org.apache.calcite.rel.metadata

Class RelMdCollation

java.lang.Object

org.apache.calcite.rel.metadata.RelMdCollation

public class RelMdCollation
extends Object

RelMdCollation supplies a default implementation of RelMetadataQuery.collations(org.apache.calcite.rel.RelNode) for the standard logical algebra.

Field Summary

Fields

Modifier and Type	Field and Description
static RelMetadataProvider	SOURCE

Method Summary

Methods

Modifier and Type	Method and Description
static List<RelCollation>	calc(RelNode input, RexProgram program) Helper method to determine a Calc's collation.
com.google.common.collect.ImmutableList<RelCollation>	collations(EnumerableMergeJoin join)
com.google.common.collect.ImmutableList<RelCollation>	collations(Filter rel)
com.google.common.collect.ImmutableList<RelCollation>	collations(HepRelVertex rel)
com.google.common.collect.ImmutableList<RelCollation>	collations(Project project)
com.google.common.collect.ImmutableList<RelCollation>	collations(RelNode rel) Fallback method to deduce collations for any relational expression not handled by a more specific method.
com.google.common.collect.ImmutableList<RelCollation>	collations(RelSubset rel)
com.google.common.collect.ImmutableList<RelCollation>	collations(Sort sort)
com.google.common.collect.ImmutableList<RelCollation>	collations(SortExchange sort)
com.google.common.collect.ImmutableList<RelCollation>	collations(TableScan scan)
com.google.common.collect.ImmutableList<RelCollation>	collations(Values values)
com.google.common.collect.ImmutableList<RelCollation>	collations(Window rel)
static List<RelCollation>	filter(RelNode input) Helper method to determine a Filter's collation.
static List<RelCollation>	limit(RelNode input) Helper method to determine a limit's collation.
static List<RelCollation>	mergeJoin(RelNode left, RelNode right, ImmutableIntList leftKeys, ImmutableIntList rightKeys) Helper method to determine a Join's collation assuming that it uses a merge-join algorithm.
static List<RelCollation>	project(RelNode input, List<? extends RexNode> projects) Helper method to determine a Project's collation.
static List<RelCollation>	sort(RelCollation collation) Helper method to determine a Sort's collation.
static List<RelCollation>	table(RelOptTable table) Helper method to determine a TableScan's collation.
static List<RelCollation>	values(RelDataType rowType, com.google.common.collect.ImmutableList<com.google.common.collect.ImmutableList<RexLiteral>> tuples) Helper method to determine a Values's collation.
static List<RelCollation>	window(RelNode input, com.google.common.collect.ImmutableList<Window.Group> groups) Helper method to determine a Window's collation.

Methods inherited from class java.lang.Object

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

Field Detail

SOURCE

public static final RelMetadataProvider SOURCE

Method Detail

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(RelNode rel)

Fallback method to deduce collations for any relational expression not handled by a more specific method.

Union, Intersect, Minus, Join, SemiJoin, Correlate do not in general return sorted results (but implementations using particular algorithms may).

Parameters:

rel - Relational expression

Returns:

Relational expression's collations

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(Window rel)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(Filter rel)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(TableScan scan)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(EnumerableMergeJoin join)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(Sort sort)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(SortExchange sort)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(Project project)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(Values values)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(HepRelVertex rel)

collations

public com.google.common.collect.ImmutableList<RelCollation> collations(RelSubset rel)

table

public static List<RelCollation> table(RelOptTable table)

Helper method to determine a TableScan's collation.

sort

public static List<RelCollation> sort(RelCollation collation)

Helper method to determine a Sort's collation.

filter

public static List<RelCollation> filter(RelNode input)

Helper method to determine a Filter's collation.

limit

public static List<RelCollation> limit(RelNode input)

Helper method to determine a limit's collation.

calc

public static List<RelCollation> calc(RelNode input,
                      RexProgram program)

Helper method to determine a Calc's collation.

project

public static List<RelCollation> project(RelNode input,
                         List<? extends RexNode> projects)

Helper method to determine a Project's collation.

window

public static List<RelCollation> window(RelNode input,
                        com.google.common.collect.ImmutableList<Window.Group> groups)

Helper method to determine a Window's collation.

A Window projects the fields of its input first, followed by the output from each of its windows. Assuming (quite reasonably) that the implementation does not re-order its input rows, then any collations of its input are preserved.

values

public static List<RelCollation> values(RelDataType rowType,
                        com.google.common.collect.ImmutableList<com.google.common.collect.ImmutableList<RexLiteral>> tuples)

Helper method to determine a Values's collation.

We actually under-report the collations. A Values with 0 or 1 rows - an edge case, but legitimate and very common - is ordered by every permutation of every subset of the columns.

So, our algorithm aims to:

• produce at most N collations (where N is the number of columns);
• make each collation as long as possible;
• do not repeat combinations already emitted - if we've emitted (a, b) do not later emit (b, a);
• probe the actual values and make sure that each collation is consistent with the data

So, for an empty Values with 4 columns, we would emit (a, b, c, d), (b, c, d), (c, d), (d).

mergeJoin

public static List<RelCollation> mergeJoin(RelNode left,
                           RelNode right,
                           ImmutableIntList leftKeys,
                           ImmutableIntList rightKeys)

Helper method to determine a Join's collation assuming that it uses a merge-join algorithm.

If the inputs are sorted on other keys in addition to the join key, the result preserves those collations too.