Domino: 8.5.1 XPages Bug in Document Data Source

A bug in 8.5.1 Domino Designer causes the field list for a Document data source to not appear in the Domino Designer data tab in right hand sidebar.

[Domino] Integer division operator

I often use code such as the following to simply divide two integers and get the result as an integer, throwing away any remainder:

…

dim x as integer, y as integer, res as integer

x = 11

y =4

res = Fix (x / y)

…

The above code would return 2 in the integer variable res.

Of course, if I had used res = x/y, res would have the value of 3, since LotusScript will implicitly round any float when converting to an integer.

Simple, right? But there actually is an operand for performing exactly this type of “integer division”.  You can use the backslash character ( \ ), as in:

…

res = x \ y

…

The backslash operand has been there forever (well, at least back to R5), but how rarely I see it used.

[SQL Server] Rename a SQL Server Database

Well, this may be obvious for SQL DBA’s, but after completing a data migration effort tonight, I needed to rename a database in SQL Server. Well, you cannot just right-click the database name in SQL Server and choose rename. Instead, you need to get all users out of the database and then open the database in single user mode. At that point, you can run a system stored proc to rename the database. Pretty simple – the second time :)

Here are the steps:

• Kick any connected users out of the database.
• Open database in single-user mode by opening Enterprise Manager and right-clicking the database name, and opening the Properties dialog. In the dialog, go to the Options tab, and select the checkbox labeled Restrict Access and then select the radio button labeled Read-Only.
• (Important) Close Enterprise Manager, to be sure SQL Server does not count that session as a connected user.
• Open Query Analyzer and run the system stored procedure named “sp_renamedb”. The proc takes parameters of the old name and new name. For example: “sp_renamedb MyOldDatabaseName MyNewDatabaseName”
• Close Query Analyzer
• Open Enterprise Manager and undo the Restrict Access setting made earlier. (Your database should now be listed under the new name).

That’s it!

Domino: ArrayUnique may cause server crash in Domino 8.0.1

Yes, if you have 8.0.1 (or earlier), or apparently any version of Domino 7.x, on your server and use the ArrayUnique LotusScript function in a server-side agent, the code may crash the server. Specifically, if the array argument has over 4,085 elements, the server will consistently crash upon executing the ArrayUnique call. there is a recent technote documenting this known bug (which can be found here. (Of course, I learned of the bug the “harder” way).

Note that this is addressed in 8.0.2 and later.

Favorite Books: The Best Software Writing 1

I have finally finished reading through this great collection of essays on software development – The Best Software Writing 1, edited by Joel Spolsky. The books is an interesting collection of writing of interest to any software developer, covering a wide spectrum of topics. I guarantee, the writing in this book will make you think differently about software development and software developers.

A few of my favorite articles include Bruce Eckel’s Strong Typing vs. Strong Testing; Paul Graham’s Great Hackers; Eric Lippert’s How Many Microsoft Employees Does it Take to Change a Lightbulb?; and where the lucky stiff’s A Quick (and Hopefully Painless) Ride Through Ruby.

CSS: IE6 compatibility for <a> tags with no href attribute

Since I still need to worry about compatibility with older browsers (especially IE) on most of my web applications, I try to make sure all of the CSS I use works under IE 6 and up, as well as FireFox and Chrome. I ran into this interesting issue last week (this does seem to be documented elsewhere, so maybe I am just the last to have encountered it). Should you have an anchor tag with no href attribute, IE will not apply any matching a:hover styles. (Althought, IE7+ and Mozilla browsers do). The reason for this is somewhat legit – IE considers an <a> tag without an “href” attribute to be a “destination” anchor tag – that is, an anchor which would be used for intra-page jumping (as in, <a name=’myBookmark’>). And IE only applies :hover styling on “source” anchors – that is, anchors which actually link to something. In my unfortunate situation, I had an anchor tag which was used exclusively to launch some JavaScript. The simple solution – to add an href=”#” attribute.

Domino, documents and content-types

After many years of developing in Notes and Domino, there are some standard design patterns I tend to use over and over. One of these is placing as much (or all) of my client-side code – including Javascript libraries and CSS style sheets – in data documents, rather than design elements. Treating this portion of your application as data has some downsides (think about template deployments) , but also has the advantage of allowing for easier code modification.

 

One drawback, however, is that you may want or need to control the content-type http header sent back from the server. One example is with CSS style sheets – W3C- compliant browsers will not respect styles in a CSS page which is returned as content-type text, or text/html – the page must return as “Content-type: text/css”. Now, IE6 will respect such CSS pages,but IE7 and Firefox will not.

 

As a side note, during development, I really prefer to use Firefox for testing my applications, given the rich debugging environment available. Even when deploying an application in an internal corporate environment, in which we can control the end users to always use a particular IE variant, I still use Firefox for development testing.

 

So, if you have a simple “CODE” form in Domino and each of your code libraries sits in a document using this form, by default Domino will serve these back as content-type: text/html. Not what you want. You cannot control the content-type header through fields on a form, or through the HTMLHead form attribute, or anything along those lines. (Don’t try to use @SetHTTPHeader for content-type in a WebQueryOpen agent – it will be ignored). But you really want something like

“text/javascript” or “text/css” to be set as the content-type header, depending on the type of code in this library document.  So, here is the basic approach I have been using:

 

• Create a subform with the basic fields used for your resource files – such as title, code, etc. And also a radio button field for the Content Type (with values of Javascript, CSS, JSON, XML, etc). And a computed DocType field which computes to “RESOURCE”.
• Create a distinct form for each resource type – for example, one form for CSS resources; one for JavaScript resources; etc. For each form, set the form’s content type as appropriate – for example, “text/javascript” or “application/json”.  Include nothing on each form other than the one subform.
• Create a view with a selection formula which includes documents created with DocType of “RESOURCE”, and with a form formula which computes to the appropriate form based on the “Content Type” radio button.

