Vertica::UDSource Class Reference

Acquires data from an external source (such as a file or URL) and produces that data in a streaming manner. More...

Inheritance diagram for Vertica::UDSource:

Collaboration diagram for Vertica::UDSource:

Public Member Functions
virtual void	destroy (ServerInterface &srvInterface)
virtual void	destroy (ServerInterface &srvInterface, SessionParamWriterMap &udSessionParams)
virtual Portion	getPortion ()
virtual vint	getSize ()
virtual std::string	getUri ()
virtual StreamState	process (ServerInterface &srvInterface, DataBuffer &output)=0
virtual size_t	requestMinBufferSize (ServerInterface &srvInterface)
virtual void	setup (ServerInterface &srvInterface)

Static Public Attributes
static const size_t	DEFAULT_MIN_BUFFER_SIZE = 1024 * 1024

Detailed Description

Acquires data from an external source (such as a file or URL) and produces that data in a streaming manner.

The output of a UDSource can be sent through one or more UDFilters followed by one UDParser.

Member Function Documentation

virtual void Vertica::UDSource::destroy ( ServerInterface &  srvInterface )

inlinevirtual

UDSource::destroy()

Will be invoked during query execution, after the last time that process() is called on this UDSource instance.

May optionally be overridden to perform tear-down/destruction.

Reimplemented from Vertica::UnsizedUDSource.

virtual Portion Vertica::UDSource::getPortion ( )

inlinevirtual

UDSource::getPortion()

Gets this source's split if the source is apportioned. Default implementation return a Portion instance from default constructor {o=-1, s=-1, t=false}.

Implements Vertica::UnsizedUDSource.

virtual vint Vertica::UDSource::getSize ( )

inlinevirtual

UDSource::getSize()

Returns the estimated number of bytes that process() will return.

This value is treated as advisory only. It is used to indicate the file size in the LOAD_STREAMS and LOAD_SOURCES tables.

IMPORTANT: getSize() can be called at any time, even before setup() is called! (Though not before or during the constructor.)

In the case of Sources whose factories can potentially produce many UDSource instances, getSize() should avoid acquiring resources that last for the life of the object. Doing otherwise can defeat Vertica's attempts to limit the maximum number of Sources that are consuming system resources at any given time. For example, if it opens a file handle and leaves that file handle open for use by process(), and if a large number of UDSources are loaded in a single statement, the query may exceed the operating system limit on file handles and crash, even though Vertica only operates on a small number of files at once. This doesn't apply to singleton Sources, Sources whose factory will only ever produce one UDSource instance.

virtual std::string Vertica::UnsizedUDSource::getUri ( )

inlinevirtualinherited

UnsizedUDSource::getUri()

Return the URI of the current source of data.

This function will be invoked during execution to fill in monitoring information.

virtual StreamState Vertica::UDSource::process ( ServerInterface &  srvInterface, DataBuffer &  output  )

pure virtual

UDSource::process()

Reads data from the input source and processes it. Vertica invokes this function repeatedly until it returns DONE or the query is cancelled by the user.

Input: an external data source.
Output: a stream of bytes.

On each invocation, process() should acquire more data and write that data to the buffer specified by output.

process() must set output.offset to the number of bytes that were written to the output buffer. It is common, though not necessary, for this to be the same as output.size. output.offset is initially uninitialized. If it is set to 0, this indicates that the output buffer is too small for process() to be able to write a unit of input to it.

Note that, unless OUTPUT_NEEDED is returned, output will be UNMODIFIED the next time process() is called. This means that pointers into the buffer will continue to be valid. It also means that output.offset may be set. So, in general, process() code should assume that buffers start at output.buf[output.offset]. Note also that, as a performance optimization, upstream operators may start processing emitted data (data between output.buf[0] and output.buf[output.offset]) before OUTPUT_NEEDED is returned. For this reason, output.offset must be strictly increasing.

process() must not block indefinitely. If it cannot proceed for an extended period of time, it should return KEEP_GOING. It will be called again shortly. Failure to do this will, among other things, prevent the query from being canceled by the user.

Returns

OUTPUT_NEEDED if this UDSource has more data to produce; DONE if has no more data to produce.

Note that it is UNSAFE to maintain pointers or references to any of these arguments (or any other argument passed by reference into any other function in this API) beyond the scope of the function call in question. For example, do not store a reference to the server interface or the input block on an instance variable. Vertica may free and replace these objects.

Implements Vertica::UnsizedUDSource.

virtual size_t Vertica::UnsizedUDSource::requestMinBufferSize ( ServerInterface &  srvInterface )

inlinevirtualinherited

Request a minimum buffer size into which this source will read data. This will be called after setup(), before the first call to process().

virtual void Vertica::UDSource::setup ( ServerInterface &  srvInterface )

inlinevirtual

UDSource::setup()

Will be invoked during query execution, prior to the first time that process() is called on this UDSource instance.

May optionally be overridden to perform setup/initialzation.

Reimplemented from Vertica::UnsizedUDSource.