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• Low cost way to host a large table yet keep the performance scalable?

  - by Leo Liang

  I have a growing table storing time series data, 500M entries now, and 200K new records every day. The total size is around 15GB for now. My clients are querying the table via a PHP script mostly, and the size of the result set is around 10K records (not very large). select * from T where timestamp > X and timestamp < Y and additionFilters And I want this operation cheap. Currently my table is hosting in Postgres 7, on a single 16G memory Box, and I would love to see some good suggestion for me to host this in low cost and also allow me to scale up for performance if needed. The table serves: 1. Query: 90% 2. Insert: 9.9% 2. Update: 0.1% <-- very rare.

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• Lookahead regex produces unexpected group

  - by Ivan Yatskevich

  I'm trying to extract a page name and query string from a URL which should not contain .html Here is an example code in Java: public class TestRegex { public static void main(String[] args) { Pattern pattern = Pattern.compile("/test/(((?!\\.html).)+)\\?(.+)"); Matcher matcher = pattern.matcher("/test/page?param=value"); System.out.println(matcher.matches()); System.out.println(matcher.group(1)); System.out.println(matcher.group(2)); } } By running this code one can get the following output: true page e What's wrong with my regex so the second group contains the letter e instead of param=value?

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• Easy way to parse a url in C++ cross platform?

  - by Andrew Bucknell

  I need to parse a url to get the protocol host path and query in an application I am writing in c++. The application is intended to be cross platform. Im surprised I cant find anything that does this in boost or poco libraries. Is it somewhere obvious Im not looking? Any suggestions on appropriate open source libs? Or is this something I just have to do my self? Its not super complicated but it seems such a common task I am surprised there isnt a common solution.

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• Problem with Full text Searching

  - by devendra

  I am searching in resumes weather the word is exist or not i am using the below query Case1: select top(10) c_resume_text from sntbl_candidates where contains(c_resume_text,'"a/dm"') in the above example only it is not working properly .It showing resumes even though there is no text like that. In Messages i am getting the following message. Informational: The full-text search condition contained noise word(s). if i try with Case 2: select top(10) c_resume_text from sntbl_candidates where contains(c_resume_text,'"a/d') i am getting proper results in case 2 can any one suggest me what to do. Thanks

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• how to prune data set?

  - by sakura90

  The MovieLens data set provides a table with columns: userid | movieid | tag | timestamp I have trouble reproducing the way they pruned the MovieLens data set used in: http://www.cse.ust.hk/~yzhen/papers/tagicofi-recsys09-zhen.pdf In 4.1 Data Set of the above paper, it writes "For the tagging information, we only keep those tags which are added on at least 3 distinct movies. As for the users, we only keep those users who used at least 3 distinct tags in their tagging history. For movies, we only keep those movies that are annotated by at least 3 distinct tags." I tried to query the database: select TMP.userid, count(*) as tagnum from (select distinct T.userid as userid, T.tag as tag from tags T) AS TMP group by TMP.userid having tagnum = 3; I got a list of 1760 users who labeled 3 distinct tags. However, some of the tags are not added on at least 3 distinct movies. Any help is appreciated.

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• SQLITE basic syntax

  - by Doori Bar

  I seem to misunderstand a basic syntax, why this sample works: sqlite3_prepare_v2(db, "insert into test values('boo','boo',0);", strlen(querystring)+1 , &stmt, NULL); if ((rc = sqlite3_step(stmt)) != SQLITE_DONE) fprintf(stderr, "Error: sqlite3_step() %d. Error Message %s;\n",rc,sqlite3_errmsg(db)); But when I try this query: "insert into test(strtest) values('boo');" I get an error: Error: sqlite3_step() 19. Error Message constraint failed; What am I missing? table test is: "create table test (blobtest BLOB(4) NOT NULL, strtest VARCHAR NOT NULL, inttest INTEGER NOT NULL );" Thanks, Doori Bar

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• [Java/Android] Multidimensional array to ListView.. how?

