Provided by: libdbd-sybase-perl_1.14-1build3_amd64 
NAME
DBD::Sybase - Sybase database driver for the DBI module
SYNOPSIS
use DBI;
$dbh = DBI->connect("dbi:Sybase:", $user, $passwd);
# See the DBI module documentation for full details
DESCRIPTION
DBD::Sybase is a Perl module which works with the DBI module to provide access to Sybase
databases.
Connecting to Sybase
The interfaces file
The DBD::Sybase module is built on top of the Sybase Open Client Client Library API. This
library makes use of the Sybase interfaces file (sql.ini on Win32 machines) to make a link
between a logical server name (e.g. SYBASE) and the physical machine / port number that
the server is running on. The OpenClient library uses the environment variable SYBASE to
find the location of the interfaces file, as well as other files that it needs (such as
locale files). The SYBASE environment is the path to the Sybase installation (eg
'/usr/local/sybase'). If you need to set it in your scripts, then you must set it in a
"BEGIN{}" block:
BEGIN {
$ENV{SYBASE} = '/opt/sybase/11.0.2';
}
my $dbh = DBI->connect('dbi:Sybase:', $user, $passwd);
Specifying the server name
The server that DBD::Sybase connects to defaults to SYBASE, but can be specified in two
ways.
You can set the DSQUERY environement variable:
$ENV{DSQUERY} = "ENGINEERING";
$dbh = DBI->connect('dbi:Sybase:', $user, $passwd);
Or you can pass the server name in the first argument to connect():
$dbh = DBI->connect("dbi:Sybase:server=ENGINEERING", $user, $passwd);
Specifying other connection specific parameters
It is sometimes necessary (or beneficial) to specify other connection properties.
Currently the following are supported:
server
Specify the server that we should connect to.
$dbh = DBI->connect("dbi:Sybase:server=BILLING",
$user, $passwd);
The default server is SYBASE, or the value of the $DSQUERY environment variable, if it
is set.
host
port
If you built DBD::Sybase with OpenClient 12.5.1 or later, then you can use the host
and port values to define the server you want to connect to. This will by-pass the
server name lookup in the interfaces file. This is useful in the case where the
server hasn't been entered in the interfaces file.
$dbh = DBI->connect("dbi:Sybase:host=db1.domain.com;port=4100",
$user, $passwd);
maxConnect
By default DBD::Sybase (and the underlying OpenClient libraries) is limited to
openening 25 simultaneous connections to one or more database servers. If you need
more than 25 connections at the same time, you can use the maxConnect option to
increase this number.
$dbh = DBI->connect("dbi:Sybase:maxConnect=100",
$user, $passwd);
database
Specify the database that should be made the default database.
$dbh = DBI->connect("dbi:Sybase:database=sybsystemprocs",
$user, $passwd);
This is equivalent to
$dbh = DBI->connect('dbi:Sybase:', $user, $passwd);
$dbh->do("use sybsystemprocs");
charset
Specify the character set that the client uses.
$dbh = DBI->connect("dbi:Sybase:charset=iso_1",
$user, $passwd);
The default charset used depends on the locale that the application runs in. If you
wish to interact with unicode varaiables (see syb_enable_utf8, below) then you should
set charset=utf8. Note however that this means that Sybase will expect all data sent
to it for char/varchar columns to be encoded in utf8 (e.g. sending iso8859-1
characters like e-grave, etc).
language
Specify the language that the client uses.
$dbh = DBI->connect("dbi:Sybase:language=us_english",
$user, $passwd);
Note that the language has to have been installed on the server (via langinstall or
sp_addlanguage) for this to work. If the language is not installed the session will
default to the default language of the server.
packetSize
Specify the network packet size that the connection should use. Using a larger packet
size can increase performance for certain types of queries. See the Sybase
documentation on how to enable this feature on the server.
$dbh = DBI->connect("dbi:Sybase:packetSize=8192",
$user, $passwd);
interfaces
Specify the location of an alternate interfaces file:
$dbh = DBI->connect("dbi:Sybase:interfaces=/usr/local/sybase/interfaces",
$user, $passwd);
loginTimeout
Specify the number of seconds that DBI->connect() will wait for a response from the
Sybase server. If the server fails to respond before the specified number of seconds
the DBI->connect() call fails with a timeout error. The default value is 60 seconds,
which is usually enough, but on a busy server it is sometimes necessary to increase
this value:
$dbh = DBI->connect("dbi:Sybase:loginTimeout=240", # wait up to 4 minutes
$user, $passwd);
timeout
Specify the number of seconds after which any Open Client calls will timeout the
connection and mark it as dead. Once a timeout error has been received on a connection
it should be closed and re-opened for further processing.
Setting this value to 0 or a negative number will result in an unlimited timeout
value. See also the Open Client documentation on CS_TIMEOUT.
$dbh = DBI->connect("dbi:Sybase:timeout=240", # wait up to 4 minutes
$user, $passwd);
scriptName
Specify the name for this connection that will be displayed in sp_who (ie in the
sysprocesses table in the program_name column).
$dbh=DBI->connect("dbi:Sybase:scriptName=myScript", $user, $password);
hostname
Specify the hostname that will be displayed by sp_who (and will be stored in the
hostname column of sysprocesses)..
$dbh=DBI->connect("dbi:Sybase:hostname=kiruna", $user, $password);
tdsLevel
Specify the TDS protocol level to use when connecting to the server. Valid values are
CS_TDS_40, CS_TDS_42, CS_TDS_46, CS_TDS_495 and CS_TDS_50. In general this is
automatically negotiated between the client and the server, but in certain cases this
may need to be forced to a lower level by the client.
$dbh=DBI->connect("dbi:Sybase:tdsLevel=CS_TDS_42", $user, $password);
NOTE: Setting the tdsLevel below CS_TDS_495 will disable a number of features, ?-style
placeholders and CHAINED non-AutoCommit mode, in particular.
encryptPassword
Specify the use of the client password encryption supported by CT-Lib. Specify a
value of 1 to use encrypted passwords.
$dbh=DBI->connect("dbi:Sybase:encryptPassword=1", $user, $password);
kerberos
Note: Requires OpenClient 11.1.1 or later.
Sybase and OpenClient can use Kerberos to perform network-based login. If you use
Kerberos for authentication you can use this feature and pass a kerberos
serverprincipal using the "kerberos=value" parameter:
$dbh = DBI->connect("dbi:Sybase:kerberos=$serverprincipal", '', '');
In addition, if you have a system for retrieving Kerberos serverprincipals at run-time
you can tell DBD::Sybase to call a perl subroutine to get the serverprincipal from
connect():
sub sybGetPrinc {
my $srv = shift;
return the serverprincipal...
