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.\" ========================================================================
.\"
.IX Title "DBD::SQLite 3"
.TH DBD::SQLite 3 "2019-08-12" "perl v5.16.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
DBD::SQLite \- Self\-contained RDBMS in a DBI Driver
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& use DBI;
\& my $dbh = DBI\->connect("dbi:SQLite:dbname=$dbfile","","");
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
SQLite is a public domain file-based relational database engine that
you can find at <https://www.sqlite.org/>.
.PP
\&\fBDBD::SQLite\fR is a Perl \s-1DBI\s0 driver for SQLite, that includes
the entire thing in the distribution.
So in order to get a fast transaction capable \s-1RDBMS\s0 working for your
perl project you simply have to install this module, and \fBnothing\fR
else.
.PP
SQLite supports the following features:
.IP "Implements a large subset of \s-1SQL92\s0" 4
.IX Item "Implements a large subset of SQL92"
See <https://www.sqlite.org/lang.html> for details.
.IP "A complete \s-1DB\s0 in a single disk file" 4
.IX Item "A complete DB in a single disk file"
Everything for your database is stored in a single disk file, making it
easier to move things around than with \s-1DBD::CSV\s0.
.IP "Atomic commit and rollback" 4
.IX Item "Atomic commit and rollback"
Yes, \fBDBD::SQLite\fR is small and light, but it supports full transactions!
.IP "Extensible" 4
.IX Item "Extensible"
User-defined aggregate or regular functions can be registered with the
\&\s-1SQL\s0 parser.
.PP
There's lots more to it, so please refer to the docs on the SQLite web
page, listed above, for \s-1SQL\s0 details. Also refer to \s-1DBI\s0 for details
on how to use \s-1DBI\s0 itself. The \s-1API\s0 works like every \s-1DBI\s0 module does.
However, currently many statement attributes are not implemented or
are limited by the typeless nature of the SQLite database.
.SH "SQLITE VERSION"
.IX Header "SQLITE VERSION"
DBD::SQLite is usually compiled with a bundled SQLite library
(SQLite version 3.29.0 as of this release) for consistency.
However, a different version of SQLite may sometimes be used for
some reasons like security, or some new experimental features.
.PP
You can look at \f(CW$DBD::SQLite::sqlite_version\fR (\f(CW\*(C`3.x.y\*(C'\fR format) or
\&\f(CW$DBD::SQLite::sqlite_version_number\fR (\f(CW\*(C`3xxxyyy\*(C'\fR format)
to find which version of SQLite is actually used. You can also
check \f(CW\*(C`DBD::SQLite::Constants::SQLITE_VERSION_NUMBER()\*(C'\fR.
.PP
You can also find how the library is compiled by calling
\&\f(CW\*(C`DBD::SQLite::compile_options()\*(C'\fR (see below).
.SH "NOTABLE DIFFERENCES FROM OTHER DRIVERS"
.IX Header "NOTABLE DIFFERENCES FROM OTHER DRIVERS"
.SS "Database Name Is A File Name"
.IX Subsection "Database Name Is A File Name"
SQLite creates a file per a database. You should pass the \f(CW\*(C`path\*(C'\fR of
the database file (with or without a parent directory) in the \s-1DBI\s0
connection string (as a database \f(CW\*(C`name\*(C'\fR):
.PP
.Vb 1
\& my $dbh = DBI\->connect("dbi:SQLite:dbname=$dbfile","","");
.Ve
.PP
The file is opened in read/write mode, and will be created if
it does not exist yet.
.PP
Although the database is stored in a single file, the directory
containing the database file must be writable by SQLite because the
library will create several temporary files there.
.PP
If the filename \f(CW$dbfile\fR is \*(L":memory:\*(R", then a private, temporary
in-memory database is created for the connection. This in-memory
database will vanish when the database connection is closed.
It is handy for your library tests.
.PP
Note that future versions of SQLite might make use of additional
special filenames that begin with the \*(L":\*(R" character. It is recommended
that when a database filename actually does begin with a \*(L":\*(R" character
you should prefix the filename with a pathname such as \*(L"./\*(R" to avoid
ambiguity.
.PP
If the filename \f(CW$dbfile\fR is an empty string, then a private,
temporary on-disk database will be created. This private database will
be automatically deleted as soon as the database connection is closed.
.PP
As of 1.41_01, you can pass \s-1URI\s0 filename (see <https://www.sqlite.org/uri.html>)
as well for finer control:
.PP
.Vb 1
\& my $dbh = DBI\->connect("dbi:SQLite:uri=file:$path_to_dbfile?mode=rwc");
.Ve
.PP
Note that this is not for remote SQLite database connection. You can
only connect to a local database.
.SS "Read-Only Database"
.IX Subsection "Read-Only Database"
You can set sqlite_open_flags (only) when you connect to a database:
.PP
.Vb 4
\& use DBD::SQLite::Constants qw/:file_open/;
\& my $dbh = DBI\->connect("dbi:SQLite:$dbfile", undef, undef, {
\& sqlite_open_flags => SQLITE_OPEN_READONLY,
\& });
.Ve
.PP
See <https://www.sqlite.org/c3ref/open.html> for details.
.PP
As of 1.49_05, you can also make a database read-only by setting
\&\f(CW\*(C`ReadOnly\*(C'\fR attribute to true (only) when you connect to a database.
Actually you can set it after you connect, but in that case, it
can't make the database read-only, and you'll see a warning (which
you can hide by turning \f(CW\*(C`PrintWarn\*(C'\fR off).
.SS "DBD::SQLite And File::Temp"
.IX Subsection "DBD::SQLite And File::Temp"
When you use File::Temp to create a temporary file/directory for
SQLite databases, you need to remember:
.IP "tempfile may be locked exclusively" 4
.IX Item "tempfile may be locked exclusively"
You may want to use \f(CW\*(C`tempfile()\*(C'\fR to create a temporary database
filename for DBD::SQLite, but as noted in File::Temp's \s-1POD,\s0
this file may have an exclusive lock under some operating systems
(notably Mac \s-1OSX\s0), and result in a \*(L"database is locked\*(R" error.
To avoid this, set \s-1EXLOCK\s0 option to false when you call \fItempfile()\fR.
.Sp
.Vb 1
\& ($fh, $filename) = tempfile($template, EXLOCK => 0);
.Ve
.IP "\s-1CLEANUP\s0 may not work unless a database is disconnected" 4
.IX Item "CLEANUP may not work unless a database is disconnected"
When you set \s-1CLEANUP\s0 option to true when you create a temporary
directory with \f(CW\*(C`tempdir()\*(C'\fR or \f(CW\*(C`newdir()\*(C'\fR, you may have to
disconnect databases explicitly before the temporary directory
is gone (notably under \s-1MS\s0 Windows).
.PP
(The above is quoted from the pod of File::Temp.)
.PP
If you don't need to keep or share a temporary database,
use \*(L":memory:\*(R" database instead. It's much handier and cleaner
for ordinary testing.
.SS "DBD::SQLite and \fIfork()\fP"
.IX Subsection "DBD::SQLite and fork()"
Follow the advice in the SQLite \s-1FAQ \s0(<https://sqlite.org/faq.html>).
.Sp
.RS 4
Under Unix, you should not carry an open SQLite database across
a \fIfork()\fR system call into the child process. Problems will result
if you do.
.RE
.PP
You shouldn't (re)use a database handle you created (probably to
set up a database schema etc) before you \fIfork()\fR. Otherwise, you
might see a database corruption in the worst case.
.PP
If you need to \fIfork()\fR, (re)open a database after you \fIfork()\fR.
You might also want to tweak \f(CW\*(C`sqlite_busy_timeout\*(C'\fR and
\&\f(CW\*(C`sqlite_use_immediate_transaction\*(C'\fR (see below), depending
on your needs.
.PP
If you need a higher level of concurrency than SQLite supports,
consider using other client/server database engines.
.SS "Accessing A Database With Other Tools"
.IX Subsection "Accessing A Database With Other Tools"
To access the database from the command line, try using \f(CW\*(C`dbish\*(C'\fR
which comes with the DBI::Shell module. Just type:
.PP
.Vb 1
\& dbish dbi:SQLite:foo.db
.Ve
.PP
On the command line to access the file \fIfoo.db\fR.
.PP
Alternatively you can install SQLite from the link above without
conflicting with \fBDBD::SQLite\fR and use the supplied \f(CW\*(C`sqlite3\*(C'\fR
command line tool.
.SS "Blobs"
.IX Subsection "Blobs"
As of version 1.11, blobs should \*(L"just work\*(R" in SQLite as text columns.
However this will cause the data to be treated as a string, so \s-1SQL\s0
statements such as length(x) will return the length of the column as a \s-1NUL\s0
terminated string, rather than the size of the blob in bytes. In order to
store natively as a \s-1BLOB\s0 use the following code:
.PP
.Vb 2
\& use DBI qw(:sql_types);
\& my $dbh = DBI\->connect("dbi:SQLite:dbfile","","");
\&
\& my $blob = \`cat foo.jpg\`;
\& my $sth = $dbh\->prepare("INSERT INTO mytable VALUES (1, ?)");
\& $sth\->bind_param(1, $blob, SQL_BLOB);
\& $sth\->execute();
.Ve
.PP
And then retrieval just works:
.PP
.Vb 4
\& $sth = $dbh\->prepare("SELECT * FROM mytable WHERE id = 1");
\& $sth\->execute();
\& my $row = $sth\->fetch;
\& my $blobo = $row\->[1];
\&
\& # now $blobo == $blob
.Ve
.SS "Functions And Bind Parameters"
.IX Subsection "Functions And Bind Parameters"
As of this writing, a \s-1SQL\s0 that compares a return value of a function
with a numeric bind value like this doesn't work as you might expect.
.PP
.Vb 4
\& my $sth = $dbh\->prepare(q{
\& SELECT bar FROM foo GROUP BY bar HAVING count(*) > ?;
\& });
\& $sth\->execute(5);
.Ve
.PP
This is because DBD::SQLite assumes that all the bind values are text
(and should be quoted) by default. Thus the above statement becomes
like this while executing:
.PP
.Vb 1
\& SELECT bar FROM foo GROUP BY bar HAVING count(*) > "5";
.Ve
.PP
There are four workarounds for this.
.IP "Use \fIbind_param()\fR explicitly" 4
.IX Item "Use bind_param() explicitly"
As shown above in the \f(CW\*(C`BLOB\*(C'\fR section, you can always use
\&\f(CW\*(C`bind_param()\*(C'\fR to tell the type of a bind value.
