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• PostgreSQL: How to index all foreign keys?

  - by biggusjimmus

  I am working with a large PostgreSQL database, and I are trying to tune it to get more performance. Our queries and updates seem to be doing a lot of lookups using foreign keys. What I would like is a relatively simple way to add Indexes to all of our foreign keys without having to go through every table (~140) and doing it manually. In researching this, I've come to find that there is no way to have Postgres do this for you automatically (like MySQL does), but I would be happy to hear otherwise there, too.

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• How to limit the number of connections to a SQL Server server from my tomcat deployed java applicati

  - by CJ

  I have an application that is deployed on tomcat on server A and sends queries to a huge variety of SQL Server databases on an server B. I am concerned that my application could overload this SQL Server database server and would like some way to preventing it making requests to connect to any database on that server if some arbitrary number of connections were already in existence and unclosed. I am looking at using connection pooling but am under the impression that this will only pool connections to a specific database on the SQL Server server, I want to control the total of these combined connections that will occur to many different databases (incidentally I can only find out the names of individual db's dynamically as they change day to day). Will connection pooling take care of this for me, are am I looking at this from the wrong perspective? I have no access to the configuration of the SQL Server server. Links to tutorials or working examples of your suggested solution are most welcome!

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• Rails: getting logic to run at end of request, regardless of filter chain aborts?

  - by JSW

  Is there a reliable mechanism discussed in rails documentation for calling a function at the end of the request, regardless of filter chain aborts? It's not after filters, because after filters don't get called if any prior filter redirected or rendered. For context, I'm trying to put some structured profiling/reporting information into the app log at the end of every request. This information is collected throughought the request lifetime via instance variables wrapped in custom controller accessors, and dumped at the end in a JSON blob for use by a post-processing script. My end goal is to generate reports about my application's logical query distribution (things that depend on controller logic, not just request URIs and parameters), performance profile (time spent in specific DB queries or blocked on webservices), failure rates (including invalid incoming requests that get rejected by before_filter validation rules), and a slew of other things that cannot really be parsed from the basic information in the application and apache logs. At a higher level, is there a different "rails way" that solves my app profiling goal?

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• Can I improve performance by refactoring SQL commands into C# classes?

  - by Matthew Jones

  Currently, my entire website does updating from SQL parameterized queries. It works, we've had no problems with it, but it can occasionally be very slow. I was wondering if it makes sense to refactor some of these SQL commands into classes so that we would not have to hit the database so often. I understand hitting the database is generally the slowest part of any web application For example, say we have a class structure like this: Project (comprised of) Tasks (comprised of) Assignments Where Project, Task, and Assignment are classes. At certain points in the site you are only working on one project at a time, and so creating a Project class and passing it among pages (using Session, Profile, something else) might make sense. I imagine this class would have a Save() method to save value changes. Does it make sense to invest the time into doing this? Under what conditions might it be worth it?

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• MySQL : delete from table that is used in the where clause

  - by Eric

  I am writing a small script to synchronize 2 MySQL tables ( t1 to be 'mirrored' to t2 ) In a step I would like to delete rows inside t2 that has been delete in t1 with the same id. I tried this query : delete from t2 where t2.id in ( select t2.id left join t1 on (t1.id=t2.id) where t1.id is null ) But Mysql forbid me to use t2 in the same time in the delete and in the select (sound logical by the way) Of course, I can split the query into 2 queries : first select IDs, then delete rows with these IDs. My question : do you have a cleaner way to delete row from t2 that does not exist anymore in t1 ? with one query only ?

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• Growing MS Access File Size problem

  - by user55886

  I have a large MS Access application with a lot of computations in VBA code. When I run it it eventually crashes due to excessive file size. There are a lot of intermediate tables and queries created and subsequently deleted, but Access does not reclaim the space. I have diligently closed all intermediate record sets and set all temporary objects to nothing, but nothing helps. The only way I can get my code to run is to run part of it, stop and repair/compress the file then restart the code. Isn't there a better way? Thanks

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• checking boolean property in XML(Spring)

  - by Abhishek Bhandari

  I am using Spring Framework . While writing coustum SQL queries , i am unable check a parameter of boolean value. For example this is not working .. do some SQl cods The above checking is not working , it is evaluating as equal in both the cases when booleanVariable is true and false . i tried to replace compareValue ="tree" and "false". As that is a monkey work i do sometimes . is it possible to check the boolean property in XML like above .

