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Disclaimed copyright. Preparing for release 2.0. (CVS 250)

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drh
2001-09-16 00:13:26 +00:00
parent 872ff86f2c
commit b19a2bc603
77 changed files with 768 additions and 2079 deletions
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29
www/arch.tcl
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@ -1,7 +1,7 @@
#
# Run this Tcl script to generate the sqlite.html file.
#
set rcsid {$Id: arch.tcl,v 1.3 2000/09/29 13:30:55 drh Exp $}
set rcsid {$Id: arch.tcl,v 1.4 2001/09/16 00:13:29 drh Exp $}
puts {<html>
<head>
@ -112,19 +112,24 @@ source file <b>vdbe.c</b>. The virtual machine also has
its own header file <b>vdbe.h</b> that defines an interface
between the virtual machine and the rest of the SQLite library.</p>
<h2>Backend</h2>
<h2>B-tree Driver</h2>
<p>The last layer in the design of SQLite is the backend. The
backend implements an interface between the virtual machine and
the underlying data file library -- GDBM in this case. The interface
is designed to make it easy to substitute a different database
library, such as the Berkeley DB.
The backend abstracts many of the low-level details to help
reduce the complexity of the virtual machine.</p>
<p>An SQLite database is maintained on disk using a B-tree implementation
found in the <b>btree.c</b> source file. A separate B-tree is used for
each table and index in the database but all B-trees are stored in the
same disk file. Each page of a B-tree is 1024 bytes in size. The data
is stored with the key in an area called "payload". Up to 236 bytes of
payload can be stored with each B-tree entry. Any additional payload
is stored in a chain of overflow pages.</p>
<p>The backend is contained in the single source file <b>dbbe.c</b>.
The backend also has a header file <b>dbbe.h</b> that defines the
interface between the backend and the rest of the SQLite library.</p>
<h2>Page Cache</h2>
<p>The page cache provides the rollback and atomic commit abstraction
and takes care of reader/writer locking of the database file. The
B-tree driver requests particular pages from the page cache and notifies
the page cache when it wants to modify pages and commit or rollback its
changes and the page cache handles all the messy details of making sure
the requests are handled quickly, safely, and efficiently.</p>
}
puts {