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DBD::SQLite(3)	      User Contributed Perl Documentation	DBD::SQLite(3)

NAME
       DBD::SQLite - Self-contained RDBMS in a DBI Driver

SYNOPSIS
	 use DBI;
	 my $dbh = DBI->connect("dbi:SQLite:dbname=$dbfile","","");

DESCRIPTION
       SQLite is a public domain file-based relational database engine that
       you can find at <http://www.sqlite.org/>.

       DBD::SQLite is a Perl DBI driver for SQLite, that includes the entire
       thing in the distribution.  So in order to get a fast transaction
       capable RDBMS working for your perl project you simply have to install
       this module, and nothing else.

       SQLite supports the following features:

       Implements a large subset of SQL92
	   See <http://www.sqlite.org/lang.html> for details.

       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 DBD::CSV.

       Atomic commit and rollback
	   Yes, DBD::SQLite is small and light, but it supports full
	   transactions!

       Extensible
	   User-defined aggregate or regular functions can be registered with
	   the SQL parser.

       There's lots more to it, so please refer to the docs on the SQLite web
       page, listed above, for SQL details. Also refer to DBI for details on
       how to use DBI itself. The API works like every DBI module does.
       However, currently many statement attributes are not implemented or are
       limited by the typeless nature of the SQLite database.

NOTABLE DIFFERENCES FROM OTHER DRIVERS
   Database Name Is A File Name
       SQLite creates a file per a database. You should pass the "path" of the
       database file (with or without a parent directory) in the DBI
       connection string (as a database "name"):

	 my $dbh = DBI->connect("dbi:SQLite:dbname=$dbfile","","");

       The file is opened in read/write mode, and will be created if it does
       not exist yet.

       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.

       If the filename $dbfile is ":memory:", 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.

       Note that future versions of SQLite might make use of additional
       special filenames that begin with the ":" character. It is recommended
       that when a database filename actually does begin with a ":" character
       you should prefix the filename with a pathname such as "./" to avoid
       ambiguity.

       If the filename $dbfile 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.

   Accessing A Database With Other Tools
       To access the database from the command line, try using "dbish" which
       comes with the DBI::Shell module. Just type:

	 dbish dbi:SQLite:foo.db

       On the command line to access the file foo.db.

       Alternatively you can install SQLite from the link above without
       conflicting with DBD::SQLite and use the supplied "sqlite3" command
       line tool.

   Blobs
       As of version 1.11, blobs should "just work" in SQLite as text columns.
       However this will cause the data to be treated as a string, so SQL
       statements such as length(x) will return the length of the column as a
       NUL terminated string, rather than the size of the blob in bytes. In
       order to store natively as a BLOB use the following code:

	 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();

       And then retrieval just works:

	 $sth = $dbh->prepare("SELECT * FROM mytable WHERE id = 1");
	 $sth->execute();
	 my $row = $sth->fetch;
	 my $blobo = $row->[1];

	 # now $blobo == $blob

   Functions And Bind Parameters
       As of this writing, a SQL that compares a return value of a function
       with a numeric bind value like this doesn't work as you might expect.

	 my $sth = $dbh->prepare(q{
	   SELECT bar FROM foo GROUP BY bar HAVING count(*) > ?;
	 });
	 $sth->execute(5);

       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:

	 SELECT bar FROM foo GROUP BY bar HAVING count(*) > "5";

       There are three workarounds for this.

       Use bind_param() explicitly
	   As shown above in the "BLOB" section, you can always use
	   "bind_param()" to tell the type of a bind value.

	     use DBI qw(:sql_types);  # Don't 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();

       Add zero to make it a number
	   This is somewhat weird, but works anyway.

	     my $sth = $dbh->prepare(q{
	       SELECT bar FROM foo GROUP BY bar HAVING count(*) > (? + 0);
	     });
	     $sth->execute(5);

       Set "sqlite_see_if_its_a_number" database handle attribute
	   As of version 1.32_02, you can use "sqlite_see_if_its_a_number" to
	   let DBD::SQLite to see if the bind values are numbers or not.

	     $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);

	   You can set it to true when you connect to a database.

	     my $dbh = DBI->connect('dbi:SQLite:foo', undef, undef, {
	       AutoCommit => 1,
	       RaiseError => 1,
	       sqlite_see_if_its_a_number => 1,
	     });

	   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
	   "sqlite3" command line tool, this attribute would help you.

   Placeholders
       SQLite supports several placeholder expressions, including "?"  and
       ":AAAA". Consult the DBI and sqlite documentation for details.

