Oracle International Corporation

Thomas Baby

Nipun Agarwal

Zhen Hua Liu

Sam Idicula

Sivasankaran Chandrasekar

Ravi Murthy

Eric Sedlar

Beda Christoph Hammerschmidt

Anguel Novoselsky

Vikram Kapoor

Asha Tarachandani

Ning Zhang

Abhyudaya Agrawal

Sukhendu Chakraborty

Muralidhar Krishnaprasad

Yunrui Li

Kumar Rajamani

Mahesh Baburao Girkar

Vikas Arora

Vivekanandhan Raja

Meeten Bhavsar

Thomas Chang

Hui Joe Chang

Sachin Bhatkar

Visar Nimani

Mark Ture

Hui Ouyang

Cindy Hsin

Andre Kruglikov

Mark Davis

Wesley Lin

Hiroshi Koide

Kongyi Zhou

Philip Yam

Sachin Vijaykumar Sonawane

Junyan Ding

James W Warner

Chon Hei Lei

Ciya Liao

George Eadon

Giridhar Ravipati

Ramesh Kumar

Thomas F Keefe

Vikram Reddy Pesati

Geeta Arora

Qin Yu

Mohammed Irfan Rafiq

Man-Hay Tam

Ali Maleki Tabar

Steve Yang

David Liao

Siddharth Patel

Steve Chi-Ming Yang

A database session in an active standby server on which an active standby database resides receives a DML statement. The session is suspended while the statement is redirected over a database link to a primary database on which the statement is executed. Information associated with execution of the statement is communicated to the session in the active standby server. Redo records describing changes to the contents of the primary database are applied to the active standby database and control is returned to the session. Prior to commitment of a transaction including the statement, a query directed to data to which the statement was directed is received at the active standby server from a client and executed on the active standby database absent use of a database link based on whether information associated with a database session associated with the client matches the information associated with execution of the statement.

Method and system for supporting data consistency on an active standby database after DML redirection to a primary database

A container is a collection of schemas, objects, and related structures in a multitenant container database (CDB) that appears logically to an application as a separate database. Within a CDB, each container has a unique ID and name. The root database and every PDB is considered a container. PDBs isolate data and operations so that from the perspective of a user or application, each PDB appears as if it were a traditional non-CDB. A database management system that manages a container database is a container database management system (CDBMS). Data and metadata in the root database may include common schemas that make the functionality that users will often use available CDB-wide. To execute a query accessing a common schema, the common schemas may be accessed by sessions of a PDB without switching database contexts.

High-performance implementation of sharing of read-only data in a multi-tenant environment

Disclosed is a system, method, and computer program product that allows multiple partition schemes to be applied to a single object. Each scheme represents the same set of partitions, but the schemes may have different partition methods, different partition keys, and/or different partition bounds.

Multiple partitioning schemes for partitioned database objects

A method and apparatus are provided for building and using a persistent XML tree index for navigating an XML document. The XML tree index is stored separately from the XML document content, and thus is able to optimize performance through the use of fixed-sized index entries. The XML document hierarchy need not be constructed in volatile memory, so creating and using the XML tree index scales even for large documents. To evaluate a path expression including descendent or ancestral syntax, navigation links can be read from persistent storage and used directly to find the nodes specified in the path expression. The use of an abstract navigational interface allows applications to be written that are independent of the storage implementation of the index and the content. Thus, the XML tree index can index documents stored at least in a database, a persistent file system, or as a sequence of in memory.

Efficient XML tree indexing structure over XML content

Techniques are provided for diverting, to cloned metadata, live access to original metadata of an application container that is being concurrently upgraded. In an embodiment, a database server stores, within an application container of an application, original metadata that defines objects for use by pluggable databases of the application. The database server receives a maintenance request to adjust the original metadata. The database server creates, in response to receiving the maintenance request, a reference container that contains cloned metadata that is a copy of the original metadata. The database server receives, during or after creating the reference container, a read request to read one of the objects. The database server concurrently performs both of: executing the maintenance request upon the original metadata, and executing the read request upon the cloned metadata of the reference container.

Asynchronous shared application upgrade

In an approach, a database management system logically partitions a database object (such as a table) across multiple pluggable databases of a container database. When a database server receives a query at an application root, the database server consults a container map which provides a mapping between a set of partitioning criteria and a set of member pluggable databases of the application root. Using the container map, the database server identifies one or more pluggable databases of the set of member pluggable databases of the application root that contain records which potentially have the ability to match the predicates of the query. The database server then limits the execution of the query to the identified pluggable databases, effectively pruning away records contained by the other pluggable databases to increase the efficiency of executing the query.