}
$dbh = DBI->connect('dbi:Sybase:server=troll', '', '', { syb_kerberos_serverprincipal => \&sybGetPrinc });
The subroutine will be called with one argument (the server that we will connect to,
using the normal Sybase behavior of checking the DSQUERY environment variable if no
server is specified in the connect()) and is expected to return a string (the Kerberos
serverprincipal) to the caller.
sslCAFile
Specify the location of an alternate trusted.txt file for SSL connection negotiation:
$dbh->DBI->connect("dbi:Sybase:sslCAFile=/usr/local/sybase/trusted.txt.ENGINEERING", $user, $password);
bulkLogin
Set this to 1 if the connection is going to be used for a bulk-load operation (see
Experimental Bulk-Load functionality elsewhere in this document.)
$dbh->DBI->connect("dbi:Sybase:bulkLogin=1", $user, $password);
serverType
Tell DBD::Sybase what the server type is. Defaults to ASE. Setting it to something
else will prevent certain actions (such as setting options, fetching the ASE version
via @@version, etc.) and avoid spurious errors.
tds_keepalive
Set this to 1 to tell OpenClient to enable the KEEP_ALIVE attribute on the connection.
Default 1.
These different parameters (as well as the server name) can be strung together by
separating each entry with a semi-colon:
$dbh = DBI->connect("dbi:Sybase:server=ENGINEERING;packetSize=8192;language=us_english;charset=iso_1",
$user, $pwd);
Handling Multiple Result Sets
Sybase's Transact SQL has the ability to return multiple result sets from a single SQL
statement. For example the query:
select b.title, b.author, s.amount
from books b, sales s
where s.authorID = b.authorID
order by b.author, b.title
compute sum(s.amount) by b.author
which lists sales by author and title and also computes the total sales by author returns
two types of rows. The DBI spec doesn't really handle this situation, nor the more hairy
exec my_proc @p1='this', @p2='that', @p3 out
where "my_proc" could return any number of result sets (ie it could perform an unknown
number of "select" statements.
I've decided to handle this by returning an empty row at the end of each result set, and
by setting a special Sybase attribute in $sth which you can check to see if there is more
data to be fetched. The attribute is syb_more_results which you should check to see if you
need to re-start the "fetch()" loop.
To make sure all results are fetched, the basic "fetch" loop can be written like this:
{
while($d = $sth->fetch) {
... do something with the data
}
redo if $sth->{syb_more_results};
}
You can get the type of the current result set with $sth->{syb_result_type}. This returns
a numerical value, as defined in $SYBASE/$SYBASE_OCS/include/cspublic.h:
#define CS_ROW_RESULT (CS_INT)4040
#define CS_CURSOR_RESULT (CS_INT)4041
#define CS_PARAM_RESULT (CS_INT)4042
#define CS_STATUS_RESULT (CS_INT)4043
#define CS_MSG_RESULT (CS_INT)4044
#define CS_COMPUTE_RESULT (CS_INT)4045
In particular, the return status of a stored procedure is returned as CS_STATUS_RESULT
(4043), and is normally the last result set that is returned in a stored proc execution,
but see the syb_do_proc_status attribute for an alternative way of handling this result
type. See Executing Stored Procedures elsewhere in this document for more information.
If you add a
use DBD::Sybase;
to your script then you can use the symbolic values (CS_xxx_RESULT) instead of the numeric
values in your programs, which should make them easier to read.
See also the "$sth-"syb_output_params> call to handle stored procedures that only return
OUTPUT parameters.
$sth->execute() failure mode behavior
DBD::Sybase has the ability to handle multi-statement SQL commands in a single batch. For
example, you could insert several rows in a single batch like this:
$sth = $dbh->prepare("
insert foo(one, two, three) values(1, 2, 3)
insert foo(one, two, three) values(4, 5, 6)
insert foo(one, two, three) values(10, 11, 12)
insert foo(one, two, three) values(11, 12, 13)
");
$sth->execute;
If any one of the above inserts fails for any reason then $sth->execute will return
"undef", HOWEVER the inserts that didn't fail will still be in the database, unless
"AutoCommit" is off.
It's also possible to write a statement like this:
$sth = $dbh->prepare("
insert foo(one, two, three) values(1, 2, 3)
select * from bar
insert foo(one, two, three) values(10, 11, 12)
");
$sth->execute;
If the second "insert" is the one that fails, then $sth->execute will NOT return "undef".
The error will get flagged after the rows from "bar" have been fetched.
I know that this is not as intuitive as it could be, but I am constrained by the Sybase
API here.
As an aside, I know that the example above doesn't really make sense, but I need to
illustrate this particular sequence... You can also see the t/fail.t test script which
shows this particular behavior.
Sybase Specific Attributes
There are a number of handle attributes that are specific to this driver. These
attributes all start with syb_ so as to not clash with any normal DBI attributes.
Database Handle Attributes
The following Sybase specific attributes can be set at the Database handle level:
syb_show_sql (bool)
If set then the current statement is included in the string returned by $dbh->errstr.
syb_show_eed (bool)
If set, then extended error information is included in the string returned by
$dbh->errstr. Extended error information include the index causing a duplicate insert
to fail, for example.
syb_err_handler (subroutine ref)
This attribute is used to set an ad-hoc error handler callback (ie a perl subroutine)
that gets called before the normal error handler does it's job. If this subroutine
returns 0 then the error is ignored. This is useful for handling PRINT statements in
Transact-SQL, for handling messages from the Backup Server, showplan output, dbcc
output, etc.
The subroutine is called with nine parameters:
o the Sybase error number
o the severity
o the state
o the line number in the SQL batch
o the server name (if available)
o the stored procedure name (if available)
o the message text
o the current SQL command buffer
o either of the strings "client" (for Client Library errors) or
"server" (for server errors, such as SQL syntax errors, etc),
allowing you to identify the error type.
As a contrived example, here is a port of the distinct error and message handlers from
the Sybase documentation:
Example:
sub err_handler {
my($err, $sev, $state, $line, $server,
$proc, $msg, $sql, $err_type) = @_;
my @msg = ();
if($err_type eq 'server') {
push @msg,
('',
'Server message',
sprintf('Message number: %ld, Severity %ld, State %ld, Line %ld',
$err,$sev,$state,$line),
(defined($server) ? "Server '$server' " : '') .
(defined($proc) ? "Procedure '$proc'" : ''),
"Message String:$msg");
} else {
push @msg,
('',
'Open Client Message:',
sprintf('Message number: SEVERITY = (%ld) NUMBER = (%ld)',
$sev, $err),
"Message String: $msg");
}
print STDERR join("\n",@msg);
return 0; ## CS_SUCCEED
}
In a simpler and more focused example, this error handler traps showplan messages:
%showplan_msgs = map { $_ => 1} (3612 .. 3615, 6201 .. 6299, 10201 .. 10299);
sub err_handler {
my($err, $sev, $state, $line, $server,
$proc, $msg, $sql, $err_type) = @_;
if($showplan_msgs{$err}) { # it's a showplan message
print SHOWPLAN "$err - $msg\n";
return 0; # This is not an error
}
return 1;
}
and this is how you would use it:
$dbh = DBI->connect('dbi:Sybase:server=troll', 'sa', '');
$dbh->{syb_err_handler} = \&err_handler;
$dbh->do("set showplan on");
open(SHOWPLAN, ">>/var/tmp/showplan.log") || die "Can't open showplan log: $!";
$dbh->do("exec someproc"); # get the showplan trace for this proc.
$dbh->disconnect;
NOTE - if you set the error handler in the DBI->connect() call like this
$dbh = DBI->connect('dbi:Sybase:server=troll', 'sa', '',
{ syb_err_handler => \&err_handler });
then the err_handler() routine will get called if there is an error during
the connect itself. This is new behavior in DBD::Sybase 0.95.
syb_flush_finish (bool)
If $dbh->{syb_flush_finish} is set then $dbh->finish will drain any results remaining
for the current command by actually fetching them. The default behaviour is to issue
a ct_cancel(CS_CANCEL_ALL), but this appears to cause connections to hang or to fail
in certain cases (although I've never witnessed this myself.)
syb_dynamic_supported (bool)
This is a read-only attribute that returns TRUE if the dataserver you are connected to
supports ?-style placeholders. Typically placeholders are not supported when using
DBD::Sybase to connect to a MS-SQL server.
syb_chained_txn (bool)
If set then we use CHAINED transactions when AutoCommit is off. Otherwise we issue an
explicit BEGIN TRAN as needed. The default is on if it is supported by the server.
This attribute should usually be used only during the connect() call:
$dbh = DBI->connect('dbi:Sybase:', $user, $pwd, {syb_chained_txn => 1});
Using it at any other time with AutoCommit turned off will force a commit on the
current handle.
syb_quoted_identifier (bool)
If set, then identifiers that would normally clash with Sybase reserved words can be
quoted using "identifier". In this case strings must be quoted with the single quote.
This attribute can only be set if the database handle is idle (no active statement
handle.)
Default is for this attribute to be off.
syb_rowcount (int)
Setting this attribute to non-0 will limit the number of rows returned by a SELECT, or
affected by an UPDATE or DELETE statement to the rowcount value. Setting it back to 0
clears the limit.
This attribute can only be set if the database handle is idle.
Default is for this attribute to be 0.
syb_do_proc_status (bool)
Setting this attribute causes $sth->execute() to fetch the return status of any
executed stored procs in the SQL being executed. If the return status is non-0 then
$sth->execute() will report that the operation failed.
NOTE The result status is NOT the first result set that is fetched from a stored proc
execution. If the procedure includes SELECT statements then these will be fetched
first, which means that "$sth-"execute> will NOT return a failure in that case as
DBD::Sybase won't have seen the result status yet at that point.
The RaiseError will NOT be triggered by a non-0 return status if there isn't an
associated error message either generated by Sybase (duplicate insert error, etc) or
generated in the procedure via a T-SQL "raiserror" statement.
Setting this attribute does NOT affect existing $sth handles, only those that are
created after setting it. To change the behavior of an existing $sth handle use
$sth->{syb_do_proc_status}.
The proc status is available in $sth->{syb_proc_status} after all the result sets in
the procedure have been processed.
The default is for this attribute to be off.
syb_use_bin_0x
If set, BINARY and VARBINARY values are prefixed with '0x' in the result. The default
is off.
syb_binary_images
If set, IMAGE data is returned in raw binary format. Otherwise the data is converted
to a long hex string. The default is off.
syb_oc_version (string)
Returns the identification string of the version of Client Library that this binary is
currently using. This is a read-only attribute.
For example:
troll (7:59AM):348 > perl -MDBI -e '$dbh = DBI->connect("dbi:Sybase:", "sa"); print "$dbh->{syb_oc_version}\n";'
Sybase Client-Library/11.1.1/P/Linux Intel/Linux 2.2.5 i586/1/OPT/Mon Jun 7 07:50:21 1999
This is very useful information to have when reporting a problem.
syb_server_version
syb_server_version_string
These two attributes return the Sybase server version, respectively version string,
and can be used to turn server-specific functionality on or off.
Example:
print "$dbh->{syb_server_version}\n$dbh->{syb_server_version_string}\n";
prints
12.5.2
Adaptive Server Enterprise/12.5.2/EBF 12061 ESD#2/P/Linux Intel/Enterprise Linux/ase1252/1844/32-bit/OPT/Wed Aug 11 21:36:26 2004
syb_failed_db_fatal (bool)
If this is set, then a connect() request where the database specified doesn't exist or
is not accessible will fail. This needs to be set in the attribute hash passed during
the DBI->connect() call to be effective.
Default: off
syb_no_child_con (bool)
If this attribute is set then DBD::Sybase will not allow multiple simultaneously
active statement handles on one database handle (i.e. multiple $dbh->prepare() calls
without completely processing the results from any existing statement handle). This
can be used to debug situations where incorrect or unexpected results are found due to
the creation of a sub-connection where the connection attributes (in particular the
current database) are different.
Default: off
syb_bind_empty_string_as_null (bool)
If this attribute is set then an empty string (i.e. "") passed as a parameter to an
$sth->execute() call will be converted to a NULL value. If the attribute is not set
then an empty string is converted to a single space.
Default: off
syb_cancel_request_on_error (bool)
If this attribute is set then a failure in a multi-statement request (for example, a
stored procedure execution) will cause $sth->execute() to return failure, and will
cause any other results from this request to be discarded.
The default value (on) changes the behavior that DBD::Sybase exhibited up to version
0.94.
Default: on
syb_date_fmt (string)
Defines the date/time conversion string when fetching data. See the entry for the
"syb_date_fmt()" method elsewhere in this document for a description of the available
formats.
syb_has_blk (bool)
This read-only attribute is set to TRUE if the BLK API is available in this version of
DBD::Sybase.
syb_disconnect_in_child (bool)
Sybase client library allows using opened connections across a fork (i.e. the opened
connection can be used in the child process). DBI by default will set flags such that
this connection will be closed when the child process terminates. This is in most
cases not what you want. DBI provides the InactiveDestroy attribute to control this,
but you have to set this attribute manually as it defaults to False (i.e. when DESTROY
is called for the handle the connection is closed). The syb_disconnect_in_child
attribute attempts to correct this - the default is for this attribute to be False -
thereby inhibitting the closing of the connection(s) when the current process ID
doesn't match the process ID that created the connection.
