SqLite Database

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Last update: 15-11-2023

SQLite was designed to allow the program to be operated without installing a database management system or requiring a database administrator. Unlike client–server database management systems, the SQLite engine has no standalone processes with which the application program communicates. Instead, a linker integrates the SQLite library — statically or dynamically — into an application program which uses SQLite's functionality through simple function calls, reducing latency in database operations; for simple queries with little concurrency, SQLite performance profits from avoiding the overhead of inter-process communication.

Due to the serverless design, SQLite applications require less configuration than client–server databases. SQLite is called zero-conf[17] because it does not require service management (such as startup scripts) or access control based on GRANT and passwords. Access control is handled by means of file-system permissions given to the database file itself. Databases in client–server systems use file-system permissions that give access to the database files only to the daemon process, which handles its locks internally, allowing concurrent writes from several processes.

SQLite stores the whole database (definitions, tables, indices, and the data itself) as a single cross-platform file on a host machine, allowing several processes or threads to access the same database concurrently. It implements this simple design by locking the database file during writing. Write access may fail with an error code, or it can be retried until a configurable timeout expires. SQLite read operations can be multitasked, though due to the serverless design, writes can only be performed sequentially. This concurrent access restriction does not apply to temporary tables, and it is relaxed in version 3.7 as write-ahead logging (WAL) enables concurrent reads and writes.[18] Since SQLite has to rely on file-system locks, it is not the preferred choice for write-intensive deployments.[19]

SQLite uses PostgreSQL as a reference platform. "What would PostgreSQL do" is used to make sense of the SQL standard. [20][21] One major deviation is that, with the exception of primary keys, SQLite does not enforce type checking; the type of a value is dynamic and not strictly constrained by the schema (although the schema will trigger a conversion when storing if such a conversion is potentially reversible). SQLite strives to follow Postel's rule.[22]

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