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sqitchtutorial-oracle(User Contributed Perl Documentatsqitchtutorial-oracle(3)

Name
       sqitchtutorial-oracle - A tutorial introduction to Sqitch change
       management on Oracle

Synopsis
	 sqitch	*

Description
       This tutorial explains how to create a sqitch-enabled Oracle project,
       use a VCS for deployment	planning, and work with	other developers to
       make sure changes remain	in sync	and in the proper order.

       We'll start by creating new project from	scratch, a fictional
       antisocial networking site called Flipr.	All examples use Git
       <http://git-scm.com/> as	the VCS	and Oracle
       <http://www.oracle.com/us/products/database/> as	the storage engine.
       Note that you will need to set $ORACLE_HOME
       <http://www.orafaq.com/wiki/ORACLE_HOME>	so that	all the	database
       connections will	work.

       If you'd	like to	manage an PostgreSQL database, see sqitchtutorial.

       If you'd	like to	manage an SQLite database, see sqitchtutorial-sqlite.

       If you'd	like to	manage an MySQL	database, see sqitchtutorial-mysql.

       If you'd	like to	manage an Firebird database, see sqitchtutorial-
       firebird.

       If you'd	like to	manage an Vertica database, see	sqitchtutorial-
       vertica.

   VM Configuration
       Some instructions for setting up	a VM for following along in this
       tutorial.

       o   See t/oracle.t for instructions on downloading, installing, and
	   configuring the Oracle developer days VM.

       o   Connect as the DBA via SQL*Plus:

	     sqlplus sys/oracle@localhost/ORCL as sysdba

       o   Give	user "scott" the access	it needs:

	     ALTER USER	scott IDENTIFIED BY tiger;
	     GRANT ALL PRIVILEGES TO scott;

       o   Add this entry to tnsnames.ora:

	     FLIPR_TEST	=
	       (DESCRIPTION =
		 (ADDRESS = (PROTOCOL =	TCP)(HOST = localhost)(PORT = 1521))
		 (CONNECT_DATA =
		   (SERVER = DEDICATED)
		   (SERVICE_NAME = orcl)
		 )
	       )

Starting a New Project
       Usually the first thing to do when starting a new project is to create
       a source	code repository. So let's do that with Git:

	 > mkdir flipr
	 > cd flipr
	 > git init .
	 Initialized empty Git repository in /flipr/.git/
	 > touch README.md
	 > git add .
	 > git commit -am 'Initialize project, add README.'
	 [master (root-commit) 1bd134b]	Initialize project, add	README.
	  1 file changed, 38 insertions(+)
	  create mode 100644 README.md

       If you're a Git user and	want to	follow along the history, the
       repository used in these	examples is on GitHub
       <https://github.com/theory/sqitch-oracle-intro>.

       Now that	we have	a repository, let's get	started	with Sqitch. Every
       Sqitch project must have	a name associated with it, and,	optionally, a
       unique URI. We recommend	including the URI, as it increases the
       uniqueness of object identifiers	internally, so let's specify one when
       we initialize Sqitch:

	 > sqitch init flipr --uri https://github.com/theory/sqitch-oracle-intro/ --engine oracle
	 Created sqitch.conf
	 Created sqitch.plan
	 Created deploy/
	 Created revert/
	 Created verify/

       Let's have a look at sqitch.conf:

	 > cat sqitch.conf
	 [core]
	       engine =	oracle
	       # plan_file = sqitch.plan
	       # top_dir = .
	 # [engine "oracle"]
	       # target	= db:oracle:
	       # registry =
	       # client	= /usr/local/instantclient_11_2/sqlplus

       Good, it	picked up on the fact that we're creating changes for the
       Oracle engine, thanks to	the "-engine oracle" option, and saved it to
       the file.  Furthermore, it wrote	a commented-out	"[engine "oracle"]"
       section with all	the available Oracle engine-specific settings
       commented out and ready to be edited as appropriate. This includes the
       path to SQL*Plus	<http://www.orafaq.com/wiki/SQL*Plus> in my
       $ORACLE_HOME.

       By default, Sqitch will read sqitch.conf	in the current directory for
       settings. But it	will also read ~/.sqitch/sqitch.conf for user-specific
       settings. Let's tell it who we are, since this data will	be used	in all
       of our projects:

	 > sqitch config --user	user.name 'Marge N. OXVera'
	 > sqitch config --user	user.email 'marge@example.com'

       Have a look at ~/.sqitch/sqitch.conf and	you'll see this:

	 > cat ~/.sqitch/sqitch.conf
	 [user]
	       name = Marge N. OXVera
	       email = marge@example.com

       Which means that	Sqitch will always properly identify us	when planning
       and committing changes. Back to the repository. Have a look at the plan
       file, sqitch.plan:

	 > cat sqitch.plan
	 %syntax-version=1.0.0
	 %project=flipr
	 %uri=https://github.com/theory/sqitch-oracle-intro/

       Note that it has	picked up on the name and URI of the app we're
       building.  Sqitch uses this data	to manage cross-project	dependencies.
       The "%syntax-version" pragma is always set by Sqitch, so	that it	always
       knows how to parse the plan, even if the	format changes in the future.

       Let's commit these changes and start creating the database changes.

	 > git add .
	 > git commit -am 'Initialize Sqitch configuration.'
	 [master bd82f41] Initialize Sqitch configuration.
	  2 files changed, 19 insertions(+)
	  create mode 100644 sqitch.conf
	  create mode 100644 sqitch.plan

Our First Change
       First, our project will need an Oracle user and accompanying schema.
       This creates a nice namespace for all of	the objects that will be part
       of the flipr app. Run this command:

	 > sqitch add appschema	-n 'App	user and schema	for all	flipr objects.'
	 Created deploy/appschema.sql
	 Created revert/appschema.sql
	 Created verify/appschema.sql
	 Added "appschema" to sqitch.plan

       The "add" command adds a	database change	to the plan and	writes deploy,
       revert, and verify scripts that represent the change. Now we edit these
       files. The "deploy" script's job	is to create the user. So we add this
       to deploy/appschema.sql:

	 CREATE	USER flipr IDENTIFIED BY whatever;

       The "revert" script's job is to precisely revert	the change to the
       deploy script, so we add	this to	revert/appschema.sql:

	 DROP USER flipr;

       Now we can try deploying	this change. We'll assume you have an Oracle
       SID named "flipr_test" set up in	your
       "TNSNAMES.ORA|http://www.orafaq.com/wiki/Tnsnames.ora" file:

	 > sqitch deploy db:oracle://scott:tiger@/flipr_test
	 Adding	registry tables	to db:oracle://scott:@/flipr_test
	 Deploying changes to db:oracle://scott:@/flipr_test
	   + appschema .. ok

       First Sqitch created the	registry tables	used to	track database
       changes.	The structure and name of the registry varies between
       databases, but in Oracle	they are simply	stored in the current schema
       -- that is, the schema with the same name as the	user you've connected
       as. In this example, that schema	is "scott". Ideally, only Sqitch data
       will be stored in this schema, so it probably makes the most sense to
       create a	superuser named	"sqitch" or something similar and use it to
       deploy changes.

       If you'd	like it	to use a different database as the registry database,
       use "sqitch engine add oracle $name" to configure it (or	via the
       "target"	command; more below). This will	be useful if you don't want to
       use the same registry database to manage	multiple databases on the same
       server.

       Next, Sqitch deploys changes to the target database, which we specified
       on the command-line. We only have one change so far; the	"+" reinforces
       the idea	that the change	is being added to the database.

       With this change	deployed, if you connect to the	database, you'll be
       able to see the schema:

	 > echo	"SELECT	username FROM all_users	WHERE username = 'FLIPR';" \
	 | sqlplus -S scott/tiger@flipr_test
	 USERNAME
	 ------------------------------
	 FLIPR

   Trust, But Verify
       But that's too much work. Do you	really want to do something like that
       after every deploy?