.Sp
.Vb 1
\& use DBI qw(:sql_types); # Don\*(Aqt forget this
\&
\& my $sth = $dbh\->prepare(q{
\& SELECT bar FROM foo GROUP BY bar HAVING count(*) > ?;
\& });
\& $sth\->bind_param(1, 5, SQL_INTEGER);
\& $sth\->execute();
.Ve
.IP "Add zero to make it a number" 4
.IX Item "Add zero to make it a number"
This is somewhat weird, but works anyway.
.Sp
.Vb 4
\& my $sth = $dbh\->prepare(q{
\& SELECT bar FROM foo GROUP BY bar HAVING count(*) > (? + 0);
\& });
\& $sth\->execute(5);
.Ve
.IP "Use \s-1SQL\s0 \fIcast()\fR function" 4
.IX Item "Use SQL cast() function"
This is more explicit way to do the above.
.Sp
.Vb 4
\& my $sth = $dbh\->prepare(q{
\& SELECT bar FROM foo GROUP BY bar HAVING count(*) > cast(? as integer);
\& });
\& $sth\->execute(5);
.Ve
.ie n .IP "Set ""sqlite_see_if_its_a_number"" database handle attribute" 4
.el .IP "Set \f(CWsqlite_see_if_its_a_number\fR database handle attribute" 4
.IX Item "Set sqlite_see_if_its_a_number database handle attribute"
As of version 1.32_02, you can use \f(CW\*(C`sqlite_see_if_its_a_number\*(C'\fR
to let DBD::SQLite to see if the bind values are numbers or not.
.Sp
.Vb 5
\& $dbh\->{sqlite_see_if_its_a_number} = 1;
\& my $sth = $dbh\->prepare(q{
\& SELECT bar FROM foo GROUP BY bar HAVING count(*) > ?;
\& });
\& $sth\->execute(5);
.Ve
.Sp
You can set it to true when you connect to a database.
.Sp
.Vb 5
\& my $dbh = DBI\->connect(\*(Aqdbi:SQLite:foo\*(Aq, undef, undef, {
\& AutoCommit => 1,
\& RaiseError => 1,
\& sqlite_see_if_its_a_number => 1,
\& });
.Ve
.Sp
This is the most straightforward solution, but as noted above,
existing data in your databases created by DBD::SQLite have not
always been stored as numbers, so this *might* cause other obscure
problems. Use this sparingly when you handle existing databases.
If you handle databases created by other tools like native \f(CW\*(C`sqlite3\*(C'\fR
command line tool, this attribute would help you.
.Sp
As of 1.41_04, \f(CW\*(C`sqlite_see_if_its_a_number\*(C'\fR works only for
bind values with no explicit type.
.Sp
.Vb 10
\& my $dbh = DBI\->connect(\*(Aqdbi:SQLite:foo\*(Aq, undef, undef, {
\& AutoCommit => 1,
\& RaiseError => 1,
\& sqlite_see_if_its_a_number => 1,
\& });
\& my $sth = $dbh\->prepare(\*(AqINSERT INTO foo VALUES(?)\*(Aq);
\& # \*(Aq1.230\*(Aq will be inserted as a text, instead of 1.23 as a number,
\& # even though sqlite_see_if_its_a_number is set.
\& $sth\->bind_param(1, \*(Aq1.230\*(Aq, SQL_VARCHAR);
\& $sth\->execute;
.Ve
.SS "Placeholders"
.IX Subsection "Placeholders"
SQLite supports several placeholder expressions, including \f(CW\*(C`?\*(C'\fR
and \f(CW\*(C`:AAAA\*(C'\fR. Consult the \s-1DBI\s0 and SQLite documentation for
details.
.PP
<https://www.sqlite.org/lang_expr.html#varparam>
.PP
Note that a question mark actually means a next unused (numbered)
placeholder. You're advised not to use it with other (numbered or
named) placeholders to avoid confusion.
.PP
.Vb 4
\& my $sth = $dbh\->prepare(
\& \*(Aqupdate TABLE set a=?1 where b=?2 and a IS NOT ?1\*(Aq
\& );
\& $sth\->execute(1, 2);
.Ve
.SS "Pragma"
.IX Subsection "Pragma"
SQLite has a set of \*(L"Pragma\*(R"s to modify its operation or to query
for its internal data. These are specific to SQLite and are not
likely to work with other \s-1DBD\s0 libraries, but you may find some of
these are quite useful, including:
.IP "journal_mode" 4
.IX Item "journal_mode"
You can use this pragma to change the journal mode for SQLite
databases, maybe for better performance, or for compatibility.
.Sp
Its default mode is \f(CW\*(C`DELETE\*(C'\fR, which means SQLite uses a rollback
journal to implement transactions, and the journal is deleted
at the conclusion of each transaction. If you use \f(CW\*(C`TRUNCATE\*(C'\fR
instead of \f(CW\*(C`DELETE\*(C'\fR, the journal will be truncated, which is
usually much faster.
.Sp
A \f(CW\*(C`WAL\*(C'\fR (write-ahead log) mode is introduced as of SQLite 3.7.0.
This mode is persistent, and it stays in effect even after
closing and reopening the database. In other words, once the \f(CW\*(C`WAL\*(C'\fR
mode is set in an application or in a test script, the database
becomes inaccessible by older clients. This tends to be an issue
when you use a system \f(CW\*(C`sqlite3\*(C'\fR executable under a conservative
operating system.
.Sp
To fix this, You need to issue \f(CW\*(C`PRAGMA journal_mode = DELETE\*(C'\fR
(or \f(CW\*(C`TRUNCATE\*(C'\fR) beforehand, or install a newer version of
\&\f(CW\*(C`sqlite3\*(C'\fR.
.IP "legacy_file_format" 4
.IX Item "legacy_file_format"
If you happen to need to create a SQLite database that will also
be accessed by a very old SQLite client (prior to 3.3.0 released
in Jan. 2006), you need to set this pragma to \s-1ON\s0 before you create
a database.
.IP "reverse_unordered_selects" 4
.IX Item "reverse_unordered_selects"
You can set this pragma to \s-1ON\s0 to reverse the order of results of
\&\s-1SELECT\s0 statements without an \s-1ORDER BY\s0 clause so that you can see
if applications are making invalid assumptions about the result
order.
.Sp
Note that SQLite 3.7.15 (bundled with DBD::SQLite 1.38_02) enhanced
its query optimizer and the order of results of a \s-1SELECT\s0 statement
without an \s-1ORDER BY\s0 clause may be different from the one of the
previous versions.
.IP "synchronous" 4
.IX Item "synchronous"
You can set set this pragma to \s-1OFF\s0 to make some of the operations
in SQLite faster with a possible risk of database corruption
in the worst case. See also \*(L"Performance\*(R" section below.
.PP
See <https://www.sqlite.org/pragma.html> for more details.
.SS "Foreign Keys"
.IX Subsection "Foreign Keys"
SQLite has started supporting foreign key constraints since 3.6.19
(released on Oct 14, 2009; bundled in DBD::SQLite 1.26_05).
To be exact, SQLite has long been able to parse a schema with foreign
keys, but the constraints has not been enforced. Now you can issue
a \f(CW\*(C`foreign_keys\*(C'\fR pragma to enable this feature and enforce the
constraints, preferably as soon as you connect to a database and
you're not in a transaction:
.PP
.Vb 1
\& $dbh\->do("PRAGMA foreign_keys = ON");
.Ve
.PP
And you can explicitly disable the feature whenever you like by
turning the pragma off:
.PP
.Vb 1
\& $dbh\->do("PRAGMA foreign_keys = OFF");
.Ve
.PP
As of this writing, this feature is disabled by default by the
SQLite team, and by us, to secure backward compatibility, as
this feature may break your applications, and actually broke
some for us. If you have used a schema with foreign key constraints
but haven't cared them much and supposed they're always ignored for
SQLite, be prepared, and please do extensive testing to ensure
that your applications will continue to work when the foreign keys
support is enabled by default.
.PP
See <https://www.sqlite.org/foreignkeys.html> for details.
.SS "Transactions"
.IX Subsection "Transactions"
DBI/DBD::SQLite's transactions may be a bit confusing. They behave
differently according to the status of the \f(CW\*(C`AutoCommit\*(C'\fR flag:
.IP "When the AutoCommit flag is on" 4
.IX Item "When the AutoCommit flag is on"
You're supposed to always use the auto-commit mode, except you
explicitly begin a transaction, and when the transaction ended,
you're supposed to go back to the auto-commit mode. To begin a
transaction, call \f(CW\*(C`begin_work\*(C'\fR method, or issue a \f(CW\*(C`BEGIN\*(C'\fR
statement. To end it, call \f(CW\*(C`commit/rollback\*(C'\fR methods, or issue
the corresponding statements.
.Sp
.Vb 1
\& $dbh\->{AutoCommit} = 1;
\&
\& $dbh\->begin_work; # or $dbh\->do(\*(AqBEGIN TRANSACTION\*(Aq);
\&
\& # $dbh\->{AutoCommit} is turned off temporarily during a transaction;
\&
\& $dbh\->commit; # or $dbh\->do(\*(AqCOMMIT\*(Aq);
\&
\& # $dbh\->{AutoCommit} is turned on again;
.Ve
.IP "When the AutoCommit flag is off" 4
.IX Item "When the AutoCommit flag is off"
You're supposed to always use the transactional mode, until you
explicitly turn on the AutoCommit flag. You can explicitly issue
a \f(CW\*(C`BEGIN\*(C'\fR statement (only when an actual transaction has not
begun yet) but you're not allowed to call \f(CW\*(C`begin_work\*(C'\fR method
(if you don't issue a \f(CW\*(C`BEGIN\*(C'\fR, it will be issued internally).
You can commit or roll it back freely. Another transaction will
automatically begin if you execute another statement.
.Sp
.Vb 1
\& $dbh\->{AutoCommit} = 0;
\&
\& # $dbh\->do(\*(AqBEGIN TRANSACTION\*(Aq) is not necessary, but possible
\&
\& ...
\&
\& $dbh\->commit; # or $dbh\->do(\*(AqCOMMIT\*(Aq);
\&
\& # $dbh\->{AutoCommit} stays intact;
\&
\& $dbh\->{AutoCommit} = 1; # ends the transactional mode
.Ve
.PP
This \f(CW\*(C`AutoCommit\*(C'\fR mode is independent from the autocommit mode
of the internal SQLite library, which always begins by a \f(CW\*(C`BEGIN\*(C'\fR
statement, and ends by a \f(CW\*(C`COMMIT\*(C'\fR or a \f(CW\*(C`ROLLBACK\*(C'\fR.
.SS "Transaction and Database Locking"
.IX Subsection "Transaction and Database Locking"
The default transaction behavior of SQLite is \f(CW\*(C`deferred\*(C'\fR, that
means, locks are not acquired until the first read or write
operation, and thus it is possible that another thread or process
could create a separate transaction and write to the database after
the \f(CW\*(C`BEGIN\*(C'\fR on the current thread has executed, and eventually
cause a \*(L"deadlock\*(R". To avoid this, DBD::SQLite internally issues
a \f(CW\*(C`BEGIN IMMEDIATE\*(C'\fR if you begin a transaction by calling
\&\f(CW\*(C`begin_work\*(C'\fR or by turning off \f(CW\*(C`AutoCommit\*(C'\fR (since 1.38_01).
.PP
If you really need to turn off this feature for some reasons,
set \f(CW\*(C`sqlite_use_immediate_transaction\*(C'\fR database handle attribute
to false, and the default \f(CW\*(C`deferred\*(C'\fR transaction will be used.
.PP
.Vb 3
\& my $dbh = DBI\->connect("dbi:SQLite::memory:", "", "", {
\& sqlite_use_immediate_transaction => 0,
\& });
.Ve
.PP
Or, issue a \f(CW\*(C`BEGIN\*(C'\fR statement explicitly each time you begin
a transaction.
.PP
See <http://sqlite.org/lockingv3.html> for locking details.
.ie n .SS """$sth\->finish"" and Transaction Rollback"
.el .SS "\f(CW$sth\->finish\fP and Transaction Rollback"
.IX Subsection "$sth->finish and Transaction Rollback"
As the \s-1DBI\s0 doc says, you almost certainly do \fBnot\fR need to
call \*(L"finish\*(R" in \s-1DBI\s0 method if you fetch all rows (probably in a loop).
However, there are several exceptions to this rule, and rolling-back
of an unfinished \f(CW\*(C`SELECT\*(C'\fR statement is one of such exceptional
cases.
.PP
SQLite prohibits \f(CW\*(C`ROLLBACK\*(C'\fR of unfinished \f(CW\*(C`SELECT\*(C'\fR statements in
a transaction (See <http://sqlite.org/lang_transaction.html> for
details). So you need to call \f(CW\*(C`finish\*(C'\fR before you issue a rollback.
.PP
.Vb 10
\& $sth = $dbh\->prepare("SELECT * FROM t");
\& $dbh\->begin_work;
\& eval {
\& $sth\->execute;
\& $row = $sth\->fetch;
\& ...
\& die "For some reason";
\& ...
\& };
\& if($@) {
\& $sth\->finish; # You need this for SQLite
\& $dbh\->rollback;
\& } else {
\& $dbh\->commit;
\& }
.Ve
.SS "Processing Multiple Statements At A Time"
.IX Subsection "Processing Multiple Statements At A Time"
\&\s-1DBI\s0's statement handle is not supposed to process multiple
statements at a time. So if you pass a string that contains multiple
statements (a \f(CW\*(C`dump\*(C'\fR) to a statement handle (via \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`do\*(C'\fR),
DBD::SQLite only processes the first statement, and discards the
rest.
.PP
If you need to process multiple statements at a time, set
a \f(CW\*(C`sqlite_allow_multiple_statements\*(C'\fR attribute of a database handle
to true when you connect to a database, and \f(CW\*(C`do\*(C'\fR method takes care
of the rest (since 1.30_01, and without creating \s-1DBI\s0's statement
handles internally since 1.47_01). If you do need to use \f(CW\*(C`prepare\*(C'\fR
or \f(CW\*(C`prepare_cached\*(C'\fR (which I don't recommend in this case, because
typically there's no placeholder nor reusable part in a dump),
you can look at \f(CW\*(C`$sth\->{sqlite_unprepared_statements}\*(C'\fR to retrieve
what's left, though it usually contains nothing but white spaces.
.SS "\s-1TYPE\s0 statement attribute"
.IX Subsection "TYPE statement attribute"
Because of historical reasons, DBD::SQLite's \f(CW\*(C`TYPE\*(C'\fR statement
handle attribute returns an array ref of string values, contrary to
the \s-1DBI\s0 specification. This value is also less useful for SQLite
users because SQLite uses dynamic type system (that means,
the datatype of a value is associated with the value itself, not
with its container).
.PP
As of version 1.61_02, if you set \f(CW\*(C`sqlite_prefer_numeric_type\*(C'\fR
database handle attribute to true, \f(CW\*(C`TYPE\*(C'\fR statement handle
attribute returns an array of integer, as an experiment.
.SS "Performance"
.IX Subsection "Performance"
SQLite is fast, very fast. Matt processed his 72MB log file with it,
inserting the data (400,000+ rows) by using transactions and only
committing every 1000 rows (otherwise the insertion is quite slow),
and then performing queries on the data.
.PP
Queries like count(*) and avg(bytes) took fractions of a second to
return, but what surprised him most of all was:
.PP
.Vb 5
\& SELECT url, count(*) as count
\& FROM access_log
\& GROUP BY url
\& ORDER BY count desc
\& LIMIT 20
.Ve
.PP
To discover the top 20 hit URLs on the site (<http://axkit.org>),
and it returned within 2 seconds. He was seriously considering
switching his log analysis code to use this little speed demon!
.PP
Oh yeah, and that was with no indexes on the table, on a 400MHz \s-1PIII.\s0
.PP
For best performance be sure to tune your hdparm settings if you
are using linux. Also you might want to set:
.PP
.Vb 1
\& PRAGMA synchronous = OFF
.Ve
.PP
Which will prevent SQLite from doing fsync's when writing (which
slows down non-transactional writes significantly) at the expense
of some peace of mind. Also try playing with the cache_size pragma.
.PP
The memory usage of SQLite can also be tuned using the cache_size
pragma.
.PP
.Vb 1
\& $dbh\->do("PRAGMA cache_size = 800000");
.Ve
.PP
The above will allocate 800M for \s-1DB\s0 cache; the default is 2M.
Your sweet spot probably lies somewhere in between.
.SH "DRIVER PRIVATE ATTRIBUTES"
.IX Header "DRIVER PRIVATE ATTRIBUTES"
.SS "Database Handle Attributes"
.IX Subsection "Database Handle Attributes"
.IP "sqlite_version" 4
.IX Item "sqlite_version"
Returns the version of the SQLite library which \fBDBD::SQLite\fR is using,
e.g., \*(L"3.26.0\*(R". Can only be read.
.IP "sqlite_unicode" 4
.IX Item "sqlite_unicode"
If set to a true value, \fBDBD::SQLite\fR will turn the \s-1UTF\-8\s0 flag on for all
text strings coming out of the database (this feature is currently disabled
for perl < 5.8.5). For more details on the \s-1UTF\-8\s0 flag see
perlunicode. The default is for the \s-1UTF\-8\s0 flag to be turned off.
.Sp
Also note that due to some bizarreness in SQLite's type system (see
<https://www.sqlite.org/datatype3.html>), if you want to retain
blob-style behavior for \fBsome\fR columns under \f(CW\*(C`$dbh\->{sqlite_unicode} = 1\*(C'\fR (say, to store images in the database), you have to state so
explicitly using the 3\-argument form of \*(L"bind_param\*(R" in \s-1DBI\s0 when doing
updates:
.Sp
.Vb 3
\& use DBI qw(:sql_types);
\& $dbh\->{sqlite_unicode} = 1;
\& my $sth = $dbh\->prepare("INSERT INTO mytable (blobcolumn) VALUES (?)");
\&
\& # Binary_data will be stored as is.
\& $sth\->bind_param(1, $binary_data, SQL_BLOB);
.Ve
.Sp
Defining the column type as \f(CW\*(C`BLOB\*(C'\fR in the \s-1DDL\s0 is \fBnot\fR sufficient.
.Sp
This attribute was originally named as \f(CW\*(C`unicode\*(C'\fR, and renamed to
\&\f(CW\*(C`sqlite_unicode\*(C'\fR for integrity since version 1.26_06. Old \f(CW\*(C`unicode\*(C'\fR
attribute is still accessible but will be deprecated in the near future.
.IP "sqlite_allow_multiple_statements" 4
.IX Item "sqlite_allow_multiple_statements"
If you set this to true, \f(CW\*(C`do\*(C'\fR method will process multiple
statements at one go. This may be handy, but with performance
penalty. See above for details.
.IP "sqlite_use_immediate_transaction" 4
.IX Item "sqlite_use_immediate_transaction"
If you set this to true, DBD::SQLite tries to issue a \f(CW\*(C`begin
immediate transaction\*(C'\fR (instead of \f(CW\*(C`begin transaction\*(C'\fR) when
necessary. See above for details.
.Sp
As of version 1.38_01, this attribute is set to true by default.
If you really need to use \f(CW\*(C`deferred\*(C'\fR transactions for some reasons,
set this to false explicitly.
.IP "sqlite_see_if_its_a_number" 4
.IX Item "sqlite_see_if_its_a_number"
If you set this to true, DBD::SQLite tries to see if the bind values
are number or not, and does not quote if they are numbers. See above
for details.
.IP "sqlite_extended_result_codes" 4
.IX Item "sqlite_extended_result_codes"
If set to true, DBD::SQLite uses extended result codes where appropriate
(see <https://www.sqlite.org/rescode.html>).
.IP "sqlite_defensive" 4
.IX Item "sqlite_defensive"
If set to true, language features that allow ordinary \s-1SQL\s0 to deliberately
corrupt the database file are prohibited.
.SS "Statement Handle Attributes"
.IX Subsection "Statement Handle Attributes"
.IP "sqlite_unprepared_statements" 4
.IX Item "sqlite_unprepared_statements"
Returns an unprepared part of the statement you pass to \f(CW\*(C`prepare\*(C'\fR.
Typically this contains nothing but white spaces after a semicolon.
See above for details.
.SH "METHODS"
.IX Header "METHODS"
See also to the \s-1DBI\s0 documentation for the details of other common
methods.