Implementing a logically partitioned data warehouse using a container map

In an approach, memory usage within a database management system is optimized by designating an application root which stores data and metadata for database objects that are common across pluggable databases which support the same application. In addition, the application root can be used to manage access to the pluggable databases by defining common users which are created at the application root, but can be used to access any of the member pluggable databases. Furthermore, different versions of the same application can be supported concurrently by maintaining separate application roots for each version. For instance, when an upgrade is applied to the application root, a clone can be created and the update can be applied to the clone. Then, the member pluggable databases which are to be upgraded can be synchronized to the clone, while leaving other pluggable databases servicing the previous version of the application.

Application containers in container databases

In an approach, when a pluggable database within a container database is transported to a new container database, the pluggable database is replaced with a proxy pluggable database storing forwarding information for the pluggable database. When a command is received that is to be executed on the proxy pluggable database, the database server handling the command uses the forwarding information stored within the proxy pluggable database to forward the command to a second database receiver responsible for the new container database for execution on the pluggable database. The result of executing the command is then returned to the first database server. Thus, application code which references the pluggable database within the original container database does not have to be rewritten to reference the new location and can remain agnostic as to the actual location of the pluggable database.

Proxy databases

A query may be rewritten to leverage information stored in a structured XML index. An operator in the query may be analyzed to determine an input source database object for the operator by traversing an operator tree rooted at the operator. The path expressions associated with the operator tree may be fused together to form an effective path expression for the operator. If the effective path expression directly matches a path expression derived from the index, the query may be rewritten using references to the index. Operators in a query that have effective paths that refer to data in the same index table may be grouped together. A single subquery may be written for a group of operators. Also, a structured XML index may be used as an implied schema for indexed XML data. This implied schema may be used to optimize queries that refer to the indexed XML data.

Leveraging structured XML index data for evaluating database queries

A method and apparatus for automatically analyzing and providing feedback regarding the optimizability of a relational database query. A query developer's primary goal is to ensure that queries and DML operations are rewritten for the most efficient execution. Rewrite diagnosability captures metadata for each attempted query optimization including success or failure and the reasons for failure. The metadata is stored in association with the operators that were not removed through rewriting. Once all optimizations have been attempted and rewriting is complete, the metadata is selectively displayed based on the cost to perform the associated operation. The context of performing the operation may affect the cost. The cost may be based at least on the type of operation and where within the query tree the operation is located. A query developer may configure the database system not to execute the resulting query plan based on one or more criteria.

Technique and framework to provide diagnosability for XML query/DML rewrite and XML index selection

Techniques and approaches are provided for creating indexes and column constraints on structured XML data that is stored in a relational database. Data Definition Language (DDL) Create Index and Create Constraint commands have extended syntax that allows the specification of a path-based expression instead of requiring a column and table name. A mapping created by the system when an XML Schema is registered stores the correspondence of XML data elements to automatically-created database tables and columns that are given names only useful for the internal system. When a user provides a path-based expression in a DDL when creating an index or constraint, the path-based expression is translated to the underlying database constructs using the mapping. Issues are addressed for handling path-based expressions that evaluate to more than one element. Additional index optimization is described using data type information available in the XML schema to select the optimal index type.

XPath-based creation of relational indexes and constraints over XML data stored in relational tables

Disclosed is a method, system, and program product for providing an efficient mechanism to provide updateable relational views over XML. This will allow application developers to write both queries and updates using a relational (SQL) syntax, even though the underlying data is stored as XML. According to some approaches, this is accomplished by implementing a reverse mapping from the data within the views to the node addresses of the corresponding data in the underlying XML document.

Method and system for implementing efficient updatable relational views over XML data

A method, device, and non-transitory computer-readable storage medium are provided for efficiently registering a relational schema. In co-compilation and data guide approaches, a subset of entities from schema descriptions are selected for physical registration, and other entities from the schema descriptions are not physically registered. In the co-compilation approach, a first schema description references a second schema description, and the subset includes a set of entities from the second schema description that are used by the first schema description. In the data guide approach, the subset includes entities that are used by a set of structured documents. In a pay-as-you-go approach, schema registration includes logically registering entities without creating relational database structures corresponding to the entities. A database server may execute database commands that reference the logically registered entities. A request to store data for the entities may be executed by creating relational database structures to store the data.

Efficiently registering a relational schema

Techniques for estimating a cost of executing a query are provided. A query includes multiple predicates, each of which is associated with a selectivity value that indicates a percentage of input that satisfies the condition of the corresponding predicate. The selectivity values are used to determine an estimated cost of executing the query. In one technique, a group of multiple predicates of a query are treated as a single predicate. Thus, a single selectivity value, rather than multiple selectivity values, is determined for that group. In a related technique, instead of determining a selectivity value of a predicate in isolation with respect to other predicates of a query, the selectivity value of a set of one or more predicates in a query is generated based on other predicates in the query.

Determining predicate selectivity in query costing

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Maple Valley, WA, United States of America

Thomas Baby