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• Newbie database index question

  - by RenderIn

  I have a table with multiple indexes, several of which duplicate the same columns: Index 1 columns: X, B, C, D Index 2 columns: Y, B, C, D Index 3 columns: Z, B, C, D I'm not very knowledgeable on indexing in practice, so I'm wondering if somebody can explain why X, Y and Z were paired with these same columns. B is an effective date. C is a semi-unique key ID for this table for a specific effective date B. D is a sequence that identifies the priority of this record for the identifier C. Why not just create 6 indexes, one for each X, Y, Z, B, C, D? I want to add an index to another column T, but in some contexts I'll only be querying on T alone while in others I will also be specifying the B, C and D columns... so should I create just one index like above or should I create one for T and one for (T, B, C, D)? I've not had as much luck as expected when googling for comprehensive coverage of indexing. Any resources where I can get a through explanation and lots of examples of B-tree indexing?

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• Lua Operator Overloading

  - by Pessimist

  I've found some places on the web saying that operators in Lua are overloadable but I can't seem to find any example. Can someone provide an example of, say, overloading the + operator to work like the .. operator works for string concatenation? EDIT 1: to Alexander Gladysh and RBerteig: If operator overloading only works when both operands are the same type and changing this behavior wouldn't be easy, then how come the following code works? (I don't mean any offense, I just started learning this language): printf = function(fmt, ...) io.write(string.format(fmt, ...)) end Set = {} Set.mt = {} -- metatable for sets function Set.new (t) local set = {} setmetatable(set, Set.mt) for _, l in ipairs(t) do set[l] = true end return set end function Set.union (a,b) -- THIS IS THE PART THAT MANAGES OPERATOR OVERLOADING WITH OPERANDS OF DIFFERENT TYPES -- if user built new set using: new_set = some_set + some_number if type(a) == "table" and type(b) == "number" then print("building set...") local mixedset = Set.new{} for k in pairs(a) do mixedset[k] = true end mixedset[b] = true return mixedset -- elseif user built new set using: new_set = some_number + some_set elseif type(b) == "table" and type(a) == "number" then print("building set...") local mixedset = Set.new{} for k in pairs(b) do mixedset[k] = true end mixedset[a] = true return mixedset end if getmetatable(a) ~= Set.mt or getmetatable(b) ~= Set.mt then error("attempt to 'add' a set with a non-set value that is also not a number", 2) end local res = Set.new{} for k in pairs(a) do res[k] = true end for k in pairs(b) do res[k] = true end return res end function Set.tostring (set) local s = "{" local sep = "" for e in pairs(set) do s = s .. sep .. e sep = ", " end return s .. "}" end function Set.print (s) print(Set.tostring(s)) end s1 = Set.new{10, 20, 30, 50} s2 = Set.new{30, 1} Set.mt.__add = Set.union -- now try to make a new set by unioning a set plus a number: s3 = s1 + 8 Set.print(s3) --> {1, 10, 20, 30, 50}

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• R: convert data.frame columns from factors to characters

  - by Mike Dewar

  Hi, I have a data frame. Let's call him bob: > head(bob) phenotype exclusion GSM399350 3- 4- 8- 25- 44+ 11b- 11c- 19- NK1.1- Gr1- TER119- GSM399351 3- 4- 8- 25- 44+ 11b- 11c- 19- NK1.1- Gr1- TER119- GSM399352 3- 4- 8- 25- 44+ 11b- 11c- 19- NK1.1- Gr1- TER119- GSM399353 3- 4- 8- 25+ 44+ 11b- 11c- 19- NK1.1- Gr1- TER119- GSM399354 3- 4- 8- 25+ 44+ 11b- 11c- 19- NK1.1- Gr1- TER119- GSM399355 3- 4- 8- 25+ 44+ 11b- 11c- 19- NK1.1- Gr1- TER119- I'd like to concatenate the rows of this data frame (this will be another question). But look: > class(bob$phenotype) [1] "factor" Bob's columns are factors. So, for example: > as.character(head(bob)) [1] "c(3, 3, 3, 6, 6, 6)" "c(3, 3, 3, 3, 3, 3)" [3] "c(29, 29, 29, 30, 30, 30)" I don't begin to understand this, but I guess these are indices into the levels of the factors of the columns (of the court of king caractacus) of bob? Not what I need. Strangely I can go through the columns of bob by hand, and do bob$phenotype <- as.character(bob$phenotype) which works fine. And, after some typing, I can get a data.frame whose columns are characters rather than factors. So my question is: how can I do this automatically? How do I convert a data.frame with factor columns into a data.frame with character columns without having to manually go through each column? Bonus question: why does the manual approach work?