  - by Yverman

  I have a query result set which I like to edit first and then put it to my ListView. Without editing my data first, I could use SimpleCursorAdapter like that: ListAdapter adapter = new SimpleCursorAdapter( this, R.layout.list_item, mCursor, new String[] { "address", "city" }, new int[] { R.id.address, R.id.zip_city }); this.setListAdapter(adapter); But now, I put everything in a multidimensional array like that: if(mCursor.isFirst()) { //create a new array String[][] listData = new String[mCursor.getCount()][3]; int i = 0; do { listData[i] = new String[] { mCursor.getString(mCursor.getColumnIndex("address")), mCursor.getString(mCursor.getColumnIndex("zip")) + " " + mCursor.getString(mCursor.getColumnIndex("city")), calculateDistance(Double.parseDouble(mCursor.getString(mCursor.getColumnIndex("diff")))) }; i++; } while(mCursor.moveToNext()); } So my problem is now, I have no idea how to put this to my ListView. Could someone help me here? Sorry for my bad english and Java knowledge. :)

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• Getting Wikipedia infoboxes in a format that Ruby can understand

  - by hadees

  I am trying to get the data from Wikipedia's infoboxes into a hash or something so that I can use it in my Ruby on Rails program. Specifically I'm interested in the Infobox company and Infobox person. The example I have been using is "Ford Motor Company". I want to get the company info for that and the person info for the people linked to in Ford's company box. I've tried figuring out how to do this from the Wikipedia API or DBPedia but I haven't had much luck. I know wikipedia can return some things as json which I could parse with ruby but I haven't been able to figure out how to get the infobox. In the case of DBPedia I am kind of lost on how to even query it to get the info for Ford Motor Company.

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• Making DiveIntoPython3 work in IE8 (fixing a Javascript performance issue)

  - by srid

  I am trying to fix the performance problem with Dive Into Python 3 on IE8. Visit this page in IE8 and, after a few moments, you will see the following popup: I traced down the culprit down to this line in j/dip3.js ... find("tr:nth-child(" + (i+1) + ") td:nth-child(2)"); If I disable it (and return from the function immediately), the "Stop executing this script?" dialog does not appear as the page now loads fairly fast. I am no Javascript/jquery expert, so I ask you fellow developers as to why this query is making IE slow. Is there a fix for it? Edit: you can download the entire webpage (980K) for local viewing/editing.

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• When should I open and close a connection to SQL Server

  - by Martin

  I have a simple static class with a few methods in it. Each of those methods open a SqlConnection, query the database and close the connection. This way, I am sure that I always close the connection to the database, but on the other hand, I don't like to always open and close connection. Below is an example of what my methods look like. public static void AddSomething(string something) { using (SqlConnection connection = new SqlConnection("...")) { connection.Open(); // ... connection.Close(); } } Considering that the methods are inside a static class, should I have a static member containing a single SqlConnection? How and when should I drop it? What are the best practices?

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• SQL Server 2005 Fail: Return Dates As Strings

  - by Abs

  Hello all, I am using the SQL Server PHP Driver, I think this question can be answered without knowing what this is. I have come across this many times, what does it mean by NAMES? Column names?: SET NAMES utf8 Is there a query similar to the above that will get my dates to be returned as a string? For some reason on my SQL Sever 2008 on Vista, this works: $connectionInfo = array('Database' => $dbname, 'ReturnDatesAsStrings' => true) But the above 'ReturnDatesAsStrings' does not work on my SQL Server 2005 on a windows server machine? I can't execute any queries after setting the above! Does SQL Server 2005 support ReturnDatesAsStrings? Is there some other parameter I can pass to do the same? Thanks all for any help EDIT I should of mentioned this but if there is a solution I am hoping for one that is in the form of a setting that can be set before any queries can be executed as I do not have control on what queries will be executed.

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• Get data types from arbitrary sql statement in SQL Server 2008

  - by Christopherous 5000

  Given some arbitrary SQL I would like to get the data types of the returned columns. The statement might join many tables, views, TVFs, etc. I know I could create a view based on the query and get the datatypes from that, hoping there's a quicker way. Only think I've been able to think of is writing a .net utility to run the SQL and examine the results, wondering if there is a TSQL answer. i.e. Given (not real tables just an example) SELECT p.Name AS PersonName, p.Age, a.Account as AccountName FROM Person as p LEFT JOIN Account as a ON p.Id = a.OwnerId I would like to have something like PersonName: (nvarchar(255), not null) Age: (smallInt, not null) etc...

