I am developing a multi-tenant app. I chose the "Shared Database/Separate Schemas" approach.
My idea is to have a default schema (dbo) and when deploying this schema, to do an update on the tenants' schemas (tenantA, tenantB, tenantC); in other words, to make synchronized schemas.
How can I synchronize the schemas of tenants with the default schema?
I am using SQL Server 2008.
First thing you will need is a table or other mechanism to store the version information of the schema. If nothing else so that you can bind your application and schema together. There is nothing more painful than a version of the application against the wrong schema—failing, corrupting data, etc.
The application should reject or shutdown if its not the right version—you might get some blowback when its not right, but protects you from the really bad day when the database corrupts the valuable data.
You'll need a way to track changes such as Subversion or something else—from SQL you can export the initial schema. From here you will need a mechanism to track changes using a nice tool like SQL compare and then track the schema changes and match to an update in version number in the target database.
We keep each delta in a separate folder beneath the upgrade utility we built. This utility signs onto the server, reads the version info and then applies the transform scripts from the next version in the database until it can find no more upgrade scripts in its sub folder. This gives us the ability upgrade a database no matter how old it is to the current version. If there are data transforms unique the tenant, these are going to get tricky.
Of course you should always make a backup of the database that writes to an external file preferable with an human identifiable version number so you can find it and restore it when the script(s) go bad. And eventually it will so just plan on figuring out how to recover and restore.
I saw there is some sort of schema upgrader tool in the new VS 2010 but I haven't used it. That might also be useful to you.
There is no magic command to synchronize the schemas as far as I know. You would need to use a tool - either built in house or bought (Check out Red Gate's SQL Compare and SQL Examiner - you need to tweak them to compare different schemas).
Just synchronizing can often be tricky business though. If you added a column, do you need to also fill that column with data? If you split a column into two new columns there has to be conversion code for something like that.
My suggestion would be to very carefully track any scripts that you run against the dbo schema and make sure that they also get run against the other schemas when appropriate. You can then use a tool like SQL Compare as an occasional sanity check to look for any unexpected differences.
Related
In the scope of responsible programming and versioning, I would like to start to version my database changes especially since I am developing on my database instance then moving it to production. I haven't found any thing that truly makes sense to me on how to do this. I am using Visual Studio 2010 Pro as my IDE. Is there a document that makes this process simple and able to detect changes to the database with relative ease? Or what should I change in my workflow to make this easier?
One way that I've successfully done this sort of thing in the past, is via Sql Source Control. Visual Studio does not offer this functionality for you.
Alternatively, you can use SSMS to generate the Database scripts for you and save it as a file; then you can check in the script. You would chose whether you generate the whole DB script in one file or whether you do it on an object by object basis. The syncing part will have to be done by you by executing your scripts in production. In conclusion a total nightmare.
Redgate also offers Sql Compare, which is great for syncing databases. Take a look at their products if you or your company can afford them.
We use our own DB solution in-house which brings all the tools required for proper DB versioning. While I realize that it may not be a perfect solution for everyone, I invite you to have a look at it (it is open-source): bsn ModuleStore
The versioning aspect is as follows: the tool can script out the SQL semi-automatically, and it does reformat the source code to be in an uniform format. The files will therefore always be identical for the same source, no matter of when and by whom something has been scripted; this therefore works nicely with non-locking source control systems (especially SVN, Git or Mercurial).
The reformat puts all statements in the same form (e.g. optional keywords such as AS, INNER, OUTER etc. are dealt with), scripts everything to the "dbo" schema (even if it was in a different one), puts all identifiers into the square braces ([something]), uppercases all reserved words, does the indentation etc.
Besides versioning, the runtime part of the tool can diff the running DB and the CREATE scripts (DB source code) and apply updates automatically for all non-destructive changes (e.g. updating indexes, constraints, views, stored procedures, triggers, custom types, new tables etc.). Destructuve changes have to be scriped manually (table changes which then usually require data transformations). The runtime will make sure that all updates are performed in a transaction and rollback if the resulting DB doesn't match the CREATE scripts, therefore you get the safety of knowing that the DB is exactly on the version required by the application, even if it has been tampered with manually.
