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  • Are Multi-column Primary Keys in MySQL a optimisation problem?

    - by David
    Been looking into using multi-column primary keys and as performance is extremely important with the size of traffic and database I need to know if there is anything to consider before I start throwing out the unique ID method on many of my tables and start using mulit column primary keys. So, what are the performance/optimisation pros/cons to using multi column primary keys versus a basic single column, auto-inc primary key?

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  • How do I replace values within a data frame with a string in R?

    - by Arturito
    short version: How do I replace values within a data frame with a string found within another data frame? longer version: I'm a biologist working with many species of bees. I have a data set with many thousands of bees. Each row has a unique bee ID # along with all the relevant info about that specimen (data of capture, GPS location, etc). The species information for each bee has not been entered because it takes a long time to ID them. When IDing, I end up with boxes of hundred of bees, all of the same species. I enter these into a separate data frame. I am trying to write code that will update the original data file with species information (family, genus, species, sex, etc) as I ID the bees. Currently, in the original data file, the species info is blank and is interpreted as NA within R. I want to have R find all unique bee ID #'s and fill in the species info, but I am having trouble figuring out how to replace the NA values with a string (e.g. "Andrenidae") Here is a simple example of what I am trying to do: rawData<-data.frame(beeID=c(1:20),family=rep(NA,20)) speciesInfo<-data.frame(beeID=seq(1,20,3),family=rep("Andrenidae",7)) rawData[rawData$beeID == 4,"family"] <- speciesInfo[speciesInfo$beeID == 4,"family"] So, I am replacing things as I want, but with a number rather than the family name (a string). What I would eventually like to do is write a little loop to add in all the species info, e.g.: for (i in speciesInfo$beeID){ rawData[rawData$beeID == i,"family"] <- speciesInfo[speciesInfo$beeID == i,"family"] } Thanks in advance for any advice! Cheers, Zak EDIT: I just noticed that the first two methods below add a new column each time, which would cause problems if I needed to add species info multiple times (which I typically do). For example: rawData<-data.frame(beeID=c(1:20),family=rep(NA,20)) Andrenidae<-data.frame(beeID=seq(1,20,3),family=rep("Andrenidae",7)) Halictidae<-data.frame(beeID=seq(1,20,3)+1,family=rep("Halictidae",7)) # using join library(plyr) rawData <- join(rawData, Andrenidae, by = "beeID", type = "left") rawData <- join(rawData, Halictidae, by = "beeID", type = "left") # using merge rawData <- merge(x=rawData,y=Andrenidae,by='beeID',all.x=T,all.y=F) rawData <- merge(x=rawData,y=Halictidae,by='beeID',all.x=T,all.y=F) Is there a way to either collapse the columns so that I have one, unified data frame? Or a way to update the rawData rather than adding a new column each time? Thanks in advance!

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  • What are the reasons *not* to use a GUID for a primary key?

    - by Yarin
    Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables) I know I'll never lose sleep over duplicate keys, merging tables, etc. To me it just makes sense philosophically that any given record should be unique across all domains, and that that uniqueness should be represented in a consistent way from table to table. I realize it will never be the most performant option, but putting performance aside, I'd like to know if there are philosophical arguments against this practice?

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  • Self Authenticating Links in Django

    - by awolf
    In my web app I would like to be able to email self-authenticating links to users. These links will contain a unique token (uuid). When they click the link the token being present in the query string will be enough to authenticate them and they won't have to enter their username and password. What's the best way to do this?

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  • Android: Text primary key with different name

    - by Echilon
    I have an existing Windows app for which I'm writing an Android port. The app uses a unique string as the primary key, but the SQLite methods in Android all seem to work with integers and a column names _id, whereas my ID column isn't called this. Is there a way to let Android know I have a key with a different column name?

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  • Decoding relationship between two numbers?

    - by Nimbuz
    Is there any way (or calculator) to determine the relationship between two numbers. For example on one the temporary event ID cards, the Unique ID is 20309825 but the barcode when decoded reads 8336902052. What could be the relationship between these numbers, if any? Thanks in advance for your help!

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  • Can anyone write a XSL-fo for this XML File with SVG tags?

