Perl Dbi Error Handling
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Go to comments The DBI module lets you handle errors yourself if you don't like its built-in behavior. DBI lets you handle the errors at perl dbi execute return value either the database or the statement handle level by specifying attributes: my $dbh
Perl Dbi Connect Error Handling
= DBI->connect( ..., ..., \%attr ); my $sth = $dbh->prepare( ..., \%attr ); There are several attributes that affect error perl dbi handleerror handling, each of which you can use with either a connection or a statement handle: Attribute Type Default PrintWarn Boolean On PrintError Boolean On RaiseError Boolean Off HandleError Code Ref Off ShowErrorStatement
Perl Dbi Errstr
Boolean Off These attributes are inherited by anything derived from the handle where you set them. The PrintWarn and PrintError attributes do just what they say. They are on by default, and they don't stop your program. In this example, you prepare a statement that expects one bind parameter, but when you execute it, you give two parameters instead: use DBI; my $dbh = DBI->connect( 'dbi:SQLite:dbname=test.db', perl dbi try catch '', '', {} ); my $sth = $dbh->prepare( 'SELECT * FROM Cats WHERE id = ?' ); $sth->execute( 1, 2 ); while( my @row = $sth->fetchrow_array ) { print "row: @row\n"; } print "Got to the end\n"; Since PrintError is true by default, DBI prints the error, but it allows the program to continue even though there was an error: DBD::SQLite::st execute failed: called with 2 bind variables when 1 are needed at dbi-test.pl line 12. Got to the end If you set the ShowErrorStatement attribute, you get a better error message because DBI appends the SQL statement that you tried to execute. You can set this either database handle or the statement handle, but if you don't know which statement is causing the problem, it's easier to set it as part of the database handle: # The rest of the program is the same my $dbh = DBI->connect( 'dbi:SQLite:dbname=test.db', '', '', { ShowErrorStatement => 1, } ); The error message shows the SQL statement, but the program still continues: DBD::SQLite::st execute failed: called with 2 bind variables when 1 are needed [for Statement "SELECT * FROM Cats WHERE id = ?"] at dbi-tes
native database engine error message from the last DBI method called. $h->state()Returns a state code in the standard SQLSTATE five character format The above three methods deal with error messages. DBI dynamic attributeDescription $DBI::errEquivalent
Dbi Error Fatal
to $h->err() $DBI::errstrEquivalent to $h->errstr() $DBI::stateEquivalent to $h->state() The second table gives a list
Try Catch In Perl
of DBI dynamic attributes, which are related to error handling. These attributes have a short lifespan. They should be used immediately dbi err fatal after the method that might cause an error. Default error handling By default, the errors are returned by Perl DBI methods. #!/usr/bin/perl use strict; use DBI; my $dsn = "dbi:SQLite:dbname=test.db"; my $user = ''; https://www.effectiveperlprogramming.com/2010/07/set-custom-dbi-error-handlers/ my $password = ''; my $dbh = DBI->connect($dsn, $user, $password) or die "Can't connect to database: $DBI::errstr"; my $sth = $dbh->prepare( q{ SELECT Id, Name, Price FROM Cars } ) or die "Can't prepare statement: $DBI::errstr"; my $rc = $sth->execute() or die "Can't execute statement: $DBI::errstr"; while (my($id, $name, $price) = $sth->fetchrow()) { print "$id $name $price\n"; } # check for problems which may have terminated the fetch early http://zetcode.com/db/sqliteperltutorial/err/ warn $DBI::errstr if $DBI::err; $sth->finish(); $dbh->disconnect(); In the first script we deal with the default behaviour of returning error codes. my $dbh = DBI->connect($dsn, $user, $password) or die "Can't connect to database: $DBI::errstr"; We call the connect() method to create a database connection. If the attempt fails, the method returns undef and sets both $DBI::err and $DBI::errstr attributes. The die() method prints the error message in case of a failure and terminates the script. my $sth = $dbh->prepare( q{ SELECT Id, Name, Price FROM Cars } ) or die "Can't prepare statement: $DBI::errstr"; We call the prepare() statement. If the method fails, the die() method prints an error message and terminates the script. my $rc = $sth->execute() or die "Can't execute statement: $DBI::errstr"; Again. We call the execute() method and check for errors. The method returns undef if it fails. warn $DBI::errstr if $DBI::err; We check for problems which may have terminated the fetch method early. Raising exceptions Checking for errors each time we call a DBI method may be tedious. We could easily forget to do so if we have a larger script. The preferred way of dealing with possible errors is to raise exceptions. To raise exceptions, we set the RaiseError attribute to
