Data aggregation server for managing a multi-dimensional database and database management system having data aggregation server integrated therein

Abstract

Improved method of and apparatus for aggregating data elements in multidimensional databases (MDDB). In one aspect of the present invention, the apparatus is realized in the form of a high-performance stand-alone (i.e. external) aggregation server which can be plugged-into conventional OLAP systems to achieve significant improments in system performance. In accordance with the principles of the present invention, the stand-alone aggregation server contains a scalable MDDB and a high-performance aggregation engine that are integrated into the modular architecture of the aggregation server. The stand-alone aggregation server of the present invention can uniformly distribute data elements among a plurality of processors, for balanced loading and processing, and therefore is highly scalable. The stand-alone aggregation server of the present invention can be used to realize (i) an improved MDDB for supporting on-line analytical processing (OLAP) operations, (ii) an improved Internet URL Directory for supporting on-line information searching operations by Web-enabled client machines, as well as (iii) diverse types of MDDB-based systems for supporting real-time control of processes in response to complex states of information reflected in the MDDB. In another aspect of the present invention, the apparatus is integrated within a database management system (DBMS). The improved DBMS can be used to realize achieving a significant increase in system performance (e.g. deceased access / search time), user flexibility and ease of use. The improved DBMS system of the present invention can be used to realize an improved Data Warehouse for supporting on-line analytical processing (OLAP) operations or to realize an improved informational database system, operational database system, or the like.

Description

RELATED CASES[0001] This is a Continuation-in-part of: copending U.S. application Ser. No. 09 / 514,611 entitled "Stand-Alone Cartridge-Style Data Aggregation Server And Method of And System For Managing Multi-Dimensional Databases using the Same", filed Feb. 28, 2000, and U.S. application Ser. No. 09 / 634,748 entitled "Relational Database Management System Having Integrated Non-Relational Multi-Dimensional Data Store of Aggregated Data Elements" filed Aug. 9, 2000; each said Application being commonly owned by HyperRoll, Limited, and incorporated herein by reference in its entirety.[0002] 1. Field of Invention[0003] The present invention relates to a method of and system for aggregating data elements in a multi-dimensional database (MDDB) supported upon a computing platform and also to provide an improved method of and system for managing data elements within a MDDB during on-line analytical processing (OLAP) operations and as an integral part of a database management system.[0004] 2....

AI Technical Summary

Benefits of technology

[0088] Accordingly, it is a further object of the present invention to provide an improved method of and system for managing data elements within a multidimensional database (MDDB) using a novel stand-alone (i.e. external) data aggregation server, achieving a significant increase in system performance (e.g. deceased access / search time) using a stand-alone scalable data aggregation server.

Problems solved by technology

The volume of information that is available to corporations is rapidly increasing and frequently overwhelming.

Building a Data Warehouse has its own special challenges (e.g. using common data model, common business dictionary, etc.) and is a complex endeavor.

However, just having a Data Warehouse does not provide organizations with the often-heralded business benefits of data warehousing.

In all the prior art OLAP servers, the process of storing, indexing and handling MDDB utilize complex data structures to largely improve the retrieval speed, as part of the querying process, at the cost of slowing down the storing and aggregation.

The query-bounded structure, that must support fast retrieval of queries in a restricting environment of high sparcity and multi-hierarchies, is not the optimal one for fast aggregation.

However, requirements (2) and (3) fundamentally limit MOLAP's capability, because to be effective and to meet end-user requirements, MOLAP databases need a high degree of aggregation.

By contrast, the ROLAP system architecture allows the construction of systems requiring a low degree of aggregation, but such systems are significantly slower than systems based on MOLAP system architecure principles.

The resulting long aggregation times of ROLAP systems impose severe limitations on its volumes and dimensional capabilities.

However, prior art MOLAP systems have limited capabilities to dynamically create data aggregations or to calculate business metrics that have not been precalculated and stored in the MDDB.

