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  • Five Query Optimizations in MySQL

    Query optimization is an often overlooked part of applications. Sean Hull encourages at least some attention to query optimization up front and helps you identify some of the more common optimizations you may run across.

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  • How to get hibernate3-maven-plugin hbm2ddl to find JDBC driver?

    - by HDave
    I have a Java project I am building with Maven. I am now trying to get the hibernate3-maven-plugin to run the hbm2ddl tool to generate a schema.sql file I can use to create the database schema from my annotated domain classes. This is a JPA application that uses Hibernate as the provider. In my persistence.xml file I call out the mysql driver: <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/> <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/> When I run Maven, I see it processing all my classes, but when it goes to output the schema, I get the following error: ERROR org.hibernate.connection.DriverManagerConnectionProvider - JDBC Driver class not found: com.mysql.jdbc.Driver java.lang.ClassNotFoundException: com.mysql.jdbc.Driver I have the MySQL driver as a dependency of this module. However it seems like the hbm2ddl tool cannot find it. I would have guessed that the Maven plugin would have known to search the local Maven file repository for this driver. What gives? The relevant part of my pom.xml is this: <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>hibernate3-maven-plugin</artifactId> <executions> <execution> <phase>process-classes</phase> <goals> <goal>hbm2ddl</goal> </goals> </execution> </executions> <configuration> <components> <component> <name>hbm2ddl</name> <implementation>jpaconfiguration</implementation> </component> </components> <componentProperties> <persistenceunit>my-unit</persistenceunit> </componentProperties> </configuration> </plugin>

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  • Shouldn't prepared statements be much faster?

    - by silversky
    $s = explode (" ", microtime()); $s = $s[0]+$s[1]; $con = mysqli_connect ('localhost', 'test', 'pass', 'db') or die('Err'); for ($i=0; $i<1000; $i++) { $stmt = $con -> prepare( " SELECT MAX(id) AS max_id , MIN(id) AS min_id FROM tb "); $stmt -> execute(); $stmt->bind_result($M,$m); $stmt->free_result(); $rand = mt_rand( $m , $M ).'<br/>'; $res = $con -> prepare( " SELECT * FROM tb WHERE id >= ? LIMIT 0,1 "); $res -> bind_param("s", $rand); $res -> execute(); $res->free_result(); } $e = explode (" ", microtime()); $e = $e[0]+$e[1]; echo number_format($e-$s, 4, '.', ''); // and: $link = mysql_connect ("localhost", "test", "pass") or die (); mysql_select_db ("db") or die ("Unable to select database".mysql_error()); for ($i=0; $i<1000; $i++) { $range_result = mysql_query( " SELECT MAX(`id`) AS max_id , MIN(`id`) AS min_id FROM tb "); $range_row = mysql_fetch_object( $range_result ); $random = mt_rand( $range_row->min_id , $range_row->max_id ); $result = mysql_query( " SELECT * FROM tb WHERE id >= $random LIMIT 0,1 "); } defenitly prepared statements are much more safer but also every where it says that they are much faster BUT in my test on the above code I have: - 2.45 sec for prepared statements - 5.05 sec for the secon example What do you think I'm doing wrong? Should I use the second solution or I should try to optimize the prep stmt?

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  • MySQL Input Parameters Add Flexibility to Crosstab Stored Procedures

    When generating a result set where the query contains an unknown number of column and/or row values we can use a combination of Prepared Statements, which allows us to tailor the output based on the number of data values. We can also add input parameters to a procedure to assign the field names, aliases, and even the aggregate function!

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  • MySQL Input Parameters Add Flexibility to Crosstab Stored Procedures

    When generating a result set where the query contains an unknown number of column and/or row values we can use a combination of Prepared Statements, which allows us to tailor the output based on the number of data values. We can also add input parameters to a procedure to assign the field names, aliases, and even the aggregate function!

