摘要:
Systems, methods, and other embodiments associated with access control for graph data at the instance-level are described. One example method includes accepting data access constraints that are expressed as match and apply pattern pairs to enforce security policies. A user query on graph data with a security policy restricts the returned data to data that the user is authorized to access. For this purpose, a user query that includes query selection criteria corresponding to one or more match pattern criteria based on the resource referenced in the query is rewritten to include security conditions specified in the associated apply pattern to restrict access to the graph data.
摘要:
Systems, methods, and other embodiments associated with resource description framework (RDF) security are described. One example method includes generating, based on sensitivity labels associated with the contents of a triple in an RDF record, a sensitivity label. The example method may also include comparing the sensitivity label to an access label associated with an entity requesting an action associated with the record to be performed. The example method may also include performing the action upon determining that the entity has sufficient permission to request the action.
摘要:
Systems, methods, and other embodiments associated with resource description framework (RDF) security are described. One example method includes generating, based on sensitivity labels associated with the contents of a triple in an RDF record, a sensitivity label. The example method may also include comparing the sensitivity label to an access label associated with an entity requesting an action associated with the record to be performed. The example method may also include performing the action upon determining that the entity has sufficient permission to request the action.
摘要:
Systems, methods, and other embodiments associated with access control for graph data at the instance-level are described. One example method includes accepting data access constraints that are expressed as match and apply pattern pairs to enforce security policies. A user query on graph data with a security policy restricts the returned data to data that the user is authorized to access. For this purpose, a user query that includes query selection criteria corresponding to one or more match pattern criteria based on the resource referenced in the query is rewritten to include security conditions specified in the associated apply pattern to restrict access to the graph data.
摘要:
Techniques are provided for freeing up resources before operations that change the resources have successfully completed. Resources are freed up by committing database transactions that perform portions of operations before the operations themselves have successfully completed. If the operations fail to complete successfully, then “compensation information” is used to remove the effects of the committed changes that were performed as part of the operation. Techniques are also provided for allowing database transactions to update values without retaining exclusive locks on those values. Operational constraints set forth conditions that must be satisfied before an update is allowed to proceed. If an attempt is made to update a particular value that has changes that may be undone, then the database server determines a plurality of “possible result values” for the particular value. If the possible result values satisfy the operational constraint conditions, then the update is allowed to proceed.
摘要:
Techniques are provided for freeing up resources before operations that change the resources have successfully completed. Resources are freed up by committing database transactions that perform portions of operations before the operations themselves have successfully completed. If the operations fail to complete successfully, then “compensation information” is used to remove the effects of the committed changes that were performed as part of the operation. Techniques are also provided for allowing database transactions to update values without retaining exclusive locks on those values. Operational constraints set forth conditions that must be satisfied before an update is allowed to proceed. If an attempt is made to update a particular value that has changes that may be undone, then the database server determines a plurality of “possible result values” for the particular value. If the possible result values satisfy the operational constraint conditions, then the update is allowed to proceed.
摘要:
A method and apparatus for efficiently storing and retrieving data in a database using index-only tables is disclosed. Storing a row of data in a database using index-only tables involves storing in a leaf node an index entry that includes a key value along with all other values in the row of data. If the row of data exceeds a predetermined size, then a portion of the row of data is stored in a user specified overflow area. Retrieving a row of data from an index-only table for a user-supplied key involves identifying a leaf node for the key, and reading a row of data from the index entry and any remaining portion from the overflow area when the row exceeds the predetermined size.
摘要:
A method and apparatus for building, maintaining, and using a multi-level index is provided. The multi-level index is accessed using a key. The key is divided into multiple portions referred to as sub-keys. The first level of the multi-level index is built on a first-level sub-key. Each index entry at the first-level is for a particular first-level sub-key value, and either includes sub-entries associated with second-level sub-key values or a reference to a second-level data retrieval structure. All second-level data retrieval structures are built on the portion of the key that has been designated as the second-level sub-key. As the vocabulary of the first-level sub-key becomes exhausted, fewer maintenance operations will have to be performed to maintain the first-level data retrieval structure. This decreases the overhead and increases the concurrency in a database system that uses the multiple-level index. The multi-level index structure is especially suited for queries that retrieve all values for a given first-level sub-key. The structure also has reduced storage costs compared to a single-level index structure, since first-level sub-key values are stored only once for each nested group.
摘要:
Techniques for history enabling a table in a database system so that past versions of rows of the history-enabled table are available for temporal querying. The table is history enabled by adding a start time column to the table and creating a history table for the history-enabled table. The start time field's value in a row of the history-enabled table indicates when the contents of the row last changed. The rows of the history table are copies of rows of the history-enabled table that have been deleted or updated. The rows include end time fields whose values indicate when the row was updated or deleted. A history table's row thus indicates a period in which the history table's row was in the history-enabled table. Temporal queries are performed on a view which is the union of the history-enabled table and the history table.
摘要:
Techniques for history enabling a table in a database system so that past versions of rows of the history-enabled table are available for temporal querying. The table is history enabled by adding a start time column to the table and creating a history table for the history-enabled table. The start time field's value in a row of the history-enabled table indicates when the contents of the row last changed. The rows of the history table are copies of rows of the history-enabled table that have been deleted or updated. The rows include end time fields whose values indicate when the row was updated or deleted. A history table's row thus indicates a period in which the history table's row was in the history-enabled table. Temporal queries are performed on a view which is the union of the history-enabled table and the history table.