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• Can I improve performance by refactoring SQL commands into classes?

  - by Matthew Jones

  Currently, my entire website does updating from SQL parameterized queries. It works, we've had no problems with it, but it can occasionally be very slow. I was wondering if it makes sense to refactor some of these SQL commands into classes so that we would not have to hit the database so often. I understand hitting the database is generally the slowest part of any web application For example, say we have a class structure like this: Project (comprised of) Tasks (comprised of) Assignments Where Project, Task, and Assignment are classes. At certain points in the site you are only working on one project at a time, and so creating a Project class and passing it among pages (using Session, Profile, something else) might make sense. I imagine this class would have a Save() method to save value changes. Does it make sense to invest the time into doing this? Under what conditions might it be worth it?

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• How can I write a MySQL query to check multiple rows?

  - by Matt

  I have a MySQL table containing data on product features: feature_id feature_product_id feature_finder_id feature_text feature_status_yn 1 1 1 Webcam y 2 1 1 Speakers y 3 1 1 Bluray n I want to write a MySQL query that allows me to search for all products that have a 'y' feature_status_yn value for a given feature_product_id and return the feature_product_id. The aim is to use this as a search tool to allow me to filter results to product IDs only matching the requested feature set. A query of SELECT feature_id FROM product_features WHERE feature_finder_id = '1' AND feature_status_yn = 'y' will return all of the features of a given product. But how can I select all products (feature_product_id) that have a 'y' value when they are on separate lines? Multiple queries might be one way to do it, but I'm wondering whether there's a more elegant solution based purely in SQL.

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• Performing complex query with Dynamics CRM 4.0

  - by dub

  Hi, I have two custom entites, Product and ProductType, linked together in many-to-one relationship. Product has a lookup field to ProductType. I'm trying to write a query to fetch Type1 products with a price over 100, and Type2 products with a price lower than 100. Here's how I would do it in SQL : select * from Product P inner join ProductType T on T.Id = P.TypeId where (T.Code = 'Type1' and P.Price >= 100) or (T.Code = 'Type2' and P.Price < 100) I can't figure out a way to build a QueryExpression to do exactly that. I know I could do it with two queries, but I'd like to minimize roundtrips to the server. Is there a way to perform that query in only one operation ? Thanks!

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• Why does SQLAlchemy with psycopg2 use_native_unicode have poor performance?

  - by Bob Dover

  I'm having a difficult time figuring out why a simple SELECT query is taking such a long time with sqlalchemy using raw SQL (I'm getting 14600 rows/sec, but when running the same query through psycopg2 without sqlalchemy, I'm getting 38421 rows/sec). After some poking around, I realized that toggling sqlalchemy's use_native_unicode parameter in the create_engine call actually makes a huge difference. This query takes 0.5secs to retrieve 7300 rows: from sqlalchemy import create_engine engine = create_engine("postgresql+psycopg2://localhost...", use_native_unicode=True) r = engine.execute("SELECT * FROM logtable") fetched_results = r.fetchall() This query takes 0.19secs to retrieve the same 7300 rows: engine = create_engine("postgresql+psycopg2://localhost...", use_native_unicode=False) r = engine.execute("SELECT * FROM logtable") fetched_results = r.fetchall() The only difference between the 2 queries is use_native_unicode. But sqlalchemy's own docs state that it is better to keep use_native_unicode=True (http://docs.sqlalchemy.org/en/latest/dialects/postgresql.html). Does anyone know why use_native_unicode is making such a big performance difference? And what are the ramifications of turning off use_native_unicode?

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• How to 'insert if not exists' in MySQL?

  - by warren

  I started by googling, and found this article which talks about mutex tables. I have a table with ~14 million records. If I want to add more data in the same format, is there a way to ensure the record I want to insert does not already exist without using a pair of queries (ie, one query to check and one to insert is the result set is empty)? Does a unique constraint on a field guarantee the insert will fail if it's already there? It seems that with merely a constraint, when I issue the insert via php, the script croaks.

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• Zend Framework multiple databases

  - by Uffo

  I'm currently using only one database with Zend Framework, but now I have to add ONE MORE. I'm using this code right now: public static function setupDatabase() { $config = self::$registry->configuration; $db = Zend_Db::factory($config->db->adapter, $config->db->toArray()); $db->query("SET NAMES 'utf8'"); self::$registry->database = $db; Zend_Db_Table::setDefaultAdapter($db); } What code do I need to write in order to use ONE MORE database; and how I will reference it, when I need to make some queries or so.. Best Regards!