    - by atrueguy
    Hi all this XML file is very unique with SVG tags, I am stuck in writing an XSL-fo for this xml file, can one help me out in writing a XSL FO, if not the exact answer, atleast give me a idea of how to write, please see the xml file in the below link. http://kzekaa.bay.livefilestore.com/y1pDRDfrEn98IkEO7MQ9MEkC-RQE4QxwsrgVV57WrGWK_AEsqzpwJWkydbnE3NVwrMNT2l9mIG7rErd_NPO94Fmrhrm2Z_zleID/Cleaned_file_source.xml

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  • overwrite existing entity via bulkloader.Loader

    - by Ray Yun
    I was going to CSV based export/import for large data with app engine. My idea was just simple. First column of CSV would be key of entity. If it's not empty, that row means existing entity and should overwrite old one. Else, that row is new entity and should create new one. I could export key of entity by adding key property. class FrontExporter(bulkloader.Exporter): def __init__(self): bulkloader.Exporter.__init__(self, 'Front', [ ('__key__', str, None), ('name', str, None), ]) But when I was trying to upload CSV, it had failed because bulkloader.Loader.generate_key() was just for "key_name" not "key" itself. That means all exported entities in CSV should have unique 'key_name' if I want to modify-and-reupload them. class FrontLoader(bulkloader.Loader): def __init__(self): bulkloader.Loader.__init__(self, 'Front', [ ('_UNUSED', lambda x: None), ('name', lambda x: x.decode('utf-8')), ]) def generate_key(self,i,values): # first column is key keystr = values[0] if len(keystr)==0: return None return keystr I also tried to load key directly without using generate_key(), but both failed. class FrontLoader(bulkloader.Loader): def __init__(self): bulkloader.Loader.__init__(self, 'Front', [ ('Key', db.Key), # not working. just create new one. ('__key__', db.Key), # same... So, how can I overwrite existing entity which has no 'key_name'? It would be horrible if I should give unique name to all entities..... From the first answer, I could handle this problem. :) def create_entity(self, values, key_name=None, parent=None): # if key_name is None: # print 'key_name is None' # else: # print 'key_name=<',key_name,'> : length=',len(key_name) Validate(values, (list, tuple)) assert len(values) == len(self._Loader__properties), ( 'Expected %d columns, found %d.' % (len(self._Loader__properties), len(values))) model_class = GetImplementationClass(self.kind) properties = { 'key_name': key_name, 'parent': parent, } for (name, converter), val in zip(self._Loader__properties, values): if converter is bool and val.lower() in ('0', 'false', 'no'): val = False properties[name] = converter(val) if key_name is None: entity = model_class(**properties) #print 'create new one' else: entity = model_class.get(key_name) for key, value in properties.items(): setattr(entity, key, value) #print 'overwrite old one' entities = self.handle_entity(entity) if entities: if not isinstance(entities, (list, tuple)): entities = [entities] for entity in entities: if not isinstance(entity, db.Model): raise TypeError('Expected a db.Model, received %s (a %s).' % (entity, entity.__class__)) return entities def generate_key(self,i,values): # first column is key if values[0] is None or values[0] in ('',' ','-','.'): return None return values[0]

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  • How to turn dynamic URL into static URL

    - by Rafael Carvalho
    I am developing a website using PHP and Apache. I wanna turn my URLs from www.example.com/book.php?book=title into something like this, if it is possible of course: www.example.com/book/title Notice that the title of the books are unique and cannot be repeated. I`ve read about this, but none of the posts were clear enough for a beginner like me. Do you guys know any tutorial that explains that? Thanks.

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  • mysql insert multiple rows, return rows that failed

    - by Glenn
    When I try to insert (lets say) 30 rows in my table. For example INSERT INTO customers(cust_name, cust_address, cust_city, cust_state, cust_zip, cust_country) VALUES( 'Pep E. LaPew', '100 Main Street', 'Los Angeles', 'CA', '90046', 'USA' ), ( 'M. Martian', '42 Galaxy Way', 'New York', 'NY', '11213', 'USA' ), ... ; And cust_name has to be unique. How can I then identify the records that failed to insert because their cust_name already exists? Is it possible to return them?