Also, multiple "modules" can be used in a single database. Each module is stored as a schema and independent of other schemas, thereby making it possible to add or remove modules from one single DB, and avoiding the need to create multiple databases for different parts of the application. Also, the use of schemas to do this makes sure that there are no name collisions.
It may be worth noting that the toolset has no dependency to the SMO, it is autonomous.
Save Your Database scripts at SVN. Here is the Refernce How to use SVN Tortoise
OR
Save your database script at VSS. Here is the reference What is VSS ? How can we use that ?
In both cases you can keep track of the changes done so that in future you can check the history which in saved in the form of versions.
You can use Red Gate product also
EDIT
How do you pull out what what has changed?
Use comparison feature to check the changes made in the previous versions.
How do I apply the changes to the live database server?
Download the latest file from server.
I hope you are not using the Drop statements for the Table in your consolidated script. As it will delete all records from the table.
Drop statements will take place for Stored Pro, View, Function etc.
Please note that you have to run the complete latest database script file on the production server with below mentioned action plans
1. Remove Drop Statement for Schema DDL
2. Add Drop/Create Statements for Stored Proc/Views
3. Include Alter statements DML of schema.
Hope this will definitely help you.
I would like to know how you guys deal with development database changes in groups of 2 or more devs? Do you have a global db everyone access, maybe a local copy and manually apply script changes? It would be nice to see pros and cons that you've noticed for each approach and the number of devs in your team.
Start with "Evolutionary Database Design" by Martin Fowler. This sums it up nicely
There are have been other questions about DB development that may be useful too, for example Is RedGate SQL Source Control for me?
Our approach is that everyone has their own DB, the complete DB can be created from create scripts with base data if required. All the scripts required for this are in source control.
All scripts are CREATE scripts and they reflect the current state of the database schema. Upgrades are in separate SQL files which can upgrade existing DBs from a specific version to a newer one (run sequentially). After all the updates have been applied, the schema must be identical to what you would get from running the setup scripts.
We have some tools to do this (we use SQL Server and .NET):
Scripting is done with a tool which also applies a standard formatting so that the changes are well traceable with text diff tools (and by the SCM)
A runtime module takes care of comparing the existing DB objects, run updates if required, automatically apply "non-destructive" changes, then check the DB objects again to ensure a correct migration before committing the changes
The toolset is available as open-source project (licensed under LGPL), it's called the bsn ModuleStore (note that it is limited to SQL Server 2005/2008/Azure and to .NET for the runtime part).
We use what was code named "Data Dude" - the database features in TFS and Visual Studio - to deal with this. When you "get latest" and bring in code that relies on a schema change, you also bring in the revised schemas, stored procedures etc. You rigght-click the database project and Deploy; that gets your local schema and sp in sync but doesn't overwrite your data. The job of working out the script to get you from your old schema to the new one falls to Visual Studio, not to you or your DBA. We also have "populate" scripts for things like lists of provinces and a deploy runs them for you.
So much better than the old way which always fell apart at high stress times, with people checking in code then going home and nobody knowing what columns to add to make the code work etc.
I am using github for maintaining versions and code synchronization.
We are team of two and we are located at different places.
How can we make sure that our databases are synchronized.
Update:--
I am rails developer. But these days i m working on drupal projects (where database is the center of variations). So i want to make sure that team must have a synchronized database. Also the values in various tables.
I need something which keep our data values synchronized.
Centralized database is a good solution. But things get disturbed when someone works offline
if you use visual studio then you can script your database tables, views, stored procedures and functions as .sql files from a database solution and then check those into version control as well - its what i currently do at my workplace
In you dont use visual studio then you can still script your sql as .sql files [but with more work] and then version control them as necessary
Have a look at Red Gate SQL Source Control - http://www.red-gate.com/products/SQL_Source_Control/
To be honest I've never used it, but their other software is fantastic. And if all you want to do is keep the DB schema in sync (rather than full source control) then I have used their SQL Compare product very succesfully in the past.
