Name
sqitchtutorial-vertica - A tutorial introduction to Sqitch change management on Vertica
Synopsis
sqitch *
Description
This tutorial explains how to create a sqitch-enabled Vertica 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 a new project from scratch, a fictional antisocial networking site called Flipr. All examples use Git as the VCS and Vertica as the storage engine, but for the most part you can substitute other VCSes and database engines in the examples as appropriate.
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 an Oracle database, see sqitchtutorial-oracle.
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 an Exasol database, see sqitchtutorial-exasol.
If you’d like to manage a Snowflake database, see sqitchtutorial-snowflake.
Connection Configuration
Sqitch requires ODBC to connect to the Vertica database. As such, you’ll need
to make sure that the Vertica ODBC driver is properly configured. At its
simplest, on Unix-like systems, name the driver “Vertica” by adding this entry
to odbcinst.ini
(usually found in /etc
, /usr/etc
, or
/usr/local/etc
):
[Vertica]
Description = ODBC for Vertica
Driver = /opt/vertica/lib64/libverticaodbc.so
And also creating a vertica.ini
file in the same directory that contains:
[Driver]
DriverManagerEncoding=UTF-16
ODBCInstLib=/usr/lib64/libodbcinst.so
ErrorMessagesPath=/opt/vertica/lib64
You might also consider naming your database connection by putting an entry in
odbc.ini
(same directory), like so (assuming that Vertica is running on
your local host):
[dbadmin]
Description = Vertica dbadmin connection
Driver = Vertica
Database = dbadmin
Servername = localhost
UserName = dbadmin
Password = password
Port = 5433
Locale = en_US
See the Vertica ODBC Documentation for details. Specific links:
- Unix ODBC Configuration
- Additional Linux ODBC Configuration (
vertica.ini
) - Windows ODBC Configuration
- Mac OS X ODBC Configuration
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.'
If you’re a Git user and want to follow along the history, the repository used in these examples is on GitHub.
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, and will prevent the deployment of a different project with the same name. So let’s specify one when we initialize Sqitch:
> sqitch init flipr --uri https://github.com/sqitchers/sqitch-vertica-intro/ --engine vertica
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 = vertica
# plan_file = sqitch.plan
# top_dir = .
# [engine "vertica"]
# target = db:vertica:
# registry = sqitch
# client = vsql
Good, it picked up on the fact that we’re creating changes for the Vertica
engine, thanks to the --engine vertica
option, and saved it to the
file. Furthermore, it wrote a commented-out [engine "vertica"]
section with
all the available Vertica engine-specific settings commented out and ready to
be edited as appropriate.
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. Since Vertica’s vsql
client is not in the path on my system,
let’s go ahead an tell it where to find the client on our computer (don’t
bother if you’re using the
Docker image because it uses the
client inside the container, not on your host machine):
> sqitch config --user engine.vertica.client /opt/vertica/bin/vsql
And let’s also 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
[engine "vertica"]
client = /opt/vertica/bin/vsql
[user]
name = Marge N. O’Vera
email = marge@example.com
Which means that Sqitch should be able to find vsql
for any project, and
that it 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-vertica-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 a42564d] Initialize Sqitch configuration.
