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• Architecture of finding movable geotagged objects

  - by itsme

  I currently have a Postgres DB filled with approx. 300.000 data-sets of moving vehicles all over the world. My very frequently repeated query is: Give me all vehicles in a 5/10/20mile radius. Currently I spend around 600 to 1200 ms in the DB to prepare the set of located vehicle-objects. I am looking to vastly improve this time by ideally one or two orders of magnitude if possible. I am working in a Ruby on Rails 3.0beta environment if this is relevant. Any ideas how to architect the whole system to accelerate this query? Any NoSQL database able to deliver this kind of geolocation performance? I know of MongoDB working on an extension to facilitate this scenario but haven't tried it yet. Any intelligent use of Redis to achieve this? One problem with SQL-DBs here seems to be that I can't possibly use indexes because my vehicles are mostly moving around, meaning I had to constantly created DB indexes which, by itself, is probably more expensive than just doing the searching without index. Looking forward to your thoughs, Thanks!

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• Return the Column Name for row with last non-null value "Ms Access 2007"

  - by bri1969

  I have a Table, which contains a list of league players. Each season, we record their Points per Dart. Their total PPD for that season is stored in other tables and extracted through other queries, which in turn are imported to the master table "Player History" at the end of the season for use as historical data. The current query retrieves each players PPD for each season they played, when they played last, and how many seasons played. The code for Last season Played has become too long and unstable to use. it was originally created, and split into two separate columns because a single SQL was to long. (LSP1) and LSP2) which work, but as I add seasons, Access does not like the length of code. In short, i need to find a more simple code that will look at each row, and look in that row for the last non null cell and report which column that last non null value is in. So if a player played seasons 30 & 31, but did not play 32..but did play 33, the Column with the code should be titled Last Season Played, and for that Player, it would state "33" in that cell, indicating that this player last played season "33" I will provide both tables and the query.. Please help

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• Create an index only on certain rows in mysql

  - by dhruvbird

  So, I have this funny requirement of creating an index on a table only on a certain set of rows. This is what my table looks like: USER: userid, friendid, created, blah0, blah1, ..., blahN Now, I'd like to create an index on: (userid, friendid, created) but only on those rows where userid = friendid. The reason being that this index is only going to be used to satisfy queries where the WHERE clause contains "userid = friendid". There will be many rows where this is NOT the case, and I really don't want to waste all that extra space on the index. Another option would be to create a table (query table) which is populated on insert/update of this table and create a trigger to do so, but again I am guessing an index on that table would mean that the data would be stored twice. How does mysql store Primary Keys? I mean is the table ordered on the Primary Key or is it ordered by insert order and the PK is like a normal unique index? I checked up on clustered indexes (http://dev.mysql.com/doc/refman/5.0/en/innodb-index-types.html), but it seems only InnoDB supports them. I am using MyISAM (I mention this because then I could have created a clustered index on these 3 fields in the query table). I am basically looking for something like this: ALTER TABLE USERS ADD INDEX (userid, friendid, created) WHERE userid=friendid

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• Translate an IQueryable instance to LINQ syntax in a string

  - by James Dunne

  I would like to find out if anyone has existing work surrounding formatting an IQueryable instance back into a LINQ C# syntax inside a string. It'd be a nice-to-have feature for an internal LINQ-to-SQL auditing framework I'm building. Once my framework gets the IQueryable instance from a data repository method, I'd like to output something like: This LINQ query: from ce in db.EiClassEnrollment join c in db.EiCourse on ce.CourseID equals c.CourseID join cl in db.EiClass on ce.ClassID equals cl.ClassID join t in db.EiTerm on ce.TermID equals t.TermID join st in db.EiStaff on cl.Instructor equals st.StaffID where (ce.StudentID == studentID) && (ce.TermID == termID) && (cl.Campus == campusID) select new { ce, cl, t, c, st }; Generates the following LINQ-to-SQL query: DECLARE @p0 int; DECLARE @p1 int; DECLARE @p2 int; SET @p0 = 777; SET @p1 = 778; SET @p2 = 779; SELECT [t0].[ClassEnrollmentID], ..., [t4].[Name] FROM [dbo].[ei_ClassEnrollment] AS [t0] INNER JOIN [dbo].[ei_Course] AS [t1] ON [t0].[CourseID] = [t1].[CourseID] INNER JOIN [dbo].[ei_Class] AS [t2] ON [t0].[ClassID] = [t2].[ClassID] INNER JOIN [dbo].[ei_Term] AS [t3] ON [t0].[TermID] = [t3].[TermID] INNER JOIN [dbo].[ei_Staff] AS [t4] ON [t2].[Instructor] = [t4].[StaffID] WHERE ([t0].[StudentID] = @p0) AND ([t0].[TermID] = @p1) AND ([t2].[Campus] = @p2) I already have the SQL output working as you can see. I just need to find a way to get the IQueryable to translate into a string representing its original LINQ syntax (with an acceptable translation loss). I'm not afraid of writing it myself, but I'd like to see if anyone else has done this first.

