The OS Backend (VFS) To SQLite

The SQLite OS Interface or "VFS"

This article describes the SQLite OS portability layer or "VFS" - the module at the bottom of the SQLite implementation stack that provides portability across operating systems.

1.0 The VFS In Relation To The Rest Of SQLite

The internal organization of the SQLite library can be viewed as the stack of modules shown to the right. The Tokenizer, Parser, and Code Generator components are used to process SQL statements and convert them into executable programs in a virtual machine language or byte code. Roughly speaking, these top three layers implement sqlite3_prepare_v2(). The byte code generated by the top three layers is a prepared statement. The Virtual Machine module is responsible for running the SQL statement byte code. The B-Tre