DBD::Firebird(3) DBI driver for Firebird RDBMS server

SYNOPSIS


use DBI;
$dbh = DBI->connect("dbi:Firebird:db=$dbname", $user, $password);
# See the DBI module documentation for full details

DESCRIPTION

DBD::Firebird is a Perl module which works with the DBI module to provide access to Firebird databases.

MODULE DOCUMENTATION

This documentation describes driver specific behavior and restrictions. It is not supposed to be used as the only reference for the user. In any case consult the DBI documentation first !

THE DBI CLASS

DBI Class Methods

connect
To connect to a database with a minimum of parameters, use the following syntax: 

  $dbh = DBI->connect("dbi:Firebird:dbname=$dbname", $user, $password);

If omitted, $user defaults to the ISC_USER environment variable (or, failing that, the DBI-standard DBI_USER environment variable). Similarly, $password defaults to ISC_PASSWORD (or DBI_PASS). If $dbname is blank, that is, ``dbi:Firebird:dbname='', the environment variable ISC_DATABASE is substituted.

The DSN may take several optional parameters, which may be split over multiple lines. Here is an example of connect statement which uses all possible parameters: 

   $dsn =<< "DSN";
 dbi:Firebird:dbname=$dbname;
 host=$host;
 port=$port;
 ib_dialect=$dialect;
 ib_role=$role;
 ib_charset=$charset;
 ib_cache=$cache
 DSN
 $dbh =  DBI->connect($dsn, $username, $password);

The $dsn is prefixed by 'dbi:Firebird:', and consists of key-value parameters separated by semicolons. New line may be added after the semicolon. The following is the list of valid parameters and their respective meanings: 

    parameter       meaning                                 optional?
    -----------------------------------------------------------------
    database        path to the database                    required
    dbname          path to the database
    db              path to the database
    hostname        hostname / IP address                   optional
    host            hostname / IP address
    port            port number                             optional
    ib_dialect      the SQL dialect to be used              optional
    ib_role         the role of the user                    optional
    ib_charset      character set to be used                optional
    ib_cache        number of database cache buffers        optional
    ib_dbkey_scope  change default duration of RDB$DB_KEY   optional

database could be used interchangebly with dbname and db. To connect to a remote host, use the host parameter. Here is an example of DSN to connect to a remote Windows host: 

 $dsn = "dbi:Firebird:db=C:/temp/test.gdb;host=example.com;ib_dialect=3";

Database file alias can be used too in connection string. In the following example, ``billing'' is defined in aliases.conf: 

 $dsn = 'dbi:Firebird:hostname=192.168.88.5;db=billing;ib_dialect=3';

Firebird as of version 1.0 listens on port specified within the services file. To connect to port other than the default 3050, add the port number at the end of host name, separated by a slash. Example: 

 $dsn = 'dbi:Firebird:db=/data/test.gdb;host=localhost/3060';

Firebird 1.0 introduces SQL dialect to provide backward compatibility with databases created by older versions of Firebird (pre 1.0). In short, SQL dialect controls how Firebird interprets: 

 - double quotes
 - the DATE datatype
 - decimal and numeric datatypes
 - new 1.0 reserved keywords

Valid values for ib_dialect are 1 and 3 .The driver's default value is 3 (Currently it is possible to create databases in Dialect 1 and 3 only, however it is recommended that you use Dialect 3 exclusively, since Dialect 1 will eventually be deprecated. Dialect 2 cannot be used to create a database since it only serves to convert Dialect 1 to Dialect 3).

http://www.firebirdsql.org/file/documentation/reference_manuals/user_manuals/html/isql-dialects.html

ib_role specifies the role of the connecting user. SQL role is implemented by Firebird to make database administration easier when dealing with lots of users. A detailed reading can be found at: 

 http://www.ibphoenix.com/resources/documents/general/doc_59

If ib_cache is not specified, the default database's cache size value will be used. The Firebird Operation Guide discusses in full length the importance of this parameter to gain the best performance.

available_drivers
  @driver_names = DBI->available_drivers;

Implemented by DBI, no driver-specific impact.

data_sources
This method is not yet implemented.
trace
  DBI->trace($trace_level, $trace_file)

Implemented by DBI, no driver-specific impact.