2 files changed, 16 insertions(+), 0 deletions(-)
create mode 100644 sqitch.conf
create mode 100644 sqitch.plan
Our First Change
First, our project will need a 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 'Add 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 schema. So we add
this to deploy/appschema.sql
:
CREATE SCHEMA flipr;
The revert
script’s job is to precisely revert the change to the deploy
script, so we add this to revert/appschema.sql
:
DROP SCHEMA flipr;
Now we can try deploying this change. We tell Sqitch where to send the change
via a database URI, assuming the default
dbadmin
database and user and an ODBC driver named Vertica
(see
“Connection Configuration” for details). If you want to first
create a database,
simply use its name in place of dbadmin
:
> sqitch deploy 'db:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
Adding registry tables to db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
Deploying changes to db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
+ appschema .. ok
First Sqitch created registry tables used to track database changes. The
structure and name of the registry varies between databases (Vertica uses a
schema to namespace its registry, while SQLite and MySQL use separate
databases). Next, Sqitch deploys changes. We only have one 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:
> vsql -U dbadmin -c '\dn flipr'
List of schemas
Name | Owner | Comment
-------+---------+---------
flipr | dbadmin |
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 Vertica, 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. 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 v_catalog.schemata WHERE schema_name = 'flipr';
Either way, run the verify
script with the verify
command:
> sqitch verify 'db:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
Verifying db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
* 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:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
Verifying db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
* appschema .. vsql:verify/appschema.sql:5: ROLLBACK 4650: Schema "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 v_catalog.schemata WHERE schema_name = 'nonesuch';
Then the verify will look something like:
> sqitch verify 'db:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
Verifying db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
* appschema .. vsql:verify/appschema.sql:5: ERROR 2005: division by 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:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
# On database db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
# Project: flipr
# Change: f9759f0ed77964b6a3b6c7aa3b6058b4bb7db764
# Name: appschema
# Deployed: 2014-09-04 15:26:28 -0700
# 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:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
Revert all changes from db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica? [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:
> vsql -U dbadmin -c '\dn flipr'
List of schemas
Name | Owner | Comment
------+-------+---------
(0 rows)
And the status message should reflect as much:
> sqitch status 'db:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
# On database db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
No changes deployed
Of course, since nothing is deployed, the verify
command
has nothing to verify:
> sqitch verify 'db:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
Verifying db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
No changes deployed
However, we still have a record that the change happened, visible via the
log
command:
> sqitch log 'db:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
On database db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
Revert f9759f0ed77964b6a3b6c7aa3b6058b4bb7db764
Name: appschema
Committer: Marge N. O’Vera <marge@example.com>
Date: 2014-09-04 16:33:02 -0700
Add schema for all flipr objects.
Deploy f9759f0ed77964b6a3b6c7aa3b6058b4bb7db764
Name: appschema
Committer: Marge N. O’Vera <marge@example.com>
Date: 2014-09-04 15:26:28 -0700
Add 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 9bee4bd] Add flipr schema.
5 files changed, 197 insertions(+), 0 deletions(-)
create mode 100644 deploy/appschema.sql
create mode 100644 revert/appschema.sql
create mode 100644 sqitch.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:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
Deploying changes to db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
+ appschema .. ok
And now the schema should be back:
> vsql -U dbadmin -c '\dn flipr'
List of schemas
Name | Owner | Comment
-------+---------+---------
flipr | dbadmin |
When we look at the status, the deployment will be there:
> sqitch status 'db:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
# On database db:vertica://dbadmin:@localhost:5433/dbadmin?Driver=Vertica
# Project: flipr
# Change: f9759f0ed77964b6a3b6c7aa3b6058b4bb7db764
# Name: appschema
# Deployed: 2014-09-04 16:37:38 -0700
# 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:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
, aren’t
you? This database connection URI 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:vertica://dbadmin:password@localhost:5433/dbadmin?Driver=Vertica'
The target
command, inspired by
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 vertica 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: f9759f0ed77964b6a3b6c7aa3b6058b4bb7db764
# Name: appschema
# Deployed: 2014-09-04 16:37:38 -0700
# 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 and make some more changes!
> git commit -am 'Set default deployment target and always verify.'
[main 469779a] Set default deployment target and always verify.
1 files changed, 8 insertions(+), 0 deletions(-)
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 vertica
-- requires: appschema
CREATE TABLE flipr.users (
nickname VARCHAR PRIMARY KEY,
password VARCHAR NOT NULL,
fullname VARCHAR(256) NOT NULL,
twitter VARCHAR NOT NULL,
timestamp TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
A few things to notice here. On the second line, the dependence on the
appschema
change has been listed. This doesn’t do anything, but the default
deploy
Vertica template lists it here for your reference while editing
the file. Useful, right?
The table itself will be created in the flipr
schema. This is why we need
to require the appschema
change.
