=head1 NAME

ovsqlite - SQLite-based overview storage method for INN

=head1 DESCRIPTION

This method uses SQLite to store overview data.  It requires version
3.8.2 or later of the SQLite library (3.20.0+ recommended).

SQLite source, documentation, etc. are available at
L<https://www.sqlite.org/>.  Ones of the stated goals of the SQLite
file format are long-term stability and compatibility, which make that
storage method a perfect choice to store overview data.

Only one protocol version of the ovsqlite storage method currently
exists, implemented since S<INN 2.7.0>.

This method comes with a support utility (B<ovsqlite-util>) and a Perl
module (C<INN::ovsqlite_client>) which permit accessing and manipulating
overview information.  See their manual pages for more details about their
possibilities.

=head1 INSTALLATION

The configure script will automatically enable ovsqlite support if it finds
the SQLite library.  If the library isn't installed in a standard
location, you may have to specify the B<--with-sqlite3> option to help
configure find it.  For complicated cases, you can use separate
B<--with-sqlite3-include> and B<--with-sqlite3-lib> options.  Finally, if
you I<don't> want ovsqlite support even when your system has the SQLite
library, you can use the B<--without-sqlite3> option.

If you have a recent Linux installation, SQLite is most likely already
installed.  You may have to install a separate package with a name similar
to C<libsqlite3-dev> to get the required header files.

Plan on needing at least S<0.93 KB> for every article in your spool
(not counting crossposts).  So, if you have 5 million articles, you'll
need at least S<4.65 GB> of disk space for ovsqlite.  With compression
enabled, this estimate changes to S<0.4 KB> per article, so you'll
need at least S<2 GB> of disk space for 5 million articles.  Plus,
you'll need additional space for transaction logs (a few MB).

=head1 CONFIGURATION

To select ovsqlite as your overview method, set the I<ovmethod> parameter
in F<inn.conf> to C<ovsqlite>.  The database file will be created in
the directory specified by the I<pathoverview> parameter in F<inn.conf>.
Restart INN to take the change into account (after having rebuilt your
existing overview with B<makehistory>, if needed).

These additional parameters are read from the F<ovsqlite.conf>
configuration file:

=over 4

=item I<cachesize>

The SQLite in-memory page cache size in kilobytes.  The default value is
left up to the SQLite library and seems to be stable at S<2000 KB>.

=item I<compress>

If INN was built with zlib support and this parameter is true, ovsqlite
will compress overview records whenever this saves space.  This parameter
is consulted only when creating a new database.  Enabling compression
saves about S<55 %> of disk space on standard overview data.  The default
value is false.

=item I<pagesize>

The SQLite database page size in bytes.  Must be a power of 2, minimum 512,
maximum 65536.  Appropriate values include the virtual memory page size and
the filesystem allocation block size.  This parameter is consulted only
when creating a new database.  The default value is left up to the SQLite
library and varies between versions.

=item I<transrowlimit>

The maximum number of article rows that can be inserted or deleted in a
single SQL transaction.  The default value is 10000 articles.

=item I<transtimelimit>

The maximum SQL transaction lifetime in seconds.  The default value is
10 seconds.

=back

A transaction occurs every I<transrowlimit> articles or I<transtimelimit>
seconds, whichever is smaller.  You are encouraged to keep the default
value for row limits and, instead, adjust the time limit according to
how many articles your news server usually accepts per second during
normal operation (you can find statistics about incoming articles in
your daily Usenet reports).  Inserting or deleting a database row within
a transaction is very fast whereas committing a transaction is slow,
especially on rotating storage.  Setting transaction limits too low
leads to poor performance.  When rebuilding overview data, it may be
worth temporarily raising these values on systems with slow CPU or rotating
storage (for instance, multiply by 10 the default values).  Performance won't
change much on fast systems.

=head1 RUNNING

All overview database access goes through the B<ovsqlite-server> daemon.
For ordinary operation, B<rc.news> will start and stop it automatically.
If you want to touch the overview database while B<innd> isn't running, you'll
have to start B<ovsqlite-server> manually first.  See ovsqlite-server(8).

=head1 HISTORY

Initial implementation of ovsqlite written by Bo Lindbergh
<2bfjdsla52kztwejndzdstsxl9athp@gmail.com> for InterNetNews.

=head1 SEE ALSO

INN::ovsqlite_client(3pm), inn.conf(5), makehistory(8), ovsqlite-server(8),
ovsqlite-util(8), rc.news(8).

=cut
