Package org.apache.derby.impl.sql.compile

Class LikeEscapeOperatorNode

  • All Implemented Interfaces:
    Visitable
    public final class LikeEscapeOperatorNode
extends TernaryOperatorNode
    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.

    • Field Detail

      • addedEquals

        boolean addedEquals
        Fields of the class

      • escape

        java.lang.String escape

    • Constructor Detail

      • LikeEscapeOperatorNode

        LikeEscapeOperatorNode​(ValueNode receiver,
                       ValueNode leftOperand,
                       ValueNode rightOperand,
                       ContextManager cm)
        Constructor for a LikeEscapeOperatorNode receiver like pattern [ escape escapeValue ]
        Parameters:
        receiver - The left operand of the like: column, CharConstant or Parameter
        leftOperand - The right operand of the like: the pattern
        rightOperand - The optional escape clause, null if not present
        cm - The context manager

    • Method Detail

      • bindExpression

        ValueNode bindExpression​(FromList fromList,
                         SubqueryList subqueryList,
                         java.util.List<AggregateNode> aggregates)
                  throws StandardException
        implement binding for like expressions.

        overrides BindOperatorNode.bindExpression because like has special requirements for parameter binding.

        Overrides:
        bindExpression in class TernaryOperatorNode
        Parameters:
        fromList - The FROM list for the query this expression is in, for binding columns.
        subqueryList - The subquery list being built as we find SubqueryNodes
        aggregates - The aggregate list being built as we find AggregateNodes
        Returns:
        The new top of the expression tree.
        Throws:
        StandardException - thrown on failure

      • preprocess

        ValueNode preprocess​(int numTables,
                     FromList outerFromList,
                     SubqueryList outerSubqueryList,
                     PredicateList outerPredicateList)
              throws StandardException
        Preprocess an expression tree. We do a number of transformations here (including subqueries, IN lists, LIKE and BETWEEN) plus subquery flattening. NOTE: This is done before the outer ResultSetNode is preprocessed.
        Overrides:
        preprocess in class TernaryOperatorNode
        Parameters:
        numTables - Number of tables in the DML Statement
        outerFromList - FromList from outer query block
        outerSubqueryList - SubqueryList from outer query block
        outerPredicateList - PredicateList from outer query block
        Returns:
        The modified expression
        Throws:
        StandardException - Thrown on error