Re: Index on columns that have total of more than 255

Baan is an application that runs over Informix and tries to map its non-relational model to Informix by creating 'Hash Indexes'. This "hash index" is another field added to the table as a concatination of all the parts of an index, and if it is a large composit index the "hash index" is a very long string. Baan then creates an index on this "hash index" field. This bloats the data in a table by adding these huge index fields. This probably has the effect of trashing performance, index only optimization is probably not possible. The index can be used to find the row of data, and any field has to be pried loose from data pages, not read off of indexes pages. Another pitiful application built on a non-relational model is SAP. What horrible things do they do to the supporting RDBMS can only be imagined, but I heard they drag down performance too.