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• ActiveRecord table inheritence using set_table_names

  - by Jinyoung Kim

  Hi, I'm using ActiveRecord in Ruby on Rails. I have a table named documents(Document class) and I want to have another table data_documents(DataDocument) class which is effectively the same except for having different table name. In other words, I want two tables with the same behavior except for table name. class DataDocument < Document #set_table_name "data_documents" self.table_name = "data_documents" end My solution was to use class inheritance as above, yet this resulted in inconsistent SQL statement for create operation where there are both 'documents' table and 'data_documents' table. Can you figure out why and how I can make it work? >> DataDocument.create(:did=>"dd") ActiveRecord::StatementInvalid: Mysql::Error: Unknown column 'data_documents.did' in 'where clause': SELECT `documents`.id FROM `documents` WHERE (`data_documents`.`did` = BINARY 'dd') LIMIT 1 from /Users/lifidea/.gem/ruby/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/abstract_adapter.rb:212:in `log' from /Users/lifidea/.gem/ruby/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/mysql_adapter.rb:320:in `execute' from /Users/lifidea/.gem/ruby/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/mysql_adapter.rb:595:in `select' from /Users/lifidea/.gem/ruby/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/abstract/database_statements.rb:7:in `select_all_without_query_cache' from /Users/lifidea/.gem/ruby/1.8/gems/activerecord-2.3.2/lib/active_record/connection_adapters/abstract/query_cache.rb:62:in `select_all'

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• Groovlet + Tomcat: "unable to resolve class" when importing libraries

  - by Rob Hruska

  I'm having some trouble running a groovy servlet (groovlet) in tomcat that imports a library class. When I don't import anything the groovlet works correctly, but if I do import something that I expect to be on the classpath (I can import the same class successfully in a regular servlet), I see the following error: groovy.util.ScriptException: Could not parse scriptName: /MyGroovlet.groovy java.lang.RuntimeException: groovy.util.ScriptException: Could not parse scriptName: /MyGroovlet.groovy at groovy.servlet.GroovyServlet$1.call(GroovyServlet.java:123) ... Caused by: org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, /MyGroovlet.groovy: 1: unable to resolve class com.mycompany.mypackage.MyLibraryClass @ line 1, column 1. The jar containing MyLibraryClass is in shared/lib, which is loaded by tomcat by the following in catalina.properties: shared.loader=...,${catalina.base}/shared/lib/*.jar,... My groovlets are mapped as described in the user guide in my application's web.xml: <servlet> <servlet-name>GroovyServlet</servlet-name> <servlet-class>groovy.servlet.GroovyServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>GroovyServlet</servlet-name> <url-pattern>*.groovy</url-pattern> </servlet-mapping> And here's the code for the groovlet, MyGroovlet.groovy: import com.mycompany.mypackage.MyLibraryClass MyLibraryClass.someStaticMethod() My groovlet is deployed to WEB-INF/groovy/MyGroovlet.groovy, per the GroovyServlet API. When I visit http://localhost:8080/myapplication/MyGroovlet.groovy, the error described previously is written to my application logs. Is there some way that I need to explicitly declare the runtime classpath for GroovyServlet? I've tried moving the library jar to several places, including WEB-INF/lib and moving the actual MyLibraryClass.class file to WEB-INF/classes, but with no luck.

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• problem with ajax on the hosting server

  - by nelly

  when I Implemented chatting Function , I use Ajax to send messages between file to another . so , it is working well on local host . but , when I upload it in to remote server it doesn't work. can U tell me ,why ? is an Ajax need Special configuration ? there is my files that I used : Ajax .js file witch has "ajax_send" function that i used in chatbox.js file chatbox.js file wich consest of functions i used it to send data from php file to another one and it display the state (any user sign in or new sending message and so on ..) user.php file whitch responseble to write user name in the text file usersonline.txt and then display the online users in the online users column. send.php file that write on room1.text recive.php file that read room1.txt and then write the content into the chat box I beleve that the problem comes from the ajax code in Ajax.js File so please help me find out the problem and how to solve it. is ajax needs special server settings ? because it was working at the local host !