       Here's where the	"verify" script	comes in. Its job is to	test that the
       deploy did was it was supposed to. It should do so without regard to
       any data	that might be in the database, and should throw	an error if
       the deploy was not successful. In Oracle, the simplest way to do	so for
       schema is probably to simply create an object in	the schema. Put	this
       SQL into	verify/appschema.sql:

	 CREATE	TABLE flipr.verify__ (id int);
	 DROP	TABLE flipr.verify__;

       In truth, you can use any query that generates an SQL error if the
       schema doesn't exist. This works	because	Sqitch configures SQL*Plus so
       that SQL	errors cause it	to exit	with the error code (more on that
       below). Another handy way to do that is to divide by zero if an object
       doesn't exist. For example, to throw an error when the "flipr" schema
       does not	exist, you could do something like this:

	 SELECT	1/COUNT(*) FROM	sys.all_users WHERE username = 'FLIPR';

       Either way, run the "verify" script with	the "verify" command:

	 > sqitch verify db:oracle://scott:tiger@/flipr_test
	 Verifying db:oracle://scott:@/flipr_test
	   * appschema .. ok
	 Verify	successful

       Looks good! If you want to make sure that the verify script correctly
       dies if the schema doesn't exist, temporarily change the	schema name in
       the script to something that doesn't exist, something like:

	 CREATE	TABLE nonesuch.verify__	(id int);

       Then "verify" again:

	 > sqitch verify db:oracle://scott:tiger@/flipr_test
	 Verifying db:oracle://scott:@/flipr_test
	   * appschema .. CREATE TABLE nonesuch.verify__ (id int)
	 *
	 ERROR at line 1:
	 ORA-01918: user 'NONESUCH' does not exist

	 # Verify script "verify/appschema.sql"	failed.
	 not ok

	 Verify	Summary	Report
	 ---------------------
	 Changes: 1
	 Errors:  1
	 Verify	failed

       It's even nice enough to	tell us	what the problem is. Or, for the
       divide-by-zero example, change the schema name:

	 SELECT	1/COUNT(*) FROM	sys.all_users WHERE username = 'NONESUCH';

       Then the	verify will look something like:

	 > sqitch verify db:oracle://scott:tiger@/flipr_test
	 Verifying db:oracle://scott:@/flipr_test
	   * appschema ..   SELECT 1/COUNT(*) FROM sys.all_users WHERE username	= 'NONESUCH'
		   *
	 ERROR at line 1:
	 ORA-01476: divisor is equal to	zero

	 # Verify script "verify/appschema.sql"	failed.
	 not ok

	 Verify	Summary	Report
	 ---------------------
	 Changes: 1
	 Errors:  1
	 Verify	failed

       Less useful error output, but enough to alert us	that something has
       gone wrong.

       Don't forget to change the schema name back before continuing!

   Status, Revert, Log,	Repeat
       For purely informational	purposes, we can always	see how	a deployment
       was recorded via	the "status" command, which reads the registry tables
       from the	database:

	 > sqitch status db:oracle://scott:tiger@/flipr_test
	 # On database db:oracle://scott:@/flipr_test
	 # Project:  flipr
	 # Change:   c59e700589fc03568e8f35f592c0d9b7c638cbdd
	 # Name:     appschema
	 # Deployed: 2013-12-31	15:25:23 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

       Let's make sure that we can revert the change:

	 > sqitch revert db:oracle://scott:tiger@/flipr_test
	 Revert	all changes from db:oracle://scott:@/flipr_test? [Yes]
	   - appschema .. ok

       The "revert" command first prompts to make sure that we really do want
       to revert. This is to prevent unnecessary accidents. You	can pass the
       "-y" option to disable the prompt. Also,	notice the "-" before the
       change name in the output, which	reinforces that	the change is being
       removed from the	database. And now the schema should be gone:

	 > echo	"SELECT	username FROM all_users	WHERE username = 'FLIPR';" \
	 | sqlplus -S scott/tiger@flipr_test
	 no rows selected

       And the status message should reflect as	much:

	 > sqitch status db:oracle://scott:tiger@/flipr_test
	 # On database db:oracle://scott:@/flipr_test
	 No changes deployed

       Of course, since	nothing	is deployed, the "verify" command has nothing
       to verify:

	 > sqitch verify db:oracle://scott:tiger@/flipr_test
	 Verifying db:oracle://scott:@/flipr_test
	 No changes deployed

       However,	we still have a	record that the	change happened, visible via
       the "log" command:

	 > sqitch log db:oracle://scott:tiger@/flipr_test
	 On database db:oracle://scott:@/flipr_test
	 Revert	c59e700589fc03568e8f35f592c0d9b7c638cbdd
	 Name:	    appschema
	 Committer: Marge N. OXVera <marge@example.com>
	 Date:	    2013-12-31 16:19:38	-0800

	     App user and schema for all flipr objects.

	 Deploy	c59e700589fc03568e8f35f592c0d9b7c638cbdd
	 Name:	    appschema
	 Committer: Marge N. OXVera <marge@example.com>
	 Date:	    2013-12-31 15:25:23	-0800

	     App user and schema for all flipr objects.

       Note that the actions we	took are shown in reverse chronological	order,
       with the	revert first and then the deploy.

       Cool. Now let's commit it.

	 > git add .
	 > git commit -m 'Add flipr schema.'
	 [master e0e0b11] Add flipr schema.
	  4 files changed, 11 insertions(+)
	  create mode 100644 deploy/appschema.sql
	  create mode 100644 revert/appschema.sql
	  create mode 100644 verify/appschema.sql

       And then	deploy again. This time, let's use the "--verify" option, so
       that the	"verify" script	is applied when	the change is deployed:

	 > sqitch deploy --verify db:oracle://scott:tiger@/flipr_test
	 Deploying changes to db:oracle://scott:@/flipr_test
	   + appschema .. ok

       And now the schema should be back:

	 > echo	"SELECT	username FROM all_users	WHERE username = 'FLIPR';" \
	 | sqlplus -S scott/tiger@flipr_test
	 USERNAME
	 ------------------------------
	 FLIPR

       When we look at the status, the deployment will be there:

	 > sqitch status db:oracle://scott:tiger@/flipr_test
	 # On database db:oracle://scott:@/flipr_test
	 # Project:  flipr
	 # Change:   c59e700589fc03568e8f35f592c0d9b7c638cbdd
	 # Name:     appschema
	 # Deployed: 2013-12-31	16:22:01 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

On Target
       I'm getting a little tired of always having to type
       "db:oracle://scott:tiger@/flipr_test", aren't you? This database
       connection URI <https://github.com/theory/uri-db/> tells	Sqitch how to
       connect to the deployment target, but we	don't have to keep using the
       URI.  We	can name the target:

	 > sqitch target add flipr_test	db:oracle://scott:tiger@/flipr_test

       The "target" command, inspired by "git-remote" <http://git-
       scm.com/docs/git-remote>, allows	management of one or more named
       deployment targets. We've just added a target named "flipr_test", which
       means we	can use	the string "flipr_test"	for the	target,	rather than
       the URI.	But since we're	doing so much testing, we can also tell	Sqitch
       to deploy to the	"flipr_test" target by default:

	 > sqitch engine add oracle flipr_test

       Now we can omit the target argument altogether, unless we need to
       deploy to another database. Which we will, eventually, but at least our
       examples	will be	simpler	from here on in, e.g.:

	 > sqitch status
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   c59e700589fc03568e8f35f592c0d9b7c638cbdd
	 # Name:     appschema
	 # Deployed: 2013-12-31	16:22:01 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

       Yay, that allows	things to be a little more concise. Let's also make
       sure that changes are verified after deploying them:

	 > sqitch config --bool	deploy.verify true
	 > sqitch config --bool	rebase.verify true

       We'll see the "rebase" command a	bit later. In the meantime, let's
       commit the new configuration and	make some more changes!

	 > git commit -am 'Set default target and always verify.'
	 [master c4a308a] Set default target and always	verify.
	  1 file changed, 8 insertions(+)

Deploy with Dependency
       Let's add another change, this time to create a table. Our app will
       need users, of course, so we'll create a	table for them.	First, add the
       new change:

	 > sqitch add users --requires appschema -n 'Creates table to track our	users.'
	 Created deploy/users.sql
	 Created revert/users.sql
	 Created verify/users.sql
	 Added "users [appschema]" to sqitch.plan

       Note that we're requiring the "appschema" change	as a dependency	of the
       new "users" change. Although that change	has already been added to the
       plan and	therefore should always	be applied before the "users" change,
       it's a good idea	to be explicit about dependencies.

       Now edit	the scripts. When you're done, deploy/users.sql	should look
       like this:

	 -- Deploy flipr:users to oracle
	 -- requires: appschema

	 CREATE	TABLE flipr.users (
	     nickname  VARCHAR2(512 CHAR) PRIMARY KEY,
	     password  VARCHAR2(512 CHAR) NOT NULL,
	     timestamp TIMESTAMP WITH TIME ZONE	DEFAULT	CURRENT_TIMESTAMP NOT NULL
	 );

       A few things to notice here. On the second line,	the dependence on the
       "appschema" change has been listed in a comment.	This doesn't do
       anything, but the default Oracle	"deploy" template lists	it here	for
       your reference while editing the	file. Useful, right?