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• CTE and last known date processing

  - by stackoverflowuser

  Input @StartDate = '01/25/2010' @EndDate = '02/06/2010' I have 2 CTEs in a stored procedure as follows: with CTE_A as ( [gives output A..Shown below] ), with CTE_B as ( Here, I want to check if @StartDate is NOT in output A then replace it with the last known date. In this case, since @startdate is less than any date in output A hence @StartDate will become 02/01/2010. Also to check if @EndDate is NOT in output A then replace it with the last known date. In this case, since @enddate is 02/06/2010 hence it will be replace with 02/05/2010. // Here there is a query using @startDate and @EndDate. ) output A Name Date A 02/01/2010 B 02/01/2010 C 02/05/2010 D 02/10/2010

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• loading files in prolog

  - by cubearth

  hey guys, am a bit of a newbie in Prolog. And am going thru this tutorial on line and it is telling me i can load other prolog files by typing: [filename]. but ever time I try this am getting ERROR: load_files/2: Arguments are not sufficiently instantiated. What am i doing wrong? P.S. the file is in the same directory as the one am working in. and here is a copy of the entire query and error. 12 ?- [KB5]. ERROR: load_files/2: Arguments are not sufficiently instantiated

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• Repository vs Data Access

  - by vdh_ant

  Hi guys In the context of the n-tier application, is there a difference between what you would consider your data access classes to be and your repositories? I tend to think yes but I just wanted to see what other thought. My thinking is that the job of the repository is just to contain and execute the raw query itself, where as the data access class would create the context, execute the repository (passing in the context), handle mapping the data model to the domain model and return the result back up... What do you guys think? Also do you see any of this changing in a Linq to XML scenario (assuming that you change the context for the relevant XDocument)? Cheers Anthony

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• Syntax error converting the nvarchar value to a column of data type int.

  - by Phil

  I have 1,2,3,4,5,6,7,8,9 stored as nvarchar inside Level in my db. I then have a dropdownlist with values 1,2,3,4,5,6,7,8,9. When a user makes a selection (i.e 1) (Level.SelectedValue.ToString). This builds an sql query via a param like this: "Select things From MBA_EOI Where level = 1" When I run the select I get the following error: Syntax error converting the nvarchar value '1,2,3,4,5,6,7,8,9' to a column of data type int. I was under the impression that I was dealing with an Nvarchar field and the selected value as string, where does the int conversion come in? p.s I have also tried Level.SelectedItem.ToString

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• Last in First out UDP structure in MatLab.

  - by D Zondervan

  I am using MatLabs UDP function in their instrument control toolbox to send data packets from one computer to another. The first computer is constantly updating data values and sending them to the other computer, and I want that computer to be able to query the first one for the most recent values whenever it needs them. However, the default implementation of the UDP send and receive in MatLab is a FIFO structure- the first packet I send is the first the other computer receives when they execute the "fscanf" function. I want the last packet I sent to be the one the fscanf function returns. Is this possible or do I need to use a different protocol?

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• Given GPS coordinates, how do I find nearby landmarks or points-of-interest?

  - by stackoverflowuser2010

  I just bought a Google Nexus One smartphone, and I want to write a small Android application for fun. Suppose I can get my current GPS coordinates, so then how can I programmatically find nearby landmarks or points-of-interest within some radius? Is there an API to get GPS geo-tagged landmarks, like in Google Earth's database? For example, if I'm in downtown Chicago, my program would point me to all the "tourist" things to visit in that city. Ideally, it would all run on my smartphone, but if necessary, I can have the smartphone query a webserver, which would then run more queries.

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• What's a reasonable number of rows and tables to be able to join in MySQL?

