The Database Countryside Code: Best Practices for BI & SQL Users
Those ‘City Folk’ among you may not be aware but in Rural England we have what is called The Countryside Code, it’s a set of guidelines that everyone should follow in order to keep the countryside clean, tidy and a nice place to visit. You may be asking – what does this have to do with Business Intelligence and Database Administration? Well, I think it’s vital – if we all follow a fairly simple but broad set of guidelines then all classes of database user will have a better experience from Developers to DBAs and Analysts to CIOs. This isn’t really about making your databases perform better, it’s about working better with each-other and taking other people’s perspectives on board. Having been in most of the related roles over the years this is what I’d put into The Database Countryside Code…
1. Enjoy the countryside and respect its life and work
Whether your application is an ‘out of the box’ software suite, a Business Intelligence package that can be tweaked on implementation or a hand-crafted bespoke solution if you’re running against a database maintained by someone else or shared with other applications you need to take heed of this point. Remember that cooperation is key and if you build a good relationship with the DBA and the other key users of the database you’ll have a much better time of things and if there are any critical issues you’ll be included in the remediation process and may even be able to help your own users get back online faster. It’s easy to see DBAs as grouchy, narrowly focused sorts who tend to view all user activity as bothersome (I can say that as I’ve been one myself) but generally speaking if the DBA is aware of user activity at all the chances are that there’s already a problem as it’s the long running, resource intensive activity that will stand out in alerts and performance reports. Before your application goes live you should do some testing, run your designs and SQL statements / stored procedures past the DBA for some advice (but remember, you don’t have to take it) and establish some sort of procedure for reporting issues, and remember that an SLA can work both ways as you may need the DBA’s help as much as they might need yours.
2. Guard against all risk of fire
Security is a huge issue and as exploit frameworks and toolkits become more and more prevalent and feature-rich the likelihood of vulnerabilities being discovered in our applications should be treated more like a certainty. If you’re developing bespoke applications and especially web apps you’ll need to pay close attention to the OWASP Top 10 application security risks but from a database perspective the most notable threat is SQL Injection - the art of passing SQL into an application so that it might be executed by the database (as a good starting point check out OWASP’s SQL Injection Prevention Cheat Sheet). If you’re deploying packaged apps or BI tools don’t think that you’ve gotten away with it, the primary responsibility may be on software developers to avoid exploits but if they’re baked into an application you’re implementing it will affect your users and your business, so…
3. Protect wildlife, plants and trees
The most important security contribution we as implementers can bring to the table is to review and limit the privileges required by our applications. Many install guides and expensive external consultants ask for a ‘dbo’ (database owner) level user and some even ask for ‘sa’ (system administrator) or ‘root’ level privileges but don’t hand these out like candy on halloween. In most cases these high-level privileges are only required during setup and install and can be removed afterwards but often basic read/write access is all that is required (and for BI tools often read-only), it may only be achievable through a few frustrating rounds of trial and error but if you assign your applications the lowest possible permissions you will significantly reduce the risk of compromise in the future. Another important step during implementation is to make sure that your permissions are segregated, where possible have a separate user for each service and an entirely separate user for accessing each database not shared by any other application. Whilst it may seem excessive this setup will allow you to audit any security issues and identify which user was compromised and exactly what they had access to.
4. Fasten all gates
Many Business Intelligence tools include some degree of control over connection management and if you’re developing your own application you’ll have complete control over all database connections, the decision to be made is whether connections are ‘pinned’ open, closed after x minutes or closed at the end of each transaction. The preference will vary depending on the load and the usage, in most Business Intelligence use cases there tend to be a large number of users, not always connecting concurrently and issuing fairly large queries against the database followed by periods of quiet whilst a report is read – in this case there is usually no need to keep the connection open for long. On the other hand if you have users issuing a constant stream of small transactions (e.g. a Point of Sale system) the overhead of creating and dropping connections might actually add load to the database so it would be more effective in this scenario to maintain the connection.
5. Keep your dogs under close control
This applies more to developers and BI architects where your dogs are your users, if you are deploying an application that creates load on somebody else’s database you should do whatever you can to limit each user’s ability to cause long running queries – in some BI tools you are handed an option to let a query time out after x minutes and perhaps limiting the number of rows returned. If you are developing your own application you should include both of these options but make sure that you kill the query at the database level rather than just killing the thread in your application that made the request otherwise it’s equally bad if not worse since the user may simply re-issue the offending query. The actual limits are bound to vary from database to database but that’s where the first point comes in, discuss this with both your users and the DBA.