       The table itself	will been created in the "flipr" schema. This is why
       we need to require the "appschema" change.

       Notice that we've done nothing about error handling. Sqitch needs
       SQL*Plus	to return failure when a script	experiences an error, so one
       might expect that each script would need	to start with lines like
       these:

	 WHENEVER OSERROR EXIT 9
	 WHENEVER SQLERROR EXIT	SQL.SQLCODE

       However,	Sqitch always sets these error handling	parameters before it
       executes	your scripts, so you don't have	to.

       Now for the verify script. The simplest way to check that the table was
       created and has the expected columns without touching the data? Just
       select from the table with a false "WHERE" clause. Add this to
       verify/users.sql:

	 SELECT	nickname, password, timestamp
	   FROM	flipr.users
	  WHERE	1 = 1;

       Now for the revert script: all we have to do is drop the	table. Add
       this to revert/users.sql:

	 DROP TABLE flipr.users;

       Couldn't	be much	simpler, right?	Let's deploy this bad boy:

	 > sqitch deploy
	 Deploying changes to flipr_test
	   + users .. ok

       We know,	since verification is enabled, that the	table must have	been
       created.	 But for the purposes of visibility, let's have	a quick	look:

	 > echo	"DESCRIBE flipr.users;"	| sqlplus -S scott/tiger@flipr_test

	  Name					  Null?	   Type
	  ----------------------------------------- -------- ----------------------------
	  NICKNAME				  NOT NULL VARCHAR2(512	CHAR)
	  PASSWORD				  NOT NULL VARCHAR2(512	CHAR)
	  TIMESTAMP				  NOT NULL TIMESTAMP(6)	WITH TIME ZONE

       We can also verify all currently	deployed changes with the "verify"
       command:

	 > sqitch verify
	 Verifying flipr_test
	   * appschema .. ok
	   * users ...... ok
	 Verify	successful

       Now have	a look at the status:

	 > sqitch status
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   6840dc13beb0cd716b8bd3979b03a259c1e94405
	 # Name:     users
	 # Deployed: 2013-12-31	16:32:31 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

       Success!	Let's make sure	we can revert the change, as well:

	 > sqitch revert --to @HEAD^ -y
	 Reverting changes to appschema	from flipr_test
	   - users .. ok

       Note that we've used the	"--to" option to specify the change to revert
       to.  And	what do	we revert to? The symbolic tag @HEAD, when passed to
       "revert", always	refers to the last change deployed to the database.
       (For other commands, it refers to the last change in the	plan.)
       Appending the caret ("^") tells Sqitch to select	the change prior to
       the last	deployed change. So we revert to "appschema", the penultimate
       change.	The other potentially useful symbolic tag is @ROOT, which
       refers to the first change deployed to the database (or in the plan,
       depending on the	command).

       Back to the database. The "users" table should be gone but the "flipr"
       schema should still be around:

	 > echo	"DESCRIBE flipr.users;"	| sqlplus -S scott/tiger@flipr_test

	 ERROR:
	 ORA-04043: object flipr.users does not	exist

       The "status" command politely informs us	that we	have undeployed
       changes:

	 > sqitch status
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   c59e700589fc03568e8f35f592c0d9b7c638cbdd
	 # Name:     appschema
	 # Deployed: 2013-12-31	16:22:01 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Undeployed change:
	   * users

       As does the "verify" command:

	 > sqitch verify
	 Verifying flipr_test
	   * appschema .. ok
	 Undeployed change:
	   * users
	 Verify	successful

       Note that the verify is successful, because all currently-deployed
       changes are verified. The list of undeployed changes (just "users"
       here) reminds us	about the current state.

       Okay, let's commit and deploy again:

	 > git add .
	 > git commit -am 'Add users table.'
	 [master 2506312] Add users table.
	  4 files changed, 17 insertions(+)
	  create mode 100644 deploy/users.sql
	  create mode 100644 revert/users.sql
	  create mode 100644 verify/users.sql
	 > sqitch deploy
	 Deploying changes to flipr_test
	   + users .. ok

       Looks good. Check the status:

	 > sqitch status
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   6840dc13beb0cd716b8bd3979b03a259c1e94405
	 # Name:     users
	 # Deployed: 2013-12-31	16:34:28 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

       Excellent. Let's	do some	more!

Add Two	at Once
       Let's add a couple more changes to add functions	for managing users.

	 > sqitch add insert_user --requires users --requires appschema	\
	   -n 'Creates a function to insert a user.'
	 Created deploy/insert_user.sql
	 Created revert/insert_user.sql
	 Created verify/insert_user.sql
	 Added "insert_user [users appschema]" to sqitch.plan

	 > sqitch add change_pass --requires users --requires appschema	\
	   -n 'Creates a function to change a user password.'
	 Created deploy/change_pass.sql
	 Created revert/change_pass.sql
	 Created verify/change_pass.sql
	 Added "change_pass [users appschema]" to sqitch.plan

       Now might be a good time	to have	a look at the deployment plan:

	 > cat sqitch.plan
	 %syntax-version=1.0.0
	 %project=flipr
	 %uri=https://github.com/theory/sqitch-oracle-intro/

	 appschema 2013-12-31T22:34:42Z	Marge N. OXVera	<marge@example.com> # App user and schema for all flipr	objects.
	 users [appschema] 2014-01-01T00:31:20Z	Marge N. OXVera	<marge@example.com> # Creates table to track our users.
	 insert_user [users appschema] 2014-01-01T00:35:21Z Marge N. OXVera <marge@example.com>	# Creates a function to	insert a user.
	 change_pass [users appschema] 2014-01-01T00:35:28Z Marge N. OXVera <marge@example.com>	# Creates a function to	change a user password.

       Each change appears on a	single line with the name of the change, a
       bracketed list of dependencies, a timestamp, the	name and email address
       of the user who planned the change, and a note.

       Let's write the code for	the new	changes. Here's	what
       deploy/insert_user.sql should look like:

	 -- Deploy flipr:insert_user to	oracle
	 -- requires: users
	 -- requires: appschema

	 CREATE	OR REPLACE PROCEDURE flipr.insert_user(
	     nickname VARCHAR2,
	     password VARCHAR2
	 ) AS
	 BEGIN
	     INSERT INTO flipr.users VALUES(
		 nickname,
		 LOWER(	RAWTOHEX( UTL_RAW.CAST_TO_RAW(
		      sys.dbms_obfuscation_toolkit.md5(input_string => password)
		 ) ) ),
		 DEFAULT
	     );
	 END;
	 /

	 SHOW ERRORS;

	 -- Drop and die on error.
	 DECLARE
	     l_err_count INTEGER;
	 BEGIN
	     SELECT COUNT(*)
	       INTO l_err_count
	       FROM all_errors
	      WHERE owner = 'FLIPR'
		AND name  = 'INSERT_USER';

	     IF	l_err_count > 0	THEN
		 EXECUTE IMMEDIATE 'DROP PROCEDURE flipr.insert_user';
		 raise_application_error(-20001, 'Errors in FLIPR.INSERT_USER');
	     END IF;
	 END;
	 /

       The "DECLARE" PL/SQL block is to	catch compilation warnings, which are
       not normally fatal. It's	admittedly a bit convoluted
       <http://stackoverflow.com/a/16429231/79202>, but	ensures	that errors
       propagate and a broken function get dropped.

       Here's what verify/insert_user.sql might	look like:

	 -- Verify flipr:insert_user on	oracle
	 DESCRIBE flipr.insert_user;

       We simply take advantage	of the fact that "DESCRIBE" throws an
       exception if the	specified function does	not exist.