  - by Philip Brocoum

  I have one table that maps locations to postal codes. For example, New York State has about 2000 postal codes. I have another table that maps mail to the postal codes it was sent to, but this table has about 5 million rows. I want to find all the mail that was sent to New York State, which seems simple enough, but the query is unbelievably slow. I haven't been able to even wait long enough for it to finish. Is the problem that there are 5 million rows? I can't help but think that 5 million shouldn't be such a large number for a computer these days... Oh, and everything is indexed. Is SQL just not designed to handle such large joins?

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• Check for Existence of a Result in Linq-to-xml

  - by NateD

  I'm using Linq-to-XML to do a simple "is this user registered" check (no security here, just making a list of registered users for a desktop app). How do I handle the result from a query like this: var people = from person in currentDoc.Descendants("Users") where (string)person.Element("User") == searchBox.Text select person; I understand the most common way to use the result would be something like foreach (var line in people){ //do something here } but what do you do if person comes back empty, which is what would happen if the person isn't registered? I've looked around on this site and on MSDN and haven't found a really clear answer yet. Extra credit: Give a good explanation of what people contains.

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• MySQL/SQL: Update with correlated subquery from the updated table itself

  - by Roee Adler

  I have a generic question that I will try to explain using an example. Say I have a table with the fields: "id", "name", "category", "appearances" and "ratio" The idea is that I have several items, each related to a single category and "appears" several times. The ratio field should include the percentage of each item's appearances out of the total number of appearances of items in the category. In pseudo-code what I need is the following: For each category find the total sum of appearances for items related to it. For example it can be done with (select sum("appearances") from table group by category) For each item set the ratio value as the item's appearances divided by the sum found for the category above Now I'm trying to achieve this with a single update query, but can't seem to do it. What I thought I should do is: update Table T set T.ratio = T.appearances / ( select sum(S.appearances) from Table S where S.id = T.id ) But MySQL does not accept the alias T in the update column, and I did not find other ways of achieving this. Any ideas?

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• Nested mysql select statements

  - by Jimmy Kamau

  I have a query as below: $sult = mysql_query("select * from stories where `categ` = 'businessnews' and `stryid`='".mysql_query("SELECT * FROM comments WHERE `comto`='".mysql_query("select * from stories where `categ` ='businessnews'")." ORDER BY COUNT(comto) DESC")."' LIMIT 3") or die(mysql_error()); while($ow=mysql_fetch_array($sult)){ The code above should return the top 3 'stories' with the most comments {count(comto)}. The comments are stored in a different table from the stories. The code above does not return any values and doesn't show any errors. Could someone please help?

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• how to show a html webpage in a GUI in Java

  - by Robert

  Dear all, I've recently worked on a project on search query,and I am only last step away from completion. Now I have a nice URL,and can open it in "cmd /c start" statement in Java,and it causes an IE window open. However,my advisor is not satisfied with that,he wants to see this webpage(actually,two webpages) opened in a GUI interface. So could you please give a detailed instruction on how to achieve this in Java,please?If you are trying to offer me a helpful package,would you please kindly also show how to use that as well,since I am new to this GUI development,and I only know the basics of Swing. Thanks a lot,it is dued within this week.

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• Pros and cons of sorting data in DB?

  - by Roman

  Let's assume I have a table with field of type VARCHAR. And I need to get data from that table sorted alphabetically by that field. What is the best way (for performance): add sort by field to the SQL-query or sort the data when it's already fetched? I'm using Java (with Hibernate), but I can't tell anything about DB engine. It could be any popular relational database (like MySQL or MS Sql Server or Oracle or HSQL DB or any other). The amount of records in table can vary greatly but let's assume there are 5k records.

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• php mysql database users connection handling

  - by aviv

  What is the best way to handle mysql database users connection in PHP? I have a web server running a PHP application on MySQL. I have created a database user for the application: dbuser1 with limited access - only for query, insert and update tables. No alter table. Now the question is, should i use the same dbuser1 widely in my scripts, so if there are 100 current people using my system and hence 100 scripts running parallel they all connect to the database with the same dbuser1? or should i create a few users and assign each script a different user or load-balance between the dbusers ?

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