fabiano - Page 2 - Developer IT

Way to partialy match a Ruby string using Regexp

- by Fabiano PS

I'm working on 2 cases: assume I have those var: a = "hello" b = "hello-SP" b = "not_hello" 1 - Any partial matches I want to accept any string that has the var a inside, so b and c would match. 2 - Patterned match I want to match a string that has a inside, followed by '-', so b would match, c does not. I am having problem, because I always used the syntax /expression/ to define Regexp, so how dinamicaly define an RegExp on Ruby??

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Binded click loses context of my Class. JS

- by Fabiano PS

Hi, I have this problem that I probably understand but don't know how to handle, if there is a way. I have a class simplified as this: function DrawingTable(canvas_id){ this.canvas_id = canvas_id; bind_events() function bind_events(){ $(get_canvas()).click(function(e){ var canvas = get_canvas() //works do_something_in_the_instance_who_called_click() } function get_canvas(){return document.getElementById(canvas_id)} function do_something_in_the_instance_who_called_click(){ alert(this.canvas_id) //fail! } } Because when the click() is invoked for what it looks this is not inside the instance anymore, but I need to change atributes from there.. is there a way, given that may be multiple instances? I don't really know how but the get_canvas() works :) I'm using jQuery but likely not relevant

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Rails - set POST request limit (file upload)

- by Fabiano PS

I am building a file uploader for Rails, using CarrierWave. I am pretty happy about it's API, except that I don't seem to be able to cut file uploads that exceed a limit on the fly. I found this plugin for validation, but the problem is that it happens after the upload is completed. It is completely unacceptable in my case, as any user could take the site down by uploading a huge file. So, I figure that the way would be to use some Rack configuration or middleware that will limit POST body size as it receives. I am hosting on Heroku, as context. *I am aware of https://github.com/dwilkie/carrierwave_direct but it doesn't solve my issue as I have to resize first and discard the original large image.

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Showplan Operator of the Week – BookMark/Key Lookup

Fabiano continues in his mission to describe the major Showplan Operators used by SQL Server's Query Optimiser. This week he meets a star, the Key Lookup, a stalwart performer, but most famous for its role in ill-performing queries where an index does not 'cover' the data required to execute the query. If you understand why, and in what circumstances, key lookups are slow, it helps greatly with optimising query performance.

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Operator of the Week - Spools, Eager Spool

For the fifth part of Fabiano's mission to describe the major Showplan Operators used by SQL Server's Query Optimiser, he introduces the spool operators and particularly the Eager Spool, explains blocking and non-blocking and then describes how the Halloween Problem is avoided.

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Showplan Operator of the Week - Concatenation

Fabiano continues in his mission to describe, one week at a time, all the major Showplan Operators used by SQL Server's Query Optimiser to build the Query Plan. This week he gets the Concatenation operator .

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Showplan Operator of the Week - Concatenation

Fabiano continues in his mission to describe, one week at a time, all the major Showplan Operators used by SQL Server's Query Optimiser to build the Query Plan. This week he gets the Concatenation operator ....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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Showplan Operator of the week - Assert

As part of his mission to explain the Query Optimiser in practical terms, Fabiano attempts the feat of describing, one week at a time, all the major Showplan Operators used by SQL Server's Query Optimiser to build the Query Plan. He starts with Assert

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ShowPlan Operator of the Week - Merge Join

Did you ever wonder how and why your indexes affect the performances of joins? Once you've read Fabiano Amorim's unforgettable explanation, you'll learn to love the MERGE operator, and plan your indexes so as to allow the Query Optimiser to use it. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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Showplan Operator of the Week – BookMark/Key Lookup

Fabiano continues in his mission to describe the major Showplan Operators used by SQL Server's Query Optimiser. This week he meets a star, the Key Lookup, a stalwart performer, but most famous for its role in ill-performing queries where an index does not 'cover' the data required to execute the query. If you understand why, and in what circumstances, key lookups are slow, it helps greatly with optimising query performance.