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• sqlobject: No connection has been defined for this thread or process

  - by Claudiu

  I'm using sqlobject in Python. I connect to the database with conn = connectionForURI(connStr) conn.makeConnection() This succeeds, and I can do queries on the connection: g_conn = conn.getConnection() cur = g_conn.cursor() cur.execute(query) res = cur.fetchall() This works as intended. However, I also defined some classes, e.g: class User(SQLObject): class sqlmeta: table = "gui_user" username = StringCol(length=16, alternateID=True) password = StringCol(length=16) balance = FloatCol(default=0) When I try to do a query using the class: User.selectBy(username="foo") I get an exception: ... File "c:\python25\lib\site-packages\SQLObject-0.12.4-py2.5.egg\sqlobject\main.py", line 1371, in selectBy conn = connection or cls._connection File "c:\python25\lib\site-packages\SQLObject-0.12.4-py2.5.egg\sqlobject\dbconnection.py", line 837, in __get__ return self.getConnection() File "c:\python25\lib\site-packages\SQLObject-0.12.4-py2.5.egg\sqlobject\dbconnection.py", line 850, in getConnection "No connection has been defined for this thread " AttributeError: No connection has been defined for this thread or process How do I define a connection for a thread? I just realized I can pass in a connection keyword which I can give conn to to make it work, but how do I get it to work if I weren't to do that?

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• Need help with jquery json data transfer from php file

  - by Scarface

  Hey guys I am trying to return the latest 10 results of a query from a php file, through json format, to a jquery getjson function that prints results. I am getting weird problems though. For example I am only getting 8 entries returned, and some are disordered, and sometimes nothing is returned. I am not really sure what I am doing wrong, so if anyone has any ideas I would really appreciate it. This is my query ($res) SELECT time, user, message FROM comments WHERE topic_id='$topic_id' ORDER BY time DESC LIMIT 10 This is the processing of the results while($row = mysql_fetch_array($res)){ $message=$row['message']; $user=$row['user']; if($row['message'] AND $row['time'] > $_GET['time']) $data[] = $row; } $out = json_encode($data); print $out; And this is the retrieval where prepare is just a function that returns information into a div $.getJSON(files+"processing.php?action=load&time="+0+"&topic_id="+topic_id+"&t=" + (new Date()), function(json) { if(json.length) { for(i=0; i < 10; i++) { $('#comment-list').prepend(prepare(json[i])); $('#list-' + count).fadeIn(1500); } } }); function prepare(response) { count++; var string = '<li class="comment-list" id="list-'+count+'">' //organize info into a div +'</li>'; return string; }

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• How can I integrate advanced computations into a database field?

  - by ciclistadan

  My biological research involves the measurement of a cellular structure as it changes length throughout the course of observation (capturing images every minute for several hours). As my data sets have become larger I am trying to store them in an Access database, from which I would like to perform various queries about their changes in size. I know that the SELECT statement can incorporate some mathematical permutations, but I have been unable to incorporate many of my necessary calculations (probably due to my lack of knowledge). For example, one calculation involves determining the rate of change during specifically defined periods of growth. This calculation is entirely dependent on the raw data saved in the table, therefore I didn't this it would be appropriate to just calculate it in excel prior to entry into the field. So my question is, what would be the most appropriate method of performing this calculation. Should I attempt to string together a huge SELECT calculation in my QUERY, or is there a way to use another language (I know perl?) which can be called to populate the new query field? I'm not looking for someone to write the code, just where is it appropriate to incorporate each step. Also, I am currently using Office Access but would be interested in any mySQL answers as I may be moving to this platform at a later date. Thanks all!