DBI Dynamic Attributes

See Common Methods.

METHODS COMMON TO ALL DBI HANDLES

err
  $rv = $h->err;

Supported by the driver as proposed by DBI.

errstr
  $str = $h->errstr;

Supported by the driver as proposed by DBI.

state
This method is not yet implemented.
trace
  $h->trace($trace_level, $trace_filename);

Implemented by DBI, no driver-specific impact.

trace_msg
  $h->trace_msg($message_text);

Implemented by DBI, no driver-specific impact.

func
See Transactions section for information about invoking "ib_set_tx_param()" from func() method.

ATTRIBUTES COMMON TO ALL DBI HANDLES

Warn (boolean, inherited)
Implemented by DBI, no driver-specific impact.
Active (boolean, read-only)
Supported by the driver as proposed by DBI. A database handle is active while it is connected and statement handle is active until it is finished.
Kids (integer, read-only)
Implemented by DBI, no driver-specific impact.
ActiveKids (integer, read-only)
Implemented by DBI, no driver-specific impact.
CachedKids (hash ref)
Implemented by DBI, no driver-specific impact.
CompatMode (boolean, inherited)
Not used by this driver.
InactiveDestroy (boolean)
Implemented by DBI, no driver-specific impact.
PrintError (boolean, inherited)
Implemented by DBI, no driver-specific impact.
RaiseError (boolean, inherited)
Implemented by DBI, no driver-specific impact.
ChopBlanks (boolean, inherited)
Supported by the driver as proposed by DBI.
LongReadLen (integer, inherited)
Supported by the driver as proposed by DBI.The default value is 80 bytes.
LongTruncOk (boolean, inherited)
Supported by the driver as proposed by DBI.
Taint (boolean, inherited)
Implemented by DBI, no driver-specific impact.

DATABASE HANDLE OBJECTS

Database Handle Methods

selectrow_array
  @row_ary = $dbh->selectrow_array($statement, \%attr, @bind_values);

Implemented by DBI, no driver-specific impact.

selectall_arrayref
  $ary_ref = $dbh->selectall_arrayref($statement, \%attr, @bind_values);

Implemented by DBI, no driver-specific impact.

selectcol_arrayref
  $ary_ref = $dbh->selectcol_arrayref($statement, \%attr, @bind_values);

Implemented by DBI, no driver-specific impact.

prepare
  $sth = $dbh->prepare($statement, \%attr);

Supported by the driver as proposed by DBI. When AutoCommit is On, this method implicitly starts a new transaction, which will be automatically committed after the following execute() or the last fetch(), depending on the statement type. For select statements, commit automatically takes place after the last fetch(), or by explicitly calling finish() method if there are any rows remaining. For non-select statements, execute() will implicitly commits the transaction.

prepare_cached
  $sth = $dbh->prepare_cached($statement, \%attr);

Implemented by DBI, no driver-specific impact.

do
  $rv  = $dbh->do($statement, \%attr, @bind_values);

Supported by the driver as proposed by DBI. This should be used for non-select statements, where the driver doesn't take the conservative prepare - execute steps, thereby speeding up the execution time. But if this method is used with bind values, the speed advantage diminishes as this method calls prepare() for binding the placeholders. Instead of calling this method repeatedly with bind values, it would be better to call prepare() once, and execute() many times.

See the notes for the execute method elsewhere in this document. Unlike the execute method, currently this method doesn't return the number of affected rows.

commit
  $rc  = $dbh->commit;

Supported by the driver as proposed by DBI. See also the notes about Transactions elsewhere in this document.

rollback
  $rc  = $dbh->rollback;

Supported by the driver as proposed by DBI. See also the notes about Transactions elsewhere in this document.

disconnect
  $rc  = $dbh->disconnect;

Supported by the driver as proposed by DBI.

ping
  $rc = $dbh->ping;

This driver supports the ping-method, which can be used to check the validity of a database-handle. This is especially required by "Apache::DBI".

primary_key_info
  $sth = $dbh->primary_key_info('', '', $table_name);
  @pks = $dbh->primary_key('', '', $table_name);

Supported by the driver as proposed by DBI. Note that catalog and schema are ignored.

table_info
  $sth = $dbh->table_info;

All Firebird versions support the basic DBI-specified columns (TABLE_NAME, TABLE_TYPE, etc.) as well as "IB_TABLE_OWNER". Peculiar versions may return additional fields, prefixed by "IB_".

Table searching may not work as expected on older Interbase/Firebird engines which do not natively offer a TRIM() function. Some engines store TABLE_NAME in a blank-padded CHAR field, and a search for table name is performed via a SQL "LIKE" predicate, which is sensitive to blanks. That is: 

  $dbh->table_info('', '', 'FOO');  # May not find table "FOO", depending on
                                    # FB version
  $dbh->table_info('', '', 'FOO%'); # Will always find "FOO", but also tables
                                    # "FOOD", "FOOT", etc.

Future versions of DBD::Firebird may attempt to work around this irritating limitation, at the expense of efficiency.

Note that Firebird implementations do not presently support the DBI concepts of 'catalog' and 'schema', so these parameters are effectively ignored.

tables
  @names = $dbh->tables;

Returns a list of tables, excluding any 'SYSTEM TABLE' types.

type_info_all
  $type_info_all = $dbh->type_info_all;

Supported by the driver as proposed by DBI.

For further details concerning the Firebird specific data-types please read the Firebird Data Definition Guide

http://www.firebirdsql.org/en/reference-manuals/

type_info
  @type_info = $dbh->type_info($data_type);

Implemented by DBI, no driver-specific impact.

quote
  $sql = $dbh->quote($value, $data_type);

Implemented by DBI, no driver-specific impact.

Database Handle Attributes

AutoCommit (boolean)
Supported by the driver as proposed by DBI. According to the classification of DBI, Firebird is a database, in which a transaction must be explicitly started. Without starting a transaction, every change to the database becomes immediately permanent. The default of AutoCommit is on, which corresponds to the DBI's default. When setting AutoCommit to off, a transaction will be started and every commit or rollback will automatically start a new transaction. For details see the notes about Transactions elsewhere in this document.
Driver (handle)
Implemented by DBI, no driver-specific impact.
Name (string, read-only)
Not yet implemented.
RowCacheSize (integer)
Implemented by DBI, not used by the driver.
ib_softcommit (driver-specific, boolean)
Set this attribute to TRUE to use Firebird's soft commit feature (default to FALSE). Soft commit retains the internal transaction handle when committing a transaction, while the default commit behavior always closes and invalidates the transaction handle.

Since the transaction handle is still open, there is no need to start a new transaction upon every commit, so applications can gain performance improvement. Using soft commit is also desirable when dealing with nested statement handles under AutoCommit on.

Switching the attribute's value from TRUE to FALSE will force hard commit thus closing the current transaction.

ib_enable_utf8 (driver-specific, boolean)
Setting this attribute to TRUE will cause any Perl Unicode strings supplied as statement parameters to be downgraded to octet sequences before passing them to Firebird.

Also, any character data retrieved from the database (CHAR, VARCHAR, BLOB sub_type TEXT) will be upgraded to Perl Unicode strings.

Caveat: Currently this is supported only if the ib_charset DSN parameter is "UTF8". In the future, encoding and decoding to/from arbitrary character set may be implemented.

