sqitchtutorial-oracle(3pm)

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 <https://git-scm.com/> as the VCS and Oracle <https://www.oracle.com/us/products/database/> as the storage engine. Note that you will need to set $ORACLE_HOME <https://www.orafaq.com/wiki/ORACLE_HOME> so that all the database connections will work.

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

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

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

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

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

If you'd like to manage an Exasol database, see sqitchtutorial-exasol.

If you'd like to manage a Snowflake database, see sqitchtutorial-snowflake.

  Prerequisites
Sqitch requires Oracle Instant Client <https://www.oracle.com/database/technologies/instant-client.html> and the DBD::Oracle Perl module to manage Oracle databases. Skip this section if you already have them installed and configured.

Instant Client

Sqitch requires three Instant Client packages:

1.  Instant Client Basic

2.  Instant Client SQL*Plus

3.  Instant Client SDK

Download all three as appropriate for your platform and OS, unpack them and put them all in a single directory, such as instantclient in your home directory. Then set the $ORACLE_HOME environment variable to that directory and add it to the path the PATH and LD_LIBRARY_PATH variables. For example:

  export ORACLE_HOME=$HOME/instantclient
  export PATH=$ORACLE_HOME:$PATH
  export LD_LIBRARY_PATH=$ORACLE_HOME

DBD::Oracle

With these variables in place, install DBD::Oracle, like so:

  cpanm DBD::Oracle

If you run into issues, consult DBD::Oracle::Troubleshooting and the relevant platform-specific "DBD::Oracle::Troubleshooting::*" guides listed here <https://metacpan.org/dist/DBD-Oracle>.

  Test Environment
If you have an Oracle instance ready to hand, you can skip this section. For For those who don't have a handy Oracle instance lying around, try using one of the Oracle-XE Docker images <https://hub.docker.com/r/gvenzl/oracle-xe> or the Database Virtual Box Appliance <https://www.oracle.com/database/technologies/databaseappdev-vm.html>. Details on each follow.

Oracle-XE Docker Configuration

The simplest way to the Sqitch Oracle engine is with the [gvenzl/oracle-xe](https://hub.docker.com/r/gvenzl/oracle-xe) docker image. Essentially, start it like so:

  docker run -d -p 1521:1521 \
    -e ORACLE_PASSWORD=oracle \
    -e APP_USER=scott \
    -e APP_USER_PASSWORD=tiger \
    gvenzl/oracle-xe:18-slim

This will create a user (and schema) named "scott" in the pluggable database "pdb1". To create a SID named "flipr_test" pointing to the "pdb1" database, add this entry to $ORACLE_HOME/network/admin/tnsnames.ora:

  FLIPR_TEST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
      (CONNECT_DATA =
        (SERVER = DEDICATED)
        (SERVICE_NAME = pdb1)
      )
    )

Virtual Box Configuration

Some instructions for setting up the Database Virtual Box Appliance for following along in this tutorial.

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

•   Download and install VirtualBox <https://www.virtualbox.org/wiki/Downloads>.

•   Download the VM from the Database Virtual Box Appliance <https://www.oracle.com/database/technologies/databaseappdev-vm.html> page and import it into VirtualBox.

•   Once the VM is imported into VirtualBox and started, login with the username "oracle" and the password "oracle". Then, in VirtualBox, go to Settings -> Network, select the NAT adapter, and add two port forwarding rules (https://barrymcgillin.blogspot.com/2011/12/using-oracle-developer-days-virtualbox.html):

      Host Port | Guest Port
     -----------+------------
           1521 |       1521
           2222 |         22

    Then restart the VM. You should then be able to connect from your host with:

      sqlplus sys/oracle@localhost/ORCL as sysdba

    If this fails with either of these errors:

      ORA-01017: invalid username/password; logon denied ORA-21561: OID
      generation failed

    Make sure that your computer's hostname is on the localhost line of /etc/hosts (reference <https://sourceforge.net/p/tora/discussion/52737/thread/f68b89ad/>):

      > hostname
      stickywicket
      > grep 127 /etc/hosts
      127.0.0.1    localhost stickywicket

•   Give user "scott" the access it needs:

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

•   To create a SID named "flipr_test" pointing to the "pdb1" database, add this entry to $ORACLE_HOME/network/admin/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.'
  [main (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/sqitchers/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: identifiers internally, and will prevent the deployment of a different project with the same name. So let's specify one when we initialize Sqitch:

  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 = 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 <https://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. O’Vera'
  > 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. O’Vera
        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/sqitchers/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.'
  [main 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. Before going any further, unless you're using the Docker or VM environments described above, you might need to create the database <https://docs.oracle.com/cd/B28359_01/server.111/b28310/create001.htm#ADMIN11068> and configure the SID. Assuming you have an Oracle SID named "FLIPR_TEST" set up in your "TNSNAMES.ORA|https://www.orafaq.com/wiki/Tnsnames.ora" file, tell Sqitch where to send the change to a target specified as a database URI <https://github.com/libwww-perl/uri-db/>, such as

  export SQITCH_TARGET=db:oracle://$username:$password@/flipr_test

With that URI set up, we can deploy:

  > 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. O’Vera <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. O’Vera <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. O’Vera <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.'
  [main 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. O’Vera <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/libwww-perl/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" <https://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. O’Vera <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.'
  [main 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 0 = 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. O’Vera <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. O’Vera <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.'
  [main 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. O’Vera <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/sqitchers/sqitch-oracle-intro/

  appschema 2013-12-31T22:34:42Z Marge N. O’Vera <marge@example.com> # App user and schema for all flipr objects.
  users [appschema] 2014-01-01T00:31:20Z Marge N. O’Vera <marge@example.com> # Creates table to track our users.
  insert_user [users appschema] 2014-01-01T00:35:21Z Marge N. O’Vera <marge@example.com> # Creates a function to insert a user.
  change_pass [users appschema] 2014-01-01T00:35:28Z Marge N. O’Vera <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 <https://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. O’Vera <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()`.'
  [main 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. O’Vera <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.'
  [main 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. O’Vera <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!

  > cd ..
  > mv bundle flipr-v1.0.0-dev1
  > tar -czf flipr-v1.0.0-dev1.tgz flipr-v1.0.0-dev1

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. O’Vera <marge@example.com>
  #
  # Tag:
  #   @v1.0.0-dev1 - 2013-12-31 16:44:00 -0800 - Marge N. O’Vera <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/sqitchers/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. O’Vera <marge@example.com>
  #
  # Tag:
  #   @v1.0.0-dev1 - 2013-12-31 16:44:00 -0800 - Marge N. O’Vera <marge@example.com>
  #
  Nothing to deploy (up-to-date)

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

  Emergency
Let's do it:

  > git checkout main
  Switched to branch 'main'
  > 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 "main". 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 main from the origin should have raised a red flag. It's considered a bad practice not to look at what's changed in "main" before merging in a branch. What one should do is either:

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

•   Create a patch and apply that to main. 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 main:

  > 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 "main":

  > git checkout flips
  Switched to branch 'flips'
  > git rebase main
  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 <https://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 main
  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/sqitchers/sqitch-oracle-intro/

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

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

  > git checkout main
  Switched to branch 'main'
  > 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/sqitchers/sqitch-oracle-intro/

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

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

Much much better, a nice clean main 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.'
  [main 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 <https://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 main
  # Your branch is ahead of 'origin/main' 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 <https://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" <https://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.'
  [main 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. O’Vera <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) 2012-2025 David E. Wheeler, 2012-2021 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.