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Object Persistence (Data Base) Design

Object Persistence (Data Base) Design. Chapter 13. Key Definitions. Object persistence involves the selection of a storage format and optimization for performance. Four basic formats used for object persistence are: files, OO databases, and relational databases. Files. Sequential Access

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Object Persistence (Data Base) Design

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  1. Object Persistence (Data Base) Design Chapter 13

  2. Key Definitions • Object persistence involves the selection of a storage format and optimization for performance. • Four basic formats used for object persistence are: files, OO databases, and relational databases.

  3. Files • Sequential Access • Data stored in order based on a particular attribute • Typically efficient for reports using all or most of the file’s data • Random Access • Data stored in unordered fashion • Typically efficient for finding individual records

  4. Primary key Foreign key Referential integrity Structured Query Language (SQL) Tables Joining tables Objects must be converted so they can be stored in a table Relational Databases

  5. Relational databases extended to handle the storage of objects Use of user-defined data types Extended SQL Inheritance tends to be language dependent Repeating groups or multivalued attributes Object-Relational Databases

  6. Two approaches Adding persistence extensions to OO languages Separate database management systems Extents (tables) Object ID assigned Some inheritance Repeating groups or multivalued attributes Sharp learning curve Object-Oriented Databases

  7. MAPPING PROBLEM DOMAIN OBJECTS TO OBJECT PERSISTENCE FORMATS

  8. Mapping Problem Domain Objects to RDBMS Schema -- Rules

  9. OPTIMIZING RDBMS-BASED OBJECT STORAGE

  10. Dimensions of Data Storage Optimization • Storage efficiency (minimizing storage space) • Speed of access (minimizing time to retrieve desired information)

  11. Optimizing Storage Efficiency • Reduce redundant data • Limit null values • Multiple possible interpretations can lead to mistakes • A well-formed logical data model does not contain redundancy or many null values

  12. The Steps of Normalization

  13. Denormalization Clustering Intra-file Inter-file Indexing Optimizing Access Speed

  14. Guidelines for Creating Indexes • Use indexes sparingly for transaction systems • Use many indexes to increase response times in decision support systems • For each table • Create a unique index based on the primary key • Create an index based on the foreign key • Create an index for fields used frequently for grouping, sorting, or criteria

  15. Estimating Data Storage Size Field Average Size (Characters) Order number 8 Date 7 Cust ID 4 Last name 13 First name 9 State 2 Amount 4 Tax rate 2 Record Size 49 Overhead (30%) 14.7 Total Record Size 63.7 Initial Table Size 50,000 Initial Table Volume 3,185,000 Growth/Month 1,000 Table volume @ 3 years 5,478,200

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