Example: 

    $dbh = DBI->connect( 'dbi:Firebird:db=database.fdb;ib_charset=UTF8',
        { ib_enable_utf8 => 1 } );

STATEMENT HANDLE OBJECTS

Statement Handle Methods

bind_param
Supported by the driver as proposed by DBI. The SQL data type passed as the third argument is ignored.
bind_param_array
Supported by the driver as proposed by DBI. The attributes, supplied in the optional third parameter are ignored.
bind_param_inout
Not supported by this driver.
execute
  $rv = $sth->execute(@bind_values);

Supported by the driver as proposed by DBI.

fetchrow_arrayref
  $ary_ref = $sth->fetchrow_arrayref;

Supported by the driver as proposed by DBI.

fetchrow_array
  @ary = $sth->fetchrow_array;

Supported by the driver as proposed by DBI.

fetchrow_hashref
  $hash_ref = $sth->fetchrow_hashref;

Supported by the driver as proposed by DBI.

fetchall_arrayref
  $tbl_ary_ref = $sth->fetchall_arrayref;

Implemented by DBI, no driver-specific impact.

finish
  $rc = $sth->finish;

Supported by the driver as proposed by DBI.

rows
  $rv = $sth->rows;

Supported by the driver as proposed by DBI. It returns the number of fetched rows for select statements, otherwise it returns -1 (unknown number of affected rows).

bind_col
  $rc = $sth->bind_col($column_number, \$var_to_bind, \%attr);

Supported by the driver as proposed by DBI.

bind_columns
  $rc = $sth->bind_columns(\%attr, @list_of_refs_to_vars_to_bind);

Supported by the driver as proposed by DBI.

dump_results
  $rows = $sth->dump_results($maxlen, $lsep, $fsep, $fh);

Implemented by DBI, no driver-specific impact.

Statement Handle Attributes

NUM_OF_FIELDS (integer, read-only)
Implemented by DBI, no driver-specific impact.
NUM_OF_PARAMS (integer, read-only)
Implemented by DBI, no driver-specific impact.
NAME (array-ref, read-only)
Supported by the driver as proposed by DBI.
NAME_lc (array-ref, read-only)
Implemented by DBI, no driver-specific impact.
NAME_uc (array-ref, read-only)
Implemented by DBI, no driver-specific impact.
TYPE (array-ref, read-only)
Supported by the driver as proposed by DBI, with the restriction, that the types are Firebird specific data-types which do not correspond to international standards.
PRECISION (array-ref, read-only)
Supported by the driver as proposed by DBI.
SCALE (array-ref, read-only)
Supported by the driver as proposed by DBI.
NULLABLE (array-ref, read-only)
Supported by the driver as proposed by DBI.
CursorName (string, read-only)
Supported by the driver as proposed by DBI.
Statement (string, read-only)
Supported by the driver as proposed by DBI.
RowCache (integer, read-only)
Not supported by the driver.
ParamValues (hashref, read-only)
Supported by the driver as proposed by DBI.

TRANSACTION SUPPORT

The transaction behavior is controlled with the attribute AutoCommit. For a complete definition of AutoCommit please refer to the DBI documentation.

According to the DBI specification the default for AutoCommit is TRUE. In this mode, any change to the database becomes valid immediately. Any commit() or rollback() will be rejected.

If AutoCommit is switched-off, immediately a transaction will be started. A rollback() will rollback and close the active transaction, then implicitly start a new transaction. A disconnect will issue a rollback.

Firebird provides fine control over transaction behavior, where users can specify the access mode, the isolation level, the lock resolution, and the table reservation (for a specified table). For this purpose, "ib_set_tx_param()" database handle method is available.

Upon a successful "connect()", these default parameter values will be used for every SQL operation: 

    Access mode:        read_write
    Isolation level:    snapshot
    Lock resolution:    wait

Any of the above value can be changed using "ib_set_tx_param()".

ib_set_tx_param
 $dbh->func( 
    -access_mode     => 'read_write',
    -isolation_level => 'read_committed',
    -lock_resolution => 'wait',
    'ib_set_tx_param'
 );

Valid value for "-access_mode" is "read_write", or "read_only".

Valid value for "-lock_resolution" is "wait", or "no_wait". In Firebird 2.0, a timeout value for wait is introduced. This can be specified using hash ref as lock_resolution value: 

 $dbh->func(
    -lock_resolution => { wait => 5 }, # wait for 5 seconds
    'ib_set_tx_param'
 );

"-isolation_level" may be: "read_committed", "snapshot", "snapshot_table_stability".