That’s all – you can then reference any of the resource documents in a form or page’s HTMLHead formula, using a simple formula such as:

 

“/” + @webDbName + “/vwResource/myJavascript.js”

 

The resource will be served by Domino with the appropriate content-type header.

Domino: Access control lists demystified

Notes / Domino Access Control Lists (ACL’s) are fairly straightforward to understand. However, there are a few subtle nuances that are often not known or understood by even experienced developers and admins. In particular, when a user resolves into multiple ACL entries, the rules for how Domino interprets a user’s access level and roles is not always obvious.

An ACL consists of a collection of ACL Entries (and a few other items). To start, let’s look at an ACL entry. An entry contains four basic elements – the name, the access level, a set of roles, and a set of additional privileges (such as “can delete documents”, “can create shared views”, etc.) The name can be either: a user name, a group name, or a “certifier wildcard” (there is also the built-in “Default” name).

So, let’s now imagine a user attempting to access a database. The Domino server first resolves the user and computes a list of all Name and Address (NAB) groups that the user belongs to (this includes resolving membership in nested subgroups, and groups in secondary address books). This step is actually only done once per server and the resulting name/group list is cached. With the user’s name and group list in hand, the Domino server now compares this to the ACL of the database. Any given user may match any number of ACL entries (for example, a user may be listed directly in the ACL, and may be a member of two groups in the ACL and the user’s canonical name may match a certifier wildcard entry). This is all pretty basic – but it’s the next step which is more subtle: how does Domino build your access privileges when you match multiple NAB entries?

Remember those four types of ACL entries? Individual names, groups, certifier wildcards and “default”. Those are important, as the Domino server treats each of these four types as a separate step in the access resolution process, and tries to find a match for this user, in the following order:

1. Individual names
2. Groups
3. Certifier wildcards
4. the “default” entry (which always matches)

At each step, Domino finds all matching ACL entries of the particular type – if there are any matches, the user resolves to the following:

• the highest access level of all matches
• the union of the roles in all of the matches
• the union of the privileges in all of the matches

Once one or matches are found at a given step, DOMINO DOES NOT PROCEED FURTHER. This means, if a user’s name matches an individual name in the NAB, the user will receive that entry’s access level and roles. If the user also matches a group, which has a higher access level, or additional roles, the user WILL NOT receive those privileges. This also means, for example, if the user is in a group with Reader access and the default for the database is Author access, the user will only receive Reader access.

Note:all of the above steps assume that the user is authorized to access the server. If the user is not – for example, if the user’s name is listed in a terminations group (a “deny access” group) which is listed in a server document, then the user will not be allowed access to any database on that server, regardless of the database’s ACL.

SQL: Be aware of views with “Select Top 100 Percent”

In SQL Server 2003 and 2005, Microsoft made a rather subtle change to the query engine, which was to remove the “TOP” phrase from the select clause, if the top value is “100 PERCENT”. This makes perfect sense, as using “select top 100 percent …” is no different from simply using “select …” – that is the default behavior without a TOP phrase. So, what’s the problem?

Well, the problem relates to views in a SQL Server database. First, a little background. In SQL Server, as in most RDBMS’, views are a mechanism for defining a horizontal and vertical “slice” of a table (or virtual table) – a subset of the columns and rows of data. Views, in theory, are not sorted – the same way that tables are not sorted. If you want a collection of rows from a view, you add an ORDER BY clause to the select statement when you query rows from the view.  SQL Server even enforces this, by preventing creation of a view using a sql query which includes an ORDER BY  clause.

But there are scenarios  (some legitimate, some not so much) in which you may really want to force a sort on the rows of your view. And in SQL Server 2000 and earlier, you could do this via a bit of a hack – by defining your view query using “select TOP 100 PERCENT”.

An aside: Why would that work? Well, consider the case in which your view should only include the first 25% percent of the rows in a table – well, the “top 25%” only makes sense in the context of a result set which is sorted, right? (What does the “top 25%” from my employee table mean? The top by alphabetical name? By age? By hat size?) So, SQL Server allows this as a special case – you can use an ORDER BY clause in the definition of a view IF you also include a “TOP” phrase in th select clause. So, if you really wanted to force a sort on a view, but you wanted to include all of the records returned by your query, you could “trick” SQL Server into allowing this by adding the “TOP 100 PERCENT.”

So, back to the problem – as of SQL Server 2003, the SQL engine is now (in something of a pre-compile step), removing the TOP 100 PERCENT from any sql queries. And any views which existed in a SQL 2000 or earlier database which was upgraded, which made use of this little trick, would internally have the TOP phrase remove, and then also have the ORDER BY removed. The end result – the same view, but no longer sorted. And if your applications were assuming queries against that view would always be sorted, you now have a broken application.

The “correct” way to resolve this depends on the situation. If possible, the better solution is to add any sorting in the SQL statement which queries the view. But if you do absolutely need the sorting in the view definition, then you can simply change that “SELECT TOP 100 PERCENT” to “SELECT TOP 99.999 PERCENT” or “SELECT TOP 2147483647″ (the max integer size)  - just bear in mind, you are trading one hack for another.

Domino: Notes/Domino Interface now available for Google Search Appliance

This may be interesting for IBM Notes shops which are using the Google Search Appliance. There is now a “Google Enterprise Connector” available for Notes. It’s not officially supported by Google, but is on code.google.com as a free download. In taking a quick read through the Installation Manual, I was impressed to see that the installation and configuration is done through a Notes database – more Notes-like than I would have expected.

Link: http://code.google.com/p/google-enterprise-connector-notes/