SQLite transaction doesn't work as expected - php

Question

I prepared 2 files, "1.php" and "2.php".
"1.php" is like this.
<?php
$dbh = new PDO('sqlite:test1');
$dbh->beginTransaction();
print "aaa<br>";
sleep(55);
$dbh->commit();
print "bbb";
?>
and "2.php" is like this.
<?php
$dbh = new PDO('sqlite:test1');
$dbh->beginTransaction();
print "ccc<br>";
$dbh->commit();
print "ddd";
?>
and I excute "1.php". It starts a transaction and waits 55 seconds.
So when I immediately excute "2.php", my expectation is this:
"1.php" is getting transaction and
"1" holds a database lock
"2" can not begin a transaction
"2" can not get database lock so
"2" have to wait 55 seconds
BUT, but the test went another way. When I excute "2",then
"2" immediately returned it's result
"2" did not wait
so I have to think that "1" could not get transaction, or could not get database lock.
Can anyone help?

Answer 1

As I understand it, SQLite transactions do not lock the database unless
a. you make them EXCLUSIVE (they are DEFERRED by default), or
b. you actually access the database
So either you explicitly call
$dbh->exec("BEGIN EXCLUSIVE TRANSACTION");
or you make a write operation (INSERT/UPDATE) to the DB before you start to sleep().
To cite the documentation (emphasis mine):
Transactions can be deferred,
immediate, or exclusive. The default
transaction behavior is deferred.
Deferred means that no locks are
acquired on the database until the
database is first accessed. Thus with
a deferred transaction, the BEGIN
statement itself does nothing. Locks
are not acquired until the first read
or write operation. The first read
operation against a database creates a
SHARED lock and the first write
operation creates a RESERVED lock.