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  • Testing a patch to the Rails mysql adapter

    - by Sleepycat
    I wrote a little monkeypatch to the Rails MySQLAdapter and want to package it up to use it in my other projects. I am trying to write some tests for it but I am still new to testing and I am not sure how to test this. Can someone help get me started? Here is the code I want to test: unless RAILS_ENV == 'production' module ActiveRecord module ConnectionAdapters class MysqlAdapter < AbstractAdapter def select_with_explain(sql, name = nil) explanation = execute_with_disable_logging('EXPLAIN ' + sql) e = explanation.all_hashes.first exp = e.collect{|k,v| " | #{k}: #{v} "}.join log(exp, 'Explain') select_without_explain(sql, name) end def execute_with_disable_logging(sql, name = nil) #:nodoc: #Run a query without logging @connection.query(sql) rescue ActiveRecord::StatementInvalid => exception if exception.message.split(":").first =~ /Packets out of order/ raise ActiveRecord::StatementInvalid, "'Packets out of order' error was received from the database. Please update your mysql bindings (gem install mysql) and read http://dev.mysql.com/doc/mysql/en/password-hashing.html for more information. If you're on Windows, use the Instant Rails installer to get the updated mysql bindings." else raise end end alias_method_chain :select, :explain end end end end Thanks.

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  • How to design tag database structure?

    - by liuxingruo
    I have a subjects database, and I want to create a new tag database to tag the subjects, but I have no idea how to design the new tag database structure. I'm assuming the new database looks like this: tag_id tag_name tagged_subject_ids 1 tag1 1, 2, 3, 5, 10 2 tag2 2, 4, 5, 6, 10, 12 so, if I want to select the tags belong to subject 1: SELECT tag_name FROM tag_database WHERE tagged_subject_ids LIKE '1'; I think the way that I select tag may be very slow, so please help me. Thanks!

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  • SQL query duplicating results [on hold]

    - by Ben
    I have written a query that results in data being retrieved for the top 5 customers in my table per account manager. Here is the query: SELECT account_manager_id, mgap_ska_id, total FROM (SELECT account_manager_id, mgap_ska_id, mgap_growth + mgap_recovery AS total, @grp_rank := IF(@current_accmanid = account_manager_id, @grp_rank + 1, 1) AS grp_rank, @current_accmanid := account_manager_id FROM mgap_orders ORDER BY total DESC ) ranked WHERE grp_rank <= 5 and here is the result of the query: account_manager_id mgap_ska_id total 159840 5062352 61569.21 159840 5062352 61569.21 159840 5062352 61569.21 159840 5062352 61569.21 159840 5062352 61569.21 160023 5024546 52244.29 160023 5024546 52244.29 160023 5024546 52244.29 160023 5024546 52244.29 160023 5024546 52244.29 159669 5323292 50126.38 159669 5323292 50126.38 159669 5323292 50126.38 159669 5323292 50126.38 159669 5323292 50126.38 As you can see the query is partially working as needed, except Im getting duplicates for mgap_ska_id whereas it should be five individual mgap_ska_id numbers. and here is a sample of my data: mgap_ska_id account_manager_id mgap_growth mgap_recovery 5057810 64154 0 1160.78 5178114 24456 0 5773.42 5292421 160338 0 5146.04 5414091 24408 0 104.14 5057810 64154 0 1160.78 Can anyone see where Ive gone wrong in my query and how/where I might correct the error so I get the 5 top individual customers (mgap_ska_id) instead of the duplicated top single customer?

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  • Running MySQL in Batch Mode

    Anyone who has spent a fair amount of time working with databases comes to realize that common tasks like backups and data transfers should be run from a script rather than interactively. In this tutorial, we will be writing a common batch file to back up a table to a file.

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  • Is there any other efficient way to use table variable instead of using temporary table

