Iterating over Data Stored in an IMDC with the API - Aster Execution Engine

Teradata Aster® Developer Guide
Product
Aster Execution Engine
Release Number
7.00.02
Published
July 2017
Language
English (United States)
Last Update
2018-04-13
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lifecycle
previous
Product Category
Software

When an IMDC is in the iterable state, you can iterate over its data.

You cannot iterate over IMDC data during contract negotiation.
  • Iterate over the data in an iterable IMDC: 
    import java.util.List;
import java.util.ArrayList;
import com.asterdata.ncluster.sqlmr.RowFunction;
import com.asterdata.ncluster.sqlmr.data.RowEmitter;
import com.asterdata.ncluster.sqlmr.data.RowIterator;
import com.asterdata.ncluster.sqlmr.InMemoryDataCollectionRepository;
import com.asterdata.ncluster.sqlmr.data.InMemoryDataCollection;
import com.asterdata.ncluster.sqlmr.data.InMemoryDataCollectionRowIterator;
import com.asterdata.ncluster.sqlmr.data.SqlType;
import com.asterdata.ncluster.sqlmr.data.RowView;
import com.asterdata.ncluster.sqlmr.data.RowBuilder;
  
...
  public void drainOutputRows(RowEmitter outputEmitter)
  {
    ...
    //Get handle to IMDC
    InMemoryDataCollection IMDC_name =
      InMemoryDataCollectionRepository.getInMemoryDataCollection(
        "IMDC_name",
        TaskInfo);
        
    //Get iterator to iterate over rows stored in IMDC
    InMemoryDataCollectionRowIterator IMDC_rowIterator_var =
      myIMDC.newRowIterator();
        
      while( IMDC_rowIterator_var.advanceToNextRow() )
      {
         outputEmitter.addInt(IMDC_rowIterator_var.gettype_0At(0));
         outputEmitter.addDouble(IMDC_rowIterator_var.gettype_1At(1));
         ...
         outputEmitter.addString(IMDC_rowIterator_var.gettype_nAt(n));
         outputEmitter.emitRow();
      }
      ...
   }
    For example, the following code iterates over the rows of an IMDC named myIMDC, which has columns of types integer, double, and var.
    import java.util.List;
import java.util.ArrayList;
import com.asterdata.ncluster.sqlmr.RowFunction;
import com.asterdata.ncluster.sqlmr.data.RowEmitter;
import com.asterdata.ncluster.sqlmr.data.RowIterator;
import com.asterdata.ncluster.sqlmr.InMemoryDataCollectionRepository;
import com.asterdata.ncluster.sqlmr.data.InMemoryDataCollection;
import com.asterdata.ncluster.sqlmr.data.InMemoryDataCollectionRowIterator;
import com.asterdata.ncluster.sqlmr.data.SqlType;
import com.asterdata.ncluster.sqlmr.data.RowView;
import com.asterdata.ncluster.sqlmr.data.RowBuilder;
  
...
  public void drainOutputRows(RowEmitter outputEmitter)
  {
    ...
    //Get handle to IMDC
    InMemoryDataCollection myIMDC =
      InMemoryDataCollectionRepository.getInMemoryDataCollection(
        "myIMDC",
        TaskInfo);
        
    //Get iterator to iterate over rows stored in IMDC
    InMemoryDataCollectionRowIterator myIMDC_rowIterator =
      myIMDC.newRowIterator();
        
      while( myIMDC_rowIterator.advanceToNextRow() )
      {
         outputEmitter.addInt(myIMDC_rowIterator.getIntAt(0));
         outputEmitter.addDouble(myIMDC_rowIterator.getDoubleAt(1));
         outputEmitter.addString(myIMDC_rowIterator.getStringAt(2));
         outputEmitter.emitRow();
      }
      ...
   }
    An alternative to getting a handle to the IMDC is to use a variable of the type RowIterator, because InMemoryDataCollectionRowIterator extends the RowIterator interface.
The row iterator remains open until you close it. To close the row iterator, call the method RowIterator::endIteration.