org.apache.calcite.sql2rel

Class RelFieldTrimmer

java.lang.Object

org.apache.calcite.sql2rel.RelFieldTrimmer

All Implemented Interfaces:

ReflectiveVisitor

public class RelFieldTrimmer
extends Object
implements ReflectiveVisitor

Transformer that walks over a tree of relational expressions, replacing each RelNode with a 'slimmed down' relational expression that projects only the columns required by its consumer.

Uses multi-methods to fire the right rule for each type of relational expression. This allows the transformer to be extended without having to add a new method to RelNode, and without requiring a collection of rule classes scattered to the four winds.

REVIEW: jhyde, 2009/7/28: Is sql2rel the correct package for this class? Trimming fields is not an essential part of SQL-to-Rel translation, and arguably belongs in the optimization phase. But this transformer does not obey the usual pattern for planner rules; it is difficult to do so, because each RelNode needs to return a different set of fields after trimming.

TODO: Change 2nd arg of the trimFields(org.apache.calcite.rel.RelNode, org.apache.calcite.util.ImmutableBitSet, java.util.Set<org.apache.calcite.rel.type.RelDataTypeField>) method from BitSet to Mapping. Sometimes it helps the consumer if you return the columns in a particular order. For instance, it may avoid a project at the top of the tree just for reordering. Could ease the transition by writing methods that convert BitSet to Mapping and vice versa.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	RelFieldTrimmer.TrimResult Result of an attempt to trim columns from a relational expression.

Constructor Summary

Constructors

Constructor and Description
RelFieldTrimmer(SqlValidator validator) Creates a RelFieldTrimmer.
RelFieldTrimmer(SqlValidator validator, RelFactories.ProjectFactory projectFactory, RelFactories.FilterFactory filterFactory, RelFactories.JoinFactory joinFactory, RelFactories.SemiJoinFactory semiJoinFactory, RelFactories.SortFactory sortFactory, RelFactories.AggregateFactory aggregateFactory, RelFactories.SetOpFactory setOpFactory) Creates a RelFieldTrimmer.

Method Summary

Methods

Modifier and Type	Method and Description
protected RelFieldTrimmer.TrimResult	dispatchTrimFields(RelNode rel, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Invokes trimFields(org.apache.calcite.rel.RelNode, org.apache.calcite.util.ImmutableBitSet, java.util.Set<org.apache.calcite.rel.type.RelDataTypeField>), or the appropriate method for the type of the rel parameter, using multi-method dispatch.
RelNode	trim(RelNode root) Trims unused fields from a relational expression.
protected RelFieldTrimmer.TrimResult	trimChild(RelNode rel, RelNode input, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Trims the fields of an input relational expression.
protected RelFieldTrimmer.TrimResult	trimChildRestore(RelNode rel, RelNode input, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Trims a child relational expression, then adds back a dummy project to restore the fields that were removed.
RelFieldTrimmer.TrimResult	trimFields(Aggregate aggregate, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalAggregate.
RelFieldTrimmer.TrimResult	trimFields(Filter filter, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalFilter.
RelFieldTrimmer.TrimResult	trimFields(Join join, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalJoin.
RelFieldTrimmer.TrimResult	trimFields(LogicalTableFunctionScan tabFun, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalTableFunctionScan.
RelFieldTrimmer.TrimResult	trimFields(LogicalTableModify modifier, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalTableModify.
RelFieldTrimmer.TrimResult	trimFields(LogicalValues values, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalValues.
RelFieldTrimmer.TrimResult	trimFields(Project project, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalProject.
RelFieldTrimmer.TrimResult	trimFields(RelNode rel, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Visit method, per ReflectiveVisitor.
RelFieldTrimmer.TrimResult	trimFields(SetOp setOp, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for SetOp (including UNION and UNION ALL).
RelFieldTrimmer.TrimResult	trimFields(Sort sort, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for Sort.
RelFieldTrimmer.TrimResult	trimFields(TableScan tableAccessRel, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields) Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalTableScan.

Methods inherited from class java.lang.Object

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

Constructor Detail

RelFieldTrimmer

public RelFieldTrimmer(SqlValidator validator)

Creates a RelFieldTrimmer.