       And revert/insert_user.sql should look something	like this:

	 -- Revert flipr:insert_user from oracle
	 DROP PROCEDURE	flipr.insert_user;

       Now for "change_pass"; deploy/change_pass.sql might look	like this:

	 -- Deploy flipr:change_pass to	oracle
	 -- requires: users
	 -- requires: appschema

	 CREATE	OR REPLACE PROCEDURE flipr.change_pass(
	     nick    VARCHAR2,
	     oldpass VARCHAR2,
	     newpass VARCHAR2
	 ) IS
	    flipr_auth_failed EXCEPTION;
	 BEGIN
	     UPDATE flipr.users
		SET password = LOWER( RAWTOHEX(	UTL_RAW.CAST_TO_RAW(
			sys.dbms_obfuscation_toolkit.md5(input_string => newpass)
		    ) )	)
	      WHERE nickname = nick
		AND password = LOWER( RAWTOHEX(	UTL_RAW.CAST_TO_RAW(
			sys.dbms_obfuscation_toolkit.md5(input_string => oldpass)
		    ) )	);
	      IF SQL%ROWCOUNT =	0 THEN RAISE flipr_auth_failed;	END IF;
	 END;
	 /

	 SHOW ERRORS;

	 -- Drop and die on error.
	 DECLARE
	     l_err_count INTEGER;
	 BEGIN
	     SELECT COUNT(*)
	       INTO l_err_count
	       FROM all_errors
	      WHERE owner = 'FLIPR'
		AND name  = 'CHANGE_PASS';

	     IF	l_err_count > 0	THEN
		 EXECUTE IMMEDIATE 'DROP PROCEDURE flipr.CHANGE_PASS';
		 raise_application_error(-20001, 'Errors in FLIPR.CHANGE_PASS');
	     END IF;
	 END;
	 /

       We again	need the "DECLARE" PL/SQL block	to detect compilation warnings
       and make	the script die.	Use "DESCRIBE" in verify/change_pass.sql
       again:

	 -- Verify flipr:change_pass on	oracle
	 DESCRIBE flipr.change_pass;

       And of course, its "revert" script, revert/change_pass.sql, should look
       something like:

	 -- Revert flipr:change_pass from oracle
	 DROP PROCEDURE	flipr.change_pass;

       Try em out!

	 > sqitch deploy
	 Deploying changes to flipr_test
	   + insert_user .. No errors.
	 ok
	   + change_pass .. No errors.
	 ok

       Looks good. The "No errors" notices come	from the "SHOW ERRORS"
       SQL*Plus	command. It's not very useful here, but	very useful if there
       are compilation errors. If it bothers you, you can drop the "SHOW
       ERRORS" line and	select the error for display in	the "DECLARE" block,
       instead.

       Now, do we have the functions? Of course	we do, they were verified.
       Still, have a look:

	 > echo	"DESCRIBE flipr.insert_user;\nDESCRIBE flipr.change_pass;" \
	 | sqlplus -S scott/tiger@flipr_test

	 PROCEDURE flipr.insert_user
	  Argument Name			       Type		       In/Out Default?
	  ------------------------------ ----------------------- ------	--------
	  NICKNAME		       VARCHAR2		       IN
	  PASSWORD		       VARCHAR2		       IN

	 PROCEDURE flipr.change_pass
	  Argument Name			       Type		       In/Out Default?
	  ------------------------------ ----------------------- ------	--------
	  NICK			       VARCHAR2		       IN
	  OLDPASS		       VARCHAR2		       IN
	  NEWPASS		       VARCHAR2		       IN

       And what's the status?

	 > sqitch status
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   e1c9df6a95da835769eb560790588c16174f78df
	 # Name:     change_pass
	 # Deployed: 2013-12-31	16:37:22 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

       Looks good. Let's make sure revert works:

	 > sqitch revert -y --to @HEAD^^
	 Reverting changes to users from flipr_test
	   - change_pass .. ok
	   - insert_user .. ok
	 > echo	"DESCRIBE flipr.insert_user;\nDESCRIBE flipr.change_pass;" \
	 | sqlplus -S dwheeler/dwheeler@flipr_test
	 ERROR:
	 ORA-04043: object flipr.insert_user does not exist

	 ERROR:
	 ORA-04043: object flipr.change_pass does not exist

       Note the	use of "@HEAD^^" to specify that the revert be to two changes
       prior the last deployed change. Looks good. Let's do the	commit and re-
       deploy dance:

	 > git add .
	 > git commit -m 'Add `insert_user()` and `change_pass()`.'
	 [master 6b6797e] Add `insert_user()` and `change_pass()`.
	  7 files changed, 92 insertions(+)
	  create mode 100644 deploy/change_pass.sql
	  create mode 100644 deploy/insert_user.sql
	  create mode 100644 revert/change_pass.sql
	  create mode 100644 revert/insert_user.sql
	  create mode 100644 verify/change_pass.sql
	  create mode 100644 verify/insert_user.sql

	 > sqitch deploy
	 Deploying changes to flipr_test
	   + insert_user .. No errors.
	 ok
	   + change_pass .. No errors.
	 ok

	 > sqitch status
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   e1c9df6a95da835769eb560790588c16174f78df
	 # Name:     change_pass
	 # Deployed: 2013-12-31	16:38:46 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

	 > sqitch verify
	 Verifying flipr_test
	   * appschema .... ok
	   * users ........ ok
	   * insert_user .. ok
	   * change_pass .. ok
	 Verify	successful

       Great, we're fully up-to-date!

Ship It!
       Let's do	a first	release	of our app. Let's call it "1.0.0-dev1" Since
       we want to have it go out with deployments tied to the release, let's
       tag it:

	 > sqitch tag v1.0.0-dev1 -n 'Tag v1.0.0-dev1.'
	 Tagged	"change_pass" with @v1.0.0-dev1
	 > git commit -am 'Tag the database with v1.0.0-dev1.'
	 [master eae5f71] Tag the database with	v1.0.0-dev1.
	  1 file changed, 1 insertion(+)
	 > git tag v1.0.0-dev1 -am 'Tag	v1.0.0-dev1'

       We can try deploying to make sure the tag gets picked up	by deploying
       to a new	database, like so (assuming you	have an	Oracle SID named
       "flipr_dev" that	points to a different database):

	 > sqitch deploy db:oracle://scott:tiger@/flipr_dev
	 Adding	registry tables	to db:oracle://scott:@/flipr_dev
	 Deploying changes to db:oracle://scott:@/flipr_dev
	   + appschema ................. ok
	   + users ..................... ok
	   + insert_user ............... No errors.
	 ok
	   + change_pass @v1.0.0-dev1 .. No errors.
	 ok

       Great, all four changes were deployed and "change_pass" was tagged with
       "@v1.0.0-dev1". Let's have a look at the	status:

	 > sqitch status db:oracle://scott:tiger@/flipr_dev
	 # On database db:oracle://scott:tiger@/flipr_dev
	 # Project:  flipr
	 # Change:   e1c9df6a95da835769eb560790588c16174f78df
	 # Name:     change_pass
	 # Tag:	     @v1.0.0-dev1
	 # Deployed: 2013-12-31	16:40:02 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

       Note the	listing	of the tag as part of the status message. Now let's
       bundle everything up for	release:

	 > sqitch bundle
	 Bundling into bundle/
	 Writing config
	 Writing plan
	 Writing scripts
	   + appschema
	   + users
	   + insert_user
	   + change_pass @v1.0.0-dev1

       Now we can package the bundle directory and distribute it. When it gets
       installed somewhere, users can use Sqitch to deploy to the database.
       Let's try deploying it to yet another database (again, assuming you
       have a SID named	"flipr_prod":

	 > cd bundle
	 > sqitch deploy db:oracle://scott:tiger@/flipr_prod
	 Adding	registry tables	to db:oracle://scott:@/flipr_prod
	 Deploying changes to flipr_prod
	   + appschema ................. ok
	   + users ..................... ok
	   + insert_user ............... ok
	   + change_pass @v1.0.0-dev1 .. ok

       Looks much the same as before, eh? Package it up	and ship it!

Flip Out
       Now that	we've got the basics of	user management	done, let's get	to
       work on the core	of our product,	the "flip." Since other	folks are
       working on other	tasks in the repository, we'll work on a branch, so we
       can all stay out	of each	other's	way. So	let's branch:

	 > git checkout	-b flips
	 Switched to a new branch 'flips'

       Now we can add a	new change to create a table for our flips.

