org.apache.calcite.rel.metadata

Class RelMdUtil

java.lang.Object

org.apache.calcite.rel.metadata.RelMdUtil

public class RelMdUtil
extends Object

RelMdUtil provides utility methods used by the metadata provider methods.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	RelMdUtil.CardOfProjExpr Visitor that walks over a scalar expression and computes the cardinality of its result.

Field Summary

Fields

Modifier and Type	Field and Description
static SqlFunction	ARTIFICIAL_SELECTIVITY_FUNC

Constructor Summary

Constructors

Modifier	Constructor and Description
private	RelMdUtil()

Method Summary

Modifier and Type	Method and Description
static boolean	areColumnsDefinitelyUnique(RelMetadataQuery mq, RelNode rel, ImmutableBitSet colMask) Returns true if the columns represented in a bit mask are definitely known to form a unique column set.
static boolean	areColumnsDefinitelyUnique(RelMetadataQuery mq, RelNode rel, List<RexInputRef> columnRefs)
static boolean	areColumnsDefinitelyUniqueWhenNullsFiltered(RelMetadataQuery mq, RelNode rel, ImmutableBitSet colMask) Returns true if the columns represented in a bit mask are definitely known to form a unique column set, when nulls have been filtered from the columns.
static boolean	areColumnsDefinitelyUniqueWhenNullsFiltered(RelMetadataQuery mq, RelNode rel, List<RexInputRef> columnRefs)
static Boolean	areColumnsUnique(RelMetadataQuery mq, RelNode rel, List<RexInputRef> columnRefs)
static Boolean	areColumnsUniqueWhenNullsFiltered(RelMetadataQuery mq, RelNode rel, List<RexInputRef> columnRefs)
static double	capInfinity(Double d) Caps a double value at Double.MAX_VALUE if it's currently infinity
static Double	cardOfProjExpr(RelMetadataQuery mq, Project rel, RexNode expr) Computes the cardinality of a particular expression from the projection list.
static boolean	checkInputForCollationAndLimit(RelMetadataQuery mq, RelNode input, RelCollation collation, RexNode offset, RexNode fetch) Returns whether a relational expression is already sorted and has fewer rows than the sum of offset and limit.
static double	computeSemiJoinSelectivity(RelMetadataQuery mq, RelNode factRel, RelNode dimRel, List<Integer> factKeyList, List<Integer> dimKeyList) Computes the selectivity of a semijoin filter if it is applied on a fact table.
static double	computeSemiJoinSelectivity(RelMetadataQuery mq, RelNode factRel, RelNode dimRel, SemiJoin rel) Computes the selectivity of a semijoin filter if it is applied on a fact table.
static double	computeSemiJoinSelectivity(RelMetadataQuery mq, SemiJoin rel) Computes the selectivity of a semijoin filter if it is applied on a fact table.
static double	estimateFilteredRows(RelNode child, RexNode condition, RelMetadataQuery mq)
static double	estimateFilteredRows(RelNode child, RexProgram program, RelMetadataQuery mq)
static Double	getJoinDistinctRowCount(RelMetadataQuery mq, RelNode joinRel, JoinRelType joinType, ImmutableBitSet groupKey, RexNode predicate, boolean useMaxNdv) Computes the number of distinct rows for a set of keys returned from a join.
static Double	getJoinPopulationSize(RelMetadataQuery mq, RelNode joinRel, ImmutableBitSet groupKey) Computes the population size for a set of keys returned from a join
static Double	getJoinRowCount(RelMetadataQuery mq, Join join, RexNode condition) Returns an estimate of the number of rows returned by a Join.
static double	getMinusRowCount(RelMetadataQuery mq, Minus minus) Returns an estimate of the number of rows returned by a Minus.
static double	getSelectivityValue(RexNode artificialSelectivityFuncNode) Returns the selectivity value stored in a call.
static Double	getSemiJoinRowCount(RelMetadataQuery mq, RelNode left, RelNode right, JoinRelType joinType, RexNode condition) Returns an estimate of the number of rows returned by a SemiJoin.
static double	getUnionAllRowCount(RelMetadataQuery mq, Union rel) Returns an estimate of the number of rows returned by a Union (before duplicates are eliminated).
static double	guessSelectivity(RexNode predicate) Returns default estimates for selectivities, in the absence of stats.
static double	guessSelectivity(RexNode predicate, boolean artificialOnly) Returns default estimates for selectivities, in the absence of stats.
static double	linear(int x, int minX, int maxX, double minY, double maxY) Returns a point on a line.
static RexNode	makeSemiJoinSelectivityRexNode(RelMetadataQuery mq, SemiJoin rel) Creates a RexNode that stores a selectivity value corresponding to the selectivity of a semijoin.
static RexNode	minusPreds(RexBuilder rexBuilder, RexNode pred1, RexNode pred2) Takes the difference between two predicates, removing from the first any predicates also in the second
static Double	numDistinctVals(Double domainSize, Double numSelected) Returns the number of distinct values provided numSelected are selected where there are domainSize distinct values.
static void	setAggChildKeys(ImmutableBitSet groupKey, Aggregate aggRel, ImmutableBitSet.Builder childKey) Takes a bitmap representing a set of input references and extracts the ones that reference the group by columns in an aggregate.
static void	setLeftRightBitmaps(ImmutableBitSet groupKey, ImmutableBitSet.Builder leftMask, ImmutableBitSet.Builder rightMask, int nFieldsOnLeft) Separates a bit-mask representing a join into masks representing the left and right inputs into the join.
static void	splitCols(List<RexNode> projExprs, ImmutableBitSet groupKey, ImmutableBitSet.Builder baseCols, ImmutableBitSet.Builder projCols) Forms two bitmaps by splitting the columns in a bitmap according to whether or not the column references the child input or is an expression
static RexNode	unionPreds(RexBuilder rexBuilder, RexNode pred1, RexNode pred2) AND's two predicates together, either of which may be null, removing redundant filters.

