During contract negotiation, you can associate an IMDC with an input iterator. Then, when an input source is associated with the IMDC, the input iterator is provided to data-consuming methods, which iterate over the data in the IMDC. Associating an IMDC with an input iterator is an easy way to integrate the use of the IMDC with a SQL-MapReduce function.
The IMDC must exist before the data-consuming methods are invoked. You can create the IMDC with the API or a utility function, or the IMDC can be created by a SQL-MapReduce function that was called by an earlier query in the session.
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Associate an IMDC with an input iterator during contract negotiation:
public function_name (RuntimeContract contract) { ... InputInfo inputInfo = contract.getInputInfo(); contract.useInMemoryDataCollectionForInput(inputInfo, "IMDC_name"); ... }
An input iterator is now associated with the IMDC. When the IMDC exists and an input source is associated with it, the input iterator is provided to the data-consuming method, which iterates over the data in the IMDC.
For example, the function my_sqlmr associates an input iterator with the IMDC myIMDC, and the input iterator iterates over the myIMDC:
public my_sqlmr (RuntimeContract contract)
{
...
InputInfo inputInfo = contract.getInputInfo();
contract.useInMemoryDataCollectionForInput(inputInfo, "myIMDC");
...
}
public void operateOnSomeRows(
RowIterator inputIterator,
RowEmitter outputEmitter
)
{
//inputIterator iterates over data in IMDC "myIMDC"
while ( inputIterator.advanceToNextRow() )
{
outputEmitter.addFromRow(inputIterator);
outputEmitter.emitRow();
}
}