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• MultiOS "Jet Database" for QtC++?

  - by Airjoe

  Hopefully I can articulate this well: I'm porting an application I made years ago from VB6 (I know, I know!) to QtC++. In my original application, one thing I liked was that I didn't need an actual SQL server running, I could just use MS Access .mdb files. I was wondering if something similar exists for QtC++ that will work on multiple OSes- a database stored in a file, pretty much, but that I can still run SQL queries with. Not sure if something like this exists or not, but any help appreciated, thanks!

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• How do I make this Query against EF Efficient?

  - by dudeNumber4

  Using EF4. Assume I have this: IQueryable<ParentEntity> qry = myRepository.GetParentEntities(); Int32 n = 1; What I want to do is this, but EF can't compare against null. qry.Where( parent => parent.Children.Where( child => child.IntCol == n ) != null ) What works is this, but the SQL it produces (as you would imagine) is pretty inefficient: qry.Where( parent => parent.Children.Where( child => child.IntCol == n ).FirstOrDefault().IntCol == n ) How can I do something like the first comparison to null that won't be generating nested queries and so forth?

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• Post High Score and Retrieve Position

  - by majman

  I'm not so savvy with MYSQL, so my apologies in advance is this is a dumb question. I've created a super basic PHP High Scores table. Upon inserting a new score into the DB Table, I'd like to retrieve the position of that score so that I can get 10 results with the persons score falling within that range. My INSERT Query looks something like: $stmt = $mysqli->prepare("INSERT INTO highscores (name, time, score) VALUES (?, ?, ?)"); $stmt->bind_param('sdi', $name, $time, $score); UPDATE - I'm looking for a way to do this with as few queries as possible. I recall reading something about getting an INSERT ID when making an insert, but I would then still have to make a second query to get those results.

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• Oracle (Old?) Joins - A tool for conversion?

  - by Grasper

  I have been porting oracle selects, and I have been running across a lot of queries like so: SELECT e.last_name, d.department_name FROM employees e, departments d WHERE e.department_id(+) = d.department_id; ...and: SELECT last_name, d.department_id FROM employees e, departments d WHERE e.department_id = d.department_id(+); Are there any guides/tutorials for converting all of the variants of the (+) syntax? What is that syntax even called (so I can scour google)? Even better.. Is there a tool that will do this conversion for me? When was this standard phased out? Any info is appreciated.

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• COUNT issue across multiple tables

  - by Kim

  I am trying to count across 2 tables and I dont see whats wrong with my query yet I get a wrong result. User 2 does not exist in table_two, so the zero is correct. SELECT t1.creator_user_id, COUNT(t1.creator_user_id), COUNT(t2.user_id) FROM table_one AS t1 LEFT JOIN table_two AS t2 ON t2.user_id = t1.creator_user_id GROUP BY t1.creator_user_id, t2.user_id Actual result 1 192 192 2 9 0 Expected result 1 16 12 2 9 0 The result indicate a missing group by condition, but I already got both fields used. Where am I wrong ? Also, can I sum up all users that doesnt exist in table_two for t1 ? Like user 3 exists 21 times in t1, then the results would be: 1 16 12 (users with > 0 in t2 will need their own row) 2 30 0 (user 2=9 + user 3=21 => 30) Its okay for the user Id to be wrong for sum of t1 for all users with 0 in t2. If not possible, then I'll just do two queries.

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• jQuery AJAX & Multiple sp Result Sets

  - by Kevin

  Is it possible to use a stored procedure that returns multiple result sets in json format and process them as part of one request using ajax calls in jquery? In other words, I have a stored procedure that returns several result sets that are to be used with a series of select boxes that are all being filtered by the same criteria. If any of the select boxes is chosen that value is then passed to the stored procedure and all the subsequent select box updates reflect only results that match the filtered criteria. I don't want to have to call the same sp multiple times to process the results and was trying not to create multiple queries, so I'm wondering if it's possible to store more than one json result in a single request and then store and process them on the client side.

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• mySQL php query - news/ friends feed

  - by rpsep2

  I want to show a user the recent uploads from their friends. I have the users friends id's in an array: $friends A user could have, potentially, thousands of friends. I can select the uploads from 1 of a users friends with: $row = $mysqli->query("SELECT * FROM photos WHERE uploader_id = ".$friend." ORDER BY date_uploaded DESC LIMIT ".$page.", 25"); But I need to find all of a users friends uploads. I thought about doing this in a loop iterating over the $friends array, but then I'd be potentially running thousands of mysql queries. How can I do this most efficiently? so to clarify: search a 'photos' table for photos which are uploaded by specific users(friends), held in $friends variable, sort by date_uploaded and limit to x results so I can have pages 1, 2, 3 etc.