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• MySQL get list of unique items in a SET

  - by The Disintegrator

  I have a products table with a column of type SET (called especialidad), with these possible values. [0] => NADA [1] => Freestyle / BMX [2] => Street / Dirt [3] => XC / Rural Bike [4] => All Mountain [5] => Freeride / Downhill / Dual / 4x [6] => Ruta / Triathlon / Pista [7] => Comfort / City / Paseo [8] => Kids [9] => Playera / Chopper / Custom [10] => MTB recreacion [11] => Spinning / Fitness Any given product can have one or many of these i/e "Freestyle / BMX,Street / Dirt" Given a subset of the rows, I need to get a list of all the present "especialidad" values. But I need a list to be exploded and unique Article1: "Freestyle / BMX,Street / Dirt" Article2: "Street / Dirt,Kids" Article2: "Kids" Article4: "Street / Dirt,All Mountain" Article5: "Street / Dirt" I need a list like this Freestyle / BMX Street / Dirt" Kids" All Mountain" I tried with group_concat(UNIQUE) but I get a list of the permutations...

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• Fuzzy Search on Material Descriptions including numerical sizes & general descriptions of material t

  - by Kyle

  We're looking to provide a fuzzy search on an electrical materials database (i.e. conduit, cable, etc.). The problem is that, because of a lack of consistency across all material types, we could not split sizes into separate fields from the text description because some materials are rated by things other than size. I've attempted a combination of a full text search & a SQL CLR implementation of the Levenshtein search algorithm (for assistance in ranking), but my results are a little funky (i.e. they are not sorting correctly due to improper ranking). For example, if the search term is "3/4" ABCD Conduit", I'll might get back several irrelevant results in the following order: 1/2" Conduit 1/4" X 3/4" Cable 1/4" Cable Ties 3/4" DFC Conduit Tees 3/4" ABCD Conduit 3/4" Conduit I believe I've nailed the problem down to the fact that these two search algorithms do not factor in the relevance of punctuation & numeric. That is, in such a search, I'd expect the size to take precedence over any fuzzy match on the rest of the description, but my results don't reflect that. My question is: Can anyone recommend better search algorithms or different approaches that may be better suited for searching a combination of alphanumerics & punctuation characters?

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• Web Workers - Transferable Objects for JSON

  - by kclem06

  HTML 5 Web workers are very slow when using worker.postMessage on a large JSON object. I'm trying to figure out how to transfer a JSON Object to a web worker - using the 'Transferable Objects' types in Chrome, in order to increase the speed of this. Here is what I'm referring to and appears it should speed this up quite a bit: http://updates.html5rocks.com/2011/12/Transferable-Objects-Lightning-Fast I'm having trouble finding a good example of this (and I don't believe I want to use an ArrayBuffer). Any help would be appreciated. I'm imagining something like this: worker = new Worker('workers.js'); var large_json = {}; for(var i = 0; i < 20000; ++i){ large_json[i] = i; large_json["test" + i] = "string"; }; //How to make this call to use Transfer Objects? Takes approx 2 seconds to serialize this for me currently. worker.webkitPostMessage(large_json);

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• What am I doing wrong with HttpResponse content and headers when downloading a file?

  - by Slauma

  I want to download a PDF file from a SQL Server database which is stored in a binary column. There is a LinkButton on an aspx page. The event handler of this button looks like this: protected void LinkButtonDownload(object sender, EventArgs e) { ... byte[] aByteArray; // Read binary data from database into this ByteArray // aByteArray has the size: 55406 byte Response.ClearHeaders(); Response.ClearContent(); Response.BufferOutput = true; Response.AddHeader("Content-Disposition", "attachment; filename=" + "12345.pdf"); Response.ContentType = "application/pdf"; using (BinaryWriter aWriter = new BinaryWriter(Response.OutputStream)) { aWriter.Write(aByteArray, 0, aByteArray.Length); } } A "File Open/Save dialog" is offered in my browser. When I store this file "12345.pdf" to disk, the file has a size of 71523 Byte. The additional 16kB at the end of the PDF file are the HTML code of my page (as I can see when I view the file in an editor). I am confused because I was believing that ClearContent and ClearHeaders would ensure that the page content is not sent together with the file content. What am I doing wrong here? Thanks for help!

