net.sf.farrago.fennel.rel
Class FarragoMultisetSplitterRule

java.lang.Object
  org.eigenbase.relopt.RelOptRule
      net.sf.farrago.fennel.rel.FarragoMultisetSplitterRule

public class FarragoMultisetSplitterRule
extends RelOptRule

FarragoMultisetSplitterRule is a planner rule which removes multiset operations from an expression.

It works in three ways:

1. It works on relational expressions consisting of a mix between multiset and non-multisets calls, splitting them up. For example, CARDINALITY(ms) != 632
2. It works on relational expressions consisting of nested multiset calls, splitting them up. For example, CARDINALITY(ms1 MULTISET UNION ms2)
3. It also transforms a multiset call to an equivalent RelNode tree.

It uses the CalcRelSplitter for its splitting. Example: The expression CARDINALITY(ms) = 5 begins its life as: CalcRel=[=(CARD(ms),5)] After the split it, looks in principle like:

CalcRel=[=($in_ms,5]
   CalcRel=[CARD(ms)]

See CalcRelSplitter on details of the split.

CalcRel=[CARD(ms)] is intercepted in this very same rule and an equivalent RelNode tree is injected in its place.

Since:

Mar 10, 2005

Version:

$Id: //open/dev/farrago/src/net/sf/farrago/fennel/rel/FarragoMultisetSplitterRule.java#4 $

Author:

Wael Chatila

Nested Class Summary

private class	FarragoMultisetSplitterRule.MultisetRelSplitter Unmix mixing between multisets and non-multisets
private class	FarragoMultisetSplitterRule.NestedRelSplitter Unnest nested multiset calls

Field Summary

static FarragoMultisetSplitterRule

instance

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

private

FarragoMultisetSplitterRule() Creates a FarragoMultisetSplitterRule.

Method Summary

private boolean	containsNestedMultiset(RexNode node, boolean deep) Returns true if node contains a multiset call directly under another multiset call.
private boolean	containsNestedMultiset(RexProgram program) Returns true if any expression in a program contains a multiset call directly under another multiset call.
RelNode	createExistsPlanSingleRow(RelNode child, boolean neg)
private static RelNode	createLimitRel(RelNode child) Creates a relational expression which ensures that a given expression only returns one row, and throws a runtime error otherwise.
private static RelNode	createProject(CalcRel calc, RexLocalRef local, List<CorrelatorRel.Correlation> correlationList)
private static UncollectRel	createUncollect(CalcRel calc, RexLocalRef local, List<CorrelatorRel.Correlation> correlationList)
private int	findMultiset(List<RexNode> exprs)
private CorrelatorRel	insertRels(CalcRel calc, int offset) Injects an equivalent RelNode tree to a RexCall's multiset operator.
void	onMatch(RelOptRuleCall call) Receives notification about a rule match.

Methods inherited from class org.eigenbase.relopt.RelOptRule

convert, equals, equals, getOperand, getOperands, getOutConvention, getOutTrait, hashCode, matches, mergeTraitsAndConvert, mergeTraitsAndConvert, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

instance

public static final FarragoMultisetSplitterRule instance

Constructor Detail

FarragoMultisetSplitterRule

private FarragoMultisetSplitterRule()

Creates a FarragoMultisetSplitterRule.

Method Detail

findMultiset

private int findMultiset(List<RexNode> exprs)

onMatch

public void onMatch(RelOptRuleCall call)

Description copied from class: RelOptRule

Receives notification about a rule match. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RelOptRuleCall.transformTo(org.eigenbase.rel.RelNode) to register the expression.

Specified by:

onMatch in class RelOptRule

Parameters:

call - Rule call

See Also:

RelOptRule.matches(RelOptRuleCall)

insertRels

private CorrelatorRel insertRels(CalcRel calc,
                                 int offset)

Injects an equivalent RelNode tree to a RexCall's multiset operator.

If the expression is a multiset of scslar values (say an INTEGER MULTISET) then the relation's type will be a row with a single field, and that field will need to be dereferenced.

Parameters:

calc - The CalcRel that the multiset call belongs to

offset - Ordinal of the expression to transform.

createUncollect

private static UncollectRel createUncollect(CalcRel calc,
                                            RexLocalRef local,
                                            List<CorrelatorRel.Correlation> correlationList)

createProject

private static RelNode createProject(CalcRel calc,
                                     RexLocalRef local,
                                     List<CorrelatorRel.Correlation> correlationList)

createLimitRel

private static RelNode createLimitRel(RelNode child)

Creates a relational expression which ensures that a given expression only returns one row, and throws a runtime error otherwise. The result is

 ProjectRel($0)
   FilterRel[condition=CASE WHEN $0==1 THEN true ELSE throw("21000") END]
     AggregateRel[count(*), $0]

 

where 21000 is the standard CARDINALITY VIOLATION error code.

Parameters:

child - Child relational expression

Returns:

A relational expression of the same type

"Postcondition:"

return.getRowType() == child.getRowType()

containsNestedMultiset

private boolean containsNestedMultiset(RexProgram program)

Returns true if any expression in a program contains a multiset call directly under another multiset call.

containsNestedMultiset

private boolean containsNestedMultiset(RexNode node,
                                       boolean deep)

Returns true if node contains a multiset call directly under another multiset call.

createExistsPlanSingleRow

public RelNode createExistsPlanSingleRow(RelNode child,
                                         boolean neg)