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• Win32_Product InstallLocation (error)

  - by andrew

  in C#, i'm trying to get some properties from the instances of Win32_Product, but i seem to have an error saying "Object reference not set to an instance of an object." here's the code: class Package { public string productName; public string installDate; public string installLocation; } class InstalledPackages { public static List<Package> get() { List<Package> packages = new List<Package>(); string query = "SELECT * FROM Win32_Product"; ManagementScope oMs = new ManagementScope(); ObjectQuery oQuery = new ObjectQuery(query); ManagementObjectSearcher oSearcher = new ManagementObjectSearcher(oMs, oQuery); ManagementObjectCollection installedPackages = oSearcher.Get(); foreach (ManagementObject package in installedPackages) { Package p = new Package(); p.productName = package["Name"].ToString(); p.installLocation = package["InstallLocation"].ToString(); p.installDate = package["InstallDate"].ToString(); packages.Add(p); } return packages; } } the exception appears when it gets to p.installLocation = package["InstallLocation"].ToString(); also, i get one if i try to do p.installLocation = package["InstallDate2"].ToString(); if i'm asking for InstallDate it works. (i'm using Windows 7 Ultimate x64)

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• Java - multithreaded access to a local value store which is periodically cleared

  - by Telax

  I'm hoping for some advice or suggestions on how best to handle multi threaded access to a value store. My local value storage is designed to hold onto objects which are currently in use. If the object is not in use then it is removed from the store. A value is pumped into my store via thread1, its entry into the store is announced to listeners, and the value is stored. Values coming in on thread1 will either be totally new values or updates for existing values. A timer is used to periodically remove any value from the store which is not currently in use and so all that remains of this value is its ID held locally by an intermediary. Now, an active element on thread2 may wake up and try to access a set of values by passing a set of value IDs which it knows about. Some values will be stored already (great) and some may not (sadface). Those values which are not already stored will be retrieved from an external source. My main issue is that items which have not already been stored and are currently being queried for may arrive in on thread1 before the query is complete. I'd like to try and avoid locking access to the store whilst a query is being made as it may take some time.

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• What constitutes explicit creation of entities in LINQ to SQL? What elegant "solutions" are there to

  - by Marcelo Zabani

  Hi SO, I've been having problems with the rather famous "Explicit construction of entity type '##' in query is not allowed." error. Now, for what I understand, this exists because if explicit construction of these objects were allowed, tracking changes to the database would be very complicated. So I ask: What constitutes the explicit creation of these objects? In other terms: Why can I do this: Product foo = new Product(); foo.productName = "Something"; But can't do this: var bar = (from item in myDataContext.Products select new Product { productName = item.productName }).ToList(); I think that when running the LINQ query, some kind of association is made between the objects selected and the table rows retrieved (and this is why newing a Product in the first snippet of code is no problem at all, because no associations were made). I, however, would like to understand this a little more in depth (and this is my first question to you, that is: what is the difference from one snippet of code to another). Now, I've heard of a few ways to attack this problem: 1) The creation of a class that inherits the linq class (or one that has the same properties) 2) Selecting anonymous objects And this leads me to my second question: If you chose one of the the two approaches above, which one did you choose and why? What other problems did your approach introduce? Are there any other approaches?

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• MySQL Multiple Table Join

  - by hitman001

  I have a 3 tables that I'm trying to join and get distinct results. CREATE TABLE `car` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL DEFAULT '', PRIMARY KEY (`id`) ) ENGINE=InnoDB mysql> select * from car; +----+-------+ | id | name | +----+-------+ | 1 | acura | +----+-------+ CREATE TABLE `tires` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `tire_desc` varchar(255) DEFAULT NULL, `car_id` int(10) unsigned NOT NULL, PRIMARY KEY (`id`), KEY `new_fk_constraint` (`car_id`), CONSTRAINT `new_fk_constraint` FOREIGN KEY (`car_id`) REFERENCES `car` (`id`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB mysql> select * from tires; +----+-------------+--------+ | id | tire_desc | car_id | +----+-------------+--------+ | 1 | front_right | 1 | | 2 | front_left | 1 | +----+-------------+--------+ CREATE TABLE `lights` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `lights_desc` varchar(255) NOT NULL, `car_id` int(10) unsigned NOT NULL, PRIMARY KEY (`id`), KEY `new1_fk_constraint` (`car_id`), CONSTRAINT `new1_fk_constraint` FOREIGN KEY (`car_id`) REFERENCES `car` (`id`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB mysql> select * from lights; +----+-------------+--------+ | id | lights_desc | car_id | +----+-------------+--------+ | 1 | right_light | 1 | | 2 | left_light | 1 | +----+-------------+--------+ Here is my query. mysql> SELECT name, group_concat(tire_desc), group_concat(lights_desc) FROM car left join tires on car.id = tires.car_id left join lights on car.id = car_id group by car.id; +-------+-----------------------------------------------+-----------------------------------------------+ | name | group_concat(tire_desc) | group_concat(lights_desc) | +-------+-----------------------------------------------+-----------------------------------------------+ | acura | front_right,front_right,front_left,front_left | right_light,left_light,right_light,left_light | +-------+-----------------------------------------------+-----------------------------------------------+ I get duplicate entires and this is what I would like to get. +-------+-----------------------------------------------+--------------------------------+ | name | group_concat(tire_desc) | group_concat(lights_desc) | +-------+-----------------------------------------------+--------------------------------+ | acura | front_right,front_left | right_light,left_light | +-------+-----------------------------------------------+--------------------------------+ I cannot use distinct in group_concat because I might have legitimate duplicates which I would like to keep. Is there any way to do this query using joins and not using inner selects like the statement below? SELECT name, (select group_concat(tire_desc) from tires where car.id = tires.car_id), (select group_concat(lights_desc) from lights where car.id = lights.car_id) FROM car Also, if I will use inner selects, will there be any performance issues over joins?