Parameters:

validator - Validator

RelFieldTrimmer

public RelFieldTrimmer(SqlValidator validator,
               RelFactories.ProjectFactory projectFactory,
               RelFactories.FilterFactory filterFactory,
               RelFactories.JoinFactory joinFactory,
               RelFactories.SemiJoinFactory semiJoinFactory,
               RelFactories.SortFactory sortFactory,
               RelFactories.AggregateFactory aggregateFactory,
               RelFactories.SetOpFactory setOpFactory)

Creates a RelFieldTrimmer.

Parameters:

validator - Validator

Method Detail

trim

public RelNode trim(RelNode root)

Trims unused fields from a relational expression.

We presume that all fields of the relational expression are wanted by its consumer, so only trim fields that are not used within the tree.

Parameters:

root - Root node of relational expression

Returns:

Trimmed relational expression

trimChild

protected RelFieldTrimmer.TrimResult trimChild(RelNode rel,
                                   RelNode input,
                                   ImmutableBitSet fieldsUsed,
                                   Set<RelDataTypeField> extraFields)

Trims the fields of an input relational expression.

Parameters:

rel - Relational expression

input - Input relational expression, whose fields to trim

fieldsUsed - Bitmap of fields needed by the consumer

Returns:

New relational expression and its field mapping

trimChildRestore

protected RelFieldTrimmer.TrimResult trimChildRestore(RelNode rel,
                                          RelNode input,
                                          ImmutableBitSet fieldsUsed,
                                          Set<RelDataTypeField> extraFields)

Trims a child relational expression, then adds back a dummy project to restore the fields that were removed.

Sounds pointless? It causes unused fields to be removed further down the tree (towards the leaves), but it ensure that the consuming relational expression continues to see the same fields.

Parameters:

rel - Relational expression

input - Input relational expression, whose fields to trim

fieldsUsed - Bitmap of fields needed by the consumer

Returns:

New relational expression and its field mapping

dispatchTrimFields

protected final RelFieldTrimmer.TrimResult dispatchTrimFields(RelNode rel,
                                            ImmutableBitSet fieldsUsed,
                                            Set<RelDataTypeField> extraFields)

Invokes trimFields(org.apache.calcite.rel.RelNode, org.apache.calcite.util.ImmutableBitSet, java.util.Set<org.apache.calcite.rel.type.RelDataTypeField>), or the appropriate method for the type of the rel parameter, using multi-method dispatch.

Parameters:

rel - Relational expression

fieldsUsed - Bitmap of fields needed by the consumer

Returns:

New relational expression and its field mapping

trimFields

public RelFieldTrimmer.TrimResult trimFields(RelNode rel,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Visit method, per ReflectiveVisitor.

This method is invoked reflectively, so there may not be any apparent calls to it. The class (or derived classes) may contain overloads of this method with more specific types for the rel parameter.

Returns a pair: the relational expression created, and the mapping between the original fields and the fields of the newly created relational expression.

Parameters:

rel - Relational expression

fieldsUsed - Fields needed by the consumer

Returns:

relational expression and mapping

trimFields

public RelFieldTrimmer.TrimResult trimFields(Project project,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalProject.

trimFields

public RelFieldTrimmer.TrimResult trimFields(Filter filter,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalFilter.

trimFields

public RelFieldTrimmer.TrimResult trimFields(Sort sort,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for Sort.

trimFields

public RelFieldTrimmer.TrimResult trimFields(Join join,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalJoin.

trimFields

public RelFieldTrimmer.TrimResult trimFields(SetOp setOp,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for SetOp (including UNION and UNION ALL).

trimFields

public RelFieldTrimmer.TrimResult trimFields(Aggregate aggregate,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalAggregate.

trimFields

public RelFieldTrimmer.TrimResult trimFields(LogicalTableModify modifier,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalTableModify.

trimFields

public RelFieldTrimmer.TrimResult trimFields(LogicalTableFunctionScan tabFun,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalTableFunctionScan.

trimFields

public RelFieldTrimmer.TrimResult trimFields(LogicalValues values,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalValues.

trimFields

public RelFieldTrimmer.TrimResult trimFields(TableScan tableAccessRel,
                                    ImmutableBitSet fieldsUsed,
                                    Set<RelDataTypeField> extraFields)

Variant of trimFields(RelNode, ImmutableBitSet, Set) for LogicalTableScan.