org.apache.calcite.rel.metadata

Class RelMdPredicates

java.lang.Object

org.apache.calcite.rel.metadata.RelMdPredicates

public class RelMdPredicates
extends Object

Utility to infer Predicates that are applicable above a RelNode.

This is currently used by JoinPushTransitivePredicatesRule to infer Predicates that can be inferred from one side of a Join to the other.

The PullUp Strategy is sound but not complete. Here are some of the limitations:

1. For Aggregations we only PullUp predicates that only contain Grouping Keys. This can be extended to infer predicates on Aggregation expressions from expressions on the aggregated columns. For e.g.

    select a, max(b) from R1 where b > 7
      → max(b) > 7 or max(b) is null
    

2. For Projections we only look at columns that are projected without any function applied. So:

    select a from R1 where a > 7
      → "a > 7" is pulled up from the Projection.
    select a + 1 from R1 where a + 1 > 7
      → "a + 1 gt; 7" is not pulled up
    

3. There are several restrictions on Joins:
   • We only pullUp inferred predicates for now. Pulling up existing predicates causes an explosion of duplicates. The existing predicates are pushed back down as new predicates. Once we have rules to eliminate duplicate Filter conditions, we should pullUp all predicates.
   • For Left Outer: we infer new predicates from the left and set them as applicable on the Right side. No predicates are pulledUp.
   • Right Outer Joins are handled in an analogous manner.
   • For Full Outer Joins no predicates are pulledUp or inferred.

Field Summary

Fields

Modifier and Type	Field and Description
static RelMetadataProvider	SOURCE

Constructor Summary

Constructors

Constructor and Description
RelMdPredicates()

Method Summary

Methods

Modifier and Type	Method and Description
RelOptPredicateList	getPredicates(Aggregate agg) Infers predicates for an Aggregate.
RelOptPredicateList	getPredicates(Exchange exchange) Infers predicates for an Exchange.
RelOptPredicateList	getPredicates(Filter filter) Add the Filter condition to the pulledPredicates list from the child.
RelOptPredicateList	getPredicates(Join join) Infers predicates for a Join.
RelOptPredicateList	getPredicates(Project project) Infers predicates for a project.
RelOptPredicateList	getPredicates(RelNode rel)
RelOptPredicateList	getPredicates(SemiJoin semiJoin) Infers predicates for a SemiJoin.
RelOptPredicateList	getPredicates(Sort sort) Infers predicates for a Sort.
RelOptPredicateList	getPredicates(TableScan table) Infers predicates for a table scan.
RelOptPredicateList	getPredicates(Union union) Infers predicates for a Union.

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

Constructor Detail

RelMdPredicates

public RelMdPredicates()

Method Detail

getPredicates

public RelOptPredicateList getPredicates(RelNode rel)

getPredicates

public RelOptPredicateList getPredicates(TableScan table)

Infers predicates for a table scan.

getPredicates

public RelOptPredicateList getPredicates(Project project)

Infers predicates for a project.

1. create a mapping from input to projection. Map only positions that directly reference an input column.
2. Expressions that only contain above columns are retained in the Project's pullExpressions list.
3. For e.g. expression 'a + e = 9' below will not be pulled up because 'e' is not in the projection list.

    childPullUpExprs:      {a > 7, b + c < 10, a + e = 9}
    projectionExprs:       {a, b, c, e / 2}
    projectionPullupExprs: {a > 7, b + c < 10}
    

getPredicates

public RelOptPredicateList getPredicates(Filter filter)

Add the Filter condition to the pulledPredicates list from the child.

getPredicates

public RelOptPredicateList getPredicates(SemiJoin semiJoin)

Infers predicates for a SemiJoin.

getPredicates

public RelOptPredicateList getPredicates(Join join)

Infers predicates for a Join.

getPredicates

public RelOptPredicateList getPredicates(Aggregate agg)

Infers predicates for an Aggregate.

Pulls up predicates that only contains references to columns in the GroupSet. For e.g.

 childPullUpExprs : { a > 7, b + c < 10, a + e = 9}
 groupSet         : { a, b}
 pulledUpExprs    : { a > 7}
 

getPredicates

public RelOptPredicateList getPredicates(Union union)

Infers predicates for a Union.

The pulled up expression is a disjunction of its children's predicates.

getPredicates

public RelOptPredicateList getPredicates(Sort sort)

Infers predicates for a Sort.

getPredicates

public RelOptPredicateList getPredicates(Exchange exchange)

Infers predicates for an Exchange.