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, fullname, twitter, timestamp
FROM flipr.users
WHERE FALSE;
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:
> vsql -U dbadmin -c '\d flipr.users'
List of Fields by Tables
Schema | Table | Column | Type | Size | Default | Not Null | Primary Key | Foreign Key
--------+-------+-------------+-------------+------+---------+----------+-------------+-------------
flipr | users | nickname | varchar(80) | 80 | | t | t |
flipr | users | password | varchar(80) | 80 | | t | f |
flipr | users | "timestamp" | timestamptz | 8 | now() | t | f |
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: d647ac8c130a7e0b12c9049789e46afb4a4f6e53
# Name: users
# Deployed: 2014-09-04 16:42:45 -0700
# 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:
> vsql -U dbadmin -c '\d flipr.users'
Did not find any relation.
The status
command politely informs us that we have
undeployed changes:
> sqitch status
# On database flipr_test
# Project: flipr
# Change: f9759f0ed77964b6a3b6c7aa3b6058b4bb7db764
# Name: appschema
# Deployed: 2014-09-04 16:37:38 -0700
# 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 c7c24c5] Add users table.
4 files changed, 18 insertions(+), 0 deletions(-)
create mode 100644 deploy/users.sql
create mode 100644 revert/users.sql
create mode 100644 verify/users.sql
Deploying changes to flipr_test
+ users .. ok
Looks good. Check the status:
> sqitch status
# On database flipr_test
# Project: flipr
# Change: d647ac8c130a7e0b12c9049789e46afb4a4f6e53
# Name: users
# Deployed: 2014-09-04 17:42:53 -0700
# 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. Our app will need to store status messages from users. Let’s call them – and the table to store them – “flips”. And we’ll also need a view that lists user names with their flips. Let’s add changes for them both:
> 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
> sqitch add userflips -r appschema -r users -r flips \
-n 'Creates the userflips view.'
Created deploy/userflips.sql
Created revert/userflips.sql
Created verify/userflips.sql
Added "userflips [appschema users flips]" 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-vertica-intro/
appschema 2014-09-04T18:40:34Z Marge N. O’Vera <marge@example.com> # Add schema for all flipr objects.
users [appschema] 2014-09-04T23:40:15Z Marge N. O’Vera <marge@example.com> # Creates table to track our users.
flips [appschema users] 2014-09-05T00:16:58Z Marge N. O’Vera <marge@example.com> # Adds table for storing flips.
userflips [appschema users flips] 2014-09-05T00:18:43Z Marge N. O’Vera <marge@example.com> # Creates the userflips view.
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/flips.sql
should look like:
-- Deploy flipr:flips to vertica
-- requires: appschema
-- requires: users
CREATE TABLE flipr.flips (
id AUTO_INCREMENT PRIMARY KEY ,
nickname VARCHAR NOT NULL REFERENCES flipr.users(nickname),
body VARCHAR(180) NOT NULL DEFAULT '',
timestamp TIMESTAMPTZ NOT NULL DEFAULT clock_timestamp()
);
Here’s what verify/flips.sql
might look like:
-- Verify flipr:flips on vertica
SELECT id, nickname, body, timestamp
FROM flipr.flips
WHERE FALSE;
We simply take advantage of the fact that has_function_privilege()
throws
an exception if the specified function does not exist.
And revert/flips.sql
should look something like this:
-- Revert flipr:flips from vertica
DROP TABLE flipr.flips;
Now for userflips
; deploy/userflips.sql
might look like this:
-- Deploy flipr:userflips to vertica
-- requires: appschema
-- requires: users
-- requires: flips
CREATE OR REPLACE VIEW flipr.userflips AS
SELECT f.id, u.nickname, u.fullname, f.body, f.timestamp
FROM flipr.users u
JOIN flipr.flips f ON u.nickname = f.nickname;
Use a SELECT
statement in verify/userflips.sql
again:
-- Verify flipr:userflips on vertica
SELECT id, nickname, fullname, body, timestamp
FROM flipr.userflips
WHERE FALSE;
And of course, its revert
script, revert/userflips.sql
, should look
something like:
-- Revert flipr:userflips from vertica
DROP VIEW flipr.userflips;
Try em out!
