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  • Embedded Java Databases for Large Data Sets

    - by ExAmerican
    I would like to port a PHP/MySQL-based client/server application to be a standalone desktop application written in Java. The database has grown to be fairly large, with several tables with hundreds of thousands of rows. I expect these could grow to over a million entries for certain tables. What embedded database would best handle this? HSQLDB and Sqlite seem to be the obvious choices, though I'm guessing there are others out there as well. My main priorities are the ability to perform queries on large amounts of data efficiently (this thread seems to confirm Sqlite can handle this) and the ease with which I can import old data from MySQL (I remember HSQLDB being kind of a pain for that). Note: I am aware that similar questions comparing embedded databases have been posted before (for example here and here) but as my priorities differ somewhat from most applications considering the large data migration I thought it justified a new question.

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  • What do I do about a Java program that spawned two instaces of itself?

    - by user288915
    I have a java JAR file that is triggered by a SQL server job. It's been running successfully for months. The process pulls in a structured flat file to a staging database then pushes that data into an XML file. However yesterday the process was triggered twice at the same time. I can tell from a log file that gets created, it looks like the process ran twice simultaneously. This caused a lot of issues and the XML file that it kicked out was malformed and contained duplicate nodes etc. My question is, is this a known issue with Java JVM's spawning multiple instances of itself? Or should I be looking at sql server as the culprit? I'm looking into 'socket locking' or file locking to prevent multiple instances in the future. This is the first instance of this issue that I've ever heard of. More info: The job is scheduled to run every minute. The job triggers a .bat file that contains the java.exe - jar filename.jar The java program runs, scans a directory for a file and then executes a loop to process if the file if it finds one. After it processes the file it runs another loop that kicks out XML messages. I can provide code samples if that would help. Thank you, Kevin

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  • Database Compression in Python

    - by user551832
    I have hourly logs like user1:joined user2:log out user1:added pic user1:added comment user3:joined I want to compress all the flat files down to one file. There are around 30 million users in the logs and I just want the latest user log for all the logs. My end result is I want to have a log look like user1:added comment user2:log out user3:joined Now my first attempt on a small scale was to just do a dict like log['user1'] = "added comment" Will doing a dict of 30 million key/val pairs have a giant memory footprint.. Or should I use something like sqllite to store them.. then just put the contents of the sqllite table back into a file?

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  • Simple 'database' in c++

    - by DevAno1
    Hello. My task was to create pseudodatabase in c++. There are 3 tables given, that store name(char*), age(int), and sex (bool). Write a program allowing to : - add new data to the tables - show all records - sort tables with criteria : - name increasing/decreasing - age increasing/decreasing - sex Using function templates is a must. Also size of arrays must be variable, depending on the amount of records. I have some code but there are still problems there. Here's what I have: Function tabSize() for returning size of array. But currently it returns size of pointer I guess : #include <iostream> using namespace std; template<typename TYPE> int tabSize(TYPE *T) { int size = 0; size = sizeof(T) / sizeof(T[0]); return size; } How to make it return size of array, not its pointer ? Next the most important : add() for adding new elements. Inside first I get the size of array (but hence it returns value of pointer, and not size it's of no use now :/). Then I think I must check if TYPE of data is char. Or am I wrong ? // add(newElement, table) template<typename TYPE> TYPE add(TYPE L, TYPE *T) { int s = tabSize(T); //here check if TYPE = char. If yes, get the length of the new name int len = 0; while (L[len] != '\0') { len++; } //current length of table int tabLen = 0; while (T[tabLen] != '\0') { tabLen++; } //if TYPE is char //if current length of table + length of new element exceeds table size create new table if(len + tabLen > s) { int newLen = len + tabLen; TYPE newTab = new [newLen]; for(int j=0; j < newLen; j++ ){ if(j == tabLen -1){ for(int k = 0; k < len; k++){ newTab[k] = } } else { newTab[j] = T[j]; } } } //else check if tabLen + 1 is greater than s. If yes enlarge table by 1. } Am I thinking correct here ? Last functions show() is correct I guess : template<typename TYPE> TYPE show(TYPE *L) { int len = 0; while (L[len] == '\0') { len++; } for(int i=0; i<len; i++) { cout << L[i] << endl; } } and problem with sort() is as follows : Ho can I influence if sorting is decreasing or increasing ? I'm using bubble sort here. template<typename TYPE> TYPE sort(TYPE *L, int sort) { int s = tabSize(L); int len = 0; while (L[len] == '\0') { len++; } //add control increasing/decreasing sort int i,j; for(i=0;i<len;i++) { for(j=0;j<i;j++) { if(L[i]>L[j]) { int temp=L[i]; L[i]=L[j]; L[j]=temp; } } } } And main function to run it : int main() { int sort=0; //0 increasing, 1 decreasing char * name[100]; int age[10]; bool sex[10]; char c[] = "Tom"; name[0] = "John"; name[1] = "Mike"; cout << add(c, name) << endl; system("pause"); return 0; }

