US Patent 7334004 Consistent read in a distributed database environment

Techniques are provided for determining which data item version to supply to a query. According to the techniques, the determination is made by associating a new field, which indicates the time a data item version was current, with each data item version; associating a new field with each query, which indicates the last change that the query must see made by the transaction to which the query belongs; and determining which data item version to use to answer the query based, in part, on a comparison between the values of the two new fields.