net.sf.saffron.oj.rel
Class JavaAggregateRel

java.lang.Object
  |
  +--net.sf.saffron.rel.SaffronRel
        |
        +--net.sf.saffron.rel.SingleRel
              |
              +--net.sf.saffron.rel.AggregateRel
                    |
                    +--net.sf.saffron.oj.rel.JavaAggregateRel

public class JavaAggregateRel

extends AggregateRel

JavaAggregateRel implements the AggregateRel relational operator by generating code. The code looks like this:

HashMap h = new HashMap();
 for each child
   HashableArray groups = new HashableArray(
     new Object[] {
   	 child.field4,
   	 child.field2});
   Object[] aggs = h.get(groups);
   if (aggs == null) {
     aggs = new Object[<>];
     aggs[0] = agg start code;
     aggs[1] = agg start code;
     h.put(groups, aggs);
   }
   agg inc code {aggs[0], childRow}
   agg inc code {aggs[1], childRow}
 end for
 Iterator keys = h.keys();
 while (keys.hasNext()) {
 	 T row = new T();
 	 HashableArray groups = (HashableArray) keys.next();
 	 row.c0 = groups[0];
 	 row.c1 = groups[1];
 	 Object[] aggs = h.get(groups);
 	 row.c2 = agg result code {aggs[0]}
 	 row.c3 = agg result code {aggs[1]}
   emit row to parent
 }

Simplifications:

• If there is onle one group column, the HashableArray is simplified to Object.
• If there is only one aggregate, the Object[] are simplified to Object.
• todo: Write an efficient implementation if there are no group columns.
• If there are no aggregations, JavaDistinctRel is more efficient.

Nested Class Summary

Nested classes inherited from class net.sf.saffron.rel.AggregateRel

AggregateRel.Call

Field Summary

(package private) Variable

var_h

Fields inherited from class net.sf.saffron.rel.AggregateRel

aggCalls, groupCount

Fields inherited from class net.sf.saffron.rel.SingleRel

child

Fields inherited from class net.sf.saffron.rel.SaffronRel

cluster, digest, id, rowType

Constructor Summary

JavaAggregateRel(VolcanoCluster cluster, SaffronRel child, int groupCount, AggregateRel.Call[] aggCalls)

Method Summary

Object	clone()
PlanCost	computeSelfCost(SaffronPlanner planner) Returns the cost of this plan (not including children).
CallingConvention	getConvention() Returns a value from CallingConvention.
Object	implement(RelImplementor implementor, int ordinal) Create a plan for this expression according to a calling convention.

Methods inherited from class net.sf.saffron.rel.AggregateRel

deriveRowType, getAggCalls, getGroupCount

Methods inherited from class net.sf.saffron.rel.SingleRel

childrenAccept, explain, getInputs, getRows, replaceInput

Methods inherited from class net.sf.saffron.rel.SaffronRel

computeDigest, getChildExps, getCluster, getCorrelVariable, getId, getInput, getOrCreateCorrelVariable, getQualifier, getQuery, getRelTypeName, getRowType, getTable, getVariablesStopped, implementFieldAccess, isAccessTo, isDistinct, onRegister, recomputeDigest, register, registerCorrelVariable, setCorrelVariable, toString

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

var_h

Variable var_h

Constructor Detail

JavaAggregateRel

public JavaAggregateRel(VolcanoCluster cluster,
                        SaffronRel child,
                        int groupCount,
                        AggregateRel.Call[] aggCalls)

Method Detail

getConvention

public CallingConvention getConvention()

Description copied from class: SaffronRel

Returns a value from CallingConvention.

Overrides:

getConvention in class SaffronRel

clone

public Object clone()

Overrides:

clone in class AggregateRel

computeSelfCost

public PlanCost computeSelfCost(SaffronPlanner planner)

Description copied from class: SaffronRel

Returns the cost of this plan (not including children). The base implementation throws an error; derived classes should override.

Overrides:

computeSelfCost in class AggregateRel

implement

public Object implement(RelImplementor implementor,
                        int ordinal)

Description copied from class: SaffronRel

Create a plan for this expression according to a calling convention.

Overrides:

implement in class SaffronRel

Parameters:

implementor - implementor

ordinal - indicates our position in the pre-, in- and postfix walk over the tree; ordinal is -1 when called from the parent, and i when called from the i^th child.