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• ERROR! (Using Excel's named ranges from C#)

  - by mcoolbeth

  In the following, I am trying to persist a set of objects in an excel worksheet. Each time the function is called to store a value, it should allocate the next cell of the A column to store that object. However, an exception is thrown by the Interop library on the first call to get_Range(). (right after the catch block) Does anyone know what I am doing wrong? private void AddName(string name, object value) { Excel.Worksheet jresheet; try { jresheet = (Excel.Worksheet)_app.ActiveWorkbook.Sheets["jreTemplates"]; } catch { jresheet = (Excel.Worksheet)_app.ActiveWorkbook.Sheets.Add(Type.Missing, Type.Missing, Type.Missing, Type.Missing); jresheet.Visible = Microsoft.Office.Interop.Excel.XlSheetVisibility.xlSheetVeryHidden; jresheet.Name = "jreTemplates"; jresheet.Names.Add("next", "A1", true, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing); } Excel.Range cell = jresheet.get_Range("next", Type.Missing); cell.Value2 = value; string address = ((Excel.Name)cell.Name).Name; _app.ActiveWorkbook.Names.Add(name, address, false, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing); cell = cell.get_Offset(1, 0); jresheet.Names.Add("next", ((Excel.Name)cell.Name).Name, true, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing); }

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• Circular Dependency of Navigation Control in iPhone

  - by Taimur Hamza

  Hi everyone , In my view this is one of the strangest problem i have ever come across in iPhone app development. Let me explain the scenario , i have main screen 'A' on which i have a Button that directs me to another Screen say 'B'. Now on Screen 'B' i have a feature in which user can send a mail to his friend for promotion purpose e.g a user wishes to tell a frnd about this app so i used MFMailComposeViewController and a view is generated where the user types the address and click send ( subject and body of mail is automatically generated ). After sending the mail a new view opens say screen 'C' and here i want to give the user the options . 1. Go to Screen 'A' ( which is main screen of the app ) 2. Go back to Screen 'B' ( from where the user requested to send a mail to his frnd ). Now the strange part i cannot declare the variables ( Screen 'A' and 'B' ) of both these files here at in header file of screen 'C' . Even when i declare the header file at the top it generates an error. The variables can be easily be declared and used for other screens but not for these 2 screens. Can anybody please explain wats the problem.? this the text of the error "/Users/admin/Documents/AppName/Classes/A.h:42: error: expected specifier-qualifier-list before 'B'" Thanks Guys ! Taimur

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• WPF TexBox TwoWay Binding Problem when ValidationRules used

  - by ignis

  I seem to have a problem with TwoWay DataBinding - my application has a window with a bunch of textboxes that allow to edit values of the properties they are bound to. Everything works well except for textboxes that also have a validation rule defined, in which case no text is displayed in the textbox when the window opens (binding back-to-source still works fine for those). If I remove Validation rule, everything's back to normal. I searched for an answer to this for a few hours now, but somehow did not even find anyone else complaining of the same issue. I am completely new to WPF, and I am sure it is just a silly mistake I have somewhere in my code... I will greatly appreciate any feedback... <TextBox Margin="40,2,20,0" Grid.Column="0" Grid.Row="1" Background="#99FFFFFF" > <Binding Path="LastName" Mode="TwoWay" ValidatesOnDataErrors="true" UpdateSourceTrigger="LostFocus" > <Binding.ValidationRules> <validation:StringNameValidationRule /> </Binding.ValidationRules> </Binding> </TextBox>

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• Using multiple aggregate functions in an (ANSI) SQL statement