Default: off
syb_enable_utf8 (bool)
If this attribute is set then DBD::Sybase will convert UNIVARCHAR, UNICHAR, and
UNITEXT data to Perl's internal utf-8 encoding when they are retrieved. Updating a
unicode column will cause Sybase to convert any incoming data from utf-8 to its
internal utf-16 encoding.
This feature requires OpenClient 15.x to work.
Default: off
Statement Handle Attributes
The following read-only attributes are available at the statement level:
syb_more_results (bool)
See the discussion on handling multiple result sets above.
syb_result_type (int)
Returns the numeric result type of the current result set. Useful when executing
stored procedurs to determine what type of information is currently fetchable (normal
select rows, output parameters, status results, etc...).
syb_do_proc_status (bool)
See above (under Database Handle Attributes) for an explanation.
syb_proc_status (read-only)
If syb_do_proc_status is set, then the return status of stored procedures will be
available via $sth->{syb_proc_status}.
syb_no_bind_blob (bool)
If set then any IMAGE or TEXT columns in a query are NOT returned when calling
$sth->fetch (or any variation).
Instead, you would use
$sth->syb_ct_get_data($column, \$data, $size);
to retrieve the IMAGE or TEXT data. If $size is 0 then the entire item is fetched,
otherwis you can call this in a loop to fetch chunks of data:
while(1) {
$sth->syb_ct_get_data($column, \$data, 1024);
last unless $data;
print OUT $data;
}
The fetched data is still subject to Sybase's TEXTSIZE option (see the SET command in
the Sybase reference manual). This can be manipulated with DBI's LongReadLen
attribute, but "$dbh-"{LongReadLen}> must be set before $dbh->prepare() is called to
take effect (this is a change in 1.05 - previously you could call it after the
prepare() but before the execute()). Note that LongReadLen has no effect when using
DBD::Sybase with an MS-SQL server.
Note: The IMAGE or TEXT column that is to be fetched this way must be last in the
select list.
See also the description of the ct_get_data() API call in the Sybase OpenClient
manual, and the "Working with TEXT/IMAGE columns" section elsewhere in this document.
Controlling DATETIME output formats
By default DBD::Sybase will return DATETIME and SMALLDATETIME columns in the Nov 15 1998
11:13AM format. This can be changed via a private syb_date_fmt() method.
The syntax is
$dbh->syb_date_fmt($fmt);
where $fmt is a string representing the format that you want to apply.
Note that this requires DBI 1.37 or later.
The formats are based on Sybase's standard conversion routines. The following subset of
available formats has been implemented:
LONG
Nov 15 1998 11:30:11:496AM
LONGMS
New with ASE 15.5 - for bigtime/bigdatetime datatypes, includes microseconds:
Apr 7 2010 10:40:33.532315PM
SHORT
Nov 15 1998 11:30AM
DMY4_YYYY
15 Nov 1998
MDY1_YYYY
11/15/1998
DMY1_YYYY
15/11/1998
DMY2_YYYY
15.11.1998
YMD3_YYYY
19981115
HMS 11:30:11
ISO 2004-08-21 14:36:48.080
ISO_strict
2004-08-21T14:36:48.080Z
Note that Sybase has no concept of a timezone, so the trailing "Z" is really not
correct (assumes that the time is in UTC). However, there is no guarantee that the
client and the server run in the same timezone, so assuming the timezone of the client
isn't really a valid option either.
Retrieving OUTPUT parameters from stored procedures
Sybase lets you pass define OUTPUT parameters to stored procedures, which are a little
like parameters passed by reference in C (or perl.)
In Transact-SQL this is done like this
declare @id_value int, @id_name char(10)
exec my_proc @name = 'a string', @number = 1234, @id = @id_value OUTPUT, @out_name = @id_name OUTPUT
-- Now @id_value and @id_name are set to whatever 'my_proc' set @id and @out_name to
So how can we get at @param using DBD::Sybase?
If your stored procedure only returns OUTPUT parameters, then you can use this shorthand:
$sth = $dbh->prepare('...');
$sth->execute;
@results = $sth->syb_output_params();
This will return an array for all the OUTPUT parameters in the proc call, and will ignore
any other results. The array will be undefined if there are no OUTPUT params, or if the
stored procedure failed for some reason.
The more generic way looks like this:
$sth = $dbh->prepare("declare \@id_value int, \@id_name
exec my_proc @name = 'a string', @number = 1234, @id = @id_value OUTPUT, @out_name = @id_name OUTPUT");
$sth->execute;
{
while($d = $sth->fetch) {
if($sth->{syb_result_type} == 4042) { # it's a PARAM result
$id_value = $d->[0];
$id_name = $d->[1];
}
}
redo if $sth->{syb_more_results};
}
So the OUTPUT params are returned as one row in a special result set.
Multiple active statements on one $dbh
It is possible to open multiple active statements on a single database handle. This is
done by opening a new physical connection in $dbh->prepare() if there is already an active
statement handle for this $dbh.
This feature has been implemented to improve compatibility with other drivers, but should
not be used if you are coding directly to the Sybase driver.
The "syb_no_child_con" attribute controls whether this feature is turned on. If it is
FALSE (the default), then multiple statement handles are supported. If it is TRUE then
multiple statements on the same database handle are disabled. Also see below for
interaction with AutoCommit.
If AutoCommit is OFF then multiple statement handles on a single $dbh is NOT supported.
This is to avoid various deadlock problems that can crop up in this situation, and because
you will not get real transactional integrity using multiple statement handles
simultaneously as these in reality refer to different physical connections.
Working with IMAGE and TEXT columns
DBD::Sybase can store and retrieve IMAGE or TEXT data (aka "blob" data) via standard SQL
statements. The LongReadLen handle attribute controls the maximum size of IMAGE or TEXT
data being returned for each data element.
When using standard SQL the default for IMAGE data is to be converted to a hex string, but
you can use the syb_binary_images handle attribute to change this behaviour. Alternatively
you can use something like
$binary = pack("H*", $hex_string);
to do the conversion.
IMAGE and TEXT datatypes can not be passed as parameters using ?-style placeholders, and
placeholders can't refer to IMAGE or TEXT columns (this is a limitation of the TDS
protocol used by Sybase, not a DBD::Sybase limitation.)
There is an alternative way to access and update IMAGE/TEXT data using the natice
OpenClient API. This is done via $h->func() calls, and is, unfortunately, a little
convoluted.