	 > sqitch add flips -r appschema -r users -n 'Adds table for storing flips.'
	 Created deploy/flips.sql
	 Created revert/flips.sql
	 Created verify/flips.sql
	 Added "flips [appschema users]" to sqitch.plan

       You know	the drill by now. Edit deploy/flips.sql:

	 -- Deploy flipr:flips to oracle
	 -- requires: appschema
	 -- requires: users

	 CREATE	TABLE flipr.flips (
	     id	       INTEGER		   PRIMARY KEY,
	     nickname  VARCHAR2(512 CHAR)  NOT NULL REFERENCES flipr.users(nickname),
	     body      VARCHAR2(180 CHAR)  NOT NULL,
	     timestamp TIMESTAMP WITH TIME ZONE	DEFAULT	CURRENT_TIMESTAMP NOT NULL
	 );

	 CREATE	SEQUENCE flipr.flip_id_seq START WITH 1	INCREMENT BY 1 NOCACHE;

	 CREATE	OR REPLACE TRIGGER flipr.flip_pk BEFORE	INSERT ON flipr.flips
	 FOR EACH ROW WHEN (NEW.id IS NULL)
	 DECLARE
	     v_id flipr.flips.id%TYPE;
	 BEGIN
	     SELECT flipr.flip_id_seq.nextval INTO v_id	FROM DUAL;
	     :new.id :=	v_id;
	 END;
	 /

       Edit verify/flips.sql:

	 -- Verify flipr:flips on oracle
	 DESCRIBE flipr.flips;

       And edit	revert/flips.sql:

	 -- Revert flipr:flips from oracle
	 DROP TRIGGER  flipr.flip_pk;
	 DROP SEQUENCE flipr.flip_id_seq;
	 DROP TABLE    flipr.flips;

       And give	it a whirl:

	 > sqitch deploy
	 Deploying changes to flipr_test
	   + flips .. ok

       Look good?

	 > sqitch status --show-tags
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   8e1573bb5ce5dfc239d5370c33d6e10820234aad
	 # Name:     flips
	 # Deployed: 2013-12-31	16:51:54 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 # Tag:
	 #   @v1.0.0-dev1 - 2013-12-31 16:44:00	-0800 -	Marge N. OXVera	<marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

       Note the	use of "--show tags" to	show all the deployed tags. Now	make
       it so:

	 > git add .
	 > git commit -am 'Add flips table.'
	 [flips	bbea131] Add flips table.
	  4 files changed, 32 insertions(+)
	  create mode 100644 deploy/flips.sql
	  create mode 100644 revert/flips.sql
	  create mode 100644 verify/flips.sql

Wash, Rinse, Repeat
       Now comes the time to add functions to manage flips. I'm	sure you have
       things nailed down now. Go ahead	and add	"insert_flip" and
       "delete_flip" changes and commit	them. The "insert_flip"	deploy script
       might look something like:

	 -- Deploy flipr:insert_flip to	oracle
	 -- requires: flips
	 -- requires: appschema

	 CREATE	OR REPLACE PROCEDURE flipr.insert_flip(
	     nickname  VARCHAR2,
	     body      VARCHAR2
	 ) AS
	 BEGIN
	     INSERT INTO flipr.flips (nickname,	body)
	     VALUES (nickname, body);
	 END;
	 /

	 SHOW ERRORS;

	 -- Drop and die on error.
	 DECLARE
	     l_err_count INTEGER;
	 BEGIN
	     SELECT COUNT(*)
	       INTO l_err_count
	       FROM all_errors
	      WHERE owner = 'FLIPR'
		AND name  = 'INSERT_FLIP';

	     IF	l_err_count > 0	THEN
		 EXECUTE IMMEDIATE 'DROP PROCEDURE flipr.insert_flip';
		 raise_application_error(-20001, 'Errors in FLIPR.INSERT_FLIP');
	     END IF;
	 END;
	 /

       And the "delete_flip" deploy script might look something	like:

	 -- Deploy flipr:delete_flip to	oracle
	 -- requires: flips
	 -- requires: appschema

	 CREATE	OR REPLACE PROCEDURE flipr.delete_flip(
	     flip_id INTEGER
	 ) IS
	     flipr_flip_delete_failed EXCEPTION;
	 BEGIN
	     DELETE FROM flipr.flips WHERE id =	flip_id;
	     IF	SQL%ROWCOUNT = 0 THEN RAISE flipr_flip_delete_failed; END IF;
	 END;
	 /

	 SHOW ERRORS;

	 -- Drop and die on error.
	 DECLARE
	     l_err_count INTEGER;
	 BEGIN
	     SELECT COUNT(*)
	       INTO l_err_count
	       FROM all_errors
	      WHERE owner = 'FLIPR'
		AND name  = 'DELETE_FLIP';

	     IF	l_err_count > 0	THEN
		 EXECUTE IMMEDIATE 'DROP PROCEDURE flipr.delete_flip';
		 raise_application_error(-20001, 'Errors in FLIPR.DELETE_FLIP');
	     END IF;
	 END;
	 /

       The "verify" scripts are:

	 -- Verify flipr:insert_flip on	oracle
	 DESCRIBE flipr.insert_flip;

       And:

	 -- Verify flipr:delete_flip on	oracle
	 DESCRIBE flipr.delete_flip;

       The "revert" scripts are:

	 -- Revert flipr:insert_flip from oracle
	 DROP PROCEDURE	flipr.insert_flip;

       And:

	 -- Revert flipr:delete_flip from oracle
	 DROP PROCEDURE	flipr.delete_flip;

       Check the example git repository	<https://github.com/theory/sqitch-
       oracle-intro> for the complete details. Test "deploy" and "revert",
       then commit it to the repository. The status should end up looking
       something like this:

	 > sqitch status --show-tags
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   a47be5a474eaad1a28546666eadeb0eba3ac12dc
	 # Name:     delete_flip
	 # Deployed: 2013-12-31	16:54:31 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 # Tag:
	 #   @v1.0.0-dev1 - 2013-12-31 16:44:00	-0800 -	Marge N. OXVera	<marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

       Good, we've finished this feature. Time to merge	back into "master".

   Emergency
       Let's do	it:

	 > git checkout	master
	 Switched to branch 'master'
	 > git pull
	 Updating eae5f71..a16f97c
	 Fast-forward
	  deploy/delete_list.sql | 35 +++++++++++++++++++++++++++++++++++
	  deploy/insert_list.sql | 33 +++++++++++++++++++++++++++++++++
	  deploy/lists.sql	 | 10 ++++++++++
	  revert/delete_list.sql |  3 +++
	  revert/insert_list.sql |  3 +++
	  revert/lists.sql	 |  3 +++
	  sqitch.plan		 |  4 ++++
	  verify/delete_list.sql |  3 +++
	  verify/insert_list.sql |  3 +++
	  verify/lists.sql	 |  5 +++++
	  10 files changed, 102	insertions(+)
	  create mode 100644 deploy/delete_list.sql
	  create mode 100644 deploy/insert_list.sql
	  create mode 100644 deploy/lists.sql
	  create mode 100644 revert/delete_list.sql
	  create mode 100644 revert/insert_list.sql
	  create mode 100644 revert/lists.sql
	  create mode 100644 verify/delete_list.sql
	  create mode 100644 verify/insert_list.sql
	  create mode 100644 verify/lists.sql

       Hrm, that's interesting.	Looks like someone made	some changes to
       "master".  They added list support. Well, let's see what	happens	when
       we merge	our changes.

	 > git merge --no-ff flips
	 Auto-merging sqitch.plan
	 CONFLICT (content): Merge conflict in sqitch.plan
	 Automatic merge failed; fix conflicts and then	commit the result.

       Oh, a conflict in sqitch.plan. Not too surprising, since	both the
       merged "lists" branch and our "flips" branch added changes to the plan.
       Let's try a different approach.

       The truth is, we	got lazy. Those	changes	when we	pulled master from the
       origin should have raised a red flag. It's considered a bad practice
       not to look at what's changed in	"master" before	merging	in a branch.
       What one	should do is either:

       o   Rebase the flips branch from	master before merging. This "rewinds"
	   the branch changes, pulls from "master", and	then replays the
	   changes back	on top of the pulled changes.

       o   Create a patch and apply that to master. This is the	sort of	thing
	   you might have to do	if you're sending changes to another user,
	   especially if the VCS is not	Git.

       So let's	restore	things to how they were	at master:

	 > git reset --hard HEAD
	 HEAD is now at	a16f97c	Merge branch 'lists'

       That throws out our botched merge. Now let's go back to our branch and
       rebase it on "master":

	 > git checkout	flips
	 Switched to branch 'flips'
	 > git rebase master
	 First,	rewinding head to replay your work on top of it...
	 Applying: Add flips table.
	 Using index info to reconstruct a base	tree...
	 M     sqitch.plan
	 Falling back to patching base and 3-way merge...
	 Auto-merging sqitch.plan
	 CONFLICT (content): Merge conflict in sqitch.plan
	 Failed	to merge in the	changes.
	 Patch failed at 0001 Add flips	table.
	 The copy of the patch that failed is found in:
	    .git/rebase-apply/patch

	 When you have resolved	this problem, run "git rebase --continue".
	 If you	prefer to skip this patch, run "git rebase --skip" instead.
	 To check out the original branch and stop rebasing, run "git rebase --abort".