> sqitch deploy
Deploying changes to flipr_test
+ flips ...... ok
+ userflips .. ok
Do we have the new table and view? Of course we do, they were verified. Still, have a look:
> vsql -U dbadmin -c '\dt flipr.flips'
List of tables
Schema | Name | Kind | Owner | Comment
--------+-------+-------+---------+---------
flipr | flips | table | dbadmin |
> vsql -U dbadmin -c '\dv flipr.userflips'
List of View Fields
Schema | View | Column | Type | Size
--------+-----------+-------------+--------------+------
flipr | userflips | id | int | 8
flipr | userflips | nickname | varchar(80) | 80
flipr | userflips | fullname | varchar(256) | 256
flipr | userflips | body | varchar(180) | 180
flipr | userflips | "timestamp" | timestamptz | 8
And what’s the status?
> sqitch status
# On database flipr_test
# Project: flipr
# Change: d1f998618fb863d93049a724fd0d2b49a29add86
# Name: userflips
# Deployed: 2014-09-04 17:51:21 -0700
# 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
- userflips .. ok
- flips ...... ok
> vsql -U dbadmin -c '\d flipr.flips'
Did not find any relation.
> vsql -U dbadmin -c '\dv flipr.userflips'
No matching relations found.
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 flips table and userflips view.'
[main c40f23f] Add flips table and userflips view.
7 files changed, 41 insertions(+), 0 deletions(-)
create mode 100644 deploy/flips.sql
create mode 100644 deploy/userflips.sql
create mode 100644 revert/flips.sql
create mode 100644 revert/userflips.sql
create mode 100644 verify/flips.sql
create mode 100644 verify/userflips.sql
> sqitch deploy
Deploying changes to flipr_test
+ flips ...... ok
+ userflips .. ok
> sqitch status
# On database flipr_test
# Project: flipr
# Change: d1f998618fb863d93049a724fd0d2b49a29add86
# Name: userflips
# Deployed: 2014-09-04 17:59:34 -0700
# By: Marge N. O’Vera <marge@example.com>
#
Nothing to deploy (up-to-date)
> sqitch verify
Verifying flipr_test
* appschema .. ok
* users ...... ok
* flips ...... ok
* userflips .. 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 "userflips" with @v1.0.0-dev1
> git commit -am 'Tag the database with v1.0.0-dev1.'
[main b07ce3d] Tag the database with v1.0.0-dev1.
1 files changed, 1 insertions(+), 0 deletions(-)
> git tag v1.0.0-dev1 -am 'Tag v1.0.0-dev1'
We can try deploying to make sure the tag gets picked up like so:
> sqitch deploy
Nothing to deploy (up-to-date)
> sqitch status
# On database flipr_test
# Project: flipr
# Change: d1f998618fb863d93049a724fd0d2b49a29add86
# Name: userflips
# Tag: @v1.0.0-dev1
# Deployed: 2014-09-04 17:59:34 -0700
# By: Marge N. O’Vera <marge@example.com>
#
Nothing to deploy (up-to-date)
Note the new “Tag” line in the output of sqitch status
: no new changes
needed to be deployed, but Sqitch did deploy the tag on the userflips
change. Now let’s bundle everything up for release:
> sqitch bundle
Bundling into bundle
Writing config
Writing plan
Writing scripts
+ appschema
+ users
+ flips
+ userflips @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 another database:
> cd bundle
> sqitch deploy db:vertica://dbadmin:password@db.example.com:5433/flipr?Driver=Vertica
Adding registry tables to db:vertica://dbadmin:@db.example.com:5433/flipr?Driver=Vertica
Deploying changes to db:vertica://dbadmin:@db.example.com:5433/flipr?Driver=Vertica
+ appschema ............... ok
+ users ................... ok
+ flips ................... ok
+ userflips @v1.0.0-dev1 .. ok
Notice how the tag on userflips
now appears in the deploy output. Nice, eh?