Handling IMAGE/TEXT data with syb_ct_get_data()/syb_ct_send_data()
With DBI 1.37 and later you can call all of these ct_xxx() calls directly as statement
handle methods by prefixing them with syb_, so for example
$sth->func($col, $dataref, $numbytes, 'ct_fetch_data');
becomes
$sth->syb_ct_fetch_data($col, $dataref, $numbytes);
$len = ct_fetch_data($col, $dataref, $numbytes)
The ct_get_data() call allows you to fetch IMAGE/TEXT data in raw format, either in
one piece or in chunks. To use this function you must set the syb_no_bind_blob
statement handle to TRUE.
ct_get_data() takes 3 parameters: The column number (starting at 1) of the query, a
scalar ref and a byte count. If the byte count is 0 then we read as many bytes as
possible.
Note that the IMAGE/TEXT column must be last in the select list for this to work.
The call sequence is:
$sth = $dbh->prepare("select id, img from some_table where id = 1");
$sth->{syb_no_bind_blob} = 1;
$sth->execute;
while($d = $sth->fetchrow_arrayref) {
# The data is in the second column
$len = $sth->syb_ct_get_data(2, \$img, 0);
# with DBI 1.33 and earlier, this would be
# $len = $sth->func(2, \$img, 0, 'ct_get_data');
}
ct_get_data() returns the number of bytes that were effectively fetched, so that when
fetching chunks you can do something like this:
while(1) {
$len = $sth->syb_ct_get_data(2, $imgchunk, 1024);
... do something with the $imgchunk ...
last if $len != 1024;
}
To explain further: Sybase stores IMAGE/TEXT data separately from normal table data,
in a chain of pagesize blocks (a Sybase database page is defined at the server level,
and can be 2k, 4k, 8k or 16k in size.) To update an IMAGE/TEXT column Sybase needs to
find the head of this chain, which is known as the "text pointer". As there is no
where clause when the ct_send_data() API is used we need to retrieve the text pointer
for the correct data item first, which is done via the ct_data_info(CS_GET) call.
Subsequent ct_send_data() calls will then know which data item to update.
$status = ct_data_info($action, $column, $attr)
ct_data_info() is used to fetch or update the CS_IODESC structure for the IMAGE/TEXT
data item that you wish to update. $action should be one of "CS_SET" or "CS_GET",
$column is the column number of the active select statement (ignored for a CS_SET
operation) and $attr is a hash ref used to set the values in the struct.
ct_data_info() must be first called with CS_GET to fetch the CS_IODESC structure for
the IMAGE/TEXT data item that you wish to update. Then you must update the value of
the total_txtlen structure element to the length (in bytes) of the IMAGE/TEXT data
that you are going to insert, and optionally set the log_on_update to TRUE to enable
full logging of the operation.
ct_data_info(CS_GET) will fail if the IMAGE/TEXT data for which the CS_IODESC is being
fetched is NULL. If you have a NULL value that needs updating you must first update it
to some non-NULL value (for example an empty string) using standard SQL before you can
retrieve the CS_IODESC entry. This actually makes sense because as long as the data
item is NULL there is no text pointer and no TEXT page chain for that item.
See the ct_send_data() entry below for an example.
ct_prepare_send()
ct_prepare_send() must be called to initialize a IMAGE/TEXT write operation. See the
ct_send_data() entry below for an example.
ct_finish_send()
ct_finish_send() is called to finish/commit an IMAGE/TEXT write operation. See the
ct_send_data() entry below for an example.
ct_send_data($image, $bytes)
Send $bytes bytes of $image to the database. The request must have been set up via
ct_prepare_send() and ct_data_info() for this to work. ct_send_data() returns TRUE on
success, and FALSE on failure.
In this example, we wish to update the data in the img column where the id column is
1. We assume that DBI is at version 1.37 or later and use the direct method calls:
# first we need to find the CS_IODESC data for the data
$sth = $dbh->prepare("select img from imgtable where id = 1");
$sth->execute;
while($sth->fetch) { # don't care about the data!
$sth->syb_ct_data_info('CS_GET', 1);
}
# OK - we have the CS_IODESC values, so do the update:
$sth->syb_ct_prepare_send();
# Set the size of the new data item (that we are inserting), and make
# the operation unlogged
$sth->syb_ct_data_info('CS_SET', 1, {total_txtlen => length($image), log_on_update => 0});
# now transfer the data (in a single chunk, this time)
$sth->syb_ct_send_data($image, length($image));
# commit the operation
$sth->syb_ct_finish_send();
The ct_send_data() call can also transfer the data in chunks, however you must know
the total size of the image before you start the insert. For example:
# update a database entry with a new version of a file:
my $size = -s $file;
# first we need to find the CS_IODESC data for the data
$sth = $dbh->prepare("select img from imgtable where id = 1");
$sth->execute;
while($sth->fetch) { # don't care about the data!
$sth->syb_ct_data_info('CS_GET', 1);
}
# OK - we have the CS_IODESC values, so do the update:
$sth->syb_ct_prepare_send();
# Set the size of the new data item (that we are inserting), and make
# the operation unlogged
$sth->syb_ct_data_info('CS_SET', 1, {total_txtlen => $size, log_on_update => 0});
# open the file, and store it in the db in 1024 byte chunks.
open(IN, $file) || die "Can't open $file: $!";
while($size) {
$to_read = $size > 1024 ? 1024 : $size;
$bytesread = read(IN, $buff, $to_read);
$size -= $bytesread;
$sth->syb_ct_send_data($buff, $bytesread);
}
close(IN);
# commit the operation
$sth->syb_ct_finish_send();
AutoCommit, Transactions and Transact-SQL
When $h->{AutoCommit} is off all data modification SQL statements that you issue
(insert/update/delete) will only take effect if you call $dbh->commit.
DBD::Sybase implements this via two distinct methods, depending on the setting of the
$h->{syb_chained_txn} attribute and the version of the server that is being accessed.
If $h->{syb_chained_txn} is off, then the DBD::Sybase driver will send a BEGIN TRAN before
the first $dbh->prepare(), and after each call to $dbh->commit() or $dbh->rollback(). This
works fine, but will cause any SQL that contains any CREATE TABLE (or other DDL)
statements to fail. These CREATE TABLE statements can be burried in a stored procedure
somewhere (for example, "sp_helprotect" creates two temp tables when it is run). You can
get around this limit by setting the "ddl in tran" option (at the database level, via
"sp_dboption".) You should be aware that this can have serious effects on performance as
this causes locks to be held on certain system tables for the duration of the transaction.
If $h->{syb_chained_txn} is on, then DBD::Sybase sets the CHAINED option, which tells
Sybase not to commit anything automatically. Again, you will need to call $dbh->commit()
to make any changes to the data permanent.
