| 摘要 |
Techniques are provided for supplying a data item to a query that must see a particular snapshot of a database. For a plurality of data item versions that reside in a plurality of nodes, CLONE-TIME information is maintained that indicates when for each data item version of the plurality of data item versions, a clone branch to which the data item version belongs, is cloned from the current version of a data item; it is determined which data item versions of the plurality of data item versions contain all changes that must be seen by the query based, at least in part, on the CLONE-TIME information; and a data item version is selected to supply to the query from those data item versions that contain all changes that must be seen by the query.
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