Now, 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
Making a Hash of Things
Now that we’ve got the basics of the app done, let’s add a feature. Gotta track the hashtags associated with flips, right? Let’s add a table for them. But 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:
Making a Hash of Things
Now that we’ve got the basics of the app done, let’s add a feature. Gotta track the hashtags associated with flips, right? Let’s add a table for them. But 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 hashtags
Switched to a new branch 'hashtags'
Now we can add a new change to create a table for hashtags.
> sqitch add hashtags --requires flips -n 'Adds table for storing hashtags.'
Created deploy/hashtags.sql
Created revert/hashtags.sql
Created verify/hashtags.sql
Added "hashtags [appschema flips]" to sqitch.plan
You know the drill by now. Add this to deploy/hashtags.sql
CREATE TABLE flipr.hashtags (
flip_id BIGINT NOT NULL REFERENCES flipr.Flips(id),
hashtag VARCHAR(128) NOT NULL,
PRIMARY KEY (flip_id, hashtag)
);
Again, select from the table in verify/hashtags.sql
:
SELECT flip_id, hashtag FROM flipr.hashtags WHERE FALSE;
And drop it in revert/hashtags.sql
DROP TABLE flipr.hashtags;
And give it a whirl:
> sqitch deploy
Deploying changes to flipr_test
+ hashtags .. ok
Look good?
> sqitch status --show-tags
# On database flipr_test
# Project: flipr
# Change: fda6daef73e0ac12252bf6af5f259ccb207d4197
# Name: hashtags
# Deployed: 2014-09-05 10:46:20 -0700
# By: Marge N. O’Vera <marge@example.com>
#
# Tag:
# @v1.0.0-dev1 - 2014-09-05 09:09:38 -0700 - 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. Make sure we can
revert, too:
> sqitch rebase -y --onto @HEAD^
Reverting changes to userflips @v1.0.0-dev1 from flipr_test
- hashtags .. ok
> sqitch deploy
Deploying changes to flipr_test
+ hashtags .. ok
Great! Now make it so:
> git add .
> git commit -m 'Add hashtags table.'
[hashtags d893e9c] Add hashtags table.
4 files changed, 18 insertions(+), 0 deletions(-)
create mode 100644 deploy/hashtags.sql
create mode 100644 revert/hashtags.sql
create mode 100644 verify/hashtags.sql
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 b07ce3d..05d3e5d
Fast-forward
deploy/lists.sql | 10 ++++++++++
revert/lists.sql | 3 +++
sqitch.plan | 2 ++
verify/lists.sql | 5 +++++
4 files changed, 20 insertions(+), 0 deletions(-)
create mode 100644 deploy/lists.sql
create mode 100644 revert/lists.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 hashtags
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 hashtags
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
hashtags
branch from main before merging. This “rewinds” the branch changes, pulls frommain
, 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 05d3e5d Merge branch 'lists'
That throws out our botched merge. Now let’s go back to our branch and rebase
it on main
:
> git checkout hashtags
Switched to branch 'hashtags'
> git rebase main
First, rewinding head to replay your work on top of it...
Applying: Add hashtags table.
Using index info to reconstruct a base tree...
<stdin>:16: new blank line at EOF.
+
warning: 1 line adds whitespace errors.
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 hashtags table.
When you have resolved this problem run "git rebase --continue".
If you would prefer to skip this patch, instead run "git rebase --skip".
To restore 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:
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
HEAD is now at d893e9c Add hashtags table.
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 hashtags table.
Using index info to reconstruct a base tree...
<stdin>:16: new blank line at EOF.
+
warning: 1 line adds whitespace errors.
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-vertica-intro/
appschema 2014-09-04T18:40:34Z Marge N. O’Vera <marge@example.com> # Add schema for all flipr objects.
users [appschema] 2014-09-04T23:40:15Z Marge N. O’Vera <marge@example.com> # Creates table to track our users.
flips [appschema users] 2014-09-05T00:16:58Z Marge N. O’Vera <marge@example.com> # Adds table for storing flips.
userflips [appschema users flips] 2014-09-05T00:18:43Z Marge N. O’Vera <marge@example.com> # Creates the userflips view.