  - by morpheous

  I have aggregate functions foo(), foobar(), fredstats(), barneystats() I want to create a domain specific query language (DSQL) above my DB, to facilitate using a domain language to query the DB. The 'language' comprises of algebraic expressions (or more specifically SQL like criteria) which I use to generate (ANSI) SQL statements which are sent to the db engine. The following lines are examples of what the language statements will look like, and hopefully, it will help further clarify the concept: **Example 1** DQL statement: foobar('yellow') between 1 and 3 and fredstats('weight') > 42 Translation: fetch all rows in an underlying table where computed values for aggregate function foobar() is between 1 and 3 AND computed value for AGG FUNC fredstats() is greater than 42 **Example 2** DQL statement: fredstats('weight') < barneystats('weight') AND foo('fighter') in (9,10,11) AND foobar('green') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 3** DQL statement: foobar('green') / foobar('red') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 4** DQL statement: foobar('green') - foobar('red') >= 42 Translation: Fetch all rows where the specified criteria matches Given the following information: The table upon which the queries above are being executed is called 'tbl' table 'tbl' has the following structure (id int, name varchar(32), weight float) The result set returns only the tbl.id, tbl.name and the names of the aggregate functions as columns in the result set - so for example the foobar() AGG FUNC column will be called foobar in the result set. So for example, the first DQL query will return a result set with the following columns: id, name, foobar, fredstats Given the above, my questions then are: What would be the underlying SQL required for Example1 ? What would be the underlying SQL required for Example3 ? Given an algebraic equation comprising of AGGREGATE functions, Is there a way of generalizing the algorithm needed to generate the required ANSI SQL statement(s)? I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible.

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• Ordering view by highest group count question - Ruby on Rails

  - by bgadoci

  I've read the couple of questions about this on stack overflow but can't seem to find the answer. I am trying to display the tags in my blog by the ones with the highest count in the tags table. Thanks to KandadaBoggu for helping me get the tags feature of the blog I am designing working. Here is the basics and my question. Tag belongs_to :post and Post has_many :tags. The tags table is simple really, consisting of the normal scaffolded fields plus post_id and tag_name (I actually called the column 'tag_name' instead of just 'name'). in my /views/posts/index.html/erb file I correctly am displaying the tags by group and the amount of times they are being used (appearing in the tags table). I just want to know how to order them by the highest count. Here is the code, and I currently have it set to updated_at: PostsController def index @tag_counts = Tag.count(:group => :tag_name, :order => 'updated_at DESC', :limit => 10) conditions, joins = {}, nil unless(params[:tag_name] || "").empty? conditions = ["tags.tag_name = ? ", params[:tag_name]] joins = :tags end @posts=Post.all(:joins => joins, :conditions=> conditions, :order => 'created_at DESC').paginate :page => params[:page], :per_page => 5 respond_to do |format| format.html # index.html.erb format.xml { render :xml => @posts } format.json { render :json => @posts } format.atom end end

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• Hibernate : Opinions in Composite PK vs Surrogate PK

  - by Albert Kam

  As i understand it, whenever i use @Id and @GeneratedValue on a Long field inside JPA/Hibernate entity, i'm actually using a surrogate key, and i think this is a very nice way to define a primary key considering my not-so-good experiences in using composite primary keys, where : there are more than 1 business-value-columns combination that become a unique PK the composite pk values get duplicated across the table details cannot change the business value inside that composite PK I know hibernate can support both types of PK, but im left wondering by my previous chats with experienced colleagues where they said that composite PK is easier to deal with when doing complex SQL queries and stored procedure processes. They went on saying that when using surrogate keys will complicate things when doing joining and there are several condition when it's impossible to do some stuffs when using surrogate keys. Although im sorry i cant explain the detail here since i was not clear enough when they explain it. Maybe i'll put more details next time. Im currently trying to do a project, and want to try out surrogate keys, since it's not getting duplicated across tables, and we can change the business-column values. And when the need for some business value combination uniqueness, i can use something like : @Table(name="MY_TABLE", uniqueConstraints={ @UniqueConstraint(columnNames={"FIRST_NAME", "LAST_NAME"}) // name + lastName combination must be unique But im still in doubt because of the previous discussion about the composite key. Could you share your experiences in this matter ? Thank you !

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• Generating code -- is there an easy way to get a proper string representation of nullable type?