       <http://www.sqlite.org/lang_expr.html#varparam>

       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.

	 my $sth = $dbh->prepare(
	   'update TABLE set a=?1 where b=?2 and a IS NOT ?1'
	 );
	 $sth->execute(1, 2);

   Foreign Keys
       BE PREPARED! WOLVES APPROACH!!

       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 pragma
       actually to enable this feature and enforce the constraints.

       To do this, issue the following pragma (see below), preferably as soon
       as you connect to a database and you're not in a transaction:

	 $dbh->do("PRAGMA foreign_keys = ON");

       And you can explicitly disable the feature whenever you like by turning
       the pragma off:

	 $dbh->do("PRAGMA foreign_keys = OFF");

       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. It is very
       likely that the sqlite team will turn it default-on in the future, and
       we plan to do it NO LATER THAN they do so.

       See <http://www.sqlite.org/foreignkeys.html> for details.

   Pragma
       SQLite has a set of "Pragma"s to modifiy its operation or to query for
       its internal data. These are specific to SQLite and are not likely to
       work with other DBD libraries, but you may find some of these are quite
       useful. DBD::SQLite actually sets some (like "show_datatypes") for you
       when you connect to a database.	See
       <http://www.sqlite.org/pragma.html> for details.

   Transactions
       DBI/DBD::SQLite's transactions may be a bit confusing. They behave
       differently according to the status of the "AutoCommit" flag:

       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 "begin_work" method, or issue a "BEGIN"
	   statement. To end it, call "commit/rollback" methods, or issue the
	   corresponding statements.

	     $dbh->{AutoCommit} = 1;

	     $dbh->begin_work; # or $dbh->do('BEGIN TRANSACTION');

	     # $dbh->{AutoCommit} is turned off temporarily during a transaction;

	     $dbh->commit; # or $dbh->do('COMMIT');

	     # $dbh->{AutoCommit} is turned on again;

       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
	   "BEGIN" statement (only when an actual transaction has not begun
	   yet) but you're not allowed to call "begin_work" method (if you
	   don't issue a "BEGIN", it will be issued internally).  You can
	   commit or roll it back freely. Another transaction will
	   automatically begins if you execute another statement.

	     $dbh->{AutoCommit} = 0;

	     # $dbh->do('BEGIN TRANSACTION') is not necessary, but possible

	     ...

	     $dbh->commit; # or $dbh->do('COMMIT');

	     # $dbh->{AutoCommit} stays intact;

	     $dbh->{AutoCommit} = 1;  # ends the transactional mode

       This "AutoCommit" mode is independent from the autocommit mode of the
       internal SQLite library, which always begins by a "BEGIN" statement,
       and ends by a "COMMIT" or a <ROLLBACK>.

   Transaction and Database Locking
       Transaction by "AutoCommit" or "begin_work" is nice and handy, but
       sometimes you may get an annoying "database is locked" error.  This
       typically happens when someone begins a transaction, and tries to write
       to a database while other person is reading from the database (in
       another transaction). You might be surprised but SQLite doesn't lock a
       database when you just begin a normal (deferred) transaction to
       maximize concurrency. It reserves a lock when you issue a statement to
       write, but until you actually try to write with a "commit" statement,
       it allows other people to read from the database. However, reading from
       the database also requires "shared lock", and that prevents to give you
       the "exclusive lock" you reserved, thus you get the "database is
       locked" error, and other people will get the same error if they try to
       write afterwards, as you still have a "pending" lock. "busy_timeout"
       doesn't help in this case.

       To avoid this, set a transaction type explicitly. You can issue a
       "begin immediate transaction" (or "begin exclusive transaction") for
       each transaction, or set "sqlite_use_immediate_transaction" database
       handle attribute to true (since 1.30_02) to always use an immediate
       transaction (even when you simply use "begin_work" or turn off the
       "AutoCommit".).

	 my $dbh = DBI->connect("dbi:SQLite::memory:", "", "", {
	   sqlite_use_immediate_transaction => 1,
	 });

       Note that this works only when all of the connections use the same
       (non-deferred) transaction. See <http://sqlite.org/lockingv3.html> for
       locking details.

   Processing Multiple Statements At A Time
       DBI's statement handle is not supposed to process multiple statements
       at a time. So if you pass a string that contains multiple statements (a
       "dump") to a statement handle (via "prepare" or "do"), DBD::SQLite only
       processes the first statement, and discards the rest.

       Since 1.30_01, you can retrieve those ignored (unprepared) statements
       via "$sth->{sqlite_unprepared_statements}". It usually contains nothing
       but white spaces, but if you really care, you can check this attribute
       to see if there's anything left undone. Also, if you set a
       "sqlite_allow_multiple_statements" attribute of a database handle to
       true when you connect to a database, "do" method automatically checks
       the "sqlite_unprepared_statements" attribute, and if it finds anything
       undone (even if what's left is just a single white space), it repeats
       the process again, to the end.

   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.

       Queries like count(*) and avg(bytes) took fractions of a second to
       return, but what surprised him most of all was:

	 SELECT url, count(*) as count
	 FROM access_log
	 GROUP BY url
	 ORDER BY count desc
	 LIMIT 20

       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!

       Oh yeah, and that was with no indexes on the table, on a 400MHz PIII.

       For best performance be sure to tune your hdparm settings if you are
       using linux. Also you might want to set:

	 PRAGMA synchronous = OFF

       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.

       The memory usage of SQLite can also be tuned using the cache_size
       pragma.

	 $dbh->do("PRAGMA cache_size = 800000");

       The above will allocate 800M for DB cache; the default is 2M.  Your
       sweet spot probably lies somewhere in between.

DRIVER PRIVATE ATTRIBUTES
   Database Handle Attributes
       sqlite_version
	   Returns the version of the SQLite library which DBD::SQLite is
	   using, e.g., "2.8.0". Can only be read.

       sqlite_unicode
	   If set to a true value, DBD::SQLite will turn the UTF-8 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 UTF-8
	   flag see perlunicode. The default is for the UTF-8 flag to be
	   turned off.

	   Also note that due to some bizarreness in SQLite's type system (see
	   <http://www.sqlite.org/datatype3.html>), if you want to retain
	   blob-style behavior for some columns under "$dbh->{sqlite_unicode}
	   = 1" (say, to store images in the database), you have to state so
	   explicitly using the 3-argument form of "bind_param" in DBI when
	   doing updates:

	     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);

	   Defining the column type as "BLOB" in the DDL is not sufficient.

	   This attribute was originally named as "unicode", and renamed to
	   "sqlite_unicode" for integrity since version 1.26_06. Old "unicode"
	   attribute is still accessible but will be deprecated in the near
	   future.

       sqlite_allow_multiple_statements
	   If you set this to true, "do" method will process multiple
	   statements at one go. This may be handy, but with performance
	   penalty. See above for details.

       sqlite_use_immediate_transaction
	   If you set this to true, DBD::SQLite tries to issue a "begin
	   immediate transaction" (instead of "begin transaction") when
	   necessary. See above for details.

       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.

   Statement Handle Attributes
       sqlite_unprepared_statements
	   Returns an unprepared part of the statement you pass to "prepare".
	   Typically this contains nothing but white spaces after a semicolon.
	   See above for details.

METHODS
       See also to the DBI documentation for the details of other common
       methods.

   table_info
	 $sth = $dbh->table_info(undef, $schema, $table, $type, \%attr);

       Returns all tables and schemas (databases) as specified in "table_info"
       in DBI.	The schema and table arguments will do a "LIKE" search. You
       can specify an ESCAPE character by including an 'Escape' attribute in
       \%attr. The $type argument accepts a comma separated list of the
       following types 'TABLE', 'VIEW', 'LOCAL TEMPORARY' and 'SYSTEM TABLE'
       (by default all are returned).  Note that a statement handle is
       returned, and not a direct list of tables.

       The following fields are returned:

       TABLE_CAT: Always NULL, as SQLite does not have the concept of
       catalogs.

       TABLE_SCHEM: 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.

       TABLE_NAME: The name of the table or view.

       TABLE_TYPE: The type of object returned. Will be one of 'TABLE',
       'VIEW', 'LOCAL TEMPORARY' or 'SYSTEM TABLE'.

   primary_key, primary_key_info
	 @names = $dbh->primary_key(undef, $schema, $table);
	 $sth	= $dbh->primary_key_info(undef, $schema, $table, \%attr);

       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 mothods is usually "undef", and you'll usually set
       "undef" for the second one (unless you want to know the primary keys of
       temporary tables).

DRIVER PRIVATE METHODS
       The following methods can be called via the func() method with a little
       tweak, but the use of func() method is now discouraged by the DBI
       author for various reasons (see DBI's document
       http://search.cpan.org/dist/DBI/lib/DBI/DBD.pm#Using_install_method()_to_expose_driver-private_methods
       <http://search.cpan.org/dist/DBI/lib/DBI/DBD.pm#Using_install_method()_to_expose_driver-
       private_methods> for details). So, if you're using DBI >= 1.608, use
       these "sqlite_" methods. If you need to use an older DBI, you can call
       these like this:

	 $dbh->func( ..., "(method name without sqlite_ prefix)" );

   $dbh->sqlite_last_insert_rowid()
       This method returns the last inserted rowid. If you specify an INTEGER
       PRIMARY KEY as the first column in your table, that is the column that
       is returned.  Otherwise, it is the hidden ROWID column. See the sqlite
       docs for details.

       Generally you should not be using this method. Use the DBI
       last_insert_id method instead. The usage of this is:

	 $h->last_insert_id($catalog, $schema, $table_name, $field_name [, \%attr ])

       Running "$h->last_insert_id("","","","")" is the equivalent of running
       "$dbh->sqlite_last_insert_rowid()" directly.

   $dbh->sqlite_busy_timeout()
       Retrieve the current busy timeout.

   $dbh->sqlite_busy_timeout( $ms )
       Set the current busy timeout. The timeout is in milliseconds.

   $dbh->sqlite_create_function( $name, $argc, $code_ref )
       This method will register a new function which will be usable in an SQL
       query. The method's parameters are:

       $name
	   The name of the function. This is the name of the function as it
	   will be used from SQL.

       $argc
	   The number of arguments taken by the function. If this number is
	   -1, the function can take any number of arguments.

       $code_ref
	   This should be a reference to the function's implementation.

       For example, here is how to define a now() function which returns the
       current number of seconds since the epoch:

	 $dbh->sqlite_create_function( 'now', 0, sub { return time } );

       After this, it could be use from SQL as:

	 INSERT INTO mytable ( now() );

       REGEXP function

       SQLite includes syntactic support for an infix operator 'REGEXP', but
       without any implementation. The "DBD::SQLite" 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

	 SELECT * from table WHERE column REGEXP '\bA\w+'

       If you want case-insensitive searching, use perl regex flags, like this
       :

	 SELECT * from table WHERE column REGEXP '(?i:\bA\w+)'

       The default REGEXP implementation can be overridden through the
       "create_function" API described above.

       Note that regexp matching will not use SQLite indices, but will iterate
       over all rows, so it could be quite costly in terms of performance.

   $dbh->sqlite_create_collation( $name, $code_ref )
       This method manually registers a new function which will be usable in
       an SQL query as a COLLATE option for sorting. Such functions can also
       be registered automatically on demand: see section "COLLATION
       FUNCTIONS" below.

       The method's parameters are:

       $name
	   The name of the function exposed to SQL.

       $code_ref
	   Reference to the function's implementation.	The driver will check
	   that this is a proper sorting function.

   $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 SQL
       statement. The callback is invoked as

	 $code_ref->($dbh, $collation_name)

       and should register the desired collation using
       "sqlite_create_collation".

       An initial callback is already registered by "DBD::SQLite", so for most
       common cases it will be simpler to just add your collation sequences in
       the %DBD::SQLite::COLLATION hash (see section "COLLATION FUNCTIONS"
       below).

   $dbh->sqlite_create_aggregate( $name, $argc, $pkg )
       This method will register a new aggregate function which can then be
       used from SQL. The method's parameters are:

       $name
	   The name of the aggregate function, this is the name under which
	   the function will be available from SQL.

       $argc
	   This is an integer which tells the SQL parser how many arguments
	   the function takes. If that number is -1, the function can take any
	   number of arguments.

       $pkg
	   This is the package which implements the aggregator interface.

       The aggregator interface consists of defining three methods:

       new()
	   This method will be called once to create an object which should be
	   used to aggregate the rows in a particular group. The step() and
	   finalize() methods will be called upon the reference return by the
	   method.

       step(@_)
	   This method will be called once for each row in the aggregate.

       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, finalize() will be called
	   right after new().

       Here is a simple aggregate function which returns the variance (example
       adapted from pysqlite):

	 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 ) {
		 $sigma += ($x - $mu)**2;
	     }
	     $sigma = $sigma / ($n - 1);

	     return $sigma;
	 }

	 $dbh->sqlite_create_aggregate( "variance", 1, 'variance' );

       The aggregate function can then be used as:

	 SELECT group_name, variance(score)
	 FROM results
	 GROUP BY group_name;

       For more examples, see the DBD::SQLite::Cookbook.

   $dbh->sqlite_progress_handler( $n_opcodes, $code_ref )
       This method registers a handler to be invoked periodically during long
       running calls to SQLite.