    - by varta shrimali
    we are writing script to display banners on a web page where we are using temporary table in mysql procedure. Is there any other efficient way to use table variable instead of using temporary table we are using following code: -- banner location CURSOR -- DECLARE banner_location_cursor CURSOR FOR select bm.id as masterId, bm.section as masterName, bs.id as locationId, bs.sectionName as locationName from banner_master as bm inner join banner_section as bs on bm.id=bs.masterId where bm.section=sCode ; -- DECLARE banner CURSORS DECLARE banner_cursor CURSOR FOR SELECT bd.id as bannerId, bd.sectionId, bd.bannerName, bd.websiteURL, bd.paymentType, bd.status, bd.startDate, bd.endDate, bd.bannerDisplayed, bs.id, bs.sectionName from banner_detail as bd inner join banner_section as bs on bs.id=bd.sectionId where bs.id= location_id and bd.status='A' and (dates between cast(bd.startDate as DATE) and cast(bd.endDate as DATE)) order by rand(), bd.bannerDisplayed asc limit 1 ; DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_rows = 1; SET dates = (select curdate()); -- RESULTS TABLE WHICH WILL BE RETURNED -- CREATE temporary TABLE test ( b_id INT, s_id INT, b_name varchar(128), w_url varchar(128), p_type varchar(128), st char(1), s_date datetime, e_date datetime, b_display int, sec_id int, s_name varchar(128) ); -- OPEN banner location CURSOR OPEN banner_location_cursor; the_loop: LOOP FETCH banner_location_cursor INTO master_id, master_name, location_id, location_name; IF no_more_rows THEN CLOSE banner_location_cursor; leave the_loop; END IF; OPEN banner_cursor; -- select FOUND_ROWS(); the_loop2: LOOP FETCH banner_cursor INTO banner_id, section_id, banner_name, website_url, payment, status, start_date, end_date, banner_displayed, sec_id, section_name; IF no_more_rows THEN set no_more_rows = 0; CLOSE banner_cursor; leave the_loop2; END IF; INSERT INTO test ( b_id, s_id, b_name , w_url, p_type, st, s_date, e_date, b_display, sec_id, s_name ) VALUES ( banner_id, section_id, banner_name, website_url, payment, status, start_date, end_date, banner_displayed, sec_id, section_name ); UPDATE banner_detail set bannerDisplayed = (banner_displayed+1) where id = banner_id; END LOOP the_loop2; END LOOP the_loop; -- RETURN result SELECT * FROM test; -- DROP RESULTS TABLE DROP TABLE test; END

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  • MySQL CASE Statements in Multi-Aggregated Crosstab Columns

    Inserting additional columns to a crosstab query is less straightforward than adding row data, because SQL naturally groups data by rows. Moreover, the efficacy of the CASE statement within an aggregate function decreases in direct proportion to the complexity of the criteria. Read on to learn more...

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  • MySQL CASE Statements in Multi-Aggregated Crosstab Columns

    Inserting additional columns to a crosstab query is less straightforward than adding row data, because SQL naturally groups data by rows. Moreover, the efficacy of the CASE statement within an aggregate function decreases in direct proportion to the complexity of the criteria. Read on to learn more...

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  • ClassNotFoundException com.mysql.jdbc.Driver

    - by Dusk
    This question might have asked here number of times . After doing some google search for the above error and doing some update, I can't understand why I'm still getting that error. I've already put my driver-- mysql-connector-java-5.1.5-bin in the classpath: Java_Home\jre\lib\ Java_Home\jre\lib\ext\ Java_Home\lib and the code which I'm using to connect to mysql database is: try{ Class.forName("com.mysql.jdbc.Driver"); Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/mail","root",""); Statement stmt = con.createStatement(); ResultSet rs = stmt.executeQuery("select message_body from deadletter"); String dbtime; while (rs.next()) { dbtime = rs.getString(1); System.out.println(dbtime); } con.close(); } catch (SQLException e) { System.out.println("Connection Failed! Check output console"); e.printStackTrace(); } } and the complete stacktrace of the above exception is: java.lang.ClassNotFoundException: com.mysql.jdbc:Driver at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:169) at mail.main(mail.java:114) Now, what's wrong I'm doing here?

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  • Grouping with operands question

    - by Filip
    I have a table: mysql> desc kursy_bid; +-----------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+-------------+------+-----+---------+-------+ | datetime | datetime | NO | PRI | NULL | | | currency | varchar(6) | NO | PRI | NULL | | | value | varchar(10) | YES | | NULL | | +-----------+-------------+------+-----+---------+-------+ 3 rows in set (0.01 sec) I would like to select some rows from a table, grouped by some time interval (can be one day) where I will have the first row and the last row of the group, the max(value) and min(value). I tried: select datetime, (select value order by datetime asc limit 1) open, (select value order by datetime desc limit 1) close, max(value), min(value) from kursy_bid_test where datetime > '2009-09-14 00:00:00' and currency = 'eurpln' group by month(datetime), day(datetime), hour(datetime); but the output is: | open | close | datetime | max(value) | min(value) | +--------+--------+---------------------+------------+------------+ | 1.4581 | 1.4581 | 2009-09-14 00:00:05 | 4.1712 | 1.4581 | | 1.4581 | 1.4581 | 2009-09-14 01:00:01 | 1.4581 | 1.4581 | As you see open and close is the same (but they shouldn't be). What should be the query to do what I want?

