org.apache.derby.impl.sql.compile

Class LikeEscapeOperatorNode

java.lang.Object

org.apache.derby.impl.sql.compile.QueryTreeNode

org.apache.derby.impl.sql.compile.ValueNode

org.apache.derby.impl.sql.compile.LikeEscapeOperatorNode

All Implemented Interfaces:

Visitable

public final class LikeEscapeOperatorNode
extends ValueNode

This node represents a like comparison operator (no escape) If the like pattern is a constant or a parameter then if possible the like is modified to include a >= and < operator. In some cases the like can be eliminated. By adding =, >= or < operators it may allow indexes to be used to greatly narrow the search range of the query, and allow optimizer to estimate number of rows to affected. constant or parameter LIKE pattern with prefix followed by optional wild card e.g. Derby% CHAR(n), VARCHAR(n) where n < 255 >= prefix padded with '' to length n -- e.g. Derby <= prefix appended with '￿' -- e.g. Derby￿ [ can eliminate LIKE if constant. ] CHAR(n), VARCHAR(n), LONG VARCHAR where n >= 255 >= prefix backed up one characer <= prefix appended with '￿' no elimination of like parameter like pattern starts with wild card e.g. %Derby CHAR(n), VARCHAR(n) where n <= 256 >= '' padded with '' to length n <= '￿' no elimination of like CHAR(n), VARCHAR(n), LONG VARCHAR where n > 256 >= NULL <= '￿' Note that the Unicode value '￿' is defined as not a character value and can be used by a program for any purpose. We use it to set an upper bound on a character range with a less than predicate. We only need a single '￿' appended because the string 'Derby￿￿' is not a valid String because '￿' is not a valid character.

Method Summary

Modifier and Type	Method and Description
void	bindComparisonOperator() Bind this operator
java.lang.String	toString() Convert this object to a String.

Methods inherited from class org.apache.derby.impl.sql.compile.ValueNode

checkIsBoolean, selectivity, setCollationInfo, setCollationInfo, setNullability, updatableByCursor

Methods inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode

accept, addTag, bindOffsetFetch, bindRowMultiSet, bindUserCatalogType, bindUserType, checkReliability, checkReliability, createTypeDependency, getBeginOffset, getDataDictionary, getEndOffset, getExecutionFactory, getGenericConstantActionFactory, getOffsetOrderedNodes, getOptimizerFactory, getOptimizerTracer, getParameterTypes, getUDTDesc, isAtomic, makeConstantAction, makeTableName, makeTableName, optimizerTracingIsOn, orReliability, referencesSessionSchema, setBeginOffset, setEndOffset, taggedWith, treePrint

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

bindComparisonOperator

public void bindComparisonOperator()
                            throws StandardException

Bind this operator

Throws:

StandardException - Thrown on error

toString

public java.lang.String toString()

Convert this object to a String. See comments in QueryTreeNode.java for how this should be done for tree printing.

Overrides:

toString in class ValueNode

Returns:

This object as a String