RelStructuredTypeFlattener

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org.eigenbase.sql2rel
Class RelStructuredTypeFlattener

java.lang.Object
  org.eigenbase.sql2rel.RelStructuredTypeFlattener

All Implemented Interfaces:: ReflectiveVisitor

public class RelStructuredTypeFlattener
extends Object
implements ReflectiveVisitor
extends Object
implements ReflectiveVisitor

RelStructuredTypeFlattener removes all structured types from a tree of relational expressions. Because it must operate globally on the tree, it is implemented as an explicit self-contained rewrite operation instead of via normal optimizer rules. This approach has the benefit that real optimizer and codegen rules never have to deal with structured types.

As an example, suppose we have a structured type ST(A1 smallint, A2 bigint), a table T(c1 ST, c2 double), and a query select t.c2, t.c1.a2 from t. After SqlToRelConverter executes, the unflattened tree looks like:


 ProjectRel(C2=[$1], A2=[$0.A2])
   TableAccessRel(table=[T])

After flattening, the resulting tree looks like


 ProjectRel(C2=[$3], A2=[$2])
   FtrsIndexScanRel(table=[T], index=[clustered])

The index scan produces a flattened row type

(boolean, smallint,
 bigint, double)

(the boolean is a null indicator for c1), and the projection picks out the desired attributes (omitting $0 and $1 altogether). After optimization, the projection might be pushed down into the index scan, resulting in a final tree like


 FtrsIndexScanRel(table=[T], index=[clustered], projection=[3, 2])

Version:: $Id: //open/dev/farrago/src/org/eigenbase/sql2rel/RelStructuredTypeFlattener.java#32 $
Author:: John V. Sichi

Nested Class Summary
`private class`	`RelStructuredTypeFlattener.RewriteRelVisitor`
`private class`	`RelStructuredTypeFlattener.RewriteRexShuttle`
`static interface`	`RelStructuredTypeFlattener.SelfFlatteningRel`

Field Summary
`private RelNode`	`currentRel`
`private RelDataType`	`flattenedRootType`
`private int`	`iRestructureInput`
`private Map<RelNode,RelNode>`	`oldToNewRelMap`
`(package private) boolean`	`restructured`
`private RexBuilder`	`rexBuilder`
`private RelStructuredTypeFlattener.RewriteRelVisitor`	`visitor`

Constructor Summary
`RelStructuredTypeFlattener(RexBuilder rexBuilder)`

Method Summary
`private int`	`calculateFlattenedOffset(RelDataType rowType, int ordinal)`
`protected RexNode`	`flattenFieldAccesses(RexNode exp)`
`private void`	`flattenNullLiteral(RelDataType type, List<RexNode> flattenedExps, List<String> flattenedFieldNames)`
`private void`	`flattenProjection(RexNode exp, String fieldName, List<RexNode> flattenedExps, List<String> flattenedFieldNames)`
`private void`	`flattenProjections(RexNode[] exps, String[] fieldNames, String prefix, List<RexNode> flattenedExps, List<String> flattenedFieldNames)`
`private int`	`getNewForOldInput(int oldOrdinal)` Maps the ordinal of a field pre-flattening to the ordinal of the corresponding field post-flattening, and optionally returns its type.
`protected RelNode`	`getNewForOldRel(RelNode oldRel)`
`private boolean`	`isConstructor(RexNode rexNode)`
`private RexNode`	`restructure(RelDataType structuredType)`
`private RexNode[]`	`restructureFields(RelDataType structuredType)`
`RelNode`	`rewrite(RelNode root, boolean restructure)`
`void`	`rewriteGeneric(RelNode rel)`
`void`	`rewriteRel(AggregateRel rel)`
`void`	`rewriteRel(CalcRel rel)`
`void`	`rewriteRel(CollectRel rel)`
`void`	`rewriteRel(CorrelatorRel rel)`
`void`	`rewriteRel(FilterRel rel)`
`void`	`rewriteRel(IntersectRel rel)`
`void`	`rewriteRel(JoinRel rel)`
`void`	`rewriteRel(MinusRel rel)`
`void`	`rewriteRel(OneRowRel rel)`
`void`	`rewriteRel(ProjectRel rel)`
`void`	`rewriteRel(RelStructuredTypeFlattener.SelfFlatteningRel rel)`
`void`	`rewriteRel(SamplingRel rel)`
`void`	`rewriteRel(SortRel rel)`
`void`	`rewriteRel(TableAccessRel rel)`
`void`	`rewriteRel(TableFunctionRel rel)`
`void`	`rewriteRel(TableModificationRel rel)`
`void`	`rewriteRel(UncollectRel rel)`
`void`	`rewriteRel(UnionRel rel)`
`void`	`rewriteRel(ValuesRel rel)`
`protected void`	`setNewForOldRel(RelNode oldRel, RelNode newRel)`
`void`	`updateRelInMap(Map<RelNode,SortedSet<CorrelatorRel.Correlation>> mapRefRelToCorVar)`
`void`	`updateRelInMap(SortedMap<CorrelatorRel.Correlation,CorrelatorRel> mapCorVarToCorRel)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

rexBuilder

private final RexBuilder rexBuilder

visitor

private final RelStructuredTypeFlattener.RewriteRelVisitor visitor

oldToNewRelMap

private Map<RelNode,RelNode> oldToNewRelMap

currentRel

private RelNode currentRel

iRestructureInput

private int iRestructureInput

flattenedRootType

private RelDataType flattenedRootType

restructured

boolean restructured

Constructor Detail