       An example use for this interface is to keep a GUI updated during a
       large query. The parameters are:

       $n_opcodes
	   The progress handler is invoked once for every $n_opcodes virtual
	   machine opcodes in SQLite.

       $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 "Cancel" button on a GUI dialog box.

	   Set this argument to "undef" if you want to unregister a previous
	   progress handler.

   $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
       "sqlite_commit_hook" is overridden. A reference to the previous
       callback (if any) is returned.  Registering an "undef" disables the
       callback.

       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
       explicitly call "$dbh->rollback()" afterwards would yield an error).

   $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
       "sqlite_rollback_hook" is overridden. A reference to the previous
       callback (if any) is returned.  Registering an "undef" disables the
       callback.

   $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
       "sqlite_update_hook" is overridden. A reference to the previous
       callback (if any) is returned.  Registering an "undef" disables the
       callback.

       The callback will be called as

	 $code_ref->($action_code, $database, $table, $rowid)

       where

       $action_code
	   is an integer equal to either "DBD::SQLite::INSERT",
	   "DBD::SQLite::DELETE" or "DBD::SQLite::UPDATE" (see "Action
	   Codes");

       $database
	   is the name of the database containing the affected row;

       $table
	   is the name of the table containing the affected row;

       $rowid
	   is the unique 64-bit signed integer key of the affected row within
	   that table.

   $dbh->sqlite_set_authorizer( $code_ref )
       This method registers an authorizer callback to be invoked whenever SQL
       statements are being compiled by the "prepare" in DBI method.  The
       authorizer callback should return "DBD::SQLite::OK" to allow the
       action, "DBD::SQLite::IGNORE" to disallow the specific action but allow
       the SQL statement to continue to be compiled, or "DBD::SQLite::DENY" to
       cause the entire SQL statement to be rejected with an error. If the
       authorizer callback returns any other value, then then "prepare" call
       that triggered the authorizer will fail with an error message.

       An authorizer is used when preparing SQL statements from an untrusted
       source, to ensure that the SQL 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 SQL 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 SQL is being prepared that
       disallows everything except SELECT statements.

       The callback will be called as

	 $code_ref->($action_code, $string1, $string2, $database, $trigger_or_view)

       where

       $action_code
	   is an integer that specifies what action is being authorized (see
	   "Action Codes").

       $string1, $string2
	   are strings that depend on the action code (see "Action Codes").

       $database
	   is the name of the database ("main", "temp", etc.) if applicable.

       $trigger_or_view
	   is the name of the inner-most trigger or view that is responsible
	   for the access attempt, or "undef" if this access attempt is
	   directly from top-level SQL code.

   $dbh->sqlite_backup_from_file( $filename )
       This method accesses the SQLite Online Backup API, 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 DB.

   $dbh->sqlite_backup_to_file( $filename )
       This method accesses the SQLite Online Backup API, and will take a
       backup of the currently connected database, and write it out to the
       named file.

   $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:

	 $dbh->sqlite_enable_load_extension(1);
	 $sth = $dbh->prepare("select load_extension('libsqlitefunctions.so')")
	 or die "Cannot prepare: " . $dbh->errstr();

   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 SQLITE_OMIT_COMPILEOPTION_DIAGS.

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 "DBD::Sqlite" module must be explicitly "use"d at
       compile time. For example, an authorizer that forbids any DELETE
       operation would be written as follows :

	 use DBD::SQLite;
	 $dbh->sqlite_set_authorizer(sub {
	   my $action_code = shift;
	   return $action_code == DBD::SQLite::DELETE ? DBD::SQLite::DENY
						      : DBD::SQLite::OK;
	 });

       The list of constants implemented in "DBD::SQLite" is given below; more
       information can be found ad at
       <http://www.sqlite.org/c3ref/constlist.html>.

   Authorizer Return Codes
	 OK
	 DENY
	 IGNORE

   Action Codes
       The "set_authorizer" method registers a callback function that is
       invoked to authorize certain SQL 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.

	 # 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

COLLATION FUNCTIONS
   Definition
       SQLite v3 provides the ability for users to supply arbitrary comparison
       functions, known as user-defined "collation sequences" or "collating
       functions", to be used for comparing two text values.
       <http://www.sqlite.org/datatype3.html#collation> explains how
       collations are used in various SQL expressions.

   Builtin collation sequences
       The following collation sequences are builtin within SQLite :

       BINARY
	   Compares string data using memcmp(), regardless of text encoding.

       NOCASE
	   The same as binary, except the 26 upper case characters of ASCII
	   are folded to their lower case equivalents before the comparison is
	   performed. Note that only ASCII characters are case folded. SQLite
	   does not attempt to do full UTF case folding due to the size of the
	   tables required.