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  • DB2 increase bufferpool size and compressed tables not equal better performance. Why?

    - by Mestika
    Hi, I’m working on tuning and increasing the performance of my IBM DB2 version 9.7 database. I’ve been searching around the net for the last couple of days and learned that if I created my tables in COMPRESS mode and created one more bufferpool and set both of them to access 1024mb, then the performance in my queries should increase because of the less I/Os to the disks. However, when I run my time analysis, the performance Decrease. I added the new additions to my regular database with the indexes I’ve used all the time. Each time I search google I come up with the statement that: Increased bufferpool size and several bufferpools AND a table compression SHOULD prove to get better performance. I’m very puzzled about the total unexpected result. Are there some tuning mechanisms I’ve forgot or does anyone have a explanation for this odd behavior? Sincerely Mestika

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  • Why use Entity Framework over Linq2SQL if...

    - by Refracted Paladin
    To be clear, I am not asking for a side by side comparision which has already been asked Ad Nauseum here on SO. I am also Not asking if Linq2Sql is dead as I don't care. What I am asking is this.... I am building internal apps only for a non-profit organization. I am the only developer on staff. We ALWAYS use SQL Server as our Database backend. I design and build the Databases as well. I have used L2S successfully a couple of times already. Taking all this into consideration can someone offer me a compelling reason that I should use EF instead of L2S? I was at Code Camp this weekend and after an hour long demonstration on EF, all of which I could have done in L2S, I asked this same question. The speakers answer was, "L2S is dead..." Very well then! NOT! (see here) I understand EF is what MS WANTS us to use in the future(see here) and that it offers many more customization options. What I can't figure out is if any of that should, or does, matter for me in this environment. One particular issue we have here is that I inherited the Core App which was built on 4 different SQL Data bases. L2S has great difficulty with this but when I asked the aforementioned speaker if EF would help me in this regard he said "No!"

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  • Getting the last element of a Postgres array, declaratively

    - by Wojciech Kaczmarek
    How to obtain the last element of the array in Postgres? I need to do it declaratively as I want to use it as a ORDER BY criteria. I wouldn't want to create a special PGSQL function for it, the less changes to the database the better in this case. In fact, what I want to do is to sort by the last word of a specific column containing multiple words. Changing the model is not an option here. In other words, I want to push Ruby's sort_by {|x| x.split[-1]} into the database level. I can split a value into array of words with Postgres string_to_array or regexp_split_to_array functions, then how to get its last element?

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  • can't save form content to database, help plsss!!

    - by dana
    i'm trying to save 100 caracters form user in a 'microblog' minimal application. my code seems to not have any mystakes, but doesn't work. the mistake is in views.py, i can't save the foreign key to user table models.py looks like this: class NewManager(models.Manager): def create_post(self, post, username): new = self.model(post=post, created_by=username) new.save() return new class New(models.Model): post = models.CharField(max_length=120) date = models.DateTimeField(auto_now_add=True) created_by = models.ForeignKey(User, blank=True) objects = NewManager() class NewForm(ModelForm): class Meta: model = New fields = ['post'] # widgets = {'post': Textarea(attrs={'cols': 80, 'rows': 20}) def save_new(request): if request.method == 'POST': created_by = User.objects.get(created_by = user) date = request.POST.get('date', '') post = request.POST.get('post', '') new_obj = New(post=post, date=date, created_by=created_by) new_obj.save() return HttpResponseRedirect('/') else: form = NewForm() return render_to_response('news/new_form.html', {'form': form},context_instance=RequestContext(request)) i didn't mention imports here - they're done right, anyway. my mistake is in views.py, when i try to save it says: local variable 'created_by' referenced before assignment it i put created_py as a parameter, the save needs more parameters... it is really weird help please!!