.SS "table_info"
.IX Subsection "table_info"
.Vb 1
\& $sth = $dbh\->table_info(undef, $schema, $table, $type, \e%attr);
.Ve
.PP
Returns all tables and schemas (databases) as specified in \*(L"table_info\*(R" in \s-1DBI\s0.
The schema and table arguments will do a \f(CW\*(C`LIKE\*(C'\fR search. You can specify an
\&\s-1ESCAPE\s0 character by including an 'Escape' attribute in \e%attr. The \f(CW$type\fR
argument accepts a comma separated list of the following types '\s-1TABLE\s0',
\&'\s-1VIEW\s0', '\s-1LOCAL TEMPORARY\s0' and '\s-1SYSTEM TABLE\s0' (by default all are returned).
Note that a statement handle is returned, and not a direct list of tables.
.PP
The following fields are returned:
.PP
\&\fB\s-1TABLE_CAT\s0\fR: Always \s-1NULL,\s0 as SQLite does not have the concept of catalogs.
.PP
\&\fB\s-1TABLE_SCHEM\s0\fR: The name of the schema (database) that the table or view is
in. The default schema is 'main', temporary tables are in 'temp' and other
databases will be in the name given when the database was attached.
.PP
\&\fB\s-1TABLE_NAME\s0\fR: The name of the table or view.
.PP
\&\fB\s-1TABLE_TYPE\s0\fR: The type of object returned. Will be one of '\s-1TABLE\s0', '\s-1VIEW\s0',
\&'\s-1LOCAL TEMPORARY\s0' or '\s-1SYSTEM TABLE\s0'.
.SS "primary_key, primary_key_info"
.IX Subsection "primary_key, primary_key_info"
.Vb 2
\& @names = $dbh\->primary_key(undef, $schema, $table);
\& $sth = $dbh\->primary_key_info(undef, $schema, $table, \e%attr);
.Ve
.PP
You can retrieve primary key names or more detailed information.
As noted above, SQLite does not have the concept of catalogs, so the
first argument of the methods is usually \f(CW\*(C`undef\*(C'\fR, and you'll usually
set \f(CW\*(C`undef\*(C'\fR for the second one (unless you want to know the primary
keys of temporary tables).
.SS "foreign_key_info"
.IX Subsection "foreign_key_info"
.Vb 2
\& $sth = $dbh\->foreign_key_info(undef, $pk_schema, $pk_table,
\& undef, $fk_schema, $fk_table);
.Ve
.PP
Returns information about foreign key constraints, as specified in
\&\*(L"foreign_key_info\*(R" in \s-1DBI\s0, but with some limitations :
.IP "\(bu" 4
information in rows returned by the \f(CW$sth\fR is incomplete with
respect to the \*(L"foreign_key_info\*(R" in \s-1DBI\s0 specification. All requested fields
are present, but the content is \f(CW\*(C`undef\*(C'\fR for some of them.
.PP
The following nonempty fields are returned :
.PP
\&\fB\s-1PKTABLE_NAME\s0\fR:
The primary (unique) key table identifier.
.PP
\&\fB\s-1PKCOLUMN_NAME\s0\fR:
The primary (unique) key column identifier.
.PP
\&\fB\s-1FKTABLE_NAME\s0\fR:
The foreign key table identifier.
.PP
\&\fB\s-1FKCOLUMN_NAME\s0\fR:
The foreign key column identifier.
.PP
\&\fB\s-1KEY_SEQ\s0\fR:
The column sequence number (starting with 1), when
several columns belong to a same constraint.
.PP
\&\fB\s-1UPDATE_RULE\s0\fR:
The referential action for the \s-1UPDATE\s0 rule.
The following codes are defined:
.PP
.Vb 5
\& CASCADE 0
\& RESTRICT 1
\& SET NULL 2
\& NO ACTION 3
\& SET DEFAULT 4
.Ve
.PP
Default is 3 ('\s-1NO ACTION\s0').
.PP
\&\fB\s-1DELETE_RULE\s0\fR:
The referential action for the \s-1DELETE\s0 rule.
The codes are the same as for \s-1UPDATE_RULE.\s0
.PP
\&\fB\s-1DEFERRABILITY\s0\fR:
The following codes are defined:
.PP
.Vb 3
\& INITIALLY DEFERRED 5
\& INITIALLY IMMEDIATE 6
\& NOT DEFERRABLE 7
.Ve
.PP
\&\fB\s-1UNIQUE_OR_PRIMARY\s0\fR:
Whether the column is primary or unique.
.PP
\&\fBNote\fR: foreign key support in SQLite must be explicitly turned on through
a \f(CW\*(C`PRAGMA\*(C'\fR command; see \*(L"Foreign keys\*(R" earlier in this manual.
.SS "statistics_info"
.IX Subsection "statistics_info"
.Vb 2
\& $sth = $dbh\->statistics_info(undef, $schema, $table,
\& $unique_only, $quick);
.Ve
.PP
Returns information about a table and it's indexes, as specified in
\&\*(L"statistics_info\*(R" in \s-1DBI\s0, but with some limitations :
.IP "\(bu" 4
information in rows returned by the \f(CW$sth\fR is incomplete with
respect to the \*(L"statistics_info\*(R" in \s-1DBI\s0 specification. All requested fields
are present, but the content is \f(CW\*(C`undef\*(C'\fR for some of them.
.PP
The following nonempty fields are returned :
.PP
\&\fB\s-1TABLE_SCHEM\s0\fR:
The name of the schema (database) that the table is in. The default schema is 'main', temporary tables are in 'temp' and other databases will be in the name given when the database was attached.
.PP
\&\fB\s-1TABLE_NAME\s0\fR:
The name of the table
.PP
\&\fB\s-1NON_UNIQUE\s0\fR:
Contains 0 for unique indexes, 1 for non-unique indexes
.PP
\&\fB\s-1INDEX_NAME\s0\fR:
The name of the index
.PP
\&\fB\s-1TYPE\s0\fR:
SQLite uses 'btree' for all it's indexes
.PP
\&\fB\s-1ORDINAL_POSITION\s0\fR:
Column sequence number (starting with 1).
.PP
\&\fB\s-1COLUMN_NAME\s0\fR:
The name of the column
.SS "ping"
.IX Subsection "ping"
.Vb 1
\& my $bool = $dbh\->ping;
.Ve
.PP
returns true if the database file exists (or the database is in-memory), and the database connection is active.
.SH "DRIVER PRIVATE METHODS"
.IX Header "DRIVER PRIVATE METHODS"
The following methods can be called via the \fIfunc()\fR method with a little
tweak, but the use of \fIfunc()\fR method is now discouraged by the \s-1DBI\s0 author
for various reasons (see \s-1DBI\s0's document
<https://metacpan.org/pod/DBI::DBD#Using\-\fIinstall_method()\fR\-to\-expose\-driver\-private\-methods>
for details). So, if you're using \s-1DBI\s0 >= 1.608, use these \f(CW\*(C`sqlite_\*(C'\fR
methods. If you need to use an older \s-1DBI\s0, you can call these like this:
.PP
.Vb 1
\& $dbh\->func( ..., "(method name without sqlite_ prefix)" );
.Ve
.PP
Exception: \f(CW\*(C`sqlite_trace\*(C'\fR should always be called as is, even with \f(CW\*(C`func()\*(C'\fR
method (to avoid conflict with \s-1DBI\s0's \fItrace()\fR method).
.PP
.Vb 1
\& $dbh\->func( ..., "sqlite_trace");
.Ve
.ie n .SS "$dbh\->\fIsqlite_last_insert_rowid()\fP"
.el .SS "\f(CW$dbh\fP\->\fIsqlite_last_insert_rowid()\fP"
.IX Subsection "$dbh->sqlite_last_insert_rowid()"
This method returns the last inserted rowid. If you specify an \s-1INTEGER PRIMARY
KEY\s0 as the first column in your table, that is the column that is returned.
Otherwise, it is the hidden \s-1ROWID\s0 column. See the SQLite docs for details.
.PP
Generally you should not be using this method. Use the \s-1DBI\s0 last_insert_id
method instead. The usage of this is:
.PP
.Vb 1
\& $h\->last_insert_id($catalog, $schema, $table_name, $field_name [, \e%attr ])
.Ve
.PP
Running \f(CW\*(C`$h\->last_insert_id("","","","")\*(C'\fR is the equivalent of running
\&\f(CW\*(C`$dbh\->sqlite_last_insert_rowid()\*(C'\fR directly.
.ie n .SS "$dbh\->\fIsqlite_db_filename()\fP"
.el .SS "\f(CW$dbh\fP\->\fIsqlite_db_filename()\fP"
.IX Subsection "$dbh->sqlite_db_filename()"
Retrieve the current (main) database filename. If the database is in-memory
or temporary, this returns an empty string, or \f(CW\*(C`undef\*(C'\fR.
.ie n .SS "$dbh\->\fIsqlite_busy_timeout()\fP"
.el .SS "\f(CW$dbh\fP\->\fIsqlite_busy_timeout()\fP"
.IX Subsection "$dbh->sqlite_busy_timeout()"
Retrieve the current busy timeout.
.ie n .SS "$dbh\->sqlite_busy_timeout( $ms )"
.el .SS "\f(CW$dbh\fP\->sqlite_busy_timeout( \f(CW$ms\fP )"
.IX Subsection "$dbh->sqlite_busy_timeout( $ms )"
Set the current busy timeout. The timeout is in milliseconds.
.ie n .SS "$dbh\->sqlite_create_function( $name, $argc, $code_ref, $flags )"
.el .SS "\f(CW$dbh\fP\->sqlite_create_function( \f(CW$name\fP, \f(CW$argc\fP, \f(CW$code_ref\fP, \f(CW$flags\fP )"
.IX Subsection "$dbh->sqlite_create_function( $name, $argc, $code_ref, $flags )"
This method will register a new function which will be usable in an \s-1SQL\s0
query. The method's parameters are:
.ie n .IP "$name" 4
.el .IP "\f(CW$name\fR" 4
.IX Item "$name"
The name of the function. This is the name of the function as it will
be used from \s-1SQL.\s0
.ie n .IP "$argc" 4
.el .IP "\f(CW$argc\fR" 4
.IX Item "$argc"
The number of arguments taken by the function. If this number is \-1,
the function can take any number of arguments.
.ie n .IP "$code_ref" 4
.el .IP "\f(CW$code_ref\fR" 4
.IX Item "$code_ref"
This should be a reference to the function's implementation.