  - by Cory Larson

  So I'm building an application that is going to do a ton of code generation with both C# and VB output (depending on project settings). I've got a CodeTemplateEngine, with two derived classes VBTemplateEngine and CSharpTemplateEngine. This question regards creating the property signatures based on columns in a database table. Using the IDataReader's GetSchemaTable method I gather the CLR type of the column, such as "System.Int32", and whether it IsNullable. However, I'd like to keep the code simple, and instead of having a property that looks like: public System.Int32? SomeIntegerColumn { get; set; } or public Nullable<System.Int32> SomeIntegerColumn { get; set; }, where the property type would be resolved with this function (from my VBTemplateEngine), public override string ResolveCLRType(bool? isNullable, string runtimeType) { Type type = TypeUtils.ResolveType(runtimeType); if (isNullable.HasValue && isNullable.Value == true && type.IsValueType) { return "System.Nullable(Of " + type.FullName + ")"; // or, for example... return type.FullName + "?"; } else { return type.FullName; } }, I would like to generate a simpler property. I hate the idea of building a Type string from nothing, and I would rather have something like: public int? SomeIntegerColumn { get; set; } Is there anything built-in anywhere, such as in the VBCodeProvider or CSharpCodeProvider classes that would somehow take care of this for me? Or is there a way to get a type alias of int? from a type string like System.Nullable'1[System.Int32]? Thanks!

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• Am I correctly extracting JPEG binary data from this mysqldump?

  - by Glenn

  I have a very old .sql backup of a vbulletin site that I ran around 8 years ago. I am trying to see the file attachments that are stored in the DB. The script below extracts them all and is verified to be JPEG by hex dumping and checking the SOI (start of image) and EOI (end of image) bytes (FFD8 and FFD9, respectively) according to the JPEG wiki page. But when I try to open them with evince, I get this message "Error interpreting JPEG image file (JPEG datastream contains no image)" What could be going on here? Some background info: sqldump is around 8 years old vbulletin 2.x was the software that stored the info most likely php 4 was used most likely mysql 4.0, possibly even 3.x the column datatype these attachments are stored in is mediumtext My Python 3.1 script: #!/usr/bin/env python3.1 import re trim_l = re.compile(b"""^INSERT INTO attachment VALUES\('\d+', '\d+', '\d+', '(.+)""") trim_r = re.compile(b"""(.+)', '\d+', '\d+'\);$""") extractor = re.compile(b"""^(.*(?:\.jpe?g|\.gif|\.bmp))', '(.+)$""") with open('attachments.sql', 'rb') as fh: for line in fh: data = trim_l.findall(line)[0] data = trim_r.findall(data)[0] data = extractor.findall(data) if data: name, data = data[0] try: filename = 'files/%s' % str(name, 'UTF-8') ah = open(filename, 'wb') ah.write(data) except UnicodeDecodeError: continue finally: ah.close() fh.close() update The JPEG wiki page says FF bytes are section markers, with the next byte indicating the section type. I see some that are not listed in the wiki page (specifically, I see a lot of 5C bytes, so FF5C). But the list is of "common markers" so I'm trying to find a more complete list. Any guidance here would also be appreciated.

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• Retrieving many huge sized EPS files and converting them to JPEG in ASP.NET application

  - by Ashish Gupta

  I have many (600) EPS files(300 KB - 1 MB) in database. In my ASP.NET application (using ASP.NET 4.0) I need to retrieve them one by one and call a web service which would convert the content to the JPEG file and update the database (JPEGContent column with the JPEG content). However, retrieving the content for 600 of them itself takes too long from the SQL management studio itself (takes 5 minutes for 10 EPS contents). So I have two issues:- 1) How to get the EPS content ( unfortunately, selecting certain number of content is not an option :-( ):- Approach 1:- foreach(var DataRow in DataTable.Rows) { // get the Id and byte[] of EPS // Call the web method to convert EPS content to JPEG which would also update the database. } or foreach(var DataRow in DataTable.Rows) { // get only the Id of EPS // Hit database to get the content of EPS // Call the web method to convert EPS content to JPEG which would also update the database. } or Any other approach? 2) Converting EPS to JPEG using a web method for 600 contents. Ofcourse, each call would be a long running operation. Would task parellel library (TPL) be a better way to achieve this? Also, is doing the entire thing in a SQL CLR function a good idea?

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• Ruby on Rails: How to sanitize a string for SQL when not using find and other built-in methods?

