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The implementation of extended key segments in c-treeDB allows a single extended key segment definition to be used by more than one actual key segment. Extended key segment definitions may be set for all segments of a table, all segments of an index or for each particular key segment.
If a key segment mode includes a modifier for an extended key segment definition CTSEG_UNCSEG or the segment mode is CTSEG_SCHSEG, and the field type is one of the Unicode types, then the particular extended key segment definition to use for this segment is determined according to the following hierarchy. Use the definition specified for:
Once an extended key segment definition has been specified at a particular level (for a particular type of segment), an attempt to specify another definition at the same level results in an error. This is in part because of the "first use" strategy noted above, and because one should not change a definition if key values already exist.