.ie n .IP "$flags" 4
.el .IP "\f(CW$flags\fR" 4
.IX Item "$flags"
You can optionally pass an extra flag bit to create_function, which then would be ORed with \s-1SQLITE_UTF8 \s0(default). As of 1.47_02 (SQLite 3.8.9), only meaning bit is \s-1SQLITE_DETERMINISTIC \s0(introduced at SQLite 3.8.3), which can make the function perform better. See C \s-1API\s0 documentation at <http://sqlite.org/c3ref/create_function.html> for details.
.PP
For example, here is how to define a \fInow()\fR function which returns the
current number of seconds since the epoch:
.PP
.Vb 1
\& $dbh\->sqlite_create_function( \*(Aqnow\*(Aq, 0, sub { return time } );
.Ve
.PP
After this, it could be used from \s-1SQL\s0 as:
.PP
.Vb 1
\& INSERT INTO mytable ( now() );
.Ve
.PP
\fI\s-1REGEXP\s0 function\fR
.IX Subsection "REGEXP function"
.PP
SQLite includes syntactic support for an infix operator '\s-1REGEXP\s0', but
without any implementation. The \f(CW\*(C`DBD::SQLite\*(C'\fR driver
automatically registers an implementation that performs standard
perl regular expression matching, using current locale. So for example
you can search for words starting with an 'A' with a query like
.PP
.Vb 1
\& SELECT * from table WHERE column REGEXP \*(Aq\ebA\ew+\*(Aq
.Ve
.PP
If you want case-insensitive searching, use perl regex flags, like this :
.PP
.Vb 1
\& SELECT * from table WHERE column REGEXP \*(Aq(?i:\ebA\ew+)\*(Aq
.Ve
.PP
The default \s-1REGEXP\s0 implementation can be overridden through the
\&\f(CW\*(C`create_function\*(C'\fR \s-1API\s0 described above.
.PP
Note that regexp matching will \fBnot\fR use SQLite indices, but will iterate
over all rows, so it could be quite costly in terms of performance.
.ie n .SS "$dbh\->sqlite_create_collation( $name, $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_create_collation( \f(CW$name\fP, \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_create_collation( $name, $code_ref )"
This method manually registers a new function which will be usable in an \s-1SQL\s0
query as a \s-1COLLATE\s0 option for sorting. Such functions can also be registered
automatically on demand: see section \*(L"\s-1COLLATION FUNCTIONS\*(R"\s0 below.
.PP
The method's parameters are:
.ie n .IP "$name" 4
.el .IP "\f(CW$name\fR" 4
.IX Item "$name"
The name of the function exposed to \s-1SQL.\s0
.ie n .IP "$code_ref" 4
.el .IP "\f(CW$code_ref\fR" 4
.IX Item "$code_ref"
Reference to the function's implementation.
The driver will check that this is a proper sorting function.
.ie n .SS "$dbh\->sqlite_collation_needed( $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_collation_needed( \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_collation_needed( $code_ref )"
This method manually registers a callback function that will
be invoked whenever an undefined collation sequence is required
from an \s-1SQL\s0 statement. The callback is invoked as
.PP
.Vb 1
\& $code_ref\->($dbh, $collation_name)
.Ve
.PP
and should register the desired collation using
\&\*(L"sqlite_create_collation\*(R".
.PP
An initial callback is already registered by \f(CW\*(C`DBD::SQLite\*(C'\fR,
so for most common cases it will be simpler to just
add your collation sequences in the \f(CW%DBD::SQLite::COLLATION\fR
hash (see section \*(L"\s-1COLLATION FUNCTIONS\*(R"\s0 below).
.ie n .SS "$dbh\->sqlite_create_aggregate( $name, $argc, $pkg, $flags )"
.el .SS "\f(CW$dbh\fP\->sqlite_create_aggregate( \f(CW$name\fP, \f(CW$argc\fP, \f(CW$pkg\fP, \f(CW$flags\fP )"
.IX Subsection "$dbh->sqlite_create_aggregate( $name, $argc, $pkg, $flags )"
This method will register a new aggregate function which can then be used
from \s-1SQL.\s0 The method's parameters are:
.ie n .IP "$name" 4
.el .IP "\f(CW$name\fR" 4
.IX Item "$name"
The name of the aggregate function, this is the name under which the
function will be available from \s-1SQL.\s0
.ie n .IP "$argc" 4
.el .IP "\f(CW$argc\fR" 4
.IX Item "$argc"
This is an integer which tells the \s-1SQL\s0 parser how many arguments the
function takes. If that number is \-1, the function can take any number
of arguments.
.ie n .IP "$pkg" 4
.el .IP "\f(CW$pkg\fR" 4
.IX Item "$pkg"
This is the package which implements the aggregator interface.
.ie n .IP "$flags" 4
.el .IP "\f(CW$flags\fR" 4
.IX Item "$flags"
You can optionally pass an extra flag bit to create_aggregate, which then would be ORed with \s-1SQLITE_UTF8 \s0(default). As of 1.47_02 (SQLite 3.8.9), only meaning bit is \s-1SQLITE_DETERMINISTIC \s0(introduced at SQLite 3.8.3), which can make the function perform better. See C \s-1API\s0 documentation at <http://sqlite.org/c3ref/create_function.html> for details.
.PP
The aggregator interface consists of defining three methods:
.IP "\fInew()\fR" 4
.IX Item "new()"
This method will be called once to create an object which should
be used to aggregate the rows in a particular group. The \fIstep()\fR and
\&\fIfinalize()\fR methods will be called upon the reference return by
the method.
.IP "step(@_)" 4
.IX Item "step(@_)"
This method will be called once for each row in the aggregate.
.IP "\fIfinalize()\fR" 4
.IX Item "finalize()"
This method will be called once all rows in the aggregate were
processed and it should return the aggregate function's result. When
there is no rows in the aggregate, \fIfinalize()\fR will be called right
after \fInew()\fR.
.PP
Here is a simple aggregate function which returns the variance
(example adapted from pysqlite):
.PP
.Vb 1
\& package variance;
\&
\& sub new { bless [], shift; }
\&
\& sub step {
\& my ( $self, $value ) = @_;
\&
\& push @$self, $value;
\& }
\&
\& sub finalize {
\& my $self = $_[0];
\&
\& my $n = @$self;
\&
\& # Variance is NULL unless there is more than one row
\& return undef unless $n || $n == 1;
\&
\& my $mu = 0;
\& foreach my $v ( @$self ) {
\& $mu += $v;
\& }
\& $mu /= $n;
\&
\& my $sigma = 0;
\& foreach my $v ( @$self ) {
\& $sigma += ($v \- $mu)**2;
\& }
\& $sigma = $sigma / ($n \- 1);
\&
\& return $sigma;
\& }
\&
\& $dbh\->sqlite_create_aggregate( "variance", 1, \*(Aqvariance\*(Aq );
.Ve
.PP
The aggregate function can then be used as:
.PP
.Vb 3
\& SELECT group_name, variance(score)
\& FROM results
\& GROUP BY group_name;
.Ve
.PP
For more examples, see the DBD::SQLite::Cookbook.
.ie n .SS "$dbh\->sqlite_progress_handler( $n_opcodes, $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_progress_handler( \f(CW$n_opcodes\fP, \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_progress_handler( $n_opcodes, $code_ref )"
This method registers a handler to be invoked periodically during long
running calls to SQLite.
.PP
An example use for this interface is to keep a \s-1GUI\s0 updated during a
large query. The parameters are:
.ie n .IP "$n_opcodes" 4
.el .IP "\f(CW$n_opcodes\fR" 4
.IX Item "$n_opcodes"
The progress handler is invoked once for every \f(CW$n_opcodes\fR
virtual machine opcodes in SQLite.
.ie n .IP "$code_ref" 4
.el .IP "\f(CW$code_ref\fR" 4
.IX Item "$code_ref"
Reference to the handler subroutine. If the progress handler returns
non-zero, the SQLite operation is interrupted. This feature can be used to
implement a \*(L"Cancel\*(R" button on a \s-1GUI\s0 dialog box.
.Sp
Set this argument to \f(CW\*(C`undef\*(C'\fR if you want to unregister a previous
progress handler.
.ie n .SS "$dbh\->sqlite_commit_hook( $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_commit_hook( \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_commit_hook( $code_ref )"
This method registers a callback function to be invoked whenever a
transaction is committed. Any callback set by a previous call to
\&\f(CW\*(C`sqlite_commit_hook\*(C'\fR is overridden. A reference to the previous
callback (if any) is returned. Registering an \f(CW\*(C`undef\*(C'\fR disables the
callback.
.PP
When the commit hook callback returns zero, the commit operation is
allowed to continue normally. If the callback returns non-zero, then
the commit is converted into a rollback (in that case, any attempt to
\&\fIexplicitly\fR call \f(CW\*(C`$dbh\->rollback()\*(C'\fR afterwards would yield an
error).
.ie n .SS "$dbh\->sqlite_rollback_hook( $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_rollback_hook( \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_rollback_hook( $code_ref )"
This method registers a callback function to be invoked whenever a
transaction is rolled back. Any callback set by a previous call to
\&\f(CW\*(C`sqlite_rollback_hook\*(C'\fR is overridden. A reference to the previous
callback (if any) is returned. Registering an \f(CW\*(C`undef\*(C'\fR disables the
callback.
.ie n .SS "$dbh\->sqlite_update_hook( $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_update_hook( \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_update_hook( $code_ref )"
This method registers a callback function to be invoked whenever a row
is updated, inserted or deleted. Any callback set by a previous call to
\&\f(CW\*(C`sqlite_update_hook\*(C'\fR is overridden. A reference to the previous
callback (if any) is returned. Registering an \f(CW\*(C`undef\*(C'\fR disables the
callback.
.PP
The callback will be called as
.PP
.Vb 1
\& $code_ref\->($action_code, $database, $table, $rowid)
.Ve
.PP
where
.ie n .IP "$action_code" 4
.el .IP "\f(CW$action_code\fR" 4
.IX Item "$action_code"
is an integer equal to either \f(CW\*(C`DBD::SQLite::INSERT\*(C'\fR,
\&\f(CW\*(C`DBD::SQLite::DELETE\*(C'\fR or \f(CW\*(C`DBD::SQLite::UPDATE\*(C'\fR
(see \*(L"Action Codes\*(R");
.ie n .IP "$database" 4
.el .IP "\f(CW$database\fR" 4
.IX Item "$database"
is the name of the database containing the affected row;
.ie n .IP "$table" 4
.el .IP "\f(CW$table\fR" 4
.IX Item "$table"
is the name of the table containing the affected row;
.ie n .IP "$rowid" 4
.el .IP "\f(CW$rowid\fR" 4
.IX Item "$rowid"
is the unique 64\-bit signed integer key of the affected row within
that table.