(ps. I don't work for them!)
You can use Sql Source Control together with Sql Data Compare to source control both: schema and data. Here is an article from redgate: Source controlling data.
These are some of the possibilities.
Using the same database. Set-up a central database where everybody can connect to. This way you are sure everybody uses the same database all the time.
After every change, export the database and commit it to the VCS. This option requires discipline and manual labor.
Use some kind of other definition of the schema. For example, Doctrine for php has the ability to build the database from a yaml definition which can be stored in the vcs. This can be easier automated then point 2.
Use some other software/script which updates the database.
I feel your pain. I had terrible trouble getting SQL Server to play nice with SVN. In the end I opted for a shared database solution. Every day I run an extensive script to backup all our schema definitions (specifically stored procedures) for version control into text files. Due to the limited number of changes this works well.
I now use this technique for our major project and personal projects too. The only negative is that it relies on being connected all the time. The other answers suggest that full database versioning is very time consuming and I tend to agree. For "live" upgrades we use the Red Gate tools, they do both schema and data compare and it works very well.
http://www.red-gate.com/products/SQL_Data_Compare/. We were using this tool for keeping databases in sync in our company. Later we had some specific demands so we had to write our own code for synchronization. Depends how complex is you database and how much changes is happening. It is much simpler if you have time when no one is working and you can lock database for syncronization.
Check out OffScale DataGrove.
This product tracks changes to the entire DB - schema and data. You can tag versions in any point in time, and return to older states of the DB with a simple command. It also allows you to create virtual, separate, copies of the same database so each team member can have his own separate DB. All the virtual copies are tracked into the same repository so it's super-easy to revert your DB to someone else's version (you simply check-out their version, just like you do with your source control). This means all your DBs can always be synchronized.
Regarding a centralized DB - just like you don't want to work on the same source code, you don't want to be working on the same DB. It means you'll constantly break each other's code and builds each time someone changes something in the DB.
I suggest that you go with a separate DB for each developer, and sync them using DataGrove.
Disclaimer - I work at OffScale :-)
Try Wizardby. This is my personal project, but I've used it in my several previous jobs with great deal of success.
Basically, it's a tool which lets you specify all changes to your database schema in a database-independent manner and then apply these changes to all your databases.
Building and maintaining a database that is then deplyed/developed further by many devs is something that goes on in software development all the time. We create a build script, and maintain further update scripts that get applied as the database grows over time. There are many ways to manage this, from manual updates to console apps/build scripts that help automate these processes.
Has anyone who has built/managed these processes moved over to a Source Control solution for database schema management? If so, what have they found the best solution to be? Are there any pitfalls that should be avoided?
Red Gate seems to be a big player in the MSSQL world and their DB source control looks very interesting:
http://www.red-gate.com/products/solutions_for_sql/database_version_control.htm
Although it does not look like it replaces the (default) data* management process, so it only replaces half the change management process from my pov.
(when I'm talking about data, I mean lookup values and that sort of thing, data that needs to be deployed by default or in a DR scenario)
We work in a .Net/MSSQL environment, but I'm sure the premise is the same across all languages.
Similar Questions
One or more of these existing questions might be helpful:
The best way to manage database changes
MySQL database change tracking
SQL Server database change workflow best practices
Verify database changes (version-control)
Transferring changes from a dev DB to a production DB
tracking changes made in database structure
Or a search for Database Change
I look after a data warehouse developed in-house by the bank where I work. This requires constant updating, and we have a team of 2-4 devs working on it.
We are fortunate because there is only the one instance of our "product", so we do not have to cater for deploying to multiple instances which may be at different versions.
We keep a creation script file for each object (table, view, index, stored procedure, trigger) in the database.
We avoid the use of ALTER TABLE whenever possible, preferring to rename a table, create the new one and migrate the data over. This means that we don't have to look through a history of ALTER scripts - we can always see the up to date version of every table by looking at its create script. The migration is performed by a separate migration script - this can be partly auto-generated.
