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DBIx::Class::MigrationUserQContributed Perl DocuDBIx::Class::Migration::FAQ(3)

       DBIx::Class::Migration::FAQ - Answers to	Frequently Asked Questions

When I run the commandline, I see a lot	of debugging output
	   SV =	IV(0x7fb4e24dc858) at 0x7fb4e24dc868
	     REFCNT = 1
	     RV	= 0x7fb4e0b0ddf8
	       SV = PVHV(0x7fb4e24c48a0) at 0x7fb4e0b0ddf8
		 REFCNT	= 1
		 STASH = 0x7fb4e2174a80	       "DBI::db"
		 ARRAY = 0x0
		 KEYS =	0
		 FILL =	0
		 MAX = 7
		 RITER = -1

       There's some debugging code somewhere in	the
       DBIx::Class::DeploymentHandler dependency chain.	 We've looked and
       can't find it :(	 A case	of beer	at the next YAPC we meet at to whoever
       can figure it out.

       Although	if you see this, there's nothing wrong.	 The command will work
       as in the documentation.	 The only issue	is that	if there's a lot of
       debugging scroll	by, you	might need to page up in your terminal to
       catch any real error messages.

       UPDATE:	I recieved an email from a contributor who has code dived a
       bit and possibly	narrowed down the issue.  I thought to report that
       stuff here.  When SQLT::Parser::DBIx::Class attempts to serialize
       schemas that are	connected it trys to serialize the connect object
       information.  This doesn't play so nice with the	way the	YAML
       serializer works, since it does try hard	to serialize objects.

       UPDATE: This may	be fixed in recent updates to the DBIC ecosystem.  If
       you are seeing this try upgraded	DBIC and SQLT and see if it goes away.

       UPDATE:	You really should not be seeing	this anymore, if you are, and
       you're on the lastest DBIC and related, please let me know.

       Contributing to the project is easy.  First you'd fork the project over
       at Github (<>), clone
       the repo	down to	your work environment and install project

	   cpanm Dist::Zilla
	   (dzil authordeps; dzil listdeps) |

       You should first	have a Modern Perl setup, including local::lib.	 If
       you need	help installing	Perl and getting started, please take a	look
       at the Learning Perl website: <>

       If Test::Postgresql58 fails to install, you are probably	running	with
       parallel	testing. Try this:

	     cpanm Test::Postgresql58)

       I realize Dist::Zilla seems to invoke feelings on nearly	religious
       vigor (both for and against).  After considering	the options I felt
       using it, but carefully constraining the	use of plugins to the default
       set was a better	option than what I've done on other projects, which is
       to have a custom	wrapper	on top of Module::Install (you can peek	at
       that if you want	over here: <>).	 I've
       decided I'd rather not continue to spend	my limited time	dealing	with
       dependency and installation management tools, when there's a rational
       solution	that many people already embrace available. The	only other
       option is to continue to	build and maintain code	for this purpose that
       nobody else uses, and possibly nobody else understands.

       If a better option with equal or	greater	maturity and community
       acceptance emerges, I'll	entertain changing.

       If the requirement of typing "cpanm Dist::Zilla"	and using the "dzil"
       command line tool for a limited number of build jobs prevents you from
       contributing, I think you are unreasonably stubborn.

       If you do contribute to the project, please be aware that I'm not
       likely to accept	patches	that include significant changes to the	way
       I'm using Dist::Zilla, including	using plugins to weave pod,
       automagically guess dependencies	and generate tests.  I'd prefer	to
       stick to	the most simple	and standard Perl practices for	building and
       installing code for the present.

I don't	want my	database sandbox files in my source control repository
       Having the database sandboxes automatically created in the "share"
       directory is a nice feature, but	can clutter your repository history.
       You really don't	need that in the source	control, since installing and
       controlling your	database is something each developer who checks	out
       the project should do.

       If you are using	"git" you can modify your ".gitignore".	 If you
       sandbox is "share/myapp-schema.db" or (if you are using the mysql or
       postgresql sandboxes) "share/myapp-schema/" you can add these lines to
       your ".gitignore"


       Other source control systems have similiar approaches (recipes welcome
       for sharing).

What's the command to run migrations on	an existing database?
	   dbic-migration -Ilib	status \
	     --dsn="DBI:mysql:database=test;host=;port=5142" \
	     --user msandbox \
	     --password	msandbox

       Would be	the general approach.