.ie n .SS "$dbh\->sqlite_set_authorizer( $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_set_authorizer( \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_set_authorizer( $code_ref )"
This method registers an authorizer callback to be invoked whenever
\&\s-1SQL\s0 statements are being compiled by the \*(L"prepare\*(R" in \s-1DBI\s0 method. The
authorizer callback should return \f(CW\*(C`DBD::SQLite::OK\*(C'\fR to allow the
action, \f(CW\*(C`DBD::SQLite::IGNORE\*(C'\fR to disallow the specific action but
allow the \s-1SQL\s0 statement to continue to be compiled, or
\&\f(CW\*(C`DBD::SQLite::DENY\*(C'\fR to cause the entire \s-1SQL\s0 statement to be rejected
with an error. If the authorizer callback returns any other value,
then \f(CW\*(C`prepare\*(C'\fR call that triggered the authorizer will fail with
an error message.
.PP
An authorizer is used when preparing \s-1SQL\s0 statements from an untrusted
source, to ensure that the \s-1SQL\s0 statements do not try to access data
they are not allowed to see, or that they do not try to execute
malicious statements that damage the database. For example, an
application may allow a user to enter arbitrary \s-1SQL\s0 queries for
evaluation by a database. But the application does not want the user
to be able to make arbitrary changes to the database. An authorizer
could then be put in place while the user-entered \s-1SQL\s0 is being
prepared that disallows everything except \s-1SELECT\s0 statements.
.PP
The callback will be called as
.PP
.Vb 1
\& $code_ref\->($action_code, $string1, $string2, $database, $trigger_or_view)
.Ve
.PP
where
.ie n .IP "$action_code" 4
.el .IP "\f(CW$action_code\fR" 4
.IX Item "$action_code"
is an integer that specifies what action is being authorized
(see \*(L"Action Codes\*(R").
.ie n .IP "$string1, $string2" 4
.el .IP "\f(CW$string1\fR, \f(CW$string2\fR" 4
.IX Item "$string1, $string2"
are strings that depend on the action code
(see \*(L"Action Codes\*(R").
.ie n .IP "$database" 4
.el .IP "\f(CW$database\fR" 4
.IX Item "$database"
is the name of the database (\f(CW\*(C`main\*(C'\fR, \f(CW\*(C`temp\*(C'\fR, etc.) if applicable.
.ie n .IP "$trigger_or_view" 4
.el .IP "\f(CW$trigger_or_view\fR" 4
.IX Item "$trigger_or_view"
is the name of the inner-most trigger or view that is responsible for
the access attempt, or \f(CW\*(C`undef\*(C'\fR if this access attempt is directly from
top-level \s-1SQL\s0 code.
.ie n .SS "$dbh\->sqlite_backup_from_file( $filename )"
.el .SS "\f(CW$dbh\fP\->sqlite_backup_from_file( \f(CW$filename\fP )"
.IX Subsection "$dbh->sqlite_backup_from_file( $filename )"
This method accesses the SQLite Online Backup \s-1API,\s0 and will take a backup of
the named database file, copying it to, and overwriting, your current database
connection. This can be particularly handy if your current connection is to the
special :memory: database, and you wish to populate it from an existing \s-1DB.\s0
.ie n .SS "$dbh\->sqlite_backup_to_file( $filename )"
.el .SS "\f(CW$dbh\fP\->sqlite_backup_to_file( \f(CW$filename\fP )"
.IX Subsection "$dbh->sqlite_backup_to_file( $filename )"
This method accesses the SQLite Online Backup \s-1API,\s0 and will take a backup of
the currently connected database, and write it out to the named file.
.ie n .SS "$dbh\->sqlite_backup_from_dbh( $another_dbh )"
.el .SS "\f(CW$dbh\fP\->sqlite_backup_from_dbh( \f(CW$another_dbh\fP )"
.IX Subsection "$dbh->sqlite_backup_from_dbh( $another_dbh )"
This method accesses the SQLite Online Backup \s-1API,\s0 and will take a backup of
the database for the passed handle, copying it to, and overwriting, your current database
connection. This can be particularly handy if your current connection is to the
special :memory: database, and you wish to populate it from an existing \s-1DB.\s0
You can use this to backup from an in-memory database to another in-memory database.
.ie n .SS "$dbh\->sqlite_backup_to_dbh( $another_dbh )"
.el .SS "\f(CW$dbh\fP\->sqlite_backup_to_dbh( \f(CW$another_dbh\fP )"
.IX Subsection "$dbh->sqlite_backup_to_dbh( $another_dbh )"
This method accesses the SQLite Online Backup \s-1API,\s0 and will take a backup of
the currently connected database, and write it out to the passed database handle.
.ie n .SS "$dbh\->sqlite_enable_load_extension( $bool )"
.el .SS "\f(CW$dbh\fP\->sqlite_enable_load_extension( \f(CW$bool\fP )"
.IX Subsection "$dbh->sqlite_enable_load_extension( $bool )"
Calling this method with a true value enables loading (external)
SQLite3 extensions. After the call, you can load extensions like this:
.PP
.Vb 3
\& $dbh\->sqlite_enable_load_extension(1);
\& $sth = $dbh\->prepare("select load_extension(\*(Aqlibsqlitefunctions.so\*(Aq)")
\& or die "Cannot prepare: " . $dbh\->errstr();
.Ve
.ie n .SS "$dbh\->sqlite_load_extension( $file, $proc )"
.el .SS "\f(CW$dbh\fP\->sqlite_load_extension( \f(CW$file\fP, \f(CW$proc\fP )"
.IX Subsection "$dbh->sqlite_load_extension( $file, $proc )"
Loading an extension by a select statement (with the \*(L"load_extension\*(R" SQLite3 function like above) has some limitations. If you need to, say, create other functions from an extension, use this method. \f(CW$file\fR (a path to the extension) is mandatory, and \f(CW$proc\fR (an entry point name) is optional. You need to call \f(CW\*(C`sqlite_enable_load_extension\*(C'\fR before calling \f(CW\*(C`sqlite_load_extension\*(C'\fR.
.ie n .SS "$dbh\->sqlite_trace( $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_trace( \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_trace( $code_ref )"
This method registers a trace callback to be invoked whenever
\&\s-1SQL\s0 statements are being run.
.PP
The callback will be called as
.PP
.Vb 1
\& $code_ref\->($statement)
.Ve
.PP
where
.ie n .IP "$statement" 4
.el .IP "\f(CW$statement\fR" 4
.IX Item "$statement"
is a \s-1UTF\-8\s0 rendering of the \s-1SQL\s0 statement text as the statement
first begins executing.
.PP
Additional callbacks might occur as each triggered subprogram is
entered. The callbacks for triggers contain a \s-1UTF\-8 SQL\s0 comment
that identifies the trigger.
.PP
See also \*(L"\s-1TRACING\*(R"\s0 in \s-1DBI\s0 for better tracing options.
.ie n .SS "$dbh\->sqlite_profile( $code_ref )"
.el .SS "\f(CW$dbh\fP\->sqlite_profile( \f(CW$code_ref\fP )"
.IX Subsection "$dbh->sqlite_profile( $code_ref )"
This method registers a profile callback to be invoked whenever
a \s-1SQL\s0 statement finishes.
.PP
The callback will be called as
.PP
.Vb 1
\& $code_ref\->($statement, $elapsed_time)
.Ve
.PP
where
.ie n .IP "$statement" 4
.el .IP "\f(CW$statement\fR" 4
.IX Item "$statement"
is the original statement text (without bind parameters).
.ie n .IP "$elapsed_time" 4
.el .IP "\f(CW$elapsed_time\fR" 4
.IX Item "$elapsed_time"
is an estimate of wall-clock time of how long that statement took to run (in milliseconds).
.PP
This method is considered experimental and is subject to change in future versions of SQLite.
.PP
See also DBI::Profile for better profiling options.
.ie n .SS "$dbh\->sqlite_table_column_metadata( $dbname, $tablename, $columnname )"
.el .SS "\f(CW$dbh\fP\->sqlite_table_column_metadata( \f(CW$dbname\fP, \f(CW$tablename\fP, \f(CW$columnname\fP )"
.IX Subsection "$dbh->sqlite_table_column_metadata( $dbname, $tablename, $columnname )"
is for internal use only.
.ie n .SS "$dbh\->\fIsqlite_db_status()\fP"
.el .SS "\f(CW$dbh\fP\->\fIsqlite_db_status()\fP"
.IX Subsection "$dbh->sqlite_db_status()"
Returns a hash reference that holds a set of status information of database connection such as cache usage. See <https://www.sqlite.org/c3ref/c_dbstatus_options.html> for details. You may also pass 0 as an argument to reset the status.
.ie n .SS "$sth\->\fIsqlite_st_status()\fP"
.el .SS "\f(CW$sth\fP\->\fIsqlite_st_status()\fP"
.IX Subsection "$sth->sqlite_st_status()"
Returns a hash reference that holds a set of status information of SQLite statement handle such as full table scan count. See <https://www.sqlite.org/c3ref/c_stmtstatus_counter.html> for details. Statement status only holds the current value.
.PP
.Vb 2
\& my $status = $sth\->sqlite_st_status();
\& my $cur = $status\->{fullscan_step};
.Ve
.PP
You may also pass 0 as an argument to reset the status.
.ie n .SS "$dbh\->sqlite_db_config( $id, $new_integer_value )"
.el .SS "\f(CW$dbh\fP\->sqlite_db_config( \f(CW$id\fP, \f(CW$new_integer_value\fP )"
.IX Subsection "$dbh->sqlite_db_config( $id, $new_integer_value )"
You can change how the connected database should behave like this:
.PP
.Vb 1
\& use DBD::SQLite::Constants qw/:database_connection_configuration_options/;
\&
\& my $dbh = DBI\->connect(\*(Aqdbi:SQLite::memory:\*(Aq);
\&
\& # This disables language features that allow ordinary SQL
\& # to deliberately corrupt the database file
\& $dbh\->sqlite_db_config( SQLITE_DBCONFIG_DEFENSIVE, 1 );
\&
\& # This disables two\-arg version of fts3_tokenizer.
