Managing XPath expressions in a database system

An apparatus for managing expressions in a database, comprising:

• means for receiving a first pathname expression that identifies a particular element within a hierarchical structure and that includes a first conditional expression relating to a particular attribute of the particular element;
• means for generating, based on the first pathname expression, position filter data that represents a level, corresponding to the particular element, within the hierarchical structure;
• means for storing the position filter data in one or more first columns of a database table, for use in determining whether a data item satisfies the first conditional expression in the pathname expression;
• means for generating, based on the first pathname expression, value filter data that represents the first conditional expression relating to the particular attribute of the particular element;
• and
• means for storing the value filter data in one or more second columns of a database table, for use in determining whether a data item satisfies the first conditional expression in the pathname expression.

A computer-readable storage medium carrying one or more sequences of instructions which, when executed, cause one or more processors to perform the steps of:

• receiving a first pathname expression that identifies a particular element within a hierarchical structure and that includes a first conditional expression relating to a particular attribute of the particular element;
• generating, based on the first pathname expression, position filter data that represents a level, corresponding to the particular element, within the hierarchical structure;
• storing the position filter data in one or more first columns of a database table, for use in determining whether a data item satisfies the first conditional expression in the pathname expression;
• generating, based on the first pathname expression, value filter data that represents the first conditional expression relating to the particular attribute of the particular element;
• and
• storing the value filter data in one or more second columns of a database table, for use in determining whether a data item satisfies the first conditional expression in the pathname expression.