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  • Sql query - selecting top 5 rows and further selecting rows only if User is present

    - by Gublooo
    Hello, I kind of stuck on how to implement this query - this is pretty similar to the query I posted earlier but I'm not able to crack it. I have a shopping table where everytime a user buys anything, a record is inserted. Some of the fields are * shopping_id (primary key) * store_id * user_id Now what I need is to pull only the list of those stores where he's among the top 5 visitors: When I break it down - this is what I want to accomplish: * Find all stores where this UserA has visited * For each of these stores - see who the top 5 visitors are. * Select the store only if UserA is among the top 5 visitors. The corresponding queries would be: select store_id from shopping where user_id = xxx select user_id,count(*) as 'visits' from shopping where store_id in (select store_id from shopping where user_id = xxx) group by user_id order by visits desc limit 5 Now I need to check in this resultset if UserA is present and select that store only if he's present. For example if he has visited a store 5 times - but if there are 5 or more people who have visited that store more than 5 times - then that store should not be selected. So I'm kind of lost here. Thanks for your help

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  • Faster &amp;amp; Stronger MySQL

    Usually an article like this one will start out with the technical word "scaling". Unfortunately, like health care reform, everyone can't always agree on what they mean by it, or even what the goal is. Learn how to make your database faster, stronger, bigger and better in this article that uses words we can all agree on.

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  • Issue in Creating an Insert Query See Description Below...

    - by Parth
    I am creating a Insert Query using PHP.. By fetching the data from a Audit table and iterating the values of it in loops.. table from which I am fetching the value has the snapshot below: The Code I am using to create is given below: mysql_select_db('information_schema'); $select = mysql_query("SELECT TABLE_NAME FROM TABLES WHERE TABLE_SCHEMA = 'pranav_test'"); $selectclumn = mysql_query("SELECT * FROM COLUMNS WHERE TABLE_SCHEMA = 'pranav_test'"); mysql_select_db('pranav_test'); $seletaudit = mysql_query("SELECT * FROM jos_audittrail WHERE live = 0"); $tables = array(); $i = 0; while($row = mysql_fetch_array($select)) { $tables[$i++] =$row['TABLE_NAME']; } while($row2 = mysql_fetch_array($seletaudit)) { $audit[] =$row2; } foreach($audit as $val) { if($val['operation'] == "INSERT") { if(in_array($val['table_name'],$tables)) { $insert = "INSERT INTO '".$val['table_name']."' ("; $selfld = mysql_query("SELECT field FROM jos_audittrail WHERE table_name = '".$val['table_name']."' AND operation = 'INSERT' AND trackid = '".$val['trackid']."'"); while($row3 = mysql_fetch_array($selfld)) { $values[] = $row3; } foreach($values as $field) { $insert .= "'".$field['field']."', "; } $insert .= "]"; $insert = str_replace(", ]",")",$insert); $insert .= " values ("; $selval = mysql_query("SELECT newvalue FROM jos_audittrail WHERE table_name = '".$val['table_name']."' AND operation = 'INSERT' AND trackid = '".$val['trackid']."' AND live = 0"); while($row4 = mysql_fetch_array($selval)) { $value[] = $row4; } /*echo "<pre>"; print_r($value);exit;*/ foreach($value as $data) { $insert .= "'".$data['newvalue']."', "; } $insert .= "["; $insert = str_replace(", [",")",$insert); } } } When I Echo the $insert out of the most outer for loop (for auditrail) The values get printed as many times as the records are found for the outer for loop..i.e 'orderby= show_noauth= show_title= link_titles= show_intro= show_section= link_section= show_category= link_category= show_author= show_create_date= show_modify_date= show_item_navigation= show_readmore= show_vote= show_icons= show_pdf_icon= show_print_icon= show_email_icon= show_hits= feed_summary= page_title= show_page_title=1 pageclass_sfx= menu_image=-1 secure=0 ', '0000-00-00 00:00:00', '13', '20', '1', '152', 'accmenu', 'IPL', 'ipl', 'index.php?option=com_content&view=archive', 'component' gets repeated , i.e. INSERT INTO 'jos_menu' ('params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type', 'params', 'checked_out_time', 'ordering', 'componentid', 'published', 'id', 'menutype', 'name', 'alias', 'link', 'type') values ('orderby= show_noauth= show_title= link_titles= show_intro= show_section= link_section= show_category= link_category= show_author= show_create_date= show_modify_date= show_item_navigation= show_readmore= show_vote= show_icons= show_pdf_icon= show_print_icon= show_email_icon= show_hits= feed_summary= page_title= show_page_title=1 pageclass_sfx= menu_image=-1 secure=0 ', '0000-00-00 00:00:00', '13', '20', '1', '152', 'accmenu', 'IPL', 'ipl', 'index.php?option=com_content&view=archive', 'component', 'orderby= show_noauth= show_title= link_titles= show_intro= show_section= link_section= show_category= link_category= show_author= show_create_date= show_modify_date= show_item_navigation= show_readmore= show_vote= show_icons= show_pdf_icon= show_print_icon= show_email_icon= show_hits= feed_summary= page_title= show_page_title=1 pageclass_sfx= menu_image=-1 secure=0 ', '0000-00-00 00:00:00', '13', '20', '1', '152', 'accmenu', 'IPL', 'ipl', 'index.php?option=com_content&view=archive', 'component', 'orderby= show_noauth= .. .. .. .. and so on What I want is I should get these Values for once, I know there is mistake using the outer Forloop, but I m not getting the idea of rectifying it.. Please help... please poke me for more clarification...