@v1.0.0-dev1 2014-09-05T16:04:48Z Marge N. O’Vera <marge@example.com> # Tag v1.0.0-dev1.
lists [appschema users] 2014-09-05T17:33:43Z Marge N. O’Vera <marge@example.com> # Adds table for storing lists.
hashtags [appschema flips] 2014-09-05T17:39:53Z Marge N. O’Vera <marge@example.com> # Adds table for storing hashtags.
Note that it has appended the changes from the merged “lists” branch, and then merged the changes from our “hashtags” branch. Test it to make sure it works as expected:
> sqitch rebase -y
Reverting all changes from flipr_test
- hashtags ................ ok
- userflips @v1.0.0-dev1 .. ok
- flips ................... ok
- users ................... ok
- appschema ............... ok
Deploying changes to flipr_test
+ appschema ............... ok
+ users ................... ok
+ flips ................... ok
+ userflips @v1.0.0-dev1 .. ok
+ lists ................... ok
+ hashtags ................ 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`.'
[hashtags 2f065a3] Add `.gitattributes` with union merge for `sqitch.plan`.
1 files changed, 1 insertions(+), 0 deletions(-)
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 hashtags -m "Merge branch 'hashtags'"
Merge made by recursive.
.gitattributes | 1 +
deploy/hashtags.sql | 10 ++++++++++
revert/hashtags.sql | 3 +++
sqitch.plan | 1 +
verify/hashtags.sql | 3 +++
5 files changed, 18 insertions(+), 0 deletions(-)
create mode 100644 .gitattributes
create mode 100644 deploy/hashtags.sql
create mode 100644 revert/hashtags.sql
create mode 100644 verify/hashtags.sql
And double-check our work:
> cat sqitch.plan
%syntax-version=1.0.0
%project=flipr
%uri=https://github.com/sqitchers/sqitch-vertica-intro/
appschema 2014-09-04T18:40:34Z Marge N. O’Vera <marge@example.com> # Add schema for all flipr objects.
users [appschema] 2014-09-04T23:40:15Z Marge N. O’Vera <marge@example.com> # Creates table to track our users.
flips [appschema users] 2014-09-05T00:16:58Z Marge N. O’Vera <marge@example.com> # Adds table for storing flips.
userflips [appschema users flips] 2014-09-05T00:18:43Z Marge N. O’Vera <marge@example.com> # Creates the userflips view.
@v1.0.0-dev1 2014-09-05T16:04:48Z Marge N. O’Vera <marge@example.com> # Tag v1.0.0-dev1.
lists [appschema users] 2014-09-05T17:33:43Z Marge N. O’Vera <marge@example.com> # Adds table for storing lists.
hashtags [appschema flips] 2014-09-05T17:39:53Z Marge N. O’Vera <marge@example.com> # Adds table for storing hashtags.
Much much better, a nice clean main now. And because it is now identical to the “hashtags” 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 "hashtags" with @v1.0.0-dev2
> git commit -am 'Tag the database with v1.0.0-dev2.'
[main 8a6a73b] Tag the database with v1.0.0-dev2.
1 files changed, 1 insertions(+), 0 deletions(-)
> 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
+ flips
+ userflips @v1.0.0-dev1
+ lists
+ hashtags @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
Well, some folks have been testing the 1.0.0-dev2
release and have demanded
that Twitter user links be added to Flipr pages. Why anyone would want to
include social network links in an anti-social networking app is beyond us
programmers, but we’re just the plumbers, right? Gotta go with what Product
demands. The upshot is that we need to update the userflips
view, which is
used for the feature in question, to include the Twitter user names.
Normally, modifying views in database changes is a PITA. You have to make changes like these:
- Copy
deploy/userflips.sql
todeploy/userflips_twitter.sql
. - Edit
deploy/userflips_twitter.sql
to drop and re-create the view with thetwitter
column to the view. - Copy
deploy/userflips.sql
torevert/userflips_twitter.sql
. Yes, copy the original change script to the new revert change. - Add a
DROP VIEW
statement torevert/userflips_twitter.sql
. - Copy
verify/userflips.sql
toverify/userflips_twitter.sql
. - Modify
verify/userflips_twitter.sql
to include a check for thetwiter
column. - Test the changes to make sure you can deploy and revert the
userflips_twitter
change.