6. Keep to public paths across farmland / Use gates and stiles to cross fences, hedges and walls
When it comes to solving problems try to stick within the basic and simple boundaries of an ordinary user, avoid using undocumented stored procedures, excessive use of user defined functions, custom data types, plugins and extended stored procedures or anything else that strays too far from a standard install of the database platform. Obviously you’ve got an app to deploy and you want to solve your problems in whatever way is best for your users but the further you are from a standard deployment the more issues you’re likely to encounter, both you and the DBA might be fully aware of this amazing new setting you tweaked to make things run better but a couple of years down the line during a disaster recovery will it all come flooding back quite as easily? What if one or both of you that setup the application have moved on to other roles? Thinking outside the box is great but be conscious of introducing risk and if you do feel that it is necessary then make sure that it’s well documented in the Run Book or the corporate wiki.
7. Leave livestock, crops and machinery alone
Since you may already have elevated privileges on your own database, a shared database or even the server you may be tempted from time to time to perform maintenance tasks or make minor ‘improvements’ to indexes or configuration settings – do not do so without the DBA’s blessing. If you’re following the rules above you’ll probably have a fairly good rapport with the DBA already so it’s likely that you’ll be granted some level of trust not to mess things up but be careful not to overreach, the DBA will be ‘in the loop’ of many changes and other requirements (e.g. critical deadlines, disaster recovery tests, unplanned maintenance) whereas you may not be aware of them so before you make any changes run them past the DBA – just in case.
8. Take your litter home / Help to keep all water clean
If you’ve ever been a DBA you’ll have seen, on more than one occasion, tables popping up called tmpSomethingorOther, tblToBeDeleted or TableName_bak but when it comes to the key questions (How long have these been around? Are they still required?) nobody seems to have a straight answer. I know myself that whilst I’ve been developing data warehouses I’ve created these sorts of tables and subsequently forgotten what they were used for, not too much of a problem if you’re ‘the guy’ but in a large team or with personnel changes over time it can be hard to know what is required and what isn’t – I came to a database once with temporary tables over five years old which had not been deleted out of fear that they were important. The moral here is an obvious one, clean up after yourself or if the table must exist for some short period of time put a note in your diary to come back and cull it.
9. Make no unnecessary noise
Be mindful of what errors you raise and what you write to public logs, if your application causes a large amount of data to be written to database or other centrally collated logs you may inadvertently make it harder to detect genuine issues which will hurt both you and and other users of the database. If you do occasionally need exhaustive logs consider adding a ‘debug mode’ into your application which can be turned on or off via a configuration setting, that way you can turn it on whilst you’re tracing a fault and need more verbose logging then turn it off when you’re done.
10. Take special care on country roads
There can be plenty of unexpected hazards on country roads so don’t always rush around everywhere at 60mph, acknowledge that whist you might want everything to go as fast as possible you could be causing some other critical process to slow or stop. Driving at night can be treacherous too as you might come across an unexpected backup window or import/export process, talk to your DBA and coordinate the major tasks. If it’s a shared server make sure you have access to the task list so that you know where to slot in your jobs and that those jobs get put back into the master list.
Really it comes down to one thing, as the great and wise Jerry Springer oft said, “take care of yourselves, and each other”.
Categories: Business Intelligence, DBA Tags: BI, DBA, logging, performance, Security, sql
Quick Tip – PostgreSQL Equivalent of ISNUMERIC()
Very much like my previous MySQL ISNUMERIC() post I have recently been setting up a data source to collect records with telephone numbers from a Postgres database and one of the essential validation tests is to make sure that the field really does contain a number.
Despite the fact that many regard Postgres as the best open source database platform I find myself frustrated by it’s lack of standard functions. I understand that Postgres is designed to be extensible and that user defined functions can be built but I need my code to be both portable and read-only so I have to work with what I’m given. Ideally what I’d be looking for is an equivalent of Microsoft SQL Server’s ISNUMERIC() or Excel’s ISNUMBER() functions but very much like MySQL I had to turn to regular expressions although as you’ll see, Postgres does not have a clean and clear REGEXP() function…
SELECT DISTINCT contact_number
FROM customers
WHERE (contact_number ~ ‘^[0-9]+$’)
I hope that helps any of you out there that encounter the same problem, thanks to the poster here for my original answer.