       Oy, that's kind of a pain. It seems like	no matter what we do, we'll
       need to resolve conflicts in that file. Except in Git. Fortunately for
       us, we can tell Git to resolve conflicts	in sqitch.plan differently.
       Because we only ever append lines to the	file, we can have it use the
       "union" merge driver, which, according to its docs <http://git-
       scm.com/docs/gitattributes#_built-in_merge_drivers>:

	   Run 3-way file level	merge for text files, but take lines from both
	   versions, instead of	leaving	conflict markers. This tends to	leave
	   the added lines in the resulting file in random order and the user
	   should verify the result. Do	not use	this if	you do not understand
	   the implications.

       This has	the effect of appending	lines from all the merging files,
       which is	exactly	what we	need. So let's give it a try. First, back out
       the botched rebase:

	 > git rebase --abort

       Now add the union merge driver to .gitattributes	for sqitch.plan	and
       rebase again:

	 > echo	sqitch.plan merge=union	> .gitattributes
	 > git rebase master
	 First,	rewinding head to replay your work on top of it...
	 Applying: Add flips table.
	 Using index info to reconstruct a base	tree...
	 M     sqitch.plan
	 Falling back to patching base and 3-way merge...
	 Auto-merging sqitch.plan
	 Applying: Add functions to insert and delete flips.
	 Using index info to reconstruct a base	tree...
	 M     sqitch.plan
	 Falling back to patching base and 3-way merge...
	 Auto-merging sqitch.plan

       Ah, that	looks a	bit better. Let's have a look at the plan:

	 > cat sqitch.plan
	 %syntax-version=1.0.0
	 %project=flipr
	 %uri=https://github.com/theory/sqitch-oracle-intro/

	 appschema 2013-12-31T22:34:42Z	Marge N. OXVera	<marge@example.com> # App user and schema for all flipr	objects.
	 users [appschema] 2014-01-01T00:31:20Z	Marge N. OXVera	<marge@example.com> # Creates table to track our users.
	 insert_user [users appschema] 2014-01-01T00:35:21Z Marge N. OXVera <marge@example.com>	# Creates a function to	insert a user.
	 change_pass [users appschema] 2014-01-01T00:35:28Z Marge N. OXVera <marge@example.com>	# Creates a function to	change a user password.
	 @v1.0.0-dev1 2014-01-01T00:39:35Z Marge N. OXVera <marge@example.com> # Tag v1.0.0-dev1.

	 lists [appschema users] 2014-01-01T00:43:46Z Marge N. OXVera <marge@example.com> # Adds table for storing lists.
	 insert_list [lists appschema] 2014-01-01T00:45:24Z Marge N. OXVera <marge@example.com>	# Creates a function to	insert a list.
	 delete_list [lists appschema] 2014-01-01T00:45:43Z Marge N. OXVera <marge@example.com>	# Creates a function to	delete a list.
	 flips [appschema users] 2014-01-01T00:51:15Z Marge N. OXVera <marge@example.com> # Adds table for storing flips.
	 insert_flip [flips appschema] 2014-01-01T00:53:00Z Marge N. OXVera <marge@example.com>	# Creates a function to	insert a flip.
	 delete_flip [flips appschema] 2014-01-01T00:53:16Z Marge N. OXVera <marge@example.com>	# Creates a function to	delete a flip.

       Note that it has	appended the changes from the merged "lists" branch,
       and then	merged the changes from	our "flips" branch. Test it to make
       sure it works as	expected:

	 > sqitch rebase -y
	 Reverting all changes from flipr_test
	   - delete_flip ............... ok
	   - insert_flip ............... ok
	   - flips ..................... ok
	   - change_pass @v1.0.0-dev1 .. ok
	   - insert_user ............... ok
	   - users ..................... ok
	   - appschema ................. ok
	 Deploying changes to flipr_test
	   + appschema ................. ok
	   + users ..................... ok
	   + insert_user ............... No errors.
	 ok
	   + change_pass @v1.0.0-dev1 .. No errors.
	 ok
	   + lists ..................... ok
	   + insert_list ............... No errors.
	 ok
	   + delete_list ............... No errors.
	 ok
	   + flips ..................... ok
	   + insert_flip ............... No errors.
	 ok
	   + delete_flip ............... No errors.
	 ok

       Note the	use of "rebase", which combines	a "revert" and a "deploy" into
       a single	command. Handy,	right? It correctly reverted our changes, and
       then deployed them all again in the proper order. So let's commit
       .gitattributes; seems worthwhile	to keep	that change:

	 > git add .
	 > git commit -m 'Add `.gitattributes` with union merge	for `sqitch.plan`.'
	 [flips	383691f] Add `.gitattributes` with union merge for `sqitch.plan`.
	  1 file changed, 1 insertion(+)
	  create mode 100644 .gitattributes

   Merges Mastered
       And now,	finally, we can	merge into "master":

	 > git checkout	master
	 Switched to branch 'master'
	 > git merge --no-ff flips -m "Merge branch 'flips'"
	 Merge made by the 'recursive' strategy.
	  .gitattributes	 |  1 +
	  deploy/delete_flip.sql | 32 ++++++++++++++++++++++++++++++++
	  deploy/flips.sql	 | 22 ++++++++++++++++++++++
	  deploy/insert_flip.sql | 32 ++++++++++++++++++++++++++++++++
	  revert/delete_flip.sql |  3 +++
	  revert/flips.sql	 |  5 +++++
	  revert/insert_flip.sql |  3 +++
	  sqitch.plan		 |  3 +++
	  verify/delete_flip.sql |  3 +++
	  verify/flips.sql	 |  3 +++
	  verify/insert_flip.sql |  3 +++
	  11 files changed, 110	insertions(+)
	  create mode 100644 .gitattributes
	  create mode 100644 deploy/delete_flip.sql
	  create mode 100644 deploy/flips.sql
	  create mode 100644 deploy/insert_flip.sql
	  create mode 100644 revert/delete_flip.sql
	  create mode 100644 revert/flips.sql
	  create mode 100644 revert/insert_flip.sql
	  create mode 100644 verify/delete_flip.sql
	  create mode 100644 verify/flips.sql
	  create mode 100644 verify/insert_flip.sql

       And double-check	our work:

	 > cat sqitch.plan
	 %syntax-version=1.0.0
	 %project=flipr
	 %uri=https://github.com/theory/sqitch-oracle-intro/

	 appschema 2013-12-31T22:34:42Z	Marge N. OXVera	<marge@example.com> # App user and schema for all flipr	objects.
	 users [appschema] 2014-01-01T00:31:20Z	Marge N. OXVera	<marge@example.com> # Creates table to track our users.
	 insert_user [users appschema] 2014-01-01T00:35:21Z Marge N. OXVera <marge@example.com>	# Creates a function to	insert a user.
	 change_pass [users appschema] 2014-01-01T00:35:28Z Marge N. OXVera <marge@example.com>	# Creates a function to	change a user password.
	 @v1.0.0-dev1 2014-01-01T00:39:35Z Marge N. OXVera <marge@example.com> # Tag v1.0.0-dev1.

	 lists [appschema users] 2014-01-01T00:43:46Z Marge N. OXVera <marge@example.com> # Adds table for storing lists.
	 insert_list [lists appschema] 2014-01-01T00:45:24Z Marge N. OXVera <marge@example.com>	# Creates a function to	insert a list.
	 delete_list [lists appschema] 2014-01-01T00:45:43Z Marge N. OXVera <marge@example.com>	# Creates a function to	delete a list.
	 flips [appschema users] 2014-01-01T00:51:15Z Marge N. OXVera <marge@example.com> # Adds table for storing flips.
	 insert_flip [flips appschema] 2014-01-01T00:53:00Z Marge N. OXVera <marge@example.com>	# Creates a function to	insert a flip.
	 delete_flip [flips appschema] 2014-01-01T00:53:16Z Marge N. OXVera <marge@example.com>	# Creates a function to	delete a flip.

