/ 
Trog-SQLite-0.001
/ Trog::SQLite

NAME

Trog::SQLite - An SQLite handle with its schema applied, its updates run, and its pragmas set

VERSION

version 0.001

SYNOPSIS

use Trog::SQLite;

my $dbh = Trog::SQLite::dbh( 'schema/app.sql', '/var/lib/app/app.db' );

Trog::SQLite::bulk_insert( $dbh, 'tags', [qw{post tag}], 'IGNORE', 1, 'perl', 1, 'sqlite' );

DESCRIPTION

dbh opens an SQLite database, applies its schema, runs the updates of that schema that it has not run yet, and sets the pragmas that let several processes share one database. It caches the handle, so every later call for that file gets the same one.

Everything here dies when something goes wrong.

Schema updates

A schema file holds the first version of the schema, version 0. Write each statement in it so that it can run again, such as CREATE TABLE IF NOT EXISTS, because dbh applies it on every new handle.

A change to the schema after the first version goes in an update file beside it. Each update has a number, from 1 up with no gaps, and its name is the name of the schema with that number:

schema/app.sql              version 0
schema/app.v1.update.sql    version 1
schema/app.v2.update.sql    version 2

Each database records its version in the table trog_sqlite_schema_version. dbh makes that table in every database that it opens, with one row and a version of 0. Then it runs each update with a number above that version, in order. Each update runs in one BEGIN IMMEDIATE transaction, together with the change to the recorded version. So an update that fails changes nothing, and the version stays where it was. When two processes open the database at the same time, the second one waits for the first, and then finds the update done.

A new database gets the schema, and then every update. So the update files together with the schema describe the current tables, and nobody needs to change the schema file after its first release.

An update file must not hold BEGIN or COMMIT, because it already runs in a transaction. Foreign keys are not enforced while the updates run, so an update can rebuild a table that other tables refer to. After each update, PRAGMA foreign_key_check must report nothing, or the update is rolled back.

FUNCTIONS

dbh($schema, $dbname)

Returns a handle to the database in the file $dbname, which is made if it does not exist. If you give $schema, its DDL and its updates are applied first, as "Schema updates" says. Omit $schema for a database that already has its schema.

The handle has RaiseError on, and these pragmas:

  • busy_timeout = 5000, so that a second process waits for five seconds for a lock rather than failing at once with database is locked.

  • journal_mode = WAL and synchronous = NORMAL, so that readers do not block a writer.

  • foreign_keys = ON, set after the updates.

The handle is cached for the rest of the process. A second call for the same $dbname returns the cached handle, and does not apply $schema again.

Do not call this during BEGIN or outside a sub. A handle must not outlive a fork, so a forked child calls forget before it calls this.

apply($db, $file)

Runs every statement in the SQL file $file on the handle $db, and returns 1. Dies if the file cannot be read, or if a statement fails.

@updates = updates($schema)

Returns the update files of the schema file $schema, as a list of [ $version, $path ] pairs in the order of their versions. See "Schema updates".

Dies if the versions have a gap, such as a v3 with no v2, because then one of the files is misnamed or missing, and running the others would skip it.

$version = schema_version($db)

Returns the version of the schema that the database of $db records. It makes the table that records it, with one row and a version of 0, if the database has none.

$version = update($db, $schema)

Runs each update of $schema that the database of $db has not run, as "Schema updates" says, and returns the version of the database afterwards. dbh calls this. Dies with the name of the file if an update fails, and that update then changes nothing.

forget()

Drops the cached handles and returns 1. A forked child calls this so that it opens its own handle and does not use the handle of its parent.

bulk_insert($dbh, $table, \@keys, $action, @values)

Inserts @values into the columns @keys of $table, and returns 1. @values is one row after another, each with one value for each key:

my @keys   = qw{A B C};
my @values = qw{1 2 3 4 5 6 7 8 9};    # three rows

$action is the conflict clause of the INSERT: one of ROLLBACK, ABORT, FAIL, IGNORE or REPLACE. With foreign keys off, REPLACE inserts a row or replaces the one with its key, with less code than ON CONFLICT ... DO UPDATE.

One statement takes as many parameters as the handle allows, which is 999 in older builds of SQLite and 32766 in newer ones. So the rows go in as many statements as that needs, which reuse one prepared statement. Split a very large @values into batches that fit in memory.

Dies if $action is not one of those, if @keys is empty, or if the number of values is not a multiple of the number of keys.

BUGS

Please report any bugs or feature requests on the bugtracker website https://github.com/Troglodyne-Internet-Widgets/Trog-SQLite/issues

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

AUTHORS

Current Maintainers:

  • George S. Baugh <george@troglodyne.net>

COPYRIGHT AND LICENSE

Copyright (c) 2026 Troglodyne LLC

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.