Methods inherited from class java.lang.Object

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

Field Detail

ARTIFICIAL_SELECTIVITY_FUNC

public static final SqlFunction ARTIFICIAL_SELECTIVITY_FUNC

Constructor Detail

RelMdUtil

private RelMdUtil()

Method Detail

makeSemiJoinSelectivityRexNode

public static RexNode makeSemiJoinSelectivityRexNode(RelMetadataQuery mq,
                                                     SemiJoin rel)

Creates a RexNode that stores a selectivity value corresponding to the selectivity of a semijoin. This can be added to a filter to simulate the effect of the semijoin during costing, but should never appear in a real plan since it has no physical implementation.

Parameters:

rel - the semijoin of interest

Returns:

constructed rexnode

getSelectivityValue

public static double getSelectivityValue(RexNode artificialSelectivityFuncNode)

Returns the selectivity value stored in a call.

Parameters:

artificialSelectivityFuncNode - Call containing the selectivity value

Returns:

selectivity value

computeSemiJoinSelectivity

public static double computeSemiJoinSelectivity(RelMetadataQuery mq,
                                                SemiJoin rel)

Computes the selectivity of a semijoin filter if it is applied on a fact table. The computation is based on the selectivity of the dimension table/columns and the number of distinct values in the fact table columns.

Parameters:

rel - semijoin rel

Returns:

calculated selectivity

computeSemiJoinSelectivity

public static double computeSemiJoinSelectivity(RelMetadataQuery mq,
                                                RelNode factRel,
                                                RelNode dimRel,
                                                SemiJoin rel)

Computes the selectivity of a semijoin filter if it is applied on a fact table. The computation is based on the selectivity of the dimension table/columns and the number of distinct values in the fact table columns.

Parameters:

factRel - fact table participating in the semijoin

dimRel - dimension table participating in the semijoin

rel - semijoin rel

Returns:

calculated selectivity

computeSemiJoinSelectivity

public static double computeSemiJoinSelectivity(RelMetadataQuery mq,
                                                RelNode factRel,
                                                RelNode dimRel,
                                                List<Integer> factKeyList,
                                                List<Integer> dimKeyList)

Computes the selectivity of a semijoin filter if it is applied on a fact table. The computation is based on the selectivity of the dimension table/columns and the number of distinct values in the fact table columns.

Parameters:

factRel - fact table participating in the semijoin

dimRel - dimension table participating in the semijoin

factKeyList - LHS keys used in the filter

dimKeyList - RHS keys used in the filter

Returns:

calculated selectivity

areColumnsDefinitelyUnique

public static boolean areColumnsDefinitelyUnique(RelMetadataQuery mq,
                                                 RelNode rel,
                                                 ImmutableBitSet colMask)

Returns true if the columns represented in a bit mask are definitely known to form a unique column set.