       RTRIM
	   The same as binary, except that trailing space characters are
	   ignored.

       In addition, "DBD::SQLite" automatically installs the following
       collation sequences :

       perl
	   corresponds to the Perl "cmp" operator

       perllocale
	   Perl "cmp" operator, in a context where "use locale" is activated.

   Usage
       You can write for example

	 CREATE TABLE foo(
	     txt1 COLLATE perl,
	     txt2 COLLATE perllocale,
	     txt3 COLLATE nocase
	 )

       or

	 SELECT * FROM foo ORDER BY name COLLATE perllocale

   Unicode handling
       If the attribute "$dbh->{sqlite_unicode}" 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 "sqlite_unicode"
       attribute is set before the first call to a perl collation sequence .
       The recommended way to activate unicode is to set the parameter at
       connection time :

	 my $dbh = DBI->connect(
	     "dbi:SQLite:dbname=foo", "", "",
	     {
		 RaiseError	=> 1,
		 sqlite_unicode => 1,
	     }
	 );

   Adding user-defined collations
       The native SQLite API for adding user-defined collations is exposed
       through methods "sqlite_create_collation" and
       "sqlite_collation_needed".

       To avoid calling these functions every time a $dbh handle is created,
       "DBD::SQLite" offers a simpler interface through the
       %DBD::SQLite::COLLATION hash : just insert your own collation functions
       in that hash, and whenever an unknown collation name is encountered in
       SQL, 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 :

	 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);

       The builtin "perl" or "perllocale" collations are predefined in that
       same hash.

       The COLLATION 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 "write-only" 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 "perl" and "perllocale").

       If you really, really need to change or delete an entry, you can always
       grab the tied object underneath %DBD::SQLite::COLLATION --- 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 requests for
       collations. In other words, if you want to change the behaviour of a
       collation within an existing $dbh, you need to call the
       "create_collation" method directly.

FULLTEXT SEARCH
       The FTS3 extension module within SQLite allows users to create special
       tables with a built-in full-text index (hereafter "FTS3 tables"). The
       full-text index allows the user to efficiently query the database for
       all rows that contain one or more instances of a specified word
       (hereafter a "token"), even if the table contains many large documents.

   Short introduction to FTS3
       The detailed documentation for FTS3 can be found at
       <http://www.sqlite.org/fts3.html>. Here is a very short example :

	 $dbh->do(<<"") or die DBI::errstr;
	 CREATE VIRTUAL TABLE fts_example USING fts3(content)

	 my $sth = $dbh->prepare("INSERT INTO fts_example(content) VALUES (?))");
	 $sth->execute($_) foreach @docs_to_insert;

	 my $results = $dbh->selectall_arrayref(<<"");
	 SELECT docid, snippet(content) FROM fts_example WHERE content MATCH 'foo'

       The key points in this example are :

       ·   The syntax for creating FTS3 tables is

	     CREATE VIRTUAL TABLE <table_name> USING fts3(<columns>)

	   where "<columns>" is a list of column names. Columns may be typed,
	   but the type information is ignored. If no columns are specified,
	   the default is a single column named "content".  In addition, FTS3
	   tables have an implicit column called "docid" (or also "rowid") for
	   numbering the stored documents.

       ·   Statements for inserting, updating or deleting records use the same
	   syntax as for regular SQLite tables.

       ·   Full-text searches are specified with the "MATCH" operator, and an
	   operand which may be a single word, a word prefix ending with '*',
	   a list of words, a "phrase query" in double quotes, or a boolean
	   combination of the above.

       ·   The builtin function "snippet(...)" builds a formatted excerpt of
	   the document text, where the words pertaining to the query are
	   highlighted.

       There are many more details to building and searching FTS3 tables, so
       we strongly invite you to read the full documentation at at
       <http://www.sqlite.org/fts3.html>.

       Incompatible change : starting from version 1.31, "DBD::SQLite" uses
       the new, recommended "Enhanced Query Syntax" for binary set operators
       (AND, OR, NOT, possibly nested with parenthesis). Previous versions of
       "DBD::SQLite" used the "Standard Query Syntax" (see
       <http://www.sqlite.org/fts3.html#section_3_2>).	Unfortunately this is
       a compilation switch, so it cannot be tuned at runtime; however, since
       FTS3 was never advertised in versions prior to 1.31, the change should
       be invisible to the vast majority of "DBD::SQLite" users. If, however,
       there are any applications that nevertheless were built using the
       "Standard Query" syntax, they have to be migrated, because the
       precedence of the "OR" operator has changed. Conversion from old to new
       syntax can be automated through DBD::SQLite::FTS3Transitional,
       published in a separate distribution.