Error: Trouble creating	a MySQL	Sandbox	when running AppArmor
       Its been	reported that the developer database sandboxing	feature
       doens't work properly when using	AppArmor.  I guess AppArmor considers
       this a security violation.  Currently I don't have a reported
       workaround other	than to	just disable AppArmor, which for developer
       level machines may or may not be	a problem.

       Here's some symptoms of this problem, if	you think you may be having

       In "/var/log/syslog" something like:

	   kernel: [18593519.090601] type=1503 audit(1281847667.413:22):
	   operation="inode_permission"	requested_mask="::r" denied_mask="::r"
	   fsuid=0 name="/etc/mysql0/my.cnf" pid=4884 profile="/usr/sbin/mysqld"

       If you need AppArmor, you'll have to setup and install MySQL the	'old
       school way.'

Error: "Failed to find share dir for dist..."
       You didn't specify a custom "--target_dir" but forgot to	make the
       "/share"	directory in your project application root.

       By default we expect to find a "/share" directory in your primary
       project root directory (contains	your "Makefile.PL" or "dist.ini", and
       the "lib" and "t" directories for example) where	we will	create
       migrations.  At this time we can't automatically	create this "/share"
       directory in the	same way we can	create all the migration files and
       directory for you.  You need to create that directory yourself:

	   mkdir share

       Patches to fix this, or suggestions welcomed.

How to run a Migration Script before changing the Schema
       If you need to run a Migration Perl Script before the SQL Changes are
       applied to your Database, you have to name your Upgrade Files properly.


       Migration will run the upgrades by the Numbers, no matter in which
       Upgrade Folder they are specified.

Can I use this even if I don't want to use DBIx::Class?
       Not everyone loves using	an ORM.	 Personally I've found DBIx::Class to
       be the only ORM that gets enough	out of my way that I prefer it over
       plain SQL, and I	highly recommend you give it a go.  However if you
       don't want to, or can not convince your fellow programers (yet :) ),
       here's one way to still use this	migrations and fixtures	system.
       Strictly	speaking, we are still using DBIx::Class behind	the scenes,
       just you	don't have to know about it or use it.

       You use a subclass of DBIx::Class::Schema::Loader in a namespace	for
       your application, like:

	   package MyApp::Schema;

	   use strict;
	   use warnings;

	   use base 'DBIx::Class::Schema::Loader';

	   our $VERSION	= 1;

	   __PACKAGE__->loader_options(	);


       You'd put that in "lib/MyApp/" along with your other
       application code.  then just use	"MyApp::Schema"	as is discussed	in the
       documentation.  This will dynamically build a schema for	you, as	long
       as you set the schema arguments to connect to your actual database.
       Then everytime someone changes the database you just up the $VERSION
       and take	it from	there.	Obviously this is a bit	more manual effort,
       but at least you	can have the ability to	populate to any	given version,
       manage fixtures,	do some	sane testing, etc.  Maybe you'll even be able
       to convince people to try out DBIx::Class!

       By the way, if you wanted, you can always dump the generated version of
       your classes using "make_schema"	(see "make_schema" in
       DBIx::Class::Migration and "make_schema"	in

I am using MySQL and when the migration	fails, it doesn't ROLLBACK
       That's because MySQL does not support transaction DDL.  Even if you
       have a transaction, MySQL will silently COMMIT when it bumps into some

I need to dump fixtures	from a existing	database
       You don't always	have the luxury	of building a new database from	the
       start.  For example, you	may have an existing database that you want to
       start to	create migrations for.	In this	case you probably want to dump
       some data directly from that existing database in order to create
       fixtures	for testing or for seeding a new database.

       DBIx::Class::Migration will let you run the "dump_all_sets" and
       "dump_named_sets" commands against an unversioned database.  For

	   dbic-migration -Ilib	-SMyApp::Schema	dump_all_sets /
	     --dsn="dbi:mysql:database=myapp;host=;port=3306"	/
	     --username	johnn /
	     --password	$PASSWORD

       In this case let's say
       "dbi:mysql:database=myapp;host=;port=3306" is a database that
       you've been managing manually and it has	some data that is useful for
       creating	your fixture sets.

       When you	run these commands against an unversioned database you will be
       warned because we have no way of	being sure what	version	of the fixture
       sets you	should be dumping.  We will just assume	that whatever the
       Schema version is, is correct.  This can	of course lead to bad or
       undumpable fixtures should your Schema and the unversioned DB not match
       properly.  Buyer	beware!