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  • Bind any version of MySql.Data using the app.config

    - by Martin Kirsche
    How do I bind any version or a range of versions of an assembly by using the app.config? I'm currently binding the MySql.Data assembly like this: <runtime> <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1" applies-to="v2.0.50727"> <qualifyAssembly partialName="MySql.Data" fullName="MySql.Data, Version=6.2.2.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d, processorArchitecture=MSIL"/> </assemblyBinding> </runtime> Any version of MySql.Data other than 6.2.2.0 is not working this way. The versions of this assembly are changing fast so I either want to bind any or all versions beginning with 6.2 to my application without changing the app.config each time.

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  • asp.net mvc select change redirect to Action

    - by mazhar kaunain baig
    I am correctly passing the action name from the Controller to the paging class and then using select list i want to redirect to that action. at this moment it is appending to the current url.i want the correct way of redirecting to the controller action manageUser using select list below What should we have here in Model.COntroller . ControllerName/ActionName/ or Just ActionName <select id="paging" onchange="location.href='<%= Model.Controller %>'+this.value"> <% for (int i = 1; i <= Model.TotalPages; i++) { %> <option id=<%=i %>><%=i %></option> <% } %> </select> public class PaginatedList<T> : List<T> { public string Controller { get; private set; } public PaginatedList(IQueryable<T> source, int pageIndex, int pageSize,string Cont) { Controller = Cont; // here is the controller } } Controller public ActionResult ManageUser(int? page) { const int pageSize = 5; var AllUser = UserRepository.GetAllUser(); var paginatedUsers = new PaginatedList<Users>(AllUser, page ?? 1, pageSize,"ManageUser/Page/"); return View(paginatedUsers); }

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  • jQuery - select onchange to slide in / slide out div or form

    - by slayaz
    Hi, I am trying to enhance a form, by showing only relevant fields depending on initial selection via a form select field. It is an order form for 3 products and all 3 products have unique properties. My idea was to hide all the content in divs, then reveal the relevant div when the product is selected. I have found some solutions that show / hide a div, but none with any animation. It doesn't have to be a slide but just something nice! The alternative is instead of revealing a div, would be to load a seperate form, but this seems unnecessary. I am not sure whether i need a plug in, as I am pretty new to jquery. What i have in the html is: <style type="text/css"> .hide { display:none; } <select> <option value="" >Please select product below</option> <option value="pro1">Product 1</option> <option value="pro2">Product 2</option> </select> <div id="pro1" class="hide" >Product 1</div> <div id="pro2" class="hide" >Product 2</div> Many thanks in advance

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