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• Automatically Persisting a Complex Java Object

  - by VeeArr

  For a project I am working on, I need to persist a number of POJOs to a database. The POJOs class definitions are sometimes highly nested, but they should flatten okay, as the nesting is tree-like and contains no cycles (and the base elements are eventually primitives/Strings). It is preferred that the solution used create one table per data type and that the tables will have one field per primitive member in the POJO. Subclassing and similar problems are not issues for this particular project. Does anybody know of any existing solutions that can: Automatically generate a CREATE TABLE definition from the class definition Automatically generate a query to persist an object to the database, given an instance of the object Automatically generate a query to retrieve an object from the database and return it as a POJO, given a key. Solutions that can do this with minimum modifications/annotions to the class files and minimum external configuration are preferred. Example: Java classes //Class to be persisted class TypeA { String guid; long timestamp; TypeB data1; TypeC data2; } class TypeB { int id; int someData; } class TypeC { int id; int otherData; } Could map to CREATE TABLE TypeA ( guid CHAR(255), timestamp BIGINT, data1_id INT, data1_someData INT, data2_id INt, data2_otherData INT ); Or something similar.

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• Programming Practice

  - by deepti

  public DataTable UserUpdateTempSettings(int install_id, int install_map_id, string Setting_value,string LogFile) { SqlConnection oConnection = new SqlConnection(sConnectionString); DataSet oDataset = new DataSet(); DataTable oDatatable = new DataTable(); SqlDataAdapter MyDataAdapter = new SqlDataAdapter(); try { oConnection.Open(); cmd = new SqlCommand("SP_HOTDOC_PRINTTEMPLATE_PERMISSION", oConnection); cmd.Parameters.Add(new SqlParameter ("@INSTALL_ID", install_id)); cmd.Parameters.Add(new SqlParameter ("@INSTALL_MAP_ID", install_map_id)); cmd.Parameters.Add(new SqlParameter("@SETTING_VALUE", Setting_value)); if (LogFile != "") { cmd.Parameters.Add(new SqlParameter("@LOGFILE",LogFile)); } cmd.CommandType = CommandType.StoredProcedure; MyDataAdapter.SelectCommand = cmd; cmd.ExecuteNonQuery(); MyDataAdapter.Fill(oDataset); oDatatable = oDataset.Tables[0]; return oDatatable; } catch (Exception ex) { Utils.ShowError(ex.Message); return oDatatable; } finally { if ((oConnection.State != ConnectionState.Closed) || (oConnection.State != ConnectionState.Broken)) { oConnection.Close(); } oDataset = null; oDatatable = null; oConnection.Dispose(); oConnection = null; } } i have used execute non query.. normally its not used with data adapter... if iam not using its giving me error.. is it bad programming practice to use execute non query with data adapter

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• Grouping by property value and writing group members

  - by Will S

  I need to group the following list by the department value but am having trouble with the LINQ syntax. Here's my list of objects: var people = new List<Person> { new Person { name = "John", department = new List<fields> {new fields { name = "department", value = "IT"}}}, new Person { name = "Sally", department = new List<fields> {new fields { name = "department", value = "IT"}}}, new Person { name = "Bob", department = new List<fields> {new fields { name = "department", value = "Finance"}}}, new Person { name = "Wanda", department = new List<fields> {new fields { name = "department", value = "Finance"}}}, }; I've toyed around with grouping. This is as far as I've got: var query = from p in people from field in p.department where field.name == "department" group p by field.value into departments select new { Department = departments.Key, Name = departments }; So can iterate over the groups, but not sure how to list the Person names - foreach (var department in query) { Console.WriteLine("Department: {0}", department.Department); foreach (var foo in department.Department) { // ?? } } Any ideas on what to do better or how to list the names of the relevant departments?

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• Optional mix of filter parameters in a search the Rails way.

  - by GSP

  I've got a simple list page with a couple of search filters status which is a simple enumeration and a test query which I want to compare against both the title and description field of my model. