摘要:
In a multi-tier data server system, data from the first tier is cached in a mid-tier cache of the middle tier. Access control information from the first tier for the data is also cached within the mid-tier cache. Caching the security information in the middle tier allows the middle tier to make access control decisions regarding requests for data made by clients in the outer tier.
摘要:
In-place XML schema evolution occurs by evaluating an existing XML schema in a database system to see if it is compatible with a new XML schema. To determine if the old schema is compatible with the new schema, a lock-step traversal is performed on the two schemas. Each instruction in the old schema is compared to instructions in the new schema. Detected differences between the two schemas are evaluated to determine if existing XML documents are still compatible with the new schema. If they are, then an in-place schema evolution operation can take place. The in-place schema operation basically, involves appending the updated object information to the underlying object type and preserving the order of elements in a document by storing element mapping information on disk.
摘要:
Evaluation of workspace-local queries on a repository that supports versioning is enabled by tracking which versions of resources that are stored in the repository are associated with particular workspaces. A mapping is created and maintained for each workspace and each workspace-enabled table, i.e., a repository table that supports multiple versions of resources in the table. The mapping, such as a bit vector, is indexed by resource identifier. A set bit indicates that a particular resource version that corresponds to the bit is associated with the particular workspace. Therefore, the mapping indicates which rows in the workspace-enabled table are in the particular workspace. Index-based and functional evaluation schemes may utilize the per workspace, per table mapping to evaluate queries on the versioned repository. A new operator (IN_WORKSPACE) is introduced, through which an evaluation routine is invoked to determine whether or not a particular row maps to a particular workspace.
摘要:
Techniques manage the presence of repeated constructs within a complex type at the time of schema registration. At registration, techniques detect repeated elements in the XML schema and analyze whether the repeated elements are from the same complex type. If so, techniques perform additional analysis to determine a minimal common ancestor. Within the context of a minimal common ancestor, techniques determine the maximum number of times an element may occur in the schema. In a choice content model, the largest maximum occurrence value is selected. In other content models, the maximum occurrence value is determined by adding together the occurrence values for the repeated elements. Then, when an object relational table is generated for the XML schema, the maximum number of times that an element appears in the schema is this value. Techniques retain the advantages of object relational storage, even after a schema evolution.
摘要:
One embodiment of the present invention provides a system that implements a security policy in a database. During operation, the system receives a request associated with a set of objects in the database. Next, the system obtains a set of access control lists (ACLs) associated with the database, wherein a respective ACL specifies one or more access privileges associated with a user or user group, and wherein a respective ACLs is not specific to a particular object in the database. The system then evaluates the ACLs to obtain a set of ACL results associated with the request and processes the request by applying the set of ACL results to the objects without evaluating the ACLs repeatedly for each of the objects.
摘要:
Efficient evaluation of resource version history queries is enabled by using a data container storing records corresponding to links between successive versions of a resource. The records include: (a) a record identifier, (b) a predecessor identifier, (c) a successor identifier, (d) a predecessor rowset, which comprises the record identifier of each record in which the predecessor identifier in this record is the successor identifier, and (e) a successor rowset, which comprises the record identifier of each record in which the successor identifier in this record is the predecessor identifier. Depending on the nature of a request, a record is identified in which a particular version is identified by either the predecessor identifier or the successor identifier. Either the predecessor or successor rowsets are recursively read, while the predecessor or successor identifiers corresponding to each record read are added to a result set, thereby forming the ancestor or descendant version history.
摘要:
One embodiment of the present invention provides a system that implements a security policy in a database. During operation, the system receives a request associated with a set of objects in the database. Next, the system obtains a set of access control lists (ACLs) associated with the database, wherein a respective ACL specifies one or more access privileges associated with a user or user group, and wherein a respective ACLs is not specific to a particular object in the database. The system then evaluates the ACLs to obtain a set of ACL results associated with the request and processes the request by applying the set of ACL results to the objects without evaluating the ACLs repeatedly for each of the objects.
摘要:
XML schema evolutions can be performed on an XML-type database using partial data copy techniques. The partial data copy techniques provide mechanisms to identify a minimal set of data in the database that needs be copied out in order for schema evolution operations to occur. Identifying the minimal set of data involves comparing an existing XML schema to a new XML schema and determining the differences between the two schemas. Based on those differences, a minimal set of data can be determined. That data can then be copied to a temporary storage location, while the XML schema and its associated database structure are updated to conform to the new XML schema. Then, the minimal set of data is copied back into the modified database structure.
摘要:
Efficient evaluation of resource version history queries is enabled by using a data container storing records corresponding to links between successive versions of a resource. The records include: (a) a record identifier, (b) a predecessor identifier, (c) a successor identifier, (d) a predecessor rowset, which comprises the record identifier of each record in which the predecessor identifier in this record is the successor identifier, and (e) a successor rowset, which comprises the record identifier of each record in which the successor identifier in this record is the predecessor identifier. Depending on the nature of a request, a record is identified in which a particular version is identified by either the predecessor identifier or the successor identifier. Either the predecessor or successor rowsets are recursively read, while the predecessor or successor identifiers corresponding to each record read are added to a result set, thereby forming the ancestor or descendant version history.
摘要:
A version history of each of a plurality of resources is stored in a table. The version history for each resource comprises a set of one or more values for the resource, wherein each value in the version history of a resource indicates the value that the resource had in a particular version of the resource. In response to a request to perform an operation that causes a given resource that is subject to a uniqueness constraint to have a particular value, it is determined whether the uniqueness constraint is violated based on whether any version of any resource other than the given resource has the particular value. The uniqueness constraint is determined to be violated if any version of any resource other than the given resource has the particular value. The uniqueness constraint is not violated by existence of a version of the given resource that has the particular value.