Parameters:

rel - the relational expression that the column mask corresponds to

colMask - bit mask containing columns that will be tested for uniqueness

Returns:

true if bit mask represents a unique column set; false if not (or if no metadata is available)

areColumnsUnique

public static Boolean areColumnsUnique(RelMetadataQuery mq,
                                       RelNode rel,
                                       List<RexInputRef> columnRefs)

areColumnsDefinitelyUnique

public static boolean areColumnsDefinitelyUnique(RelMetadataQuery mq,
                                                 RelNode rel,
                                                 List<RexInputRef> columnRefs)

areColumnsDefinitelyUniqueWhenNullsFiltered

public static boolean areColumnsDefinitelyUniqueWhenNullsFiltered(RelMetadataQuery mq,
                                                                  RelNode rel,
                                                                  ImmutableBitSet colMask)

Returns true if the columns represented in a bit mask are definitely known to form a unique column set, when nulls have been filtered from the columns.

Parameters:

rel - the relational expression that the column mask corresponds to

colMask - bit mask containing columns that will be tested for uniqueness

Returns:

true if bit mask represents a unique column set; false if not (or if no metadata is available)

areColumnsUniqueWhenNullsFiltered

public static Boolean areColumnsUniqueWhenNullsFiltered(RelMetadataQuery mq,
                                                        RelNode rel,
                                                        List<RexInputRef> columnRefs)

areColumnsDefinitelyUniqueWhenNullsFiltered

public static boolean areColumnsDefinitelyUniqueWhenNullsFiltered(RelMetadataQuery mq,
                                                                  RelNode rel,
                                                                  List<RexInputRef> columnRefs)

setLeftRightBitmaps

public static void setLeftRightBitmaps(ImmutableBitSet groupKey,
                                       ImmutableBitSet.Builder leftMask,
                                       ImmutableBitSet.Builder rightMask,
                                       int nFieldsOnLeft)

Separates a bit-mask representing a join into masks representing the left and right inputs into the join.

Parameters:

groupKey - original bit-mask

leftMask - left bit-mask to be set

rightMask - right bit-mask to be set

nFieldsOnLeft - number of fields in the left input

numDistinctVals

public static Double numDistinctVals(Double domainSize,
                                     Double numSelected)

Returns the number of distinct values provided numSelected are selected where there are domainSize distinct values.

Note that in the case where domainSize == numSelected, it's not true that the return value should be domainSize. If you pick 100 random values between 1 and 100, you'll most likely end up with fewer than 100 distinct values, because you'll pick some values more than once.

Parameters:

domainSize - number of distinct values in the domain

numSelected - number selected from the domain

Returns:

number of distinct values for subset selected

capInfinity

public static double capInfinity(Double d)

Caps a double value at Double.MAX_VALUE if it's currently infinity

Parameters:

d - the Double object

Returns:

the double value if it's not infinity; else Double.MAX_VALUE

guessSelectivity

public static double guessSelectivity(RexNode predicate)

Returns default estimates for selectivities, in the absence of stats.

Parameters:

predicate - predicate for which selectivity will be computed; null means true, so gives selectity of 1.0

Returns:

estimated selectivity

guessSelectivity

public static double guessSelectivity(RexNode predicate,
                                      boolean artificialOnly)

Returns default estimates for selectivities, in the absence of stats.

Parameters:

predicate - predicate for which selectivity will be computed; null means true, so gives selectity of 1.0

artificialOnly - return only the selectivity contribution from artificial nodes

Returns:

estimated selectivity

unionPreds

public static RexNode unionPreds(RexBuilder rexBuilder,
                                 RexNode pred1,
                                 RexNode pred2)

AND's two predicates together, either of which may be null, removing redundant filters.

Parameters:

rexBuilder - rexBuilder used to construct AND'd RexNode

pred1 - first predicate

pred2 - second predicate

Returns:

AND'd predicate or individual predicates if one is null

minusPreds

public static RexNode minusPreds(RexBuilder rexBuilder,
                                 RexNode pred1,
                                 RexNode pred2)

Takes the difference between two predicates, removing from the first any predicates also in the second

Parameters:

rexBuilder - rexBuilder used to construct AND'd RexNode

pred1 - first predicate

pred2 - second predicate

Returns:

MINUS'd predicate list

setAggChildKeys

public static void setAggChildKeys(ImmutableBitSet groupKey,
                                   Aggregate aggRel,
                                   ImmutableBitSet.Builder childKey)

Takes a bitmap representing a set of input references and extracts the ones that reference the group by columns in an aggregate.

