objects to perform further initialization on each node, once the query has been distributed.

Note that SourceFactories are singletons. Subclasses should be stateless, with no fields containing data, just methods. plan() and prepare() methods must never modify any global variables or state; they may only modify the variables that they are given as arguments. (If global state must be modified, use SourceIterator.)

Factories should be registered using the RegisterFactory() macro, defined in Vertica.h.

Member Function Documentation

virtual ssize_t Vertica::IterativeSourceFactory::getDesiredThreads ( ServerInterface &  srvInterface, ExecutorPlanContext &  planCtxt  )

inlinevirtual

Request the number of threads that the SourceFactory wants to use. This function is called on each node before prepare().

'planCtxt' contains the same parameters stored by plan() method. It also exposes the maximum number of allowed threads, via 'getMaxAllowedThreads()'. Further computations can be stored in its 'ExecutorParamWriter' object, for use in prepare().

Reimplemented in Vertica::SourceFactory.

virtual void Vertica::IterativeSourceFactory::plan ( ServerInterface &  srvInterface, NodeSpecifyingPlanContext &  planCtxt  )

inlinevirtual

Execute any planning logic required at query plan time. This method is run once per query, during query initialization. Its job is to perform parameter validation, and to modify the set of nodes that the COPY statement will run on.

plan() runs exactly once per query, on the initiator node. If it throws an exception, the query will not proceed; it will be aborted prior to distributing the query to the other nodes and running prepare().

Reimplemented in Vertica::SourceFactory.

virtual SourceIterator* Vertica::IterativeSourceFactory::prepareExecutor ( ServerInterface &  srvInterface, ExecutorPlanContext &  planCtxt  )

inlinevirtual

Prepare this SourceFactory to start creating sources. This function will be called on each node, prior to the Load operator starting to execute and prior to any other virtual functions on this class being called.

'planCtxt' contains the same data that was placed there by the plan() and getDesiredThreads() methods.