\& $dbh\->sqlite_db_config( SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER, 0 );
.Ve
.PP
\&\f(CW\*(C`sqlite_db_config\*(C'\fR returns the new value after the call. If you just want to know the current value without changing anything, pass a negative integer value.
.PP
.Vb 1
\& my $current_value = $dbh\->sqlite_db_config( SQLITE_DBCONFIG_DEFENSIVE, \-1 );
.Ve
.PP
As of this writing, \f(CW\*(C`sqlite_db_config\*(C'\fR only supports options that set an integer value. \f(CW\*(C`SQLITE_DBCONFIG_LOOKASIDE\*(C'\fR and \f(CW\*(C`SQLITE_DBCONFIG_MAINDBNAME\*(C'\fR are not supported. See also \f(CW\*(C`https://www.sqlite.org/capi3ref.html#sqlite3_db_config\*(C'\fR for details.
.ie n .SS "$dbh\->\fIsqlite_create_module()\fP"
.el .SS "\f(CW$dbh\fP\->\fIsqlite_create_module()\fP"
.IX Subsection "$dbh->sqlite_create_module()"
Registers a name for a \fIvirtual table module\fR. Module names must be
registered before creating a new virtual table using the module and
before using a preexisting virtual table for the module.
Virtual tables are explained in DBD::SQLite::VirtualTable.
.ie n .SS "$dbh\->sqlite_limit( $category_id, $new_value )"
.el .SS "\f(CW$dbh\fP\->sqlite_limit( \f(CW$category_id\fP, \f(CW$new_value\fP )"
.IX Subsection "$dbh->sqlite_limit( $category_id, $new_value )"
Sets a new run-time limit for the category, and returns the current limit.
If the new value is a negative number (or omitted), the limit is unchanged
and just returns the current limit. Category ids (\s-1SQLITE_LIMIT_LENGTH,
SQLITE_LIMIT_VARIABLE_NUMBER,\s0 etc) can be imported from DBD::SQLite::Constants.
.ie n .SS "$dbh\->\fIsqlite_get_autocommit()\fP"
.el .SS "\f(CW$dbh\fP\->\fIsqlite_get_autocommit()\fP"
.IX Subsection "$dbh->sqlite_get_autocommit()"
Returns true if the internal SQLite connection is in an autocommit mode.
This does not always return the same value as \f(CW\*(C`$dbh\->{AutoCommit}\*(C'\fR.
This returns false if you explicitly issue a \f(CW\*(C`<BEGIN\*(C'\fR> statement.
.SH "DRIVER FUNCTIONS"
.IX Header "DRIVER FUNCTIONS"
.SS "\fIDBD::SQLite::compile_options()\fP"
.IX Subsection "DBD::SQLite::compile_options()"
Returns an array of compile options (available since SQLite 3.6.23,
bundled in DBD::SQLite 1.30_01), or an empty array if the bundled
library is old or compiled with \s-1SQLITE_OMIT_COMPILEOPTION_DIAGS.\s0
.SS "\fIDBD::SQLite::sqlite_status()\fP"
.IX Subsection "DBD::SQLite::sqlite_status()"
Returns a hash reference that holds a set of status information of SQLite runtime such as memory usage or page cache usage (see <https://www.sqlite.org/c3ref/c_status_malloc_count.html> for details). Each of the entry contains the current value and the highwater value.
.PP
.Vb 3
\& my $status = DBD::SQLite::sqlite_status();
\& my $cur = $status\->{memory_used}{current};
\& my $high = $status\->{memory_used}{highwater};
.Ve
.PP
You may also pass 0 as an argument to reset the status.
.ie n .SS "DBD::SQLite::strlike($pattern, $string, $escape_char), DBD::SQLite::strglob($pattern, $string)"
.el .SS "DBD::SQLite::strlike($pattern, \f(CW$string\fP, \f(CW$escape_char\fP), DBD::SQLite::strglob($pattern, \f(CW$string\fP)"
.IX Subsection "DBD::SQLite::strlike($pattern, $string, $escape_char), DBD::SQLite::strglob($pattern, $string)"
As of 1.49_05 (SQLite 3.10.0), you can use these two functions to
see if a string matches a pattern. These may be useful when you
create a virtual table or a custom function.
See <http://sqlite.org/c3ref/strlike.html> and
<http://sqlite.org/c3ref/strglob.html> for details.
.SH "DRIVER CONSTANTS"
.IX Header "DRIVER CONSTANTS"
A subset of SQLite C constants are made available to Perl,
because they may be needed when writing
hooks or authorizer callbacks. For accessing such constants,
the \f(CW\*(C`DBD::SQLite\*(C'\fR module must be explicitly \f(CW\*(C`use\*(C'\fRd at compile
time. For example, an authorizer that forbids any
\&\s-1DELETE\s0 operation would be written as follows :
.PP
.Vb 6
\& use DBD::SQLite;
\& $dbh\->sqlite_set_authorizer(sub {
\& my $action_code = shift;
\& return $action_code == DBD::SQLite::DELETE ? DBD::SQLite::DENY
\& : DBD::SQLite::OK;
\& });
.Ve
.PP
The list of constants implemented in \f(CW\*(C`DBD::SQLite\*(C'\fR is given
below; more information can be found ad
at <https://www.sqlite.org/c3ref/constlist.html>.
.SS "Authorizer Return Codes"
.IX Subsection "Authorizer Return Codes"
.Vb 3
\& OK
\& DENY
\& IGNORE
.Ve
.SS "Action Codes"
.IX Subsection "Action Codes"
The \*(L"set_authorizer\*(R" method registers a callback function that is
invoked to authorize certain \s-1SQL\s0 statement actions. The first
parameter to the callback is an integer code that specifies what
action is being authorized. The second and third parameters to the
callback are strings, the meaning of which varies according to the
action code. Below is the list of action codes, together with their
associated strings.
.PP
.Vb 10
\& # constant string1 string2
\& # ======== ======= =======
\& CREATE_INDEX Index Name Table Name
\& CREATE_TABLE Table Name undef
\& CREATE_TEMP_INDEX Index Name Table Name
\& CREATE_TEMP_TABLE Table Name undef
\& CREATE_TEMP_TRIGGER Trigger Name Table Name
\& CREATE_TEMP_VIEW View Name undef
\& CREATE_TRIGGER Trigger Name Table Name
\& CREATE_VIEW View Name undef
\& DELETE Table Name undef
\& DROP_INDEX Index Name Table Name
\& DROP_TABLE Table Name undef
\& DROP_TEMP_INDEX Index Name Table Name
\& DROP_TEMP_TABLE Table Name undef
\& DROP_TEMP_TRIGGER Trigger Name Table Name
\& DROP_TEMP_VIEW View Name undef
\& DROP_TRIGGER Trigger Name Table Name
\& DROP_VIEW View Name undef
\& INSERT Table Name undef
\& PRAGMA Pragma Name 1st arg or undef
\& READ Table Name Column Name
\& SELECT undef undef
\& TRANSACTION Operation undef
\& UPDATE Table Name Column Name
\& ATTACH Filename undef
\& DETACH Database Name undef
\& ALTER_TABLE Database Name Table Name
\& REINDEX Index Name undef
\& ANALYZE Table Name undef
\& CREATE_VTABLE Table Name Module Name
\& DROP_VTABLE Table Name Module Name
\& FUNCTION undef Function Name
\& SAVEPOINT Operation Savepoint Name
.Ve
.SH "COLLATION FUNCTIONS"
.IX Header "COLLATION FUNCTIONS"
.SS "Definition"
.IX Subsection "Definition"
SQLite v3 provides the ability for users to supply arbitrary
comparison functions, known as user-defined \*(L"collation sequences\*(R" or
\&\*(L"collating functions\*(R", to be used for comparing two text values.
<https://www.sqlite.org/datatype3.html#collation>
explains how collations are used in various \s-1SQL\s0 expressions.
.SS "Builtin collation sequences"
.IX Subsection "Builtin collation sequences"
The following collation sequences are builtin within SQLite :
.IP "\fB\s-1BINARY\s0\fR" 4
.IX Item "BINARY"
Compares string data using \fImemcmp()\fR, regardless of text encoding.
.IP "\fB\s-1NOCASE\s0\fR" 4
.IX Item "NOCASE"
The same as binary, except the 26 upper case characters of \s-1ASCII\s0 are
folded to their lower case equivalents before the comparison is
performed. Note that only \s-1ASCII\s0 characters are case folded. SQLite
does not attempt to do full \s-1UTF\s0 case folding due to the size of the
tables required.
.IP "\fB\s-1RTRIM\s0\fR" 4
.IX Item "RTRIM"
The same as binary, except that trailing space characters are ignored.
.PP
In addition, \f(CW\*(C`DBD::SQLite\*(C'\fR automatically installs the
following collation sequences :
.IP "\fBperl\fR" 4
.IX Item "perl"
corresponds to the Perl \f(CW\*(C`cmp\*(C'\fR operator
.IP "\fBperllocale\fR" 4
.IX Item "perllocale"
Perl \f(CW\*(C`cmp\*(C'\fR operator, in a context where \f(CW\*(C`use locale\*(C'\fR is activated.
.SS "Usage"
.IX Subsection "Usage"
You can write for example
.PP
.Vb 5
\& CREATE TABLE foo(
\& txt1 COLLATE perl,
\& txt2 COLLATE perllocale,
\& txt3 COLLATE nocase
\& )
.Ve
.PP
or
.PP
.Vb 1
\& SELECT * FROM foo ORDER BY name COLLATE perllocale
.Ve
.SS "Unicode handling"
.IX Subsection "Unicode handling"
If the attribute \f(CW\*(C`$dbh\->{sqlite_unicode}\*(C'\fR is set, strings coming from
the database and passed to the collation function will be properly
tagged with the utf8 flag; but this only works if the
\&\f(CW\*(C`sqlite_unicode\*(C'\fR attribute is set \fBbefore\fR the first call to
a perl collation sequence . The recommended way to activate unicode
is to set the parameter at connection time :
.PP
.Vb 7
\& my $dbh = DBI\->connect(
\& "dbi:SQLite:dbname=foo", "", "",
\& {
\& RaiseError => 1,
\& sqlite_unicode => 1,
\& }
\& );
.Ve
.SS "Adding user-defined collations"
.IX Subsection "Adding user-defined collations"
The native SQLite \s-1API\s0 for adding user-defined collations is
exposed through methods \*(L"sqlite_create_collation\*(R" and
\&\*(L"sqlite_collation_needed\*(R".