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• How To Configure Query Cacheing in EclipseLink

  - by rustyshelf

  I have a collection of states, that I want to cache for the life of the application, preferably after it is called for the first time. I'm using EclipseLink as my persistence provider. In my EJB3 entity I have the following code: @Cache @NamedQueries({ @NamedQuery( name = "State.findAll", query = "SELECT s FROM State s", hints = { @QueryHint(name=QueryHints.CACHE_USAGE, value=CacheUsage.CheckCacheThenDatabase), @QueryHint(name=QueryHints.READ_ONLY, value=HintValues.TRUE) } ) }) This doesn't seem to do anything though, if I monitor the SQL queries going to MySQL it still does a select each time my Session Bean uses this NamedQuery. What is the correct way to configure this query so that it is only ever read once from the database, preferably across all sessions? Edit: I am calling the query like this: Query query = em.createNamedQuery("State.findAll"); List<State> states = query.getResultList();

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• Compact web server with Lua support?

  - by OverTheRainbow

  Hello, I need to find a very compact, cross-platform web server that can run Lua scripts, ie. either a regular web server like Mongoose that will forward queries to a Lua program in eg. FastCGI, or a web server itself written in Lua which will save the need to provide a separate web server. I recently started learning about Lua so am still in the dark about what is available out there, save for the three I came accross: Barracuda Embedded Web Server http://barracudaserver.com/ba/doc/ Xavante - Lua HTTP 1.1 Web server http://keplerproject.github.com/xavante/ Haserl http://haserl.sourceforge.net/ If someone's already done this recently, what solution would you recommend along with any tutorial/article that would get me started? Thank you.

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• mysql does not utilize my cpu and ram enough?

  - by vick

  Hello Everyone! I am importing a 2.5gb csv file to a mysql table. My storage engine is innodb. Here is the script: use xxx; DROP TABLE IF EXISTS `xxx`.`xxx`; CREATE TABLE `xxx`.`xxx` ( `xxx_id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(128) NOT NULL, `yy` varchar(128) NOT NULL, `yyy` varchar(64) NOT NULL, `yyyy` varchar(2) NOT NULL, `yyyyy` varchar(10) NOT NULL, `url` varchar(64) NOT NULL, `p` varchar(10) NOT NULL, `pp` varchar(10) NOT NULL, `category` varchar(256) NOT NULL, `flag` varchar(4) NOT NULL, PRIMARY KEY (`xxx_id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; set autocommit = 0; load data local infile '/home/xxx/raw.csv' into table company fields terminated by ',' optionally enclosed by '"' lines terminated by '\r\n' ( name, yy, yyy, yyyy, yyyyy, url, p, pp, category, flag ); commit; Why does my PC (core i7 920 with 6gb ram) only consume 9% cpu power and 60% ram when running these queries?

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• Why is this postgresql query so slow?

  - by user315975

  I'm no database expert, but I have enough knowledge to get myself into trouble, as is the case here. This query SELECT DISTINCT p.* FROM points p, areas a, contacts c WHERE ( p.latitude > 43.6511659465 AND p.latitude < 43.6711659465 AND p.longitude > -79.4677941889 AND p.longitude < -79.4477941889) AND p.resource_type = 'Contact' AND c.user_id = 6 is extremely slow. The points table has fewer than 2000 records, but it takes about 8 seconds to execute. There are indexes on the latitude and longitude columns. Removing the clause concering the resource_type and user_id make no difference. The latitude and longitude fields are both formatted as number(15,10) -- I need the precision for some calculations. There are many, many other queries in this project where points are compared, but no execution time problems. What's going on?

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• Does normalization really hurt performance in high traffic sites?

  - by Luke101

  I am designing a database and I would like to normalize the database. I one query I will joining about 30-40 tables. Will this hurt the website performance if it ever becomes extremely popular? This will be the main query and it will be getting called 50% of the time. The other queries I will be joining about 2 tables. I have a choice right now to normalize or not to normalize but if the normalization becomes a problem in the future i may have to rewrite 40% of the software and it may take me a long time. Does normalization really hurt in this case? Should I denormalize now while I have the time?

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