CHARACTERISTICS OF EMBEDDED DATABASE
Due to limited resources of hardware and software, it is not possible to install a huge database
server in embedded database systems. However, user's need may be meted with a database
system which is just a simple document of diskbased. It just makes use of the basic characteristics
of the database. Since the special restrictions of application environment, embedded database has
its own characteristics compared to common database systems
[1][2]
: Taking up little storage space,
reliability, manageability and security, interoperability, tailoring, portability, high-performance,
low cost, embedded, full-featured and other characteristics.
Although SQLite is an extremely lightweight relational database, it has retained most of the
features of database. Its main features are as follows
[3]
:
• Transactions are atomic, consistent, isolated, and durable (ACID) even after system
crashes and power failures.
• Zero-configuration, no setup or administration needed.
• A complete database is stored in a single cross-platform disk file.
• Supports terabyte-sized databases and gigabyte-sized strings and blobs.
• Small code footprint: less than 275KB fully configured.
• Faster than popular client/server database engines for most common operations.
• Simple, easy to use API.
• Self-contained: no external dependencies.
• Cross-platform and it is easy to port to other systems.
• Sources are in the public domain.
The internal structure of SQLite is composed of the following components: SQL compiler,
kernel, the back-end as well as the annex.
Interface is a C language library which can receive API in a wide range of language, but the
implementation in the bottom is the C language library. When a SQL statement containing the
string is implemented, the interface programs pass the string to the Tokenizer. The Tokenizer
decomposes the original string into the indicators identified by a parser and passes these
indicators to the parser. After the parser collects the symbols, it converts them to full SQL
statement, and then it calls the code generator to generate the virtual machine code and the virtual
machine code is handed to the virtual machine to implement and complete the SQL statement.
The core of the architecture of SQLite is the virtual database engine (VDBE). VDBE completes
the entire task related to data processing and it is the intermediate unit of information exchange
between and customers and the storage. SQLite database is maintained in the disk, implemented
by B -tree which is in the source file btree.c and it searches and accesses data fast through the
adjustable page cache (pager). In order to facilitate the transplant, the interface programs of
SQLite operating system uses a layer extraction. Utilities mainly solute the memory allocation,