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Lipoaspiration in your SQL Server Database

Once, when disk space was at a premium, DBAs fought hard to keep the size of their database down. Now there seems less motivation to 'fight the flab' of a database. Fabiano Amorim was watching television recently when the subject matter, cosmetic surgery, gave him the theme and inspiration for this guide to keeping your database fit and trim. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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It’s the thought that counts…

- by Tony Davis

I recently finished editing a book called Tribal SQL, and it was a fantastic experience. It’s a community-sourced book written by first-timers. Fifteen previously unpublished authors contributed one chapter each, with the seemingly simple remit to write about “what makes them passionate about working with SQL Server, something that all SQL Server DBAs and developers really need to know”. Sure, some of the writing skills were a bit rusty as one would expect from busy people, but the ideas and energy were sheer nectar. Any seasoned editor can deal easily with the problem of fixing the output of untrained writers. We can handle with the occasional technical error too, which is why we have technical reviewers. The editor’s real job is to hone the clarity and flow of ideas, making the author’s knowledge and experience accessible to as many others as possible. What the writer needs to bring, on the other hand, is enthusiasm, attention to detail, common sense, and a sense of the person behind the writing. If any of these are missing, no editor can fix it. We can see these essential characteristics in many of the more seasoned and widely-published writers about SQL. To illustrate what I mean by enthusiasm, or passion, take a look at the work of Laerte Junior or Fabiano Amorim. Both authors have English as a second language, but their energy, enthusiasm, sheer immersion in a technology and thirst to know more, drives them, with a little editorial help, to produce articles of far more practical value than one can find in the “manuals”. There’s the attention to detail of the likes of Jonathan Kehayias, or Paul Randal. Read their work and one begins to understand the knowledge coupled with incredible rigor, the willingness to bend and test every piece of advice offered to make sure it’s correct, that marks out the very best technical writing. There’s the common sense of someone like Louis Davidson. All writers, including Louis, like to stretch the grey matter of their readers, but some of the most valuable writing is that which takes a complicated idea, or distils years of experience, and expresses it in a way that sounds like simple common sense. There’s personality and humor. Contrary to what you may have been told, they can and do mix well with technical writing, as long as they don’t become a distraction. Read someone like Rodney Landrum, or Phil Factor, for numerous examples of articles that teach hard technical lessons but also make you smile at least twice along the way. Writing well is not easy and it takes a certain bravery to expose your ideas and knowledge for dissection by others, but it doesn’t mean that writing should be the preserve only of those trained in the art, or best left to the MVPs. I believe that Tribal SQL is testament to the fact that if you have passion for what you do, and really know your topic then, with a little editorial help, you can write, and people will learn from what you have to say. You can read a sample chapter, by Mark Rasmussen, in this issue of Simple-Talk and I hope you’ll consider checking out the book (if you needed any further encouragement, it’s also for a good cause, Computers4Africa). Cheers, Tony

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Write TSQL, win a Kindle.

- by Fatherjack

So recently Red Gate launched sqlmonitormetrics.red-gate.com and showed the world how to embed your own scripts harmoniously in a third party tool to get the details that you want about your SQL Server performance. The site has a way to submit your own metrics and take a copy of the ones that other people have submitted to build a library of code to keep track of key metrics of your servers performance. There have been several submissions already but they have now launched a competition to provide an incentive for you to get creative and show us what you can do with a bit of TSQL and the SQL Monitor framework*. What’s it worth? Well, if you are one of the 3 winners then you get to choose either a Kindle Fire or $199. How do you win? Simply write the T-SQL for a SQL Monitor custom metric and the relevant description and introduction for it and submit it via sqlmonitormetrics.red-gate.com before 14th Sept 2012 and then sit back and wait while the judges review your code and your aims in writing the metric. Who are the judges and how will they judge the metrics? There are two judges for this competition, Steve Jones (Microsoft SQL Server MVP, co-founder of SQLServerCentral.com, author, blogger etc) and Jonathan Allen (um, yeah, Steve has done all the good stuff, I’m here by good fortune). We will be looking to rate the metrics on each of 3 criteria: how the metric can help with performance tuning SQL Server. how having the metric running enables DBA’s to meet best practice. how interesting /original the idea for the metric is. Our combined decision will be final etc etc ** What happens to my metric? Any metrics submitted to the competition will be automatically entered into the site library and become available for sharing once the competition is over. You’ll get full credit for metrics you submit regardless of the competition results. You can enter as many metrics as you like. How long does it take? Honestly? Once you have the T-SQL sorted then so long as you can type your name and your email address you are done : http://sqlmonitormetrics.red-gate.com/share-a-metric/ What can I monitor? If you really really want a Kindle or $199 (and let’s face it, who doesn’t? ) and are momentarily stuck for inspiration, take a look at these example custom metrics that have been written by Stuart Ainsworth, Fabiano Amorim, TJay Belt, Louis Davidson, Grant Fritchey, Brad McGehee and me to start the library off. There are some great pieces of TSQL in those metrics gathering important stats about how SQL Server is performing. * – framework may not be the best word here but I was under pressure and couldnt think of a better one. If you prefer try ‘engine’, or ‘application’? I don’t know, pick something that makes sense to you. ** – for the full (legal) version of the rules check the details on sqlmonitormetrics.red-gate.com or send us an email if you want any point clarified. Disclaimer – Jonathan is a Friend of Red Gate and as such, whenever they are discussed, will have a generally positive disposition towards Red Gate tools. Other tools are often available and you should always try others before you come back and buy the Red Gate ones. All code in this blog is provided “as is” and no guarantee, warranty or accuracy is applicable or inferred, run the code on a test server and be sure to understand it before you run it on a server that means a lot to you or your manager.

