org.apache.calcite.rex

Class RexNormalize

java.lang.Object

org.apache.calcite.rex.RexNormalize

public class RexNormalize
extends Object

Context required to normalize a row-expression.

Currently, only simple normalization is supported, such as:

• $2 = $1 → $1 = $2
• $2 > $1 → $1 < $2
• 1.23 = $1 → $1 = 1.23
• OR(OR(udf($1), $2), $3) → OR($3, OR($2, udf($1)))

In the future, this component may extend to support more normalization cases for general promotion. e.g. the strategy to decide which operand is more complex should be more smart.

There is no one normalization strategy that works for all cases, and no consensus about what the desired strategies should be. So by default, the normalization is disabled. We do force normalization when computing the digest of RexCalls during planner planning.

Method Summary

Modifier and Type	Method and Description
static int	hashCode(SqlOperator operator, List<RexNode> operands) Computes the hashCode of a rex call.
static Pair<SqlOperator,List<RexNode>>	normalize(SqlOperator operator, List<RexNode> operands) Normalizes the variables of a rex call.

Methods inherited from class java.lang.Object

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

Method Detail

normalize

@API(since="1.24",
     status=EXPERIMENTAL)
public static Pair<SqlOperator,List<RexNode>> normalize(SqlOperator operator,
                                                                                                     List<RexNode> operands)

Normalizes the variables of a rex call.

Parameters:

operator - The operator

operands - The operands

Returns:

normalized variables of the call or the original if there is no need to normalize

hashCode

public static int hashCode(SqlOperator operator,
                           List<RexNode> operands)

Computes the hashCode of a rex call. We ignore the operands sequence when the call is symmetrical.

Note that the logic to decide whether operands need reordering should be strictly same with normalize(org.apache.calcite.sql.SqlOperator, java.util.List<org.apache.calcite.rex.RexNode>).