Behavior of $dbh->last_insert_id
This version of DBD::Sybase includes support for the last_insert_id() call, with the
following caveats:
The last_insert_id() call is simply a wrapper around a "select @@identity" query. To be
successful (i.e. to return the correct value) this must be executed on the same connection
as the INSERT that generated the new IDENTITY value. Therefore the statement handle that
was used to perform the insert must have been closed/freed before last_insert_id() can be
called. Otherwise last_insert_id() will be forced to open a different connection to
perform the query, and will return an invalid value (usually in this case it will return
0).
last_insert_id() ignores any parameters passed to it, and will NOT return the last
@@identity value generated in the case where placeholders were used, or where the insert
was encapsulated in a stored procedure.
Using ? Placeholders & bind parameters to $sth->execute
DBD::Sybase supports the use of ? placeholders in SQL statements as long as the underlying
library and database engine supports it. It does this by using what Sybase calls Dynamic
SQL. The ? placeholders allow you to write something like:
$sth = $dbh->prepare("select * from employee where empno = ?");
# Retrieve rows from employee where empno == 1024:
$sth->execute(1024);
while($data = $sth->fetch) {
print "@$data\n";
}
# Now get rows where empno = 2000:
$sth->execute(2000);
while($data = $sth->fetch) {
print "@$data\n";
}
When you use ? placeholders Sybase goes and creates a temporary stored procedure that
corresponds to your SQL statement. You then pass variables to $sth->execute or $dbh->do,
which get inserted in the query, and any rows are returned.
DBD::Sybase uses the underlying Sybase API calls to handle ?-style placeholders. For
select/insert/update/delete statements DBD::Sybase calls the ct_dynamic() family of Client
Library functions, which gives DBD::Sybase data type information for each parameter to the
query.
You can only use ?-style placeholders for statements that return a single result set, and
the ? placeholders can only appear in a WHERE clause, in the SET clause of an UPDATE
statement, or in the VALUES list of an INSERT statement.
The DBI docs mention the following regarding NULL values and placeholders:
Binding an `undef' (NULL) to the placeholder will not
select rows which have a NULL `product_code'! Refer to the
SQL manual for your database engine or any SQL book for
the reasons for this. To explicitly select NULLs you have
to say "`WHERE product_code IS NULL'" and to make that
general you have to say:
... WHERE (product_code = ? OR (? IS NULL AND product_code IS NULL))
and bind the same value to both placeholders.
This will not work with a Sybase database server. If you attempt the above construct you
will get the following error:
The datatype of a parameter marker used in the dynamic prepare statement could not be
resolved.
The specific problem here is that when using ? placeholders the prepare() operation is
sent to the database server for parameter resoltion. This extracts the datatypes for each
of the placeholders. Unfortunately the "? is null" construct doesn't tie the ? placeholder
with an existing table column, so the database server can't find the data type. As this
entire operation happens inside the Sybase libraries there is no easy way for DBD::Sybase
to work around it.
Note that Sybase will normally handle the "foo = NULL" construct the same way that other
systems handle "foo is NULL", so the convoluted construct that is described above is not
necessary to obtain the correct results when querying a Sybase database.
The underlying API does not support ?-style placeholders for stored procedures, but see
the section on titled Stored Procedures and Placeholders elsewhere in this document.
?-style placeholders can NOT be used to pass TEXT or IMAGE data items to the server. This
is a limitation of the TDS protocol, not of DBD::Sybase.
There is also a performance issue: OpenClient creates stored procedures in tempdb for each
prepare() call that includes ? placeholders. Creating these objects requires updating
system tables in the tempdb database, and can therefore create a performance hotspot if a
lot of prepare() statements from multiple clients are executed simultaneously. This
problem has been corrected for Sybase 11.9.x and later servers, as they create
"lightweight" temporary stored procs which are held in the server memory cache and don't
affect the system tables at all.
In general however I find that if your application is going to run against Sybase it is
better to write ad-hoc stored procedures rather than use the ? placeholders in embedded
SQL.
Out of curiosity I did some simple timings to see what the overhead of doing a prepare
with ? placehoders is vs. a straight SQL prepare and vs. a stored procedure prepare.
Against an 11.0.3.3 server (linux) the placeholder prepare is significantly slower, and
you need to do ~30 execute() calls on the prepared statement to make up for the overhead.
Against a 12.0 server (solaris) however the situation was very different, with placeholder
prepare() calls slightly faster than straight SQL prepare(). This is something that I
really don't understand, but the numbers were pretty clear.
In all cases stored proc prepare() calls were clearly faster, and consistently so.
This test did not try to gauge concurrency issues, however.
It is not possible to retrieve the last IDENTITY value after an insert done with ?-style
placeholders. This is a Sybase limitation/bug, not a DBD::Sybase problem. For example,
assuming table foo has an identity column:
$dbh->do("insert foo(col1, col2) values(?, ?)", undef, "string1", "string2");
$sth = $dbh->prepare('select @@identity')
|| die "Can't prepare the SQL statement: $DBI::errstr";
$sth->execute || die "Can't execute the SQL statement: $DBI::errstr";
#Get the data back.
while (my $row = $sth->fetchrow_arrayref()) {
print "IDENTITY value = $row->[0]\n";
}
will always return an identity value of 0, which is obviously incorrect. This behaviour
is due to the fact that the handling of ?-style placeholders is implemented using
temporary stored procedures in Sybase, and the value of @@identity is reset when the
stored procedure has executed. Using an explicit stored procedure to do the insert and
trying to retrieve @@identity after it has executed results in the same behaviour.
Please see the discussion on Dynamic SQL in the OpenClient C Programmer's Guide for
details. The guide is available on-line at http://sybooks.sybase.com/
Calling Stored Procedures
DBD::Sybase handles stored procedures in the same way as any other Transact-SQL statement.
The only real difference is that Sybase stored procedures always return an extra result
set with the return status from the proc which corresponds to the return statement in the
stored procedure code. This result set with a single row is always returned last and has a
result type of CS_STATUS_RESULT (4043).
By default this result set is returned like any other, but you can ask DBD::Sybase to
process it under the covers via the $h->{syb_do_proc_status} attribute. If this attribute
is set then DBD::Sybase will process the CS_STATUS_RESULT result set itself, place the
return status value in $sth->{syb_proc_status}, and possibly raise an error if the result
set is different from 0. Note that a non-0 return status will NOT cause $sth->execute to
return a failure code if the proc has at least one other result set that returned rows
(reason: the rows are returned and fetched before the return status is seen).
Stored Procedures and Placeholders
DBD::Sybase has the ability to use ?-style placeholders as parameters to stored proc
calls. The requirements are that the stored procedure call be initiated with an "exec" and
that it be the only statement in the batch that is being prepared():
For example, this prepares a stored proc call with named parameters:
my $sth = $dbh->prepare("exec my_proc \@p1 = ?, \@p2 = ?");
$sth->execute('one', 'two');
You can also use positional parameters:
my $sth = $dbh->prepare("exec my_proc ?, ?");
$sth->execute('one', 'two');
You may not mix positional and named parameter in the same prepare.