Categories: DBA, PostgreSQL Tags: ISNUMERIC, MySQL, Postgres, PostgreSQL, RegExp, Regular Expressions, sql
You reach a fork in the road…
Recently I’ve been working more in the smartphone world than in BI and SQL although for the time being at least I’ll be doing a bit of both so you’ll probably see more mobile app related posts in the feed. In order to provide some degree of separation I’ve created a Mobile User Interface Blog at usabl.net which contains links and screenshots of interesting designs, though any longer more technical articles will still appear here.
If you’re wondering what the crossover is between mobile apps and Business Intelligence it’s all about the user experience, in BI you generally aim to give people the information they need as quickly and efficiently as possible not necessarily in terms of software performance but in report design. I’m not the only one that’s thinking along these lines, Jen Stirrup gave an interesting talk on Data Visualisation at the inaugural SQLHerts meeting and if you’re interested in either topic you’ll most likely be able to catch both of us at the next meeting on July 28th at the University of Hertfordshire (register here).
Categories: Business Intelligence, Mobile Apps Tags: Android, BI, iPhone, Mobile, sql, sqlherts, visualisation
Reset Default Database from Command Line in SQL Server
During a recent consolidation exercise I was migrating one database at a time and then taking the old copy offline, unfortunately one of the DBs had (un-knowingly) been my default database and next time I tried to log in I received the dreaded “Cannot open user default database. Login Failed.” message.
I tried one of the workarounds proffered by Microsoft for this exact problem only to receive exactly the same error message, thankfully I then came across this excellent post on SQL Server Nation which explains the entire issue from start to end and offers a couple of fixes based on your particular scenario.
In my case it was to execute the sp_defaultdb stored procedure using the OSQL utility, for example…
osql -Sservername -E -dmaster -Q”sp_defaultdb ‘username’,'master’”
Sincere thanks to Brandon Galderisi from SQL Server Nation for the fix.
Categories: Microsoft SQL Server Tags: Microsoft SQL Server, osql, sql, SQL Server
Register an Extended Stored Procedure in SQL Server 2008 R2
Aside from those integrated into SQL Server (e.g. xp_cmdshell) it’s not often I come across the need to use Extended Stored Procedures but an application I installed recently required that I add their custom procedure to the SQL Server housing the application data. Having been years since I had last added one it took a little figuring out since I would’ve expected to find it in Management Studio under “Server Objects” or “Management” but it’s somewhere entirely different.
To add/register an Extended Stored Procedure you’ll need to right-click on…
Databases >> System Databases >> master >> Programability >> Extended Stored Procedures
…and select “New Extended Stored Procedure”.
Next you’ll have to provide a (this will be the name the procedure is called by) and the path to the DLL, you can browse to the the .dll file by clicking on the elipsis.
The next step is vital since at the moment the only people able to actually use the Extended Stored Procedure would by sysadmins. All you have to do to remedy that is click on “Permissions”, click “Search”, type “public” in the text box and click OK as follows…
All you have to do now is tick the “Execute” permission to allow the ‘public’ users of the database (effectively everybody) to be able to use the procedure.
The completed dialog box should look something like this…
Then click “OK” and all should be well.
Categories: Microsoft SQL Server Tags: Extended Stored Procedure, Management Studio, Microsoft SQL Server, sql, SQL Server, SSMS, Stored Procedure
How to Enable 32-bit Runtime Mode in SSIS
If you’re just beginning to play with SSIS on a 64-bit box you’re pretty likely to hit a roadblock if your data sources have 32-bit ODBC drivers. The error will become obvious immediately when you come to execute your package in BIDS (Business Intelligence Development Studio)…
The ODBC Driver Manager error reported in the Output window will be: ”The specified DSN contains an architecture mismatch between the Driver and Application”. Thankfully this is a pretty easy one to sort out, all you have to do is…
- Right-click on the Project name in the Solution Explorer and select Properties…
- Choose “Debugging” in the left-hand pane…
- Change the Run64BitRuntime value to False (by double-clicking on it).
For reference the help-text states that if the 64-bit SSIS runtime is not installed this setting is ignored so if you’re working on a 32-bit box in all liklihood you wouldn’t experience this issue.
- Click OK and re-run your package.
Categories: Microsoft SQL Server, SSIS Tags: 32-bit, 64-bit, Integration Services, ODBC, sql, SQL Server, SSIS