Related Modules Rose::DB::Object DBIx::Class Class::DBI more... By perlmonks.org http://search.cpan.org/perldoc?DBI CPAN RT New 14 Open 11 Stalled 4 View/Report Bugs Module Version: 1.636 Source NAME SYNOPSIS GETTING http://www.easysoft.com/developer/languages/perl/dbi-debugging.html HELP General Mailing Lists IRC Online Reporting a Bug NOTES DESCRIPTION Architecture of a DBI Application Notation and Conventions Outline perl dbi Usage General Interface Rules & Caveats Naming Conventions and Name Space SQL - A Query Language Placeholders and Bind Values THE DBI PACKAGE AND CLASS DBI Constants DBI Class Methods parse_dsn connect connect_cached available_drivers installed_drivers installed_versions data_sources trace visit_handles DBI perl dbi error Utility Functions data_string_desc data_string_diff data_diff neat neat_list looks_like_number hash sql_type_cast DBI Dynamic Attributes $DBI::err $DBI::errstr $DBI::state $DBI::rows $DBI::lasth METHODS COMMON TO ALL HANDLES err errstr state set_err trace trace_msg func can parse_trace_flags parse_trace_flag private_attribute_info swap_inner_handle visit_child_handles ATTRIBUTES COMMON TO ALL HANDLES Warn Active Executed Kids ActiveKids CachedKids Type ChildHandles CompatMode InactiveDestroy AutoInactiveDestroy PrintWarn PrintError RaiseError HandleError HandleSetErr ErrCount ShowErrorStatement TraceLevel FetchHashKeyName ChopBlanks LongReadLen LongTruncOk TaintIn TaintOut Taint Profile ReadOnly Callbacks private_your_module_name_* DBI DATABASE HANDLE OBJECTS Database Handle Methods clone data_sources do last_insert_id selectrow_array selectrow_arrayref selectrow_hashref selectall_arrayref selectall_array selectall_hashref selectcol_arrayref prepare prepare_cached commit rollback begin_work disconnect ping get_info table_info column_info primary_key_info primary_key foreign_key_info statistics_info tables type_info_all type_info quote quote_identifier take_imp_data Database Handle Attributes AutoCommit Driver Name Statement RowCacheSiz
Check the returns from DBI callsRaiseErrorTest inserts/updates workedProtect calls you expect could legitimately fail with evalsUse transactions, protect them with eval and commit or roll them back after the evalConsider adding comments to SQLWhat you get in DBI out of the box to help youDBIx::Log4perl Advantages of using DBIx::Log4perlWhere to get DBIx::Log4perlDBIx::Log4perl dependenciesDBIx::Log4perl documentationDBIx::Log4perl quick startExample DBIx::Log4perl outputCatching errors with DBIx::Log4perlAdding additional error logging to your Perl scriptLog4perl configuration fileChanging the default logging in DBIx::Log4perlLogging only SQL and parametersAppendix A: ResourcesIntroductionYou’ve read our other Perl tutorials, installed Perl DBI and a DBD and have started writing your application but it is not working properly. What can you do? This tutorial ignores syntax errors in your Perl (which you can easily track down with perl -cw) and concentrates on locating those tough to find SQL, incorrect use of the DBI interface, transaction and logic errors.Good DBI programming practiseCheck the returns from DBI callsTest the return from DBI method calls return a success value. DBI->connect("dbi:ODBC:mydsn", "xxx", "yyy") or die "$DBI::errstr"; Normally this is a true and non-zero value, but in some cases it is a true but zero value e.g. DBDs will return a true value for an insert operation that inserts zero rows, but if you know the insert should insert a row, you test the returned value is true and not "0E0" (which is true but zero). See the next section, "RaiseError" and "Test inserts worked".RaiseErrorThe handle attribute RaiseError is, by default, turned off. When the RaiseError attribute is turned on for a handle, it causes die to be called (or your HandleError routine) when an error occurs using DBI. If you turn RaiseError on in the DBI connect method, it will be inherited by all other handles created off that connection handle.Without RaiseError, the following code (by default) will print the error (because PrintError is on by default) but not cause your program to die: use DBI; $dbh = DBI->connect("dbi:ODBC:mydsn","xxx", "yyy"); $sth = $dbh->prepare("invalid sql"); $sth->execute; print "Got here without dying\n"; which when run, by default, prints an error saying your SQL is invalid but does not die, so your program continues making it difficult to track down where the error occurred or worse, compounding the problem, b