You can't mix placeholder parameters and hard coded parameters. For example
$sth = $dbh->prepare("exec my_proc \@p1 = 1, \@p2 = ?");
will not work - because the @p1 parameter isn't parsed correctly and won't be sent to the
server.
You can specify OUTPUT parameters in the usual way, but you can NOT use bind_param_inout()
to get the output result - instead you have to call fetch() and/or
$sth->func('syb_output_params'):
my $sth = $dbh->prepare("exec my_proc \@p1 = ?, \@p2 = ?, \@p3 = ? OUTPUT ");
$sth->execute('one', 'two', 'three');
my (@data) = $sth->syb_output_params();
DBD::Sybase does not attempt to figure out the correct parameter type for each parameter
(it would be possible to do this for most cases, but there are enough exceptions that I
preferred to avoid the issue for the time being). DBD::Sybase defaults all the parameters
to SQL_CHAR, and you have to use bind_param() with an explicit type value to set this to
something different. The type is then remembered, so you only need to use the explicit
call once for each parameter:
my $sth = $dbh->prepare("exec my_proc \@p1 = ?, \@p2 = ?");
$sth->bind_param(1, 'one', SQL_CHAR);
$sth->bind_param(2, 2.34, SQL_FLOAT);
$sth->execute;
....
$sth->execute('two', 3.456);
etc...
Note that once a type has been defined for a parameter you can't change it.
When binding SQL_NUMERIC or SQL_DECIMAL data you may get fatal conversion errors if the
scale or the precision exceeds the size of the target parameter definition.
For example, consider the following stored proc definition:
declare proc my_proc @p1 numeric(5,2) as...
and the following prepare/execute snippet:
my $sth = $dbh->prepare("exec my_proc \@p1 = ?");
$sth->bind_param(1, 3.456, SQL_NUMERIC);
This generates the following error:
DBD::Sybase::st execute failed: Server message number=241 severity=16 state=2 line=0
procedure=dbitest text=Scale error during implicit conversion of NUMERIC value '3.456' to
a NUMERIC field.
You can tell Sybase (and DBD::Sybase) to ignore these sorts of errors by setting the
arithabort option:
$dbh->do("set arithabort off");
See the set command in the Sybase Adaptive Server Enterprise Reference Manual for more
information on the set command and on the arithabort option.
Other Private Methods
DBD::Sybase private Database Handle Methods
$bool = $dbh->syb_isdead
Tests the connection to see if the connection has been marked DEAD by OpenClient. The
connection can get marked DEAD if an error occurs on the connection, or the connection
fails.
DBD::Sybase private Statement Handle Methods
@data = $sth->syb_describe([$assoc])
Retrieves the description of each of the output columns of the current result set.
Each element of the returned array is a reference to a hash that describes the column.
The following fields are set: NAME, TYPE, SYBTYPE, MAXLENGTH, SCALE, PRECISION,
STATUS.
You could use it like this:
my $sth = $dbh->prepare("select name, uid from sysusers");
$sth->execute;
my @description = $sth->syb_describe;
print "$description[0]->{NAME}\n"; # prints name
print "$description[0]->{MAXLENGTH}\n"; # prints 30
....
while(my $row = $sth->fetch) {
....
}
The STATUS field is a string which can be tested for the following values:
CS_CANBENULL, CS_HIDDEN, CS_IDENTITY, CS_KEY, CS_VERSION_KEY, CS_TIMESTAMP and
CS_UPDATABLE. See table 3-46 of the Open Client Client Library Reference Manual for a
description of each of these values.
The TYPE field is the data type that Sybase::CTlib converts the column to when
retrieving the data, so a DATETIME column will be returned as a CS_CHAR_TYPE column.
The SYBTYPE field is the real Sybase data type for this column.
Note that the symbolic values of the CS_xxx symbols isn't available yet in
DBD::Sybase.
Experimental Bulk-Load Functionality
NOTE: This feature requires that the libblk.a library be available at build time. This is
not always the case if the Sybase SDK isn't installed. You can test the
$dbh->{syb_has_blk} attribute to see if the BLK api calls are available in your copy of
DBD::Sybase.
Starting with release 1.04.2 DBD::Sybase has the ability to use Sybase's BLK (bulk-
loading) API to perform fast data loads. Basic usage is as follows:
my $dbh = DBI->connect('dbi:Sybase:server=MY_SERVER;bulkLogin=1', $user, $pwd);
$dbh->begin_work; # optional.
my $sth = $dbh->prepare("insert the_table values(?, ?, ?, ?, ?)",
{syb_bcp_attribs => { identity_flag => 0,
identity_column => 0 }}});
while(<DATA>) {
chomp;
my @row = split(/\|/, $_); # assume a pipe-delimited file...
$sth->execute(@row);
}
$dbh->commit;
print "Sent ", $sth->rows, " to the server\n";
$sth->finish;
First, you need to specify the new bulkLogin attribute in the connection string, which
turns on the CS_BULK_LOGIN property for the connection. Without this property the BLK api
will not be functional.
You call $dbh->prepare() with a regular INSERT statement and the special syb_bcp_attribs
attribute to turn on BLK handling of the data. The identity_flag sub-attribute can be set
to 1 if your source data includes the values for the target table's IDENTITY column. If
the target table has an IDENTITY column but you want the insert operation to generate a
new value for each row then leave identity_flag at 0, but set identity_col to the column
number of the identity column (it's usually the first column in the table, but not
always.)
The number of placeholders in the INSERT statement must correspond to the number of
columns in the table, and the input data must be in the same order as the table's physical
column order. Any column list in the INSERT statement (i.e. insert table(a, b, c,...)
values(...) is ignored.
The value of AutoCommit is ignored for BLK operations - rows are only commited when you
call $dbh->commit.
You can call $dbh->rollback to cancel any uncommited rows, but this also cancels the rest
of the BLK operation: any attempt to load rows to the server after a call to
$dbh->rollback() will fail.
If a row fails to load due to a CLIENT side error (such as a data conversion error) then
$sth->execute() will return a failure (i.e. false) and $sth->errstr will have the reason
for the error.
If a row fails on the SERVER side (for example due to a duplicate row error) then the
entire batch (i.e. between two $dbh->commit() calls) will fail. This is normal behavior
for BLK/bcp.
The Bulk-Load API is very sensitive to data conversion issues, as all the conversions are
handled on the client side, and the row is pre-formatted before being sent to the server.
By default any conversion that is flagged by Sybase's cs_convert() call will result in a
failed row. Some of these conversion errors are patently fatal (e.g. converting 'Feb 30
2001' to a DATETIME value...), while others are debatable (e.g. converting 123.456 to a
NUMERIC(6,2) which results in a loss of precision). The default behavior of failing any
row that has a conversion error in it can be modified by using a special error handler.