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  • Send activation email to user

    - by Martin
    How would I do to check if a email actially exists? Cant understand how sites do to send mails with a unique link that the users clicks to validate that he is the owner of email =/ Make a 2 new columns called activationkey and activated and store some random string, send an email with the activationkey, and update the users activated =1 that match that activation link register.php?a=activate&key=9cdfb439c7876e703e307864c9167a15 Any better ideas?

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  • iPhone app identifier?

    - by Horace Ho
    What is the unique identifier for an iPhone app? In the info.plist file, there are keys: Bundle display name Executable file Bundle identifier Bundle name If I have already submitted an app on the AppStore before. Then I change some of the keys in the project. Which of the above can be changed freely and AppStore still considers my app is same as the existing one? Thanks!

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  • Image upload storage strategies

    - by MatW
    When a user uploads an image to my site, the image goes through this process; user uploads pic store pic metadata in db, giving the image a unique id async image processing (thumbnail creation, cropping, etc) all images are stored in the same uploads folder So far the site is pretty small, and there are only ~200,000 images in the uploads directory. I realise I'm nowhere near the physical limit of files within a directory, but this approach clearly won't scale, so I was wondering if anyone had any advice on upload / storage strategies for handling large volumes of image uploads.

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  • UNIX script to parse Zone file (is this the best code?)

    - by Steve
    Hi, FOund the following on: http://mike.murraynet.net/2009/08/23/parsing-the-verisign-zone-file-with-os-x/ Can unix-masters have a look at it and see if its the best possible way to gather the unique domainsnames in a zone file? For .NET domains: grep “^[a-zA-Z0-9-]+ NS .” net.zone|sed “s/NS .//”|uniq netdomains.txt For .COM domains: grep “^[a-zA-Z0-9-]+ NS .” com.zone|sed “s/NS .//”|uniq comdomains.txt For .EDU domains: grep “^[a-zA-Z0-9-]+ NS .” edu.zone|sed “s/NS .//”|uniq edudomains.txt

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  • Django - Can you use property as the field in an aggregation function?

    - by orokusaki
    I know the short answer because I tried it. Is there any way to accomplish this though (even if only on account of a hack)? class Ticket(models.Model): account = modelfields.AccountField() uuid = models.CharField(max_length=36, unique=True) created = models.DateTimeField(auto_now_add=True) class Meta: ordering = ['created'] @property def repair_cost(self): # cost is a @property of LineItem(models.Model) return self.lineitem_set.aggregate(models.Sum('cost'))

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  • Can you make an incrementing compiler constant?

    - by Keith Nicholas
    While sounding nonsensical..... I want a Contant where every time you use it it will increment by 1 int x; int y; x = INCREMENTING_CONSTNAT; y = INCREMENTING_CONSTNAT; where x == 1; and y == 2 Note I don't want y = INCREMENTING_CONSTNAT+1 type solutions. Basically I want to use it as a compile time unique ID ( generally it wouldn't be used in code like the example but inside another macro)

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  • Is this postgres function cost efficient or still have to clean