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Execution plan warnings–The final chapter

- by Dave Ballantyne

In my previous posts (here and here), I showed examples of some of the execution plan warnings that have been added to SQL Server 2012. There is one other warning that is of interest to me : “Unmatched Indexes”. Firstly, how do I know this is the final one ? The plan is an XML document, right ? So that means that it can have an accompanying XSD. As an XSD is a schema definition, we can poke around inside it to find interesting things that *could* be in the final XML file. The showplan schema is stored in the folder Microsoft SQL Server\110\Tools\Binn\schemas\sqlserver\2004\07\showplan and by comparing schemas over releases you can get a really good idea of any new functionality that has been added. Here is the section of the Sql Server 2012 showplan schema that has been interesting me so far : <xsd:complexType name="AffectingConvertWarningType"> <xsd:annotation> <xsd:documentation>Warning information for plan-affecting type conversion</xsd:documentation> </xsd:annotation> <xsd:sequence>  </xsd:sequence> <xsd:attribute name="ConvertIssue" use="required"> <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:enumeration value="Cardinality Estimate" /> <xsd:enumeration value="Seek Plan" />  </xsd:restriction> </xsd:simpleType> </xsd:attribute> <xsd:attribute name="Expression" type ="xsd:string" use="required" /></xsd:complexType><xsd:complexType name="WarningsType"> <xsd:annotation> <xsd:documentation>List of all possible iterator or query specific warnings (e.g. hash spilling, no join predicate)</xsd:documentation> </xsd:annotation> <xsd:choice minOccurs="1" maxOccurs="unbounded"> <xsd:element name="ColumnsWithNoStatistics" type="shp:ColumnReferenceListType" minOccurs="0" maxOccurs="1" /> <xsd:element name="SpillToTempDb" type="shp:SpillToTempDbType" minOccurs="0" maxOccurs="unbounded" /> <xsd:element name="Wait" type="shp:WaitWarningType" minOccurs="0" maxOccurs="unbounded" /> <xsd:element name="PlanAffectingConvert" type="shp:AffectingConvertWarningType" minOccurs="0" maxOccurs="unbounded" /> </xsd:choice> <xsd:attribute name="NoJoinPredicate" type="xsd:boolean" use="optional" /> <xsd:attribute name="SpatialGuess" type="xsd:boolean" use="optional" /> <xsd:attribute name="UnmatchedIndexes" type="xsd:boolean" use="optional" /> <xsd:attribute name="FullUpdateForOnlineIndexBuild" type="xsd:boolean" use="optional" /></xsd:complexType> I especially like the “to be extended here” comment, high hopes that we will see more of these in the future. So “Unmatched Indexes” was a warning that I couldn’t get and many thanks must go to Fabiano Amorim (b|t) for showing me the way. Filtered indexes were introduced in Sql Server 2008 and are really useful if you only need to index only a portion of the data within a table. However, if your SQL code uses a variable as a predicate on the filtered data that matches the filtered condition, then the filtered index cannot be used as, naturally, the value in the variable may ( and probably will ) change and therefore will need to read data outside the index. As an aside, you could use option(recompile) here , in which case the optimizer will build a plan specific to the variable values and use the filtered index, but that can bring about other problems. To demonstrate this warning, we need to generate some test data : DROP TABLE #TestTab1GOCREATE TABLE #TestTab1 (Col1 Int not null, Col2 Char(7500) not null, Quantity Int not null)GOINSERT INTO #TestTab1 VALUES (1,1,1),(1,2,5),(1,2,10),(1,3,20), (2,1,101),(2,2,105),(2,2,110),(2,3,120)GO and then add a filtered index CREATE INDEX ixFilter ON #TestTab1 (Col1)WHERE Quantity = 122 Now if we execute SELECT COUNT(*) FROM #TestTab1 WHERE Quantity = 122 We will see the filtered index being scanned But if we parameterize the query DECLARE @i INT = 122SELECT COUNT(*) FROM #TestTab1 WHERE Quantity = @i The plan is very different a table scan, as the value of the variable used in the predicate can change at run time, and also we see the familiar warning triangle. If we now look at the properties pane, we will see two pieces of information “Warnings” and “UnmatchedIndexes”. So, handily, we are being told which filtered index is not being used due to parameterization.

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