.PP
To avoid calling these functions every time a \f(CW$dbh\fR handle is
created, \f(CW\*(C`DBD::SQLite\*(C'\fR offers a simpler interface through the
\&\f(CW%DBD::SQLite::COLLATION\fR hash : just insert your own
collation functions in that hash, and whenever an unknown
collation name is encountered in \s-1SQL,\s0 the appropriate collation
function will be loaded on demand from the hash. For example,
here is a way to sort text values regardless of their accented
characters :
.PP
.Vb 10
\& use DBD::SQLite;
\& $DBD::SQLite::COLLATION{no_accents} = sub {
\& my ( $a, $b ) = map lc, @_;
\& tr[XXXXXXXXXXXXXXXXXXXXXXXXXXXX]
\& [aaaaaacdeeeeiiiinoooooouuuuy] for $a, $b;
\& $a cmp $b;
\& };
\& my $dbh = DBI\->connect("dbi:SQLite:dbname=dbfile");
\& my $sql = "SELECT ... FROM ... ORDER BY ... COLLATE no_accents");
\& my $rows = $dbh\->selectall_arrayref($sql);
.Ve
.PP
The builtin \f(CW\*(C`perl\*(C'\fR or \f(CW\*(C`perllocale\*(C'\fR collations are predefined
in that same hash.
.PP
The \s-1COLLATION\s0 hash is a global registry within the current process;
hence there is a risk of undesired side-effects. Therefore, to
prevent action at distance, the hash is implemented as a \*(L"write-only\*(R"
hash, that will happily accept new entries, but will raise an
exception if any attempt is made to override or delete a existing
entry (including the builtin \f(CW\*(C`perl\*(C'\fR and \f(CW\*(C`perllocale\*(C'\fR).
.PP
If you really, really need to change or delete an entry, you can
always grab the tied object underneath \f(CW%DBD::SQLite::COLLATION\fR \-\-\-
but don't do that unless you really know what you are doing. Also
observe that changes in the global hash will not modify existing
collations in existing database handles: it will only affect new
\&\fIrequests\fR for collations. In other words, if you want to change
the behaviour of a collation within an existing \f(CW$dbh\fR, you
need to call the \*(L"create_collation\*(R" method directly.
.SH "FULLTEXT SEARCH"
.IX Header "FULLTEXT SEARCH"
SQLite is bundled with an extension module for full-text
indexing. Tables with this feature enabled can be efficiently queried
to find rows that contain one or more instances of some specified
words, in any column, even if the table contains many large documents.
.PP
Explanations for using this feature are provided in a separate document:
see DBD::SQLite::Fulltext_search.
.SH "R* TREE SUPPORT"
.IX Header "R* TREE SUPPORT"
The \s-1RTREE\s0 extension module within SQLite adds support for creating
a R\-Tree, a special index for range and multidimensional queries. This
allows users to create tables that can be loaded with (as an example)
geospatial data such as latitude/longitude coordinates for buildings within
a city :
.PP
.Vb 5
\& CREATE VIRTUAL TABLE city_buildings USING rtree(
\& id, \-\- Integer primary key
\& minLong, maxLong, \-\- Minimum and maximum longitude
\& minLat, maxLat \-\- Minimum and maximum latitude
\& );
.Ve
.PP
then query which buildings overlap or are contained within a specified region:
.PP
.Vb 5
\& # IDs that are contained within query coordinates
\& my $contained_sql = <<"";
\& SELECT id FROM city_buildings
\& WHERE minLong >= ? AND maxLong <= ?
\& AND minLat >= ? AND maxLat <= ?
\&
\& # ... and those that overlap query coordinates
\& my $overlap_sql = <<"";
\& SELECT id FROM city_buildings
\& WHERE maxLong >= ? AND minLong <= ?
\& AND maxLat >= ? AND minLat <= ?
\&
\& my $contained = $dbh\->selectcol_arrayref($contained_sql,undef,
\& $minLong, $maxLong, $minLat, $maxLat);
\&
\& my $overlapping = $dbh\->selectcol_arrayref($overlap_sql,undef,
\& $minLong, $maxLong, $minLat, $maxLat);
.Ve
.PP
For more detail, please see the SQLite R\-Tree page
(<https://www.sqlite.org/rtree.html>). Note that custom R\-Tree
queries using callbacks, as mentioned in the prior link, have not been
implemented yet.
.SH "VIRTUAL TABLES IMPLEMENTED IN PERL"
.IX Header "VIRTUAL TABLES IMPLEMENTED IN PERL"
SQLite has a concept of \*(L"virtual tables\*(R" which look like regular
tables but are implemented internally through specific functions.
The fulltext or R* tree features described in the previous chapters
are examples of such virtual tables, implemented in C code.
.PP
\&\f(CW\*(C`DBD::SQLite\*(C'\fR also supports virtual tables implemented in \fIPerl code\fR:
see DBD::SQLite::VirtualTable for using or implementing such
virtual tables. These can have many interesting uses
for joining regular \s-1DBMS\s0 data with some other kind of data within your
Perl programs. Bundled with the present distribution are :
.IP "\(bu" 4
DBD::SQLite::VirtualTable::FileContent : implements a virtual
column that exposes file contents. This is especially useful
in conjunction with a fulltext index; see DBD::SQLite::Fulltext_search.
.IP "\(bu" 4
DBD::SQLite::VirtualTable::PerlData : binds to a Perl array
within the Perl program. This can be used for simple import/export
operations, for debugging purposes, for joining data from different
sources, etc.
.PP
Other Perl virtual tables may also be published separately on \s-1CPAN.\s0
.SH "FOR DBD::SQLITE EXTENSION AUTHORS"
.IX Header "FOR DBD::SQLITE EXTENSION AUTHORS"
Since 1.30_01, you can retrieve the bundled SQLite C source and/or
header like this:
.PP
.Vb 2
\& use File::ShareDir \*(Aqdist_dir\*(Aq;
\& use File::Spec::Functions \*(Aqcatfile\*(Aq;
\&
\& # the whole sqlite3.h header
\& my $sqlite3_h = catfile(dist_dir(\*(AqDBD\-SQLite\*(Aq), \*(Aqsqlite3.h\*(Aq);
\&
\& # or only a particular header, amalgamated in sqlite3.c
\& my $what_i_want = \*(Aqparse.h\*(Aq;
\& my $sqlite3_c = catfile(dist_dir(\*(AqDBD\-SQLite\*(Aq), \*(Aqsqlite3.c\*(Aq);
\& open my $fh, \*(Aq<\*(Aq, $sqlite3_c or die $!;
\& my $code = do { local $/; <$fh> };
\& my ($parse_h) = $code =~ m{(
\& /\e*+[ ]Begin[ ]file[ ]$what_i_want[ ]\e*+
\& .+?
\& /\e*+[ ]End[ ]of[ ]$what_i_want[ ]\e*+/
\& )}sx;
\& open my $out, \*(Aq>\*(Aq, $what_i_want or die $!;
\& print $out $parse_h;
\& close $out;
.Ve
.PP
You usually want to use this in your extension's \f(CW\*(C`Makefile.PL\*(C'\fR,
and you may want to add DBD::SQLite to your extension's \f(CW\*(C`CONFIGURE_REQUIRES\*(C'\fR
to ensure your extension users use the same C source/header they use
to build DBD::SQLite itself (instead of the ones installed in their
system).
.SH "TO DO"
.IX Header "TO DO"
The following items remain to be done.
.SS "Leak Detection"
.IX Subsection "Leak Detection"
Implement one or more leak detection tests that only run during
\&\s-1AUTOMATED_TESTING\s0 and \s-1RELEASE_TESTING\s0 and validate that none of the C
code we work with leaks.
.SS "Stream \s-1API\s0 for Blobs"
.IX Subsection "Stream API for Blobs"
Reading/writing into blobs using \f(CW\*(C`sqlite2_blob_open\*(C'\fR / \f(CW\*(C`sqlite2_blob_close\*(C'\fR.
.SS "Support for custom callbacks for R\-Tree queries"
.IX Subsection "Support for custom callbacks for R-Tree queries"
Custom queries of a R\-Tree index using a callback are possible with
the SQLite C \s-1API \s0(<https://www.sqlite.org/rtree.html>), so one could
potentially use a callback that narrowed the result set down based
on a specific need, such as querying for overlapping circles.
.SH "SUPPORT"
.IX Header "SUPPORT"
Bugs should be reported to GitHub issues:
.PP
<https://github.com/DBD\-SQLite/DBD\-SQLite/issues>
.PP
or via \s-1RT\s0 if you prefer:
.PP
<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DBD\-SQLite>
.PP
Note that bugs of bundled SQLite library (i.e. bugs in \f(CW\*(C`sqlite3.[ch]\*(C'\fR)
should be reported to the SQLite developers at sqlite.org via their bug
tracker or via their mailing list.
.PP
The master repository is on GitHub:
.PP
<https://github.com/DBD\-SQLite/DBD\-SQLite>.
.PP
We also have a mailing list:
.PP
<http://lists.scsys.co.uk/cgi\-bin/mailman/listinfo/dbd\-sqlite>
.SH "AUTHORS"
.IX Header "AUTHORS"
Matt Sergeant <matt@sergeant.org>
.PP
Francis J. Lacoste <flacoste@logreport.org>
.PP
Wolfgang Sourdeau <wolfgang@logreport.org>
.PP
Adam Kennedy <adamk@cpan.org>
.PP
Max Maischein <corion@cpan.org>
.PP
Laurent Dami <dami@cpan.org>
.PP
Kenichi Ishigaki <ishigaki@cpan.org>
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
The bundled SQLite code in this distribution is Public Domain.
.PP
DBD::SQLite is copyright 2002 \- 2007 Matt Sergeant.
.PP
Some parts copyright 2008 Francis J. Lacoste.
.PP
Some parts copyright 2008 Wolfgang Sourdeau.
.PP
Some parts copyright 2008 \- 2013 Adam Kennedy.
.PP
Some parts copyright 2009 \- 2013 Kenichi Ishigaki.
.PP
Some parts derived from DBD::SQLite::Amalgamation
copyright 2008 Audrey Tang.
.PP
This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.
.PP
The full text of the license can be found in the
\&\s-1LICENSE\s0 file included with this module.