If "read_committed" is to be used with "record_version" or "no_record_version", then they should be inside an anonymous array: 

 $dbh->func( 
    -isolation_level => ['read_committed', 'record_version'],
    'ib_set_tx_param'
 );

Table reservation is supported since "DBD::Firebird 0.30". Names of the tables to reserve as well as their reservation params/values are specified inside a hashref, which is then passed as the value of "-reserving".

The following example reserves "foo_table" with "read" lock and "bar_table" with "read" lock and "protected" access: 

 $dbh->func(
    -access_mode     => 'read_write',
    -isolation_level => 'read_committed',
    -lock_resolution => 'wait',
    -reserving       =>
        {
            foo_table => {
                lock    => 'read',
            },
            bar_table => {
                lock    => 'read',
                access  => 'protected',
            },
        },
    'ib_set_tx_param'
 );

Possible table reservation parameters are:

"access" (optional)
Valid values are "shared" or "protected".
"lock" (required)
Valid values are "read" or "write".

Under "AutoCommit" mode, invoking this method doesn't only change the transaction parameters (as with "AutoCommit" off), but also commits the current transaction. The new transaction parameters will be used in any newly started transaction.

"ib_set_tx_param()" can also be invoked with no parameter in which it resets transaction parameters to the default value.

DATE, TIME, and TIMESTAMP FORMATTING SUPPORT

"DBD::Firebird" supports various formats for query results of DATE, TIME, and TIMESTAMP types.

By default, it uses ``%c'' for TIMESTAMP, ``%x'' for DATE, and ``%X'' for TIME, and pass them to ANSI C's strftime() function to format your query results. These values are respectively stored in ib_timestampformat, ib_dateformat, and ib_timeformat attributes, and may be changed in two ways:

  • At $dbh level

    This replaces the default values. Example: 

     $dbh->{ib_timestampformat} = '%m-%d-%Y %H:%M';
 $dbh->{ib_dateformat} = '%m-%d-%Y';
 $dbh->{ib_timeformat} = '%H:%M';
  • At $sth level

    This overrides the default values only for the currently prepared statement. Example: 

     $attr = {
    ib_timestampformat => '%m-%d-%Y %H:%M',
    ib_dateformat => '%m-%d-%Y',
    ib_timeformat => '%H:%M',
 };
 # then, pass it to prepare() method. 
 $sth = $dbh->prepare($sql, $attr);

Since locale settings affect the result of strftime(), if your application is designed to be portable across different locales, you may consider using these two special formats: 'TM' and 'ISO'. "TM" returns a 9-element list, much like Perl's localtime(). The "ISO" format applies sprintf()'s pattern ``%04d-%02d-%02d %02d:%02d:%02d.%04d'' for TIMESTAMP, ``%04d-%02d-%02d'' for DATE, and ``%02d:%02d:%02d.%04d'' for TIME.

"$dbh->{ib_time_all}" can be used to specify all of the three formats at once. Example: 

 $dbh->{ib_time_all} = 'TM';

EVENT ALERT SUPPORT

Event alerter is used to notify client applications whenever something is happened on the database. For this to work, a trigger should be created, which then calls POST_EVENT to post the event notification to the interested client. A client could behave in two ways: wait for the event synchronously, or register a callback which will be invoked asynchronously each time a posted event received.
"ib_init_event"
 $evh = $dbh->func(@event_names, 'ib_init_event');

Creates an event handle from a list of event names.

"ib_wait_event"
 $dbh->func($evh, 'ib_wait_event');

Wait synchronously for particular events registered via event handle $evh. Returns a hashref containing pair(s) of posted event's name and its corresponding count, or undef on failure.