However, the ROLAP architecture, despite its high volume and dimensionality superiority, suffers from several significant drawbacks as compared to MOLAP:

Full aggregation of large data volumes are very time consuming, otherwise, partial aggregation severely degrades the query response.

SQL is less capable of the sophisticated analytical functionality necessary for OLAP

ROLAP provides limited application functionality

Building a Data Warehouse has its own special challenges (e.g. using common data model, common business dictionary, etc.) and is a complex endeavor.

However, just having a Data Warehouse does not provide organizations with the often-heralded business benefits of data warehousing.

However, the querying component of RDBMS technology suffers from performance and optimization problems stemming from the very nature of the relational data model.

For large multidimensional databases, a naive implementation of these operations involves computational intensive table scans that leads to unacceptable query response times.

For large multi-dimensional databases, a naive implementation of these operations involves computational intensive table scans that typically leads to unacceptable query response times. Moreover, since the fact tables are pre-summarized and aggregated along business dimensions, these tables tend to be very large.

The first performance issue arises from computationally intensive table scans that are performed by a naive implementation of data joining.

However, these indexing schemes suffer from various performance issues as follows:

Since the tables in the star schema design typically contain the entire hierarchy of attributes (e.g. in a PERIOD dimension, this hierarchy could be day>week>month>quarter>year), a multipart key of day, week, month, quarter, year has to be created; thus, multiple meta-data definitions are required (one of each key component) to define a single relationship; this adds to the design complexity, and sluggishness in performance.

Addition or deletion of levels in the hierarchy will require physical modification of the fact table, which is time consuming process that limits flexibility.

Carrying all the segments of the compound dimensional key in the fact table increases the size of the index, thus impacting both performance and scalability.

Another performance issue arises from dimension tables that contain multiple hierarchies.

Every retrieval from fact table that stores details and aggregates must use the indicator to obtain the correct result, which impacts performance.

Notably, the snowflake schema is even more complicated than a star schema, and often requires multiple SQL statements to get the results that are required.

Another performance issue arises from the pairwise join problem.

Traditional RDBMS engines are not design for the rich set of complex queries that are issued against a star schema.

The need to retrieve related information from several tables in a single query--"join processing"--is severely limited.

Unfortunately, because the number of combinations to be evaluated grows exponentially with the number of tables being joined, the problem of selecting the best order of pairwise joins rarely can be solved in a reasonable amount of time.

Moreover, because the number of combinations is often too large, optimizers limit the selection on the basis of a criterion of directly related tables.

Unfortunately, the fact table is the very largest table in the query, so this strategy leads to selecting a pairwise join order that generates a very large intermediate result get, severely affecting query performance.

Unfortunately, parallelism can only reduce, not eliminate, the performance degradation issues related to the star schema.

The more difficult are analytical calculations, the aggregation of Boolean and comparative operators.

summary tables require that database administrators anticipate the data aggregation operations that users will require; this is a difficult task in large multi-dimensional databases (for example, in data warehouses and data mining systems), where users always need to query in new ways looking for new information and patterns.

summary tables do not provide a mechanism that allows efficient drill down to view the raw data that makes up the summary table--typically a table scan of one or more large tables is required.

there is a heavy time overhead because the vast majority of the generated information remains unvisited.

the degree of viable parallelism is limited because the subsequent levels of summary tables must be performed in pipeline, due to their hierarchies.

for very large databases, this option is not valid because of time and storage space.

Thus, in large multi-dimensional databases, such dynamic aggregation may lead to unacceptable query response times.

In view of the problems associated with joining and aggregation within RDBMS, prior art ROLAP systems have suffered from essentially the same shortcomings and drawbacks of their underlying RDBMS.

Thus, users of the DBMS cannot directly view these results.

Such requirements can present security issues, highly undesirable for system administration.

Satisfying such requirements is a costly and logistically cumbersome process.

As a result, the widespread applicability of MOLAP systems has been limited.

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