Sybase

About: Sybase is a based out in . It is known for research contribution in the topics: Query optimization & View. The organization has 527 authors who have published 499 publications receiving 17534 citations. The organization is also known as: System ware & System base.

A critique of ANSI SQL isolation levels

Abstract: ANSI SQL-92 [MS, ANSI] defines Isolation Levels in terms of phenomena: Dirty Reads, Non-Repeatable Reads, and Phantoms. This paper shows that these phenomena and the ANSI SQL definitions fail to properly characterize several popular isolation levels, including the standard locking implementations of the levels covered. Ambiguity in the statement of the phenomena is investigated and a more formal statement is arrived at; in addition new phenomena that better characterize isolation types are introduced. Finally, an important multiversion isolation type, called Snapshot Isolation, is defined.

SQL-based database system with improved indexing methodology

Abstract: A Client/Server Database System with improved methods for performing database queries, particularly DSS-type queries, is described. The system includes one or more Clients (e.g., Terminals or PCs) connected via a Network to a Server. In general operation, Clients store data in and retrieve data from one or more database tables resident on the Server by submitting SQL commands, some of which specify "queries"--criteria for selecting particular records of a table. The system implements methods for storing data vertically (i.e., by column), instead of horizontally (i.e., by row) as is traditionally done. Each column comprises a plurality of "cells" (i.e., column value for a record), which are arranged on a data page in a contiguous fashion. The system builds the value lookup table for tracking unique values in the cells. As additional unique values are inserted into the column of the user's table (i.e., maintained as the row-ordered cell array), the system assigns a small unique integer value to each unique user value. Instead of storing the original (wide) data value into the row-ordered array, the system instead stores the new (narrow) integer number into the row-ordered array. In response to a user request to retrieve a value for a given row number, the system fetches the appropriate chunk of the row-ordered array and retrieves the small integer value. This small integer value is then used to index into the value lookup table, for reconstituting the actual user data.

Database system with methodology for storing a database table by vertically partitioning all columns of the table

Abstract: A Client/Server Database System with improved methods for performing database queries, particularly DSS-type queries, is described. The system includes one or more Clients (e.g., Terminals or PCs) connected via a Network to a Server. In general operation, Clients store data in and retrieve data from one or more database tables resident on the Server by submitting SQL commands, some of which specify "queries"--criteria for selecting particular records of a table. The system implements methods for storing data vertically (i.e., by column), instead of horizontally (i.e., by row) as is traditionally done. Each column comprises a plurality of "cells" (i.e., column value for a record), which are arranged on a data page in a contiguous fashion. By storing data in a column-wise basis, the system can process a DSS query by bringing in only those columns of data which are of interest. Instead of retrieving row-based data pages consisting of information which is largely not of interest to a query, column-based pages can be retrieved consisting of information which is mostly, if not completely, of interest to the query. The retrieval itself can be done using more-efficient large block I/O transfers. The system includes data compression which is provided at the level of Cache or Buffer Managers, thus providing on-the-fly data compression in a manner which is transparent to each object. Since vertical storage of data leads to high repetition on a given data page, the system provides improved compression/decompression.

System and Methodology for Parallel Query Optimization Using Semantic-Based Partitioning

Abstract: A system and methodology for parallel query optimization using semantic-based partitioning is described. In one embodiment, for example, in a database system comprising a database storing data in database tables, a method is described for improving query performance by dynamically partitioning the data, the method comprises steps of: receiving a query requesting data from the database; generating a plurality of subplans for executing the query, each subplan including one or more operators for performing relational operations; adding operators for partitioning data and performing a given relational operation in parallel to at least some of the plurality of subplans; and building a plan for execution of the query based, at least in part, upon selecting subplans having favorable execution costs.

Development system providing methods for managing different versions of objects with a meta model

Abstract: An "Object Cycle" versioning system having an Object Cycle Server is described. The server communicates over a wire or a network for providing versioning services to multiple clients. During a user session, a user invokes operation of the system from within the development environment of the particular client being used. From the perspective of the Object Cycle Server, each client is simply "a client" (without regard to proprietary nature) which desires to store "an object." The Object Cycle Server, in turn, maps the object into a meta model which serves as a container for facilitating version control. With the model, therefore, operations supported by the system for versioning will execute correctly even if the objects are stored in a format other than a relational database, such as an object-oriented database, a file server, or other storage system. The model separates out the name of an object from where the object itself is actually stored. As additional versions of the object are created, the number of object instances increases. Once an instance has been created, versioning activities can be undertaken, such as checking in, checking out, and the like--operations which are atomic at the object level. By separating out these areas of functionality into (conceptually) different nodes of a meta model, system performance is enhanced.