  - by williamjones

  I'm trying to sanitize a string that involves user input without having to resort to manually crafting my own possibly buggy regex if possible. There are a number of methods in Rails that can allow you to enter in native SQL commands, how do people escape user input for those? The question I'm asking is a broad one, but in my particular case, I'm working with a column in my Postgres database that Rails does not natively understand as far as I know, the tsvector, which holds plain text search information. Rails is able to write and read from it as if it's a string, however, unlike a string, it doesn't seem to be automatically escaping it when I do things like vector= inside the model. For example, when I do model.name='::', where name is a string, it works fine. When I do model.vector='::' it errors out: ActiveRecord::StatementInvalid: PGError: ERROR: syntax error in tsvector: "::" "vectors" = E'::' WHERE "id" = 1 This seems to be a problem caused by lack of escaping of the semicolons, and I can manually set the vector='\:\:' fine. I also had the bright idea, maybe I can just call something like: ActiveRecord::Base.connection.execute "UPDATE medias SET vectors = ? WHERE id = 1", "::" However, this syntax doesn't work, because the raw SQL commands don't have access to find's method of escaping and inputting strings by using the ? mark. This strikes me as the same problem as calling connection.execute with any type of user input, as it all boils down to sanitizing the strings, but I can't seem to find any way to manually call Rails' SQL string sanitization methods. Can anyone provide any advice?

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• SQL View with Data from two tables

  - by Alex

  Hello! I can't seem to crack this - I have two tables (Persons and Companies), and I'm trying to create a view that: 1) shows all persons 2) also returns companies by themselves once, regardless of how many persons are related to it 3) orders by name across both tables To clarify, some sample data: (Table: Companies) Id Name 1 Banana 2 ABC Inc. 3 Microsoft 4 Bigwig (Table: Persons) Id Name RelatedCompanyId 1 Joe Smith 3 2 Justin 3 Paul Rudd 4 4 Anjolie 5 Dustin 4 The output I'm looking for is something like this: Name PersonName CompanyName RelatedCompanyId ABC Inc. NULL ABC Inc. NULL Anjolie Anjolie NULL NULL Banana NULL Banana NULL Bigwig NULL Bigwig NULL Dustin Dustin Bigwig 4 Joe Smith Joe Smith Microsoft 3 Justin Justin NULL NULL Microsoft NULL Microsoft NULL Paul Rudd Paul Rudd Bigwig 4 As you can see, the new "Name" column is ordered across both tables (the company names appear correctly in between the person names), and each company appears exactly once, regardless of how many people are related to it. Can this even be done in SQL?! P.S. I'm trying to create a view so I can use this later for easy data retrieval, fulltext indexing and make the programming side simpler by just querying the view.

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• Blob in Java/Hibernate/sql-server 2005

  - by Ramy

  Hi, I'm trying to insert an HTML blob into our sql-server2005 database. i've been using the data-type [text] for the field the blob will eventually live in. i've also put a '@Lob' annotation on the field in the domain model. The problem comes in when the HTML blob I'm attempting to store is larger than 65536 characters. Its seems that is the caracter-limit for a text data type when using the @Lob annotation. Ideally I'd like to keep the whole blob in tact rather than chunk it up into multiple rows in the database. I appreciate any help or insight that might be provided. Thanks! _Ramy Allow me to clarify annotation: @Lob @Column(length = Integer. MAX_VALUE) //per an answer on stackoverflow private String htmlBlob; database side (sql-server-2005): CREATE TABLE dbo.IndustrySectorTearSheetBlob( ... htmlBlob text NULL ... ) Still seeing truncation after 65536 characters... EDIT: i've printed out the contents of all possible strings (only 10 right now) that would be inserted into the Database. Each string seems to contain all cahracters, judging by the fact that the close html tag is present at the end of the string....

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• WPF Designer has bug with parsing generic control with overrided property