   Tokenizers
       The behaviour of full-text indexes strongly depends on how documents
       are split into tokens; therefore FTS3 table declarations can explicitly
       specify how to perform tokenization:

	 CREATE ... USING fts3(<columns>, tokenize=<tokenizer>)

       where "<tokenizer>" is a sequence of space-separated words that
       triggers a specific tokenizer, as explained below.

       SQLite builtin tokenizers

       SQLite comes with three builtin tokenizers :

       simple
	   Under the simple tokenizer, a term is a contiguous sequence of
	   eligible characters, where eligible characters are all alphanumeric
	   characters, the "_" character, and all characters with UTF
	   codepoints greater than or equal to 128. All other characters are
	   discarded when splitting a document into terms. They serve only to
	   separate adjacent terms.

	   All uppercase characters within the ASCII range (UTF codepoints
	   less than 128), are transformed to their lowercase equivalents as
	   part of the tokenization process. Thus, full-text queries are case-
	   insensitive when using the simple tokenizer.

       porter
	   The porter tokenizer uses the same rules to separate the input
	   document into terms, but as well as folding all terms to lower case
	   it uses the Porter Stemming algorithm to reduce related English
	   language words to a common root.

       icu If SQLite is compiled with the SQLITE_ENABLE_ICU pre-processor
	   symbol defined, then there exists a built-in tokenizer named "icu"
	   implemented using the ICU library, and taking an ICU locale
	   identifier as argument (such as "tr_TR" for Turkish as used in
	   Turkey, or "en_AU" for English as used in Australia). For example:

	     CREATE VIRTUAL TABLE thai_text USING fts3(text, tokenize=icu th_TH)

	   The ICU tokenizer implementation is very simple. It splits the
	   input text according to the ICU rules for finding word boundaries
	   and discards any tokens that consist entirely of white-space. This
	   may be suitable for some applications in some locales, but not all.
	   If more complex processing is required, for example to implement
	   stemming or discard punctuation, use the perl tokenizer as
	   explained below.

       Perl tokenizers

       In addition to the builtin SQLite tokenizers, "DBD::Sqlite" implements
       a perl tokenizer, that can hook to any tokenizing algorithm written in
       Perl. This is specified as follows :

	 CREATE ... USING fts3(<columns>, tokenize=perl '<perl_function>')

       where "<perl_function>" is a fully qualified Perl function name (i.e.
       prefixed by the name of the package in which that function is
       declared). So for example if the function is "my_func" in the main
       program, write

	 CREATE ... USING fts3(<columns>, tokenize=perl 'main::my_func')

       That function should return a code reference that takes a string as
       single argument, and returns an iterator (another function), which
       returns a tuple "($term, $len, $start, $end, $index)" for each term.
       Here is a simple example that tokenizes on words according to the
       current perl locale

	 sub locale_tokenizer {
	   return sub {
	     my $string = shift;

	     use locale;
	     my $regex	    = qr/\w+/;
	     my $term_index = 0;

	     return sub { # closure
	       $string =~ /$regex/g or return; # either match, or no more token
	       my ($start, $end) = ($-[0], $+[0]);
	       my $len		 = $end-$start;
	       my $term		 = substr($string, $start, $len);
	       return ($term, $len, $start, $end, $term_index++);
	     }
	   };
	 }

       There must be three levels of subs, in a kind of "Russian dolls"
       structure, because :

       ·   the external, named sub is called whenever accessing a FTS3 table
	   with that tokenizer

       ·   the inner, anonymous sub is called whenever a new string needs to
	   be tokenized (either for inserting new text into the table, or for
	   analyzing a query).

       ·   the innermost, anonymous sub is called repeatedly for retrieving
	   all terms within that string.

       Instead of writing tokenizers by hand, you can grab one of those
       already implemented in the Search::Tokenizer module :

	 use Search::Tokenizer;
	 $dbh->do(<<"") or die DBI::errstr;
	 CREATE ... USING fts3(<columns>,
			       tokenize=perl 'Search::Tokenizer::unaccent')

       or you can use "new" in Search::Tokenizer to build your own tokenizer.

   Incomplete handling of utf8 characters
       The current FTS3 implementation in SQLite is far from complete with
       respect to utf8 handling : in particular, variable-length characters
       are not treated correctly by the builtin functions "offsets()" and
       "snippet()".