    - by kiranking
    There are two tables in postgres db. english_all and english_glob First table contains words like international,confidential,booting,cooler ...etc I have written the function to get the words from english_all then perform for loop for each word to get word list which are not inserted in anglish_glob table. Word list is like I In Int Inte Inter .. b bo boo boot .. c co coo cool etc.. for some reason zwnj(zero-width non-joiner) is added during insertion to english_all table. But in function I am removing that character with regexp_replace. Postgres function for_loop_test is taking two parameter min and max based on that I am selecting words from english_all table. function code is like DECLARE inMinLength ALIAS FOR $1; inMaxLength ALIAS FOR $2; mviews RECORD; outenglishListRow english_word_list;--custom data type eng_id,english_text BEGIN FOR mviews IN SELECT id,english_all_text FROM english_all where wlength between inMinLength and inMaxLength ORDER BY english_all_text limit 30 LOOP FOR i IN 1..char_length(regexp_replace(mviews.english_all_text,'(?)$','')) LOOP FOR outenglishListRow IN SELECT distinct on (regexp_replace((substring(mviews.english_all_text from 1 for i)),'(?)$','')) mviews.id, regexp_replace((substring(mviews.english_all_text from 1 for i)),'(?)$','') where regexp_replace((substring(mviews.english_all_text from 1 for i)),'(?)$','') not in(select english_glob.english_text from english_glob where i=english_glob.wlength) order by regexp_replace((substring(mviews.english_all_text from 1 for i)),'(?)$','') LOOP RETURN NEXT outenglishListRow; END LOOP; END LOOP; END LOOP; END; Once I get the word list I will insert that into another table english_glob. My question is is there any thing I can add to or remove from function to make it more efficient. edit Let assume english_all table have words like footer,settle,question,overflow,database,kingdom If inMinLength = 5 and inmaxLength=7 then in the outer loop footer,settle,kingdom will be selected. For above 3 words inner two loop will apply to get words like f,fo,foo,foot,foote,footer,s,se,set,sett,settl .... etc. In the final process words which are bold will be entered into english_glob with another parameter like 1 to denote it is a proper word and stored in the another filed of english_glob table. Remaining word will be stored with another parameter 0 because in the next call words which are saved in database should not be fetched again. edit2: This is a complete code CREATE TABLE english_all ( id serial NOT NULL, english_all_text text NOT NULL, wlength integer NOT NULL, CONSTRAINT english_all PRIMARY KEY (id), CONSTRAINT english_all_kan_text_uq_id UNIQUE (english_all_text) ) CREATE TABLE english_glob ( id serial NOT NULL, english_text text NOT NULL, is_prop integer default 1, CONSTRAINT english_glob PRIMARY KEY (id), CONSTRAINT english_glob_kan_text_uq_id UNIQUE (english_text) ) insert into english_all(english_text) values ('ant'),('forget'),('forgive'); on function call with parameter 3 and 6 fallowing rows should fetched a an ant f fo for forg forge forget next is insert to another table based on above row insert into english_glob(english_text,is_prop) values ('a',1),('an',1), ('ant',1),('f',0), ('fo',0),('for',1), ('forg',0),('forge',1), ('forget',1), on function call next time with parameter 3 and 7 fallowing rows should fetched.(because f,fo,for,forg are all entered in english_glob table) forgi forgiv forgive

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  • Hibernate naturalID

    - by DD
    Hibernate doesnt seem to generate a notnull constraint on a field I marked as naturalID. Is this normal? @MappedSuperclass public class AbstractDomainObject extends PersistentObject { @NaturalId private String code; DB Schema: CONSTRAINT SYS_CT_47 UNIQUE(CODE) There is no not null constraint here.

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  • Need Help About Using XPathNavigator in C#?

    - by Nano HE
    Hello. My XML file as below. It mixed schema and normal elements. <?xml version="1.0" encoding="utf-8"?> <!-- R1 --> <ax:root xmlns:ax="http://amecn/software/realtime/ax"> <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <xsd:element name="EquipmentConstants"> <xsd:complexType> <xsd:sequence> <xsd:element minOccurs="0" maxOccurs="unbounded" ref="EquipmentConstant" /> </xsd:sequence> </xsd:complexType> <xsd:unique name="id"> <xsd:selector xpath=".//EquipmentConstant" /> <xsd:field xpath="@id" /> </xsd:unique> </xsd:element> ...... ...... </xsd:schema> <EquipmentConstants xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <EquipmentConstant id="0"> <Name>SerialNumber</Name> <Group>SYSTEM</Group> <Data> <Value min="0" max="10000000" scale_factor="0" unit="U_NO_UNITS" permission="NolimitedAndNoChangeable" type="xsd_string" enum="" flag="0">0</Value> </Data> <Description>Serial Number</Description> </EquipmentConstant> ..... ..... </EquipmentConstants> </ax:root> My C# code as below. I want to loop the elements from <EquipmentConstants xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> XPathDocument doc = new XPathDocument("test.xml"); XPathNavigator navigator = doc.CreateNavigator(); navigator.MoveToRoot(); // <?xml version="1.0" encoding="utf-8"?> //navigator.MoveToFirstChild(); // <!-- R1 --> // 1st, I tried to use MoveToChield(), But I failed to move there. navigator.MoveToChild("EquipmentConstants"); // Then, I also tried to use SelectSingleNode(). But I failed too. navigator.SelectSingleNode("ax/EquipmentConstants"); while (navigator.MoveToNext()) { // do something. } Could you please give me some suggestion. Thank you.

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