       Much much better, a nice	clean master now. And because it is now
       identical to the	"flips"	branch,	we can just carry on. Go ahead and tag
       it, bundle, and release:

	 > sqitch tag v1.0.0-dev2 -n 'Tag v1.0.0-dev2.'
	 Tagged	"delete_flip" with @v1.0.0-dev2
	 > git commit -am 'Tag the database with v1.0.0-dev2.'
	 [master 5427456] Tag the database with	v1.0.0-dev2.
	  1 file changed, 1 insertion(+)
	 > git tag v1.0.0-dev2 -am 'Tag	v1.0.0-dev2'
	 > sqitch bundle --dest-dir flipr-1.0.0-dev2
	 Bundling into flipr-1.0.0-dev2
	 Writing config
	 Writing plan
	 Writing scripts
	   + appschema
	   + users
	   + insert_user
	   + change_pass @v1.0.0-dev1
	   + lists
	   + insert_list
	   + delete_list
	   + flips
	   + insert_flip
	   + delete_flip @v1.0.0-dev2

       Note the	use of the "--dest-dir"	option to "sqitch bundle". Just	a
       nicer way to create the top-level directory name	so we don't have to
       rename it from bundle.

In Place Changes
       Uh-oh, someone just noticed that	MD5 hashing is not particularly
       secure. Why?  Have a look at this:

	 > echo	"
	     DELETE FROM flipr.users;
	     EXECUTE flipr.insert_user('foo', 's3cr3t');
	     EXECUTE flipr.insert_user('bar', 's3cr3t');
	     SELECT nickname, password FROM flipr.users;
	 " | sqlplus -S	scott/tiger@flipr_test

	 PL/SQL	procedure successfully completed.

	 PL/SQL	procedure successfully completed.

	 NICKNAME
	 --------------------------------------------------------------------------------
	 PASSWORD
	 --------------------------------------------------------------------------------
	 foo
	 a4d80eac9ab26a4a2da04125bc2c096a

	 bar
	 a4d80eac9ab26a4a2da04125bc2c096a

       If user "foo" ever got access to	the database, she could	quickly
       discover	that user "bar"	has the	same password and thus be able to
       exploit the account. Not	a great	idea. So we need to modify the
       "insert_user()" and "change_pass()" functions to	fix that. How?

       We'll create a function that encrypts passwords using a cryptographic
       salt <https://en.wikipedia.org/wiki/Salt_(cryptography)>. This will
       allow the password hashes to be stored with random hashing. So we'll
       need to add the function. The deploy script should be:

	 -- Deploy flipr:crypt to oracle
	 -- requires: appschema

	 CREATE	OR REPLACE FUNCTION flipr.crypt(
	     password VARCHAR2,
	     salt     VARCHAR2
	 ) RETURN VARCHAR2 IS
	     salted CHAR(10) :=	SUBSTR(salt, 0,	10);
	 BEGIN
	     RETURN salted || LOWER( RAWTOHEX( UTL_RAW.CAST_TO_RAW(
		  sys.dbms_obfuscation_toolkit.md5(input_string	=> password || salted)
	     ) ) );
	 END;
	 /

	 SHOW ERRORS;

	 -- Drop and die on error.
	 DECLARE
	     l_err_count INTEGER;
	 BEGIN
	     SELECT COUNT(*)
	       INTO l_err_count
	       FROM all_errors
	      WHERE owner = 'FLIPR'
		AND name  = 'CRYPT';

	     IF	l_err_count > 0	THEN
		 EXECUTE IMMEDIATE 'DROP PROCEDURE flipr.crypt';
		 raise_application_error(-20001, 'Errors in FLIPR.CRYPT');
	     END IF;
	 END;
	 /

       And the revert script should be:

	 -- Revert flipr:crypt.	from oracle
	 DROP FUNCTION flipr.crypt;

       And, as usual, the verify script	should just use	"DESCRIBE":

	 -- Verify flipr:crypt on oracle
	 DESCRIBE flipr.crypt;

       With that change	in place and committed,	we're ready to make use	of the
       improved	encryption. But	how to deploy the changes to "insert_user()"
       and "change_pass()"?

       Normally, modifying functions in	database changes is a PITA
       <http://www.urbandictionary.com/define.php?term=pita>. You have to make
       changes like these:

       1.  Copy	deploy/insert_user.sql to deploy/insert_user_crypt.sql.

       2.  Edit	deploy/insert_user_crypt.sql to	switch from
	   "sys.dbms_obfuscation_toolkit.md5()"	to "flipr.crypt()" and to add
	   a dependency	on the "crypt" change.

       3.  Copy	deploy/insert_user.sql to revert/insert_user_crypt.sql.	 Yes,
	   copy	the original change script to the new revert change.

       4.  Copy	verify/insert_user.sql to verify/insert_user_crypt.sql.

       5.  Edit	verify/insert_user_crypt.sql to	test that the function now
	   properly uses "flipr.crypt()".

       6.  Test	the changes to make sure you can deploy	and revert the
	   "insert_user_crypt" change.

       7.  Now do the same for the "change_pass" scripts.

       But you can have	Sqitch do it for you. The only requirement is that a
       tag appear between the two instances of a change	we want	to modify. In
       general,	you're going to	make a change like this	after a	release, which
       you've tagged anyway, right? Well we have, with "@v1.0.0-dev2" added in
       the previous section. With that,	we can let Sqitch do most of the hard
       work for	us, thanks to the "rework" command, which is similar to	"add",
       including support for the "--requires" option:

	 > sqitch rework insert_user --requires	crypt -n 'Change insert_user to	use crypt.'
	 Added "insert_user [insert_user@v1.0.0-dev2 crypt]" to	sqitch.plan.
	 Modify	these files as appropriate:
	   * deploy/insert_user.sql
	   * revert/insert_user.sql
	   * verify/insert_user.sql

       Oh, so we can edit those	files in place.	Nice! How does Sqitch do it?
       Well, in	point of fact, it has copied the files to stand	in for the
       previous	instance of the	"insert_user" change, which we can see via
       "git status":

	 > git status
	 # On branch master
	 # Your	branch is ahead	of 'origin/master' by 2	commits.
	 #   (use "git push" to	publish	your local commits)
	 #
	 # Changes not staged for commit:
	 #   (use "git add <file>..." to update	what will be committed)
	 #   (use "git checkout	-- <file>..." to discard changes in working directory)
	 #
	 #     modified:   revert/insert_user.sql
	 #     modified:   sqitch.plan
	 #
	 # Untracked files:
	 #   (use "git add <file>..." to include in what will be committed)
	 #
	 #     deploy/insert_user@v1.0.0-dev2.sql
	 #     revert/insert_user@v1.0.0-dev2.sql
	 #     verify/insert_user@v1.0.0-dev2.sql
	 no changes added to commit (use "git add" and/or "git commit -a")

       The "untracked files" part of the output	is the first thing to notice.
       They are	all named "insert_user@v1.0.0-dev2.sql". What that means is:
       "the "insert_user" change as it was implemented as of the
       "@v1.0.0-dev2" tag."  These are copies of the original scripts, and
       thereafter Sqitch will find them	when it	needs to run scripts for the
       first instance of the "insert_user" change. As such, it's important not
       to change them again. But hey, if you're	reworking the change, you
       shouldn't need to.

       The other thing to notice is that revert/insert_user.sql	has changed.
       Sqitch replaced it with the original deploy script. As of now,
       deploy/insert_user.sql and revert/insert_user.sql are identical.	This
       is on the assumption that the deploy script will	be changed (we're
       reworking it, remember?), and that the revert script should actually
       change things back to how they were before. Of course, the original
       deploy script may not be	idempotent
       <http://en.wikipedia.org/wiki/Idempotence> -- that is, able to be
       applied multiple	times without changing the result beyond the initial
       application. If it's not, you will likely need to modify	it so that it
       properly	restores things	to how they were after the original deploy
       script was deployed. Or,	more simply, it	should revert changes back to
       how they	were as-of the deployment of
       deploy/insert_user@v1.0.0-dev2.sql.

       Fortunately, our	function deploy	scripts	are already idempotent,	thanks
       to the use of the "OR REPLACE" expression. No matter how	many times a
       deployment script is run, the end result	will be	the same instance of
       the function, with no duplicates	or errors.