Returning 0 from this handler tells DBD::Sybase to fail this row, and returning 1 means
that we still want to try to send the row to the server (obviously Sybase's internal code
can still fail the row at that point.) You set the handler like this:
DBD::Sybase::syb_set_cslib_cb(\&handler);
and a sample handler:
sub cslib_handler {
my ($layer, $origin, $severity, $errno, $errmsg, $osmsg, $blkmsg) = @_;
print "Layer: $layer, Origin: $origin, Severity: $severity, Error: $errno\n";
print $msg;
print $osmsg if($osmsg);
print $blkmsg if $blkmsg;
return 1 if($errno == 36)
return 0;
}
Please see the t/xblk.t test script for some examples.
Reminder - this is an experimental implementation. It may change in the future, and it
could be buggy.
Using DBD::Sybase with MS-SQL
MS-SQL started out as Sybase 4.2, and there are still a lot of similarities between Sybase
and MS-SQL which makes it possible to use DBD::Sybase to query a MS-SQL dataserver using
either the Sybase OpenClient libraries or the FreeTDS libraries (see
http://www.freetds.org).
However, using the Sybase libraries to query an MS-SQL server has certain limitations. In
particular ?-style placeholders are not supported (although support when using the FreeTDS
libraries is possible in a future release of the libraries), and certain syb_ attributes
may not be supported.
Sybase defaults the TEXTSIZE attribute (aka LongReadLen) to 32k, but MS-SQL 7 doesn't seem
to do that correctly, resulting in very large memory requests when querying tables with
TEXT/IMAGE data columns. The work-around is to set TEXTSIZE to some decent value via
$dbh->{LongReadLen} (if that works - I haven't had any confirmation that it does) or via
$dbh->do("set textsize <somesize>");
nsql
The nsql() call is a direct port of the function of the same name that exists in
Sybase::DBlib. From 1.08 it has been extended to offer new functionality.
Usage:
@data = $dbh->func($sql, $type, $callback, $options, 'nsql');
If the DBI version is 1.37 or later, then you can also call it this way:
@data = $dbh->syb_nsql($sql, $type, $callback, $options);
This executes the query in $sql, and returns all the data in @data. The $type parameter
can be used to specify that each returned row be in array form (i.e. $type passed as
'ARRAY', which is the default) or in hash form ($type passed as 'HASH') with column names
as keys.
If $callback is specified it is taken as a reference to a perl sub, and each row returned
by the query is passed to this subroutine instead of being returned by the routine (to
allow processing of large result sets, for example).
If $options is specified and is a HASH ref, the following keys affect the value returned
by nsql():
oktypes => [...]
This generalises syb_nsql_nostatus (see below) by ignoring any result sets which are
of a type not listed.
bytype => 0|1|'merge'
If this option is set to a true value, each result set will be returned as the value
of a hash, the key of which is the result type of this result set as defined by the
CS_*_TYPE values described above. If the special value 'merge' is used, result sets of
the same type will be catenated (as nsql() does by default) into a single array of
results and the result of the nsql() call will be a single hash keyed by result type.
Usage is better written %data = $dbh->syb_nsql(...) in this case.
arglist => [...]
This option provides support for placeholders in the SQL query passed to nsql(). Each
time the SQL statement is executed the array value of this option will be passed as
the parameter list to the execute() method.
Note that if $callback is omitted, a hash reference in that parameter position will be
interpreted as an option hash if no hash reference is found in the $options parameter
position.
"nsql" also checks three special attributes to enable deadlock retry logic (Note none of
these attributes have any effect anywhere else at the moment):
syb_deadlock_retry count
Set this to a non-0 value to enable deadlock detection and retry logic within nsql().
If a deadlock error is detected (error code 1205) then the entire batch is re-
submitted up to syb_deadlock_retry times. Default is 0 (off).
syb_deadlock_sleep seconds
Number of seconds to sleep between deadlock retries. Default is 60.
syb_deadlock_verbose (bool)
Enable verbose logging of deadlock retry logic. Default is off.
syb_nsql_nostatus (bool)
If true then stored procedure return status values (i.e. results of type
CS_STATUS_RESULT) are ignored.
Deadlock detection will be added to the $dbh->do() method in a future version of
DBD::Sybase.
Multi-Threading
DBD::Sybase is thread-safe (i.e. can be used in a multi-threaded perl application where
more than one thread accesses the database server) with the following restrictions:
· perl version >= 5.8
DBD::Sybase requires the use of ithreads, available in the perl 5.8.0 release. It will
not work with the older 5.005 threading model.
· Sybase thread-safe libraries
Sybase's Client Library comes in two flavors. DBD::Sybase must find the thread-safe
version of the libraries (ending in _r on Unix/linux). This means Open Client 11.1.1
or later. In particular this means that you can't use the 10.0.4 libraries from the
free 11.0.3.3 release on linux if you want to use multi-threading.
Note: when using perl >= 5.8 with the thread-safe libraries (libct_r.so, etc) then
signal handling is broken and any signal delivered to the perl process will result in
a segmentation fault. It is recommended in that case to link with the non-threadsafe
libraries.
· use DBD::Sybase
You must include the "use DBD::Sybase;" line in your program. This is needed because
DBD::Sybase needs to do some setup before the first thread is started.
You can check to see if your version of DBD::Sybase is thread-safe at run-time by calling
DBD::Sybase::thread_enabled(). This will return true if multi-threading is available.
See t/thread.t for a simple example.
BUGS
You can run out of space in the tempdb database if you use a lot of calls with bind
variables (ie ?-style placeholders) without closing the connection and Sybase 11.5.x or
older. This is because Sybase creates stored procedures for each prepare() call. In
11.9.x and later Sybase will create "light-weight" stored procedures which don't use up
any space in the tempdb database.
The primary_key_info() method will only return data for tables where a declarative
"primary key" constraint was included when the table was created.
I have a simple bug tracking database at http://www.peppler.org/bugdb/ . You can use it
to view known problems, or to report new ones.
SEE ALSO
DBI
Sybase OpenClient C manuals.
Sybase Transact SQL manuals.
AUTHOR
DBD::Sybase by Michael Peppler
COPYRIGHT
The DBD::Sybase module is Copyright (c) 1996-2007 Michael Peppler. The DBD::Sybase module
is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.
ACKNOWLEDGEMENTS
Tim Bunce for DBI, obviously!
See also "ACKNOWLEDGEMENTS" in DBI.
POD ERRORS
Hey! The above document had some coding errors, which are explained below:
Around line 2005:
Non-ASCII character seen before =encoding in 'DEAD if'. Assuming UTF-8