   Database space for FTS3
       FTS3 stores a complete copy of the indexed documents, together with the
       fulltext index. On a large collection of documents, this can consume
       quite a lot of disk space. If copies of documents are also available as
       external resources (for example files on the filesystem), that space
       can sometimes be spared --- see the tip in the Cookbook.

R* TREE SUPPORT
       The RTREE 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 :

	 CREATE VIRTUAL TABLE city_buildings USING rtree(
	    id,		      -- Integer primary key
	    minLong, maxLong, -- Minimum and maximum longitude
	    minLat, maxLat    -- Minimum and maximum latitude
	 );

       then query which buildings overlap or are contained within a specified
       region:

	 # IDs that are contained within query coordinates
	 my $contained_sql = <<"";
	 SELECT id FROM try_rtree
	    WHERE  minLong >= ? AND maxLong <= ?
	    AND	   minLat  >= ? AND maxLat  <= ?

	 # ... and those that overlap query coordinates
	 my $overlap_sql = <<"";
	 SELECT id FROM try_rtree
	    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);

       For more detail, please see the SQLite R-Tree page
       (<http://www.sqlite.org/rtree.html>). Note that custom R-Tree queries
       using callbacks, as mentioned in the prior link, have not been
       implemented yet.

FOR DBD::SQLITE EXTENSION AUTHORS
       Since 1.30_01, you can retrieve the bundled sqlite C source and/or
       header like this:

	 use File::ShareDir 'dist_dir';
	 use File::Spec::Functions 'catfile';

	 # the whole sqlite3.h header
	 my $sqlite3_h = catfile(dist_dir('DBD-SQLite'), 'sqlite3.h');

	 # or only a particular header, amalgamated in sqlite3.c
	 my $what_i_want = 'parse.h';
	 my $sqlite3_c = catfile(dist_dir('DBD-SQLite'), 'sqlite3.c');
	 open my $fh, '<', $sqlite3_c or die $!;
	 my $code = do { local $/; <$fh> };
	 my ($parse_h) = $code =~ m{(
	   /\*+[ ]Begin[ ]file[ ]$what_i_want[ ]\*+
	   .+?
	   /\*+[ ]End[ ]of[ ]$what_i_want[ ]\*+/
	 )}sx;
	 open my $out, '>', $what_i_want or die $!;
	 print $out $parse_h;
	 close $out;

       You usually want to use this in your extension's "Makefile.PL", and you
       may want to add DBD::SQLite to your extension's "CONFIGURE_REQUIRES" 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).

TO DO
       The following items remain to be done.

   Leak Detection
       Implement one or more leak detection tests that only run during
       AUTOMATED_TESTING and RELEASE_TESTING and validate that none of the C
       code we work with leaks.

   Stream API for Blobs
       Reading/writing into blobs using "sqlite2_blob_open" /
       "sqlite2_blob_close".

   Flags for sqlite3_open_v2
       Support the full API of sqlite3_open_v2 (flags for opening the file).

   Support for custom callbacks for R-Tree queries
       Custom queries of a R-Tree index using a callback are possible with the
       SQLite C API (<http://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.

SUPPORT
       Bugs should be reported via the CPAN bug tracker at

       http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DBD-SQLite
       <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=DBD-SQLite>

       Note that bugs of bundled sqlite library (i.e. bugs in "sqlite3.[ch]")
       should be reported to the sqlite developers at sqlite.org via their bug
       tracker or via their mailing list.

AUTHORS
       Matt Sergeant <matt@sergeant.org>

       Francis J. Lacoste <flacoste@logreport.org>

       Wolfgang Sourdeau <wolfgang@logreport.org>

       Adam Kennedy <adamk@cpan.org>

       Max Maischein <corion@cpan.org>

       Laurent Dami <dami@cpan.org>

       Kenichi Ishigaki <ishigaki@cpan.org>

COPYRIGHT
       The bundled SQLite code in this distribution is Public Domain.

       DBD::SQLite is copyright 2002 - 2007 Matt Sergeant.

       Some parts copyright 2008 Francis J. Lacoste.

       Some parts copyright 2008 Wolfgang Sourdeau.

       Some parts copyright 2008 - 2011 Adam Kennedy.

       Some parts copyright 2009 - 2011 Kenichi Ishigaki.

       Some parts derived from DBD::SQLite::Amalgamation copyright 2008 Audrey
       Tang.

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

       The full text of the license can be found in the LICENSE file included
       with this module.

perl v5.12.5			  2011-05-30			DBD::SQLite(3)
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