Parameters:

groupKey - the original bitmap

aggRel - the aggregate

childKey - sets bits from groupKey corresponding to group by columns

splitCols

public static void splitCols(List<RexNode> projExprs,
                             ImmutableBitSet groupKey,
                             ImmutableBitSet.Builder baseCols,
                             ImmutableBitSet.Builder projCols)

Forms two bitmaps by splitting the columns in a bitmap according to whether or not the column references the child input or is an expression

Parameters:

projExprs - Project expressions

groupKey - Bitmap whose columns will be split

baseCols - Bitmap representing columns from the child input

projCols - Bitmap representing non-child columns

cardOfProjExpr

public static Double cardOfProjExpr(RelMetadataQuery mq,
                                    Project rel,
                                    RexNode expr)

Computes the cardinality of a particular expression from the projection list.

Parameters:

rel - RelNode corresponding to the project

expr - projection expression

Returns:

cardinality

getJoinPopulationSize

public static Double getJoinPopulationSize(RelMetadataQuery mq,
                                           RelNode joinRel,
                                           ImmutableBitSet groupKey)

Computes the population size for a set of keys returned from a join

Parameters:

joinRel - the join rel

groupKey - keys to compute the population for

Returns:

computed population size

getJoinDistinctRowCount

public static Double getJoinDistinctRowCount(RelMetadataQuery mq,
                                             RelNode joinRel,
                                             JoinRelType joinType,
                                             ImmutableBitSet groupKey,
                                             RexNode predicate,
                                             boolean useMaxNdv)

Computes the number of distinct rows for a set of keys returned from a join. Also known as NDV (number of distinct values).

Parameters:

joinRel - RelNode representing the join

joinType - type of join

groupKey - keys that the distinct row count will be computed for

predicate - join predicate

useMaxNdv - If true use formula max(left NDV, right NDV), otherwise use left NDV * right NDV.

Returns:

number of distinct rows

getUnionAllRowCount

public static double getUnionAllRowCount(RelMetadataQuery mq,
                                         Union rel)

Returns an estimate of the number of rows returned by a Union (before duplicates are eliminated).

getMinusRowCount

public static double getMinusRowCount(RelMetadataQuery mq,
                                      Minus minus)

Returns an estimate of the number of rows returned by a Minus.

getJoinRowCount

public static Double getJoinRowCount(RelMetadataQuery mq,
                                     Join join,
                                     RexNode condition)

Returns an estimate of the number of rows returned by a Join.

getSemiJoinRowCount

public static Double getSemiJoinRowCount(RelMetadataQuery mq,
                                         RelNode left,
                                         RelNode right,
                                         JoinRelType joinType,
                                         RexNode condition)

Returns an estimate of the number of rows returned by a SemiJoin.

estimateFilteredRows

public static double estimateFilteredRows(RelNode child,
                                          RexProgram program,
                                          RelMetadataQuery mq)

estimateFilteredRows

public static double estimateFilteredRows(RelNode child,
                                          RexNode condition,
                                          RelMetadataQuery mq)

linear

public static double linear(int x,
                            int minX,
                            int maxX,
                            double minY,
                            double maxY)

Returns a point on a line.

The result is always a value between minY and maxY, even if x is not between minX and maxX.

Examples:

• linear(0, 0, 10, 100, 200} returns 100 because 0 is minX
• linear(5, 0, 10, 100, 200} returns 150 because 5 is mid-way between minX and maxX
• linear(5, 0, 10, 100, 200} returns 160
• linear(10, 0, 10, 100, 200} returns 200 because 10 is maxX
• linear(-2, 0, 10, 100, 200} returns 100 because -2 is less than minX and is therefore treated as minX
• linear(12, 0, 10, 100, 200} returns 100 because 12 is greater than maxX and is therefore treated as maxX

checkInputForCollationAndLimit

public static boolean checkInputForCollationAndLimit(RelMetadataQuery mq,
                                                     RelNode input,
                                                     RelCollation collation,
                                                     RexNode offset,
                                                     RexNode fetch)

Returns whether a relational expression is already sorted and has fewer rows than the sum of offset and limit.

If this is the case, it is safe to push down a Sort with limit and optional offset.