"ib_register_callback"
 my $cb = sub { my $posted_events = $_[0]; ++$::COUNT < 6 };
 $dbh->func($evh, $cb, 'ib_register_callback');
 sub inc_count { my $posted_events = shift; ++$::COUNT < 6 };
 $dbh->func($evh, \&inc_count, 'ib_register_callback');
 # or anonyomus subroutine
 $dbh->func(
   $evh, 
   sub { my ($pe) = @_; ++$::COUNT < 6 }, 
   'ib_register_callback'
 );

Associates an event handle with an asynchronous callback. A callback will be passed a hashref as its argument, this hashref contains pair(s) of posted event's name and its corresponding count.

It is safe to call "ib_register_callback" multiple times for the same event handle. In this case, the previously registered callback will be automatically cancelled.

If the callback returns FALSE, the registered callback will be no longer invoked, but internally it is still there until the event handle goes out of scope (or undef-ed), or you call "ib_cancel_callback" to actually disassociate it from the event handle.

"ib_cancel_callback"
 $dbh->func($evh, 'ib_cancel_callback');

Unregister a callback from an event handle. This function has a limitation, however, that it can't be called from inside a callback. In many cases, you won't need this function, since when an event handle goes out of scope, its associated callback(s) will be automatically cancelled before it is cleaned up.

RETRIEVING FIREBIRD / INTERBASE SPECIFIC INFORMATION

"ib_tx_info"
 $hash_ref = $dbh->func('ib_tx_info');

Retrieve information about current active transaction.

"ib_database_info"
 $hash_ref = $dbh->func(@info, 'ib_database_info');
 $hash_ref = $dbh->func([@info], 'ib_database_info');

Retrieve database information from current connection.

"ib_plan"
 $plan = $sth->func('ib_plan');

Retrieve query plan from a prepared SQL statement. 

 my $sth = $dbh->prepare('SELECT * FROM foo');
 print $sth->func('ib_plan'); # PLAN (FOO NATURAL)
"ib_drop_database"
 $result = $dbh->func('ib_drop_database');

Drops the database, associated with the connection. The database handle is no longer valid after calling this function.

Caution is advised as the drop is irrevocable.

UNSUPPORTED SQL STATEMENTS

Here is a list of SQL statements which can't be used. But this shouldn't be a problem, because their functionality are already provided by the DBI methods.
  • SET TRANSACTION

    Use "$dbh-"func(..., 'set_tx_param')> instead.

  • DESCRIBE

    Provides information about columns that are retrieved by a DSQL statement, or about placeholders in a statement. This functionality is supported by the driver, and transparent for users. Column names are available via $sth->{NAME} attributes.

  • EXECUTE IMMEDIATE

    Calling do() method without bind value(s) will do the same.

  • CLOSE, OPEN, DECLARE CURSOR

    $sth->{CursorName} is automagically available upon executing a ``SELECT .. FOR UPDATE'' statement. A cursor is closed after the last fetch(), or by calling $sth->finish().

  • PREPARE, EXECUTE, FETCH

    Similar functionalities are obtained by using prepare(), execute(), and fetch() methods.

COMPATIBILITY WITH DBIx::* MODULES

"DBD::Firebird" is known to work with "DBIx::Recordset" 0.21, and "Apache::DBI" 0.87. Yuri Vasiliev <[email protected]> reported successful usage with Apache::AuthDBI (part of "Apache::DBI" 0.87 distribution).

The driver is untested with "Apache::Session::DBI". Doesn't work with "Tie::DBI". "Tie::DBI" calls $dbh->prepare(``LISTFIELDS $table_name'') on which Firebird fails to parse. I think that the call should be made within an eval block.

SERVICE METHODS

DBD::Firebird->create_database( { params... } )

A class method for creating empty databases.

The method croaks on error. Params may be:

db_path (string, required)
Path to database, including host name if necessary.

Examples:

server:/path/to/db.fdb
/srv/db/base.fdb
user (string, optional)
User name to be used for the request.
password (string, optional)
Password to be used for the request.
page_size (integer, optional)
Page size of the newly created database. Should be something supported by the server. Firebird 2.5 supports the following page sizes: 1024, 2048, 4096, 8192 and 16384 and defaults to 4096.
character_set (string, optional)
The default character set of the database. Firebird 2.5 defaults to "NONE".
dialect (integer, optional)
The dialect of the database. Defaults to 3.