Each time we do a release, we have a script which runs the create scripts / migration scripts in the appropriate order.
FYI: We use Visual SourceSafe (yuck!) for source code control.
I've been looking for a SQL Server source control tool - and came across a lot of premium versions that do the job - using SQL Server Management Studio as a plugin.
LiquiBase is a free one but i never quite got it working for my needs.
There is another free product out there though that works stand along from SSMS and scripts out objects and data to flat file.
These objects can then be pumped into a new SQL Server instance which will then re-create the database objects.
See gitSQL
Maybe you're asking for LiquiBase?
I have been googling a lot and I couldn't find if this even exists or I'm asking for some magic =P
Ok, so here's the deal.
I need to have a way to create a "master-structured" database which will only contain the schemas, structures, tables, store procedures, udfs, etc, everything but real data in SQL SERVER 2005 (if this is available in 2008 let me know, I could try to convince my client to pay for it =P)
Then I want to have several "children" of that master db which implement those schemas, tables, etc but each one has different data.
So when I need to create a new stored procedure or something like that, I just create it on the master database (and of course it's available on its children).
Actually I have several different databases with the same schema and different data. But the problem is to maintain congruency between them. Everytime I create a script to create some SP or add some index or whatever, I have to execute it in every database, and sometimes I could miss one =P
So let's say you have a UNIVERSE (would be the master db) and the universe has SPACES (each one represented by a child db). So the application I'm working on needs to dynamically "clone" SPACES. To do that, we have to create a new database. Nowadays I'm creating a backup of the db being cloned, restoring it as a new one and truncate the tables.
I want to be able to create a new "child" of the "master" db, which will maintain the schemas and everything, but will start with empty data.
Hope it's clear... My english is not perfect, sorry about that =P
Thanks to all!
What you really need is to version-control your database schema.
See do-you-source-control-your-databases
If you use SQL Server, I would recommend dbGhost - not expensive and does a great job of:
synchronizing 2 databases
diff-ing 2 databases
creating a database from a set of scripts (I would recommend this version).
batch support, so that you can upgrade all your databases using a single batch
You can use this infrastructure for both:
rolling development versions to test, integration and production systems
rolling your 'updated' system to multiple production deployments (especially in a hosted environment)
I would write my changes as a sql file and use OSQL or SQLCMD via a batchfile to ensure that I repeatedly executed on all the databases without thinking about it.
As an alternative I would use the VisualStudio Database Pro tools or RedGate SQL compare tools to compare and propogate the changes.
There are kludges, but the mainstream way to handle this is still to use Source Code Control (with all its other attendant benefits.) And SQL Server is increasingly SCC friendly.
Also, for many (most robust) sites it's a per-server issue as much as a per-database issue.
You can put things in master like SPs and call them from anywhere. As far as other objects like tables, you can put them in model and new databases will get them when you create a new database.
However, in order to get new tables to simply pop up in the child databases after being added to the parent, nothing.
It would be possible to create something to look through the databases and script them from a template database, and there are also commercial tools which can help discover differences between databases. You could also have a DDL trigger in the "master" database which went out and did this when you created a new table.
If you kept a nice SPACES template, you could script it out (without data) and create the new database - so there would be no need to TRUNCATE. You can script it out from SQL or an external tool.
Little trivia here. The mssqlsystemresource database works as you describe: is defined once and 'appears' in every database as the special sys schema. Unfortunately the special 'magic' needed to get this working is not available to the user databases. You'll have to use deployment techniques to keep your schema in synk. That is, apply the changes to every database as the other answers already suggested.
In theory, you could put a trigger on your UNIVERSE.sysobjects table (assuming SQL Server), and then you could enumerate master.dbo.sysdatabases to find all the child databases. If you have a special table that indicates it's a child database, you can reference child.dbo.sysobjects to find it.
Make no mistake, it would be difficult to implement. But it's one way you could do it.