But you can have Sqitch do most of the work 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
:
> sqitch rework userflips -n 'Adds userflips.twitter.'
Added "userflips [userflips@v1.0.0-dev2]" to sqitch.plan.
Modify these files as appropriate:
* deploy/userflips.sql
* revert/userflips.sql
* verify/userflips.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 userflips
change, which we can see via git status
:
> git status
# On branch main
# Changed but not updated:
# (use "git add <file>..." to update what will be committed)
# (use "git checkout -- <file>..." to discard changes in working directory)
#
# modified: revert/userflips.sql
# modified: sqitch.plan
#
# Untracked files:
# (use "git add <file>..." to include in what will be committed)
#
# deploy/userflips@v1.0.0-dev2.sql
# revert/userflips@v1.0.0-dev2.sql
# verify/userflips@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’re
all named userflips@v1.0.0-dev2.sql
. What that means is: “the userflips
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 userflips
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/userflips.sql
has changed. Sqitch
replaced it with the original deploy script. As of now,
deploy/userflips.sql
and revert/userflips.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 – 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/userflips@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 add the twitter
column to the view. Make this change to
deploy/userflips.sql
:
@@ -4,8 +4,9 @@
BEGIN;
@@ -4,6 +4,6 @@
-- requires: flips
CREATE OR REPLACE VIEW flipr.userflips AS
-SELECT f.id, u.nickname, u.fullname, f.body, f.timestamp
+SELECT f.id, u.nickname, u.fullname, u.twitter, f.body, f.timestamp
FROM flipr.users u
JOIN flipr.flips f ON u.nickname = f.nickname;
Next, modify verify/userflips.sql
to check for the twitter
column.
Here’s the diff:
@@ -1,6 +1,6 @@
-- Verify flipr:userflips on vertica
-SELECT id, nickname, fullname, body, timestamp
+SELECT id, nickname, fullname, twitter, body, timestamp
FROM flipr.userflips
WHERE FALSE;
Now try a deployment:
> sqitch deploy
Deploying changes to flipr_test
+ userflips .. ok
So, are the changes deployed?
> vsql -U dbadmin -c '\dv flipr.userflips'
List of View Fields
Schema | View | Column | Type | Size
--------+-----------+-------------+--------------+------
flipr | userflips | id | int | 8
flipr | userflips | nickname | varchar(80) | 80
flipr | userflips | fullname | varchar(256) | 256
flipr | userflips | twitter | varchar(80) | 80
flipr | userflips | body | varchar(180) | 180
flipr | userflips | "timestamp" | timestamptz | 8
Awesome, the view now includes the twitter
column. But can we revert?
> sqitch revert --to @HEAD^ -y
Reverting changes to hashtags @v1.0.0-dev2 from flipr_test
- userflips .. ok
Did that work, is the twitter
column gone?
> vsql -U dbadmin -c '\dv flipr.userflips'
List of View Fields
Schema | View | Column | Type | Size
--------+-----------+-------------+--------------+------
flipr | userflips | id | int | 8
flipr | userflips | nickname | varchar(80) | 80
flipr | userflips | fullname | varchar(256) | 256
flipr | userflips | twitter | varchar(80) | 80
flipr | userflips | body | varchar(180) | 180
flipr | userflips | "timestamp" | timestamptz | 8
Yes, it works! Sqitch properly finds the original instances of these changes in the new script files that include tags.
Excellent. Let’s go ahead and commit these changes:
> git add .
> git commit -m 'Add the twitter column to the userflips view.'
[main 95d6dd0] Add the twitter column to the userflips view.
7 files changed, 30 insertions(+), 4 deletions(-)
create mode 100644 deploy/userflips@v1.0.0-dev2.sql
create mode 100644 revert/userflips@v1.0.0-dev2.sql
create mode 100644 verify/userflips@v1.0.0-dev2.sql
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) 2012-2024 iovation Inc., David E. Wheeler
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.