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  • mysql join 3 tables and count

    - by air
    Please look at this image here is 3 tables , and out i want is uid from table1 industry from table 3 of same uid count of fid from table 2 of same uid like in the sample example output will be 2 records Thanks

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  • Storing Data as XML BLOB

    - by NBrowne
    Hi, At the moment the team i am working with is looking into the possibility of storing data which is entered by users from a series of input wizard screens as an XML blob in the database. the main reason for this being that i would like to write the input wizard as a component which can be brought into a number of systems without having to bring with it a large table structure. To try to clarify if the wizard has 100 input fields (for example) then if i go with the normal relational db structure then their will be a 1 to 1 relationship so will have 100 columns in database. So to get this working in another system will have to bring the tables,strore procedures etc into the new system. I have a number of reservations about this but i would like peoples opinions?? thanks

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  • Restricting deletion with NHibernate

    - by FrontSvin
    I'm using NHibernate (fluent) to access an old third-party database with a bunch of tables, that are not related in any explicit way. That is a child tables does have parentID columns which contains the primary key of the parent table, but there are no foreign key relations ensuring these relations. Ideally I would like to add some foreign keys, but cannot touch the database schema. My application works fine, but I would really like impose a referential integrity rule that would prohibit deletion of parent objects if they have children, e.i. something similar 'ON DELETE RESTRICT' but maintained by NHibernate. Any ideas on how to approach this would be appreciated. Should I look into the OnDelete() method on the IInterceptor interface, or are there other ways to solve this? Of course any solution will come with a performance penalty, but I can live with that.

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  • Locking DB w/ Large Reads (Ruby-on-Rails/Heroku)

    - by Splashlin
    Currently I have a Web API running on Heroku that is constantly writing information we're collecting from other data sources (currently theres about half a GB of data and it's growing very quickly). We're looking to add a reporting system on top of the current database that we can use to extract useful information out of the DB. The problem is that when we're running reports we're locking the DB and any other sites communicating with the DB are timing out. Does anyone have any solutions on how to solve this type of issue? Amazon RDS seems to have some interesting stuff with database replication but I don't know if that will solve my problems. Any advice would be greatly appreciated. Thanks

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  • Select past date from database x days from now

    - by Pr0no
    Consider the following table daterange _date trading_day ------------------------ 2011-08-01 1 2011-07-31 0 2011-07-30 0 2011-07-29 1 2011-07-28 1 2011-07-27 1 2011-07-26 1 2011-07-25 1 2011-07-24 0 2011-07-23 0 2011-07-22 1 2011-07-21 1 2011-07-20 1 2011-07-19 1 2011-07-18 1 2011-07-17 0 I'm in need of a query that returns a _date, x days before a given _date. When counting back, _days with trading_day = 0 should be ignored. A few examples: input | output -------------------------+------------ 1 day before 2011-07-19 | 2011-07-18 2 days before 2011-08-01 | 2011-07-28 (trading_day = 0 don't count) 3 days before 2011-07-29 | 2001-07-26 The first one is easy: SELECT _date FROM daterange WHERE trading_day = 0 AND _date < '2011-07-19' LIMIT 1 But I don't know how to query for the other examples. Do you?

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  • CF Client Variables: is the CDATA - CGLOBAL relationship always 1:1?

    - by ciaranarcher
    Hi We've noticed something odd with our Coldfusion 8 client variables DB. We have many more (about 3 times as many) CGlobal entries as we have CData entries. I would have assumed that the relationship would be 1:1 on the cfid column. Has any one else noticed this before? I have ruled out old data, my sample is less than 3 hours old. We're using SQL Server 2000 to host the tables. Thanks in advance, Ciaran

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  • create jar file with images and database

    - by Samurai
    Hi I am using NetBeans IDE and I have my images (what I am using in my project) in a folder named Images. When I am building jar it doesn't take that images. The code I am using to set image is, buttonObj.setIcon(new ImageIcon("\Images\a.jpg") any help please.