  - by Ivan Laktyunkin

  I've created a generic lookless control with virtual property: public abstract class TestControlBase<TValue> : Control { public static readonly DependencyProperty ValueProperty; static TestControlBase() { ValueProperty = DependencyProperty.Register("Value", typeof(TValue), typeof(TestControlBase<TValue>)); } protected TestControlBase() { Focusable = false; Value = default(TValue); } public virtual TValue Value { get { return (TValue)GetValue(ValueProperty); } set { SetValue(ValueProperty, value); } } } Then I've made a control derived from it and overrided Value property: public class TestControl : TestControlBase<int> { public override int Value { get { return base.Value; } set { base.Value = value; } } } So I use it in a Window XAML: <TestControls:TestControl /> When I open window in designer all is OK, but when I put mouse cursor to this line, or to this control in designer I receive exception: Exception has been thrown by the target of an invocation. at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Delegate.DynamicInvokeImpl(Object[] args) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) Ambiguous match found. at System.RuntimeType.GetPropertyImpl(String name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers) at System.Type.GetProperty(String name) at MS.Internal.ComponentModel.DependencyPropertyKind.get_IsDirect() at MS.Internal.ComponentModel.DependencyPropertyKind.get_IsAttached() at MS.Internal.ComponentModel.APCustomTypeDescriptor.GetProperties(Attribute[] attributes) at MS.Internal.ComponentModel.APCustomTypeDescriptor.GetProperties() at System.ComponentModel.TypeDescriptor.TypeDescriptionNode.DefaultExtendedTypeDescriptor.System.ComponentModel.ICustomTypeDescriptor.GetProperties() at System.ComponentModel.TypeDescriptor.GetPropertiesImpl(Object component, Attribute[] attributes, Boolean noCustomTypeDesc, Boolean noAttributes) at System.ComponentModel.TypeDescriptor.GetProperties(Object component) at MS.Internal.Model.ModelPropertyCollectionImpl.GetProperties(String propertyNameHint) at MS.Internal.Model.ModelPropertyCollectionImpl.<GetEnumerator>d__0.MoveNext() at MS.Internal.Designer.PropertyEditing.Model.ModelPropertyMerger.<GetFirstProperties>d__0.MoveNext() at MS.Internal.Designer.PropertyEditing.PropertyInspector.UpdateCategories(Selection selection) at MS.Internal.Designer.PropertyEditing.PropertyInspector.OnSelectionChangedIdle() Who know this problem? Please explain :) I have no ideas except that WPF Designer doesn't like generics. If I replace generics by Object all is OK.

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• CQRS - The query side

  - by mattcodes

  A lot of the blogsphere articles related to CQRS (command query repsonsibility) seperation seem to imply that all screens/viewmodels are flat. e.g. Name, Age, Location Of Birth etc.. and thus the suggestion that implementation wise we stick them into fast read source etc.. single table per view mySQL etc.. and pull them out with something like primitive SqlDataReader, kick that nasty nhibernate ORM etc.. However, whilst I agree that domain models dont mapped well to most screens, many of the screens that I work with are more dimensional, and Im sure this is pretty common in LOB apps. So my question is how are people handling screen where by for example it displays a summary of customer details and then a list of their orders with a [more detail] link etc.... I thought about keeping with the straight forward SQL query to the Query Database breaking off the outer join so can build a suitable ViewModel to View but it seems like overkill? Alternatively (this is starting to feel yuck) in CustomerSummaryView table have a text/big (whatever the type is in your DB) column called Orders, and the columns for the Order summary screen grid are seperated by , and rows by |. Even with XML datatype it still feeel dirty. Any thoughts on an optimal practice?

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• Why use SQL database?

  - by martinthenext

  I'm not quite sure stackoverflow is a place for such a general question, but let's give it a try. Being exposed to the need of storing application data somewhere, I've always used MySQL or sqlite, just because it's always done like that. As it seems like the whole world is using these databases, most of all software products, frameworks, etc. It is rather hard for a beginning developer like me to ask a question - why? Ok, say we have some object-oriented logic in our application, and objects are related to each other somehow. We need to map this logic to the storage logic, so we need relations between database objects too. This leads us to using relational database and I'm ok with that - to put it simple, our database rows sometimes will need to have references to other tables' rows. But why do use SQL language for interaction with such a database? SQL query is a text message. I can understand this is cool for actually understanding what it does, but isn't it silly to use text table and column names for a part of application that no one ever seen after deploynment? If you had to write a data storage from scratch, you would have never used this kind of solution. Personally, I would have used some 'compiled db query' bytecode, that would be assembled once inside a client application and passed to the database. And it surely would name tables and colons by id numbers, not ascii-strings. In the case of changes in table structure those byte queries could be recompiled according to new db schema, stored in XML or something like that. What are the problems of my idea? Is there any reason for me not to write it myself and to use SQL database instead?

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