After creation, the new database can be used after connecting to it with the usual DBI->connect(...)

DBD::Firebird->gfix( { params } )

A class method for simulating a subset of the functionality of the Firebird's gfix(1) utility.

Params is a hash reference, with the following keys:

db_path (string, required)
The path to the database to connect to. Should include host name if necessary.
user (string, optional)
User name to connect as. Must be SYSDBA or database owner.
password (string, optional)
Password to be used for the connection.

Note that user and password are not needed for embedded connections.

forced_writes (boolean, optional)
If given, sets the forced writes flag of the database, causing Firebird to use synchronous writes when working with that database.
buffers (integer, optional)
If given, sets the default number of buffers for the database. Can be overridden on connect time. Note that buffers are measured in database pages, not bytes.

FAQ

Why do some operations performing positioned update and delete fail when AutoCommit is on?

For example, the following code snippet fails: 

 $sth = $dbh->prepare(
 "SELECT * FROM ORDERS WHERE user_id < 5 FOR UPDATE OF comment");
 $sth->execute;
 while (@res = $sth->fetchrow_array) {
     $dbh->do("UPDATE ORDERS SET comment = 'Wonderful' WHERE 
     CURRENT OF $sth->{CursorName}");
 }

When AutoCommit is on, a transaction is started within prepare(), and committed automatically after the last fetch(), or within finish(). Within do(), a transaction is started right before the statement is executed, and gets committed right after the statement is executed. The transaction handle is stored within the database handle. The driver is smart enough not to override an active transaction handle with a new one. So, if you notice the snippet above, after the first fetchrow_array(), the do() is still using the same transaction context, but as soon as it has finished executing the statement, it commits the transaction, whereas the next fetchrow_array() still needs the transaction context!

So the secret to make this work is to keep the transaction open. This can be done in two ways:

  • Using AutoCommit = 0

    If yours is default to AutoCommit on, you can put the snippet within a block: 

     {
     $dbh->{AutoCommit} = 0;
     # same actions like above ....
     $dbh->commit;
 }
  • Using $dbh->{ib_softcommit} = 1

    This is a driver-specific attribute,You may want to look at t/70-nested-sth.t to see it in action.

Why do nested statement handles break under AutoCommit mode?

The same explanation as above applies. The workaround is also much alike: 

 {
     $dbh->{AutoCommit} = 0;
     $sth1 = $dbh->prepare("SELECT * FROM $table");
     $sth2 = $dbh->prepare("SELECT * FROM $table WHERE id = ?");
     $sth1->execute;
     while ($row = $sth1->fetchrow_arrayref) {
        $sth2->execute($row->[0]);
        $res = $sth2->fetchall_arrayref;
     }
     $dbh->commit;
 }

You may also use $dbh->{ib_softcommit} please check t/70nested-sth.t for an example on how to use it.

Why do placeholders fail to bind, generating unknown datatype error message?

You can't bind a field name. The following example will fail: 

 $sth = $dbh->prepare("SELECT (?) FROM $table");
 $sth->execute('user_id');

There are cases where placeholders can't be used in conjunction with COLLATE clause, such as this: 

 SELECT * FROM $table WHERE UPPER(author) LIKE UPPER(? COLLATE FR_CA);

This deals with the Firebird's SQL parser, not with "DBD::Firebird". The driver just passes SQL statements through the engine.

How to do automatic increment for a specific field?

Create a sequence and a trigger to associate it with the field. The following example creates a sequence named PROD_ID_SEQ, and a trigger for table ORDERS which uses the generator to perform auto increment on field PRODUCE_ID with increment size of 1. 

 $dbh->do("create sequence PROD_ID_SEQ");
 $dbh->do(
 "CREATE TRIGGER INC_PROD_ID FOR ORDERS
 BEFORE INSERT POSITION 0
 AS BEGIN
   NEW.PRODUCE_ID = NEXT VALUE FOR PROD_ID_SEQ;
 END");

From Firebird 3.0 there is Identity support

How can I perform LIMIT clause as I usually do in MySQL?