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  • Optimize MySQL database query

    - by rajeeesh
    I had a commenting application in my web site. The comments will store in a MySQL table . table structure as follows id | Comment | user | created_date ------------------------------------------------------ 12 | comment he | 1245 | 2012-03-30 12:15:00 ------------------------------------------------------ I need to run a query for listing all the comments after a specific time. ie .. a query like this SELECT * FROM comments WHERE created_date > "2012-03-29 12:15:00" ORDER BY created_date DESC Its working fine.. My question is if I got a 1-2 lakh entry in this table is this query is sufficient for the purpose ? or this query will take time to execute ? In most cases I have to show last 2 days data + periodically ( interval of 10 mins ) checking for updates with ajax from this table ... Please help Thanks

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  • [MySQL] Load data from .csv applying regex before insert into table

    - by Gabriel L. Oliveira
    I know that there is a code to import .csv data into a mysql table, and I'm using this one: LOAD DATA INFILE "file.csv" INTO TABLE foo FIELDS TERMINATED BY "," LINES TERMINATED BY "\\r\\n"; The data inside this .csv are lines like this example: 08/e0/Breast_Cancer_Res_2001_Nov_2_3(1)_55-60.tar.gz Breast Cancer Res. 2001 Nov 2; 3(1):55-60 PMC13900 b0/ac/Breast_Cancer_Res_2001_Nov_9_3(1)_61-65.tar.gz Breast Cancer Res. 2001 Nov 9; 3(1):61-65 PMC13901 I just want the first part (the .tar.gz path), always on the pattern (letter or number)(letter or number) / (letter or number)(letter or number)/... and the part starting by 'PMC', always on the pattern PMC(number...) where 'number' means a number between 0 to 9 and a letter means a letter between a to z (both upper and lower case) So, applying the LOAD DATA, and the regex, and inserting the result entries on my sql table, the result table should be: 1 08/e0/Breast_Cancer_Res_2001_Nov_2_3(1)_55-60.tar.gz PMC13900 2 b0/ac/Breast_Cancer_Res_2001_Nov_9_3(1)_61-65.tar.gz PMC13901 What should be the SQL command to do all this?

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  • Using AJAX to POST data to PHP database, then refresh

    - by cb74656
    Currently I have a button: <ul> <li><button onclick="display('1')">1</button></li> <li><button onclick="display('2')">2</button></li> <li><button onclick="display('3')">3</button></li> </ul> That when pressed, calls a javascript function, and displays PHP based on which button is pressed using AJAX. I figured this out all on my own. The AJAX gets a PHP file with a postgres query that outputs a table of data to a div. Now I want to be able to add, via form, new data and have it refresh (without reloading the page, yannknow?). I've tried a couple of things, and have hit roadblocks every time. My initial idea was to have the form submit the data using a javascript function and AJAX, then call my "display()" function after the query to reload the content. I just can't figure it out using GoogleFu. Based on my current idea, I'd like help with the following: How do I pass the form data to a javascript function. How do I use POST to pass that data to PHP using AJAX? I'm super new to javascript and AJAX. I've looked into jquery as it seems like that's the way to go, but I can't figure it out. If there's a better way to do this, I'm open to suggestions. Please forgive any misuse of nomenclature. EDIT: Once I solve this problem..., I'll have all the tools needed to finish the project preliminarily.

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  • MySQL COUNT() multiple columns

    - by liam
    Hello, I'm trying to fetch the most popular tags from all videos in my database (ignoring blank tags). I also need the 'flv' for each tag. I have this working as I want if each video has one tag: SELECT tag_1, flv, COUNT(tag_1) AS tagcount FROM videos WHERE NOT tag_1='' GROUP BY tag_1 ORDER BY tagcount DESC LIMIT 0, 10 However in my database, each video is allowed three tags - tag_1, tag_2 and tag_3. Is there a way to get the most popular tags reading from multiple columns? The record structure is: +-----------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | flv | varchar(150) | YES | | NULL | | | tag_1 | varchar(75) | YES | | NULL | | | tag_2 | varchar(75) | YES | | NULL | | | tag_3 | varchar(75) | YES | | NULL | | +-----------------+--------------+------+-----+---------+----------------+

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