How do I specify the character set for a database or table?
       Specifying the default character	set for	the whole database should be
       done when initially creating the	database, which	is outside the scope
       of DBIx::Class::Migration. Remember that	the default character set of
       the whole database will still show in the properties of individual
       tables if the table does	not have its own specified.

       To specify the character	set of an individual table, use
       sqlt_deploy_hook	{} in the DBIC result source:

	 sub sqlt_deploy_hook {
	   my ($self, $sqlt_table) = @_;
	   $sqlt_table->options({'DEFAULT CHARACTER SET' => 'utf8'});

Error: "`' is not a module name"
       Sorry this error	is vague and I am working on a fix.  You will get this
       if you have failed to provide a "schema_class", either by setting it
       with the	-S or -schema_class commandline	option flag:

	   dbic-migration -Ilib	-SMyApp::Schema
	   dbic-migration -Ilib	--schema_class MyApp::Schema

       or by exporting the %ENV:


       Or, if you have a custom	version	of DBIx::Class::Migration::Script as
       discussed in the	tutorial, you are not providing	a good "schema_class"

Error: "Attribute (schema_class) does not pass the type	constraint"
       You probably forgot to include your project "lib" directory in the Perl
       search path.  The easiest way to	fix this is to use the "I" or "lib"
       command line: option flag:

	   dbic-migration -Ilib	-SMyApp::Schema	[command]

When using the Postgresql Sandbox, I get "FATAL: could not create shared
       memory segment"
       There will be more like this:

	   FATAL:  could not create shared memory segment: Cannot allocate memory
	   DETAIL:  Failed system call was shmget(key=1, size=2138112, 03600).
	   HINT:  This error usually means that	PostgreSQL's request for a shared memory
	   segment exceeded available memory or	swap space, or exceeded	your kernel's
	   SHMALL parameter.  You can either reduce the	request	size or	reconfigure
	   the kernel with larger SHMALL.  To reduce the request size (currently 2138112
	   bytes), reduce PostgreSQL's shared memory usage, perhaps by reducing
	   shared_buffers or max_connections.

       The solution is as presented.  Since I prefer not to change my system
       settings	permanently, just add the following to a little	bash script in
       my application

	   sudo	sysctl -w kern.sysv.shmall=65536
	   sudo	sysctl -w kern.sysv.shmmax=16777216

       I don't know enough about Postgresql to know if the above settings are
       good, but they work for my testing.  Corrections	very welcome!  Ideally
       I'd try to find a way to	offer a	patch to Test::Postgresql58, although
       this seems to be	limited	to people using	Macs.

How to Release
       Here's the release steps	I currently use, should	I eventually find
       willing comainters:

       Update Version
	   You need to increment the version in	"dist.ini" and in

       Prepare Changes file
	   Update the "Changes"	file.  It would	be ideal to have been adding
	   to this as you've gone along, but you should	double check.

       Update Author's list
	   If there have been new contributors,	be sure	to give	credit

       Rebuild the README
	       pod2markdown < lib/DBIx/Class/ > README.mkdn

	   This	will make sure the "README.mkdn" file in the project root
	   matches the most recent updates.

       Check your tests
	       AUTHOR_MODE=1 prove -lvr	t

       Update the repository
	       git add @stuff_to_add
	       git commit -m $message
	       git push

       Make the	Distribution
	       dzil release
	       dzil clean

       Update the git version tag
	   I usually don't update and push the tag until we are	on CPAN.

	       git tag $VERSION	-m 'cpan release'
	       git push	--tags

       See DBIx::Class::Migration for author information

       See DBIx::Class::Migration for copyright	and license information

perl v5.32.1			  2019-03-24	DBIx::Class::Migration::FAQ(3)

NAME | When I run the commandline, I see a lot of debugging output | Contributing | Dist::Zilla? | I don't want my database sandbox files in my source control repository | What's the command to run migrations on an existing database? | Error: Trouble creating a MySQL Sandbox when running AppArmor | Error: "Failed to find share dir for dist..." | How to run a Migration Script before changing the Schema | Can I use this even if I don't want to use DBIx::Class? | I am using MySQL and when the migration fails, it doesn't ROLLBACK | I need to dump fixtures from a existing database | How do I specify the character set for a database or table? | Error: "`' is not a module name" | Error: "Attribute (schema_class) does not pass the type constraint" | When using the Postgresql Sandbox, I get "FATAL: could not create shared | How to Release | AUTHOR | COPYRIGHT & LICENSE

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