       As a result, there is no	need to	explicitly add changes.	So go ahead.
       Modify the script to switch to "crypt()". Make this change to
       deploy/insert_user.sql:

	 @@ -1,6 +1,7 @@
	  -- Deploy flipr:insert_user to oracle
	  -- requires: users
	  -- requires: appschema
	 +-- requires: crypt

	  CREATE OR REPLACE PROCEDURE flipr.insert_user(
	      nickname VARCHAR2,
	 @@ -9,9 +10,7 @@ CREATE OR REPLACE PROCEDURE flipr.insert_user(
	  BEGIN
	      INSERT INTO flipr.users VALUES(
		  nickname,
	 -	  LOWER( RAWTOHEX( UTL_RAW.CAST_TO_RAW(
	 -	       sys.dbms_obfuscation_toolkit.md5(input_string =>	password)
	 -	  ) ) ),
	 +	  flipr.crypt(password,	DBMS_RANDOM.STRING('p',	10)),
		  DEFAULT
	      );
	  END;

       Go ahead	and rework the "change_pass" change, too:

	 > sqitch rework change_pass --requires	crypt -n 'Change change_pass to	use crypt.'
	 Added "change_pass [change_pass@v1.0.0-dev2 crypt]" to	sqitch.plan.
	 Modify	these files as appropriate:
	   * deploy/change_pass.sql
	   * revert/change_pass.sql
	   * verify/change_pass.sql

       And make	this change to deploy/change_pass.sql:

	 @@ -1,6 +1,7 @@
	  -- Deploy flipr:change_pass to oracle
	  -- requires: users
	  -- requires: appschema
	 +-- requires: crypt

	  CREATE OR REPLACE PROCEDURE flipr.change_pass(
	      nick    VARCHAR2,
	 @@ -10,13 +11,9 @@ CREATE OR REPLACE PROCEDURE	flipr.change_pass(
	     flipr_auth_failed EXCEPTION;
	  BEGIN
	      UPDATE flipr.users
	 -	 SET password =	LOWER( RAWTOHEX( UTL_RAW.CAST_TO_RAW(
	 -		 sys.dbms_obfuscation_toolkit.md5(input_string => newpass)
	 -	     ) ) )
	 +	 SET password =	flipr.crypt(newpass, DBMS_RANDOM.STRING('p', 10))
	       WHERE nickname =	nick
	 -	 AND password =	LOWER( RAWTOHEX( UTL_RAW.CAST_TO_RAW(
	 -		 sys.dbms_obfuscation_toolkit.md5(input_string => oldpass)
	 -	     ) ) );
	 +	 AND password =	flipr.crypt(oldpass, password);
	       IF SQL%ROWCOUNT = 0 THEN	RAISE flipr_auth_failed; END IF;
	  END;
	  /

       And then	try a deployment:

	 > sqitch deploy
	 Deploying changes to flipr_test
	   + insert_user .. No errors.
	 ok
	   + change_pass .. No errors.
	 ok

       So, are the changes deployed?

	 > echo	"
	     DELETE FROM flipr.users;
	     EXECUTE flipr.insert_user('foo', 's3cr3t');
	     EXECUTE flipr.insert_user('bar', 's3cr3t');
	     SELECT nickname, password FROM flipr.users;
	 " | sqlplus -S	scott/tiger@flipr_test

	 PL/SQL	procedure successfully completed.

	 PL/SQL	procedure successfully completed.

	 NICKNAME
	 --------------------------------------------------------------------------------
	 PASSWORD
	 --------------------------------------------------------------------------------
	 foo
	 cP?.eR!V[pf3d91ce9b7dcfe9260c6f4bb94ed0b22

	 bar
	 Z+l"_W_JiSefb62b789c0ff114cddcccc69c422e78

       Awesome,	the stored passwords are different now.	But can	we revert,
       even though we haven't written any reversion scripts?

	 > sqitch revert --to @HEAD^^ -y
	 Reverting changes to crypt from flipr_test
	   - change_pass .. No errors.
	 ok
	   - insert_user .. No errors.
	 ok

       Did that	work, are the MD5 passwords back?

	 > echo	"
	     DELETE FROM flipr.users;
	     EXECUTE flipr.insert_user('foo', 's3cr3t');
	     EXECUTE flipr.insert_user('bar', 's3cr3t');
	     SELECT nickname, password FROM flipr.users;
	 " | sqlplus -S	scott/tiger@flipr_test

	 PL/SQL	procedure successfully completed.

	 PL/SQL	procedure successfully completed.

	 NICKNAME
	 --------------------------------------------------------------------------------
	 PASSWORD
	 --------------------------------------------------------------------------------
	 foo
	 a4d80eac9ab26a4a2da04125bc2c096a

	 bar
	 a4d80eac9ab26a4a2da04125bc2c096a

       Yes, it works! Sqitch properly finds the	original instances of these
       changes in the new script files that include tags.

       But what	about the verify script? How can we verify that	the functions
       have been modified to use "crypt()"? I think the	simplest thing to do
       is to examine the body of the function by querying the "all_source"
       <http://docs.oracle.com/cd/B19306_01/server.102/b14237/statviews_2063.htm>
       view. So	the "insert_user" verify script	looks like this:

	 -- Verify flipr:insert_user on	oracle

	 DESCRIBE flipr.insert_user;

	 SELECT	1/COUNT(*)
	   FROM	all_source
	  WHERE	type = 'PROCEDURE'
	    AND	name = 'INSERT_USER'
	    AND	text LIKE '%flipr.crypt(password, DBMS_RANDOM.STRING(''p'', 10))%';

       And the "change_pass" verify script looks like this:

	 -- Verify flipr:change_pass on	oracle

	 DESCRIBE flipr.change_pass;

	 SELECT	1/COUNT(*)
	   FROM	all_source
	  WHERE	type = 'PROCEDURE'
	    AND	name = 'CHANGE_PASS'
	    AND	text LIKE '%password = flipr.crypt(newpass, DBMS_RANDOM.STRING(''p'', 10))%';

       Make sure these pass by re-deploying:

	 > sqitch deploy
	 Deploying changes to flipr_test
	   + insert_user .. No errors.
	 ok
	   + change_pass .. No errors.
	 ok

       Excellent. Let's	go ahead and commit these changes:

	 > git add .
	 > git commit -m 'Use crypt to encrypt passwords.'
	 [master be46175] Use crypt to encrypt passwords.
	  13 files changed, 181	insertions(+), 15 deletions(-)
	  create mode 100644 deploy/change_pass@v1.0.0-dev2.sql
	  create mode 100644 deploy/insert_user@v1.0.0-dev2.sql
	  rewrite revert/change_pass.sql (98%)
	  rename revert/{change_pass.sql => change_pass@v1.0.0-dev2.sql} (100%)
	  rewrite revert/insert_user.sql (98%)
	  rename revert/{insert_user.sql => insert_user@v1.0.0-dev2.sql} (100%)
	  create mode 100644 verify/change_pass@v1.0.0-dev2.sql
	  create mode 100644 verify/insert_user@v1.0.0-dev2.sql

	 > sqitch status
	 # On database flipr_test
	 # Project:  flipr
	 # Change:   8367dc3bff7a563ec27f145421a1ffdf724cb6de
	 # Name:     change_pass
	 # Deployed: 2013-12-31	17:18:28 -0800
	 # By:	     Marge N. OXVera <marge@example.com>
	 #
	 Nothing to deploy (up-to-date)

More to	Come
       Sqitch is a work	in progress. Better integration	with version control
       systems is planned to make managing idempotent reworkings even easier.
       Stay tuned.

Author
       David E.	Wheeler	<david@justatheory.com>

License
       Copyright (c) 2012-2015 iovation	Inc.

       Permission is hereby granted, free of charge, to	any person obtaining a
       copy of this software and associated documentation files	(the
       "Software"), to deal in the Software without restriction, including
       without limitation the rights to	use, copy, modify, merge, publish,
       distribute, sublicense, and/or sell copies of the Software, and to
       permit persons to whom the Software is furnished	to do so, subject to
       the following conditions:

       The above copyright notice and this permission notice shall be included
       in all copies or	substantial portions of	the Software.

       THE SOFTWARE IS PROVIDED	"AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
       OR IMPLIED, INCLUDING BUT NOT LIMITED TO	THE WARRANTIES OF
       MERCHANTABILITY,	FITNESS	FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
       IN NO EVENT SHALL THE AUTHORS OR	COPYRIGHT HOLDERS BE LIABLE FOR	ANY
       CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN	ACTION OF CONTRACT,
       TORT OR OTHERWISE, ARISING FROM,	OUT OF OR IN CONNECTION	WITH THE
       SOFTWARE	OR THE USE OR OTHER DEALINGS IN	THE SOFTWARE.

perl v5.32.1			  2021-08-28	      sqitchtutorial-oracle(3)

Name | Synopsis | Description | Starting a New Project | Our First Change | On Target | Deploy with Dependency | Add Two at Once | Ship It! | Flip Out | Wash, Rinse, Repeat | In Place Changes | More to Come | Author | License

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