"LIMIT" clause let users to fetch only a portion rather than the whole records as the result of a query. This is particularly efficient and useful for paging feature on web pages, where users can navigate back and forth between pages.

Using Firebird 2.5.x this can be implemented by using "ROWS" . 

 http://www.firebirdsql.org/refdocs/langrefupd21-select.html#langrefupd21-select-rows

For example, to display a portion of table employee within your application: 

 # fetch record 1 - 5:
 $res = $dbh->selectall_arrayref("SELECT * FROM employee rows 1 to 5)");
 # fetch record 6 - 10: 
 $res = $dbh->selectall_arrayref("SELECT * FROM employee rows 6 to 10)");

How can I use the date/time formatting attributes?

Those attributes take the same format as the C function strftime()'s. Examples: 

 $attr = {
    ib_timestampformat => '%m-%d-%Y %H:%M',
    ib_dateformat => '%m-%d-%Y',
    ib_timeformat => '%H:%M',
 };

Then, pass it to prepare() method. 

 $sth = $dbh->prepare($stmt, $attr);
 # followed by execute() and fetch(), or:
 $res = $dbh->selectall_arrayref($stmt, $attr);

Can I set the date/time formatting attributes between prepare and fetch?

No. "ib_dateformat", "ib_timeformat", and "ib_timestampformat" can only be set during $sth->prepare. If this is a problem to you, let me know, and probably I'll add this capability for the next release.

Can I change ib_dialect after DBI->connect ?

No. If this is a problem to you, let me know, and probably I'll add this capability for the next release.

OBSOLETE FEATURES

Private Method
"set_tx_param()" is obsoleted by "ib_set_tx_param()".

TESTED PLATFORMS

Clients

Linux
FreeBSD
Solaris
Win32

Servers

Firebird 2.5.x SS , SC and Classic for Linux (32 bits and 64)
Firebird 2.5.x for Windows, FreeBSD, Solaris

AUTHORS

BUGS/LIMITATIONS

Please report bugs and feature suggestions using http://rt.cpan.org/Public/Dist/Display.html?Name=DBD-Firebird .

This module doesn't work with MSWin32 ActivePerl iThreads, and its emulated fork. Tested with MSWin32 ActivePerl build 809 (Perl 5.8.3). The whole process will block in unpredictable manner.

Under Linux, this module has been tested with several different iThreads enabled Perl releases.

No problem occurred so far.. until you try to share a DBI handle ;-)

But if you plan to use thread, you'd better use the latest stable version of Perl

On FreeBSD you need a Perl compiled with thread support.

Limitations:

  • Arrays are not (yet) supported
  • Read/Write BLOB fields block by block not (yet) supported. The maximum size of a BLOB read/write is hardcoded to about 1 MB.
  • service manager API is not supported.

COPYRIGHT & LICENSE

Copyright (c) 2010- 2012 Popa Adrian Marius <[email protected]>
Copyright (c) 2011- 2012 Stefan Suciu <[email protected]>
Copyright (c) 2011 Damyan Ivanov <[email protected]>
Copyright (c) 2011 Alexandr Ciornii <[email protected]>
Copyright (c) 2010, 2011 Mike Pomraning <[email protected]>
Copyright (c) 1999-2008 Edwin Pratomo
Portions Copyright (c) 2001-2005 Daniel Ritz

The DBD::Firebird module is free software. You may distribute under the terms of either the GNU General Public License or the Artistic License, as specified in the Perl README file.

ACKNOWLEDGEMENTS

An attempt to enumerate all who have contributed patches (may misses some): Michael Moehle, Igor Klingen, Sergey Skvortsov, Ilya Verlinsky, Pavel Zheltouhov, Peter Wilkinson, Mark D. Anderson, Michael Samanov, Michael Arnett, Flemming Frandsen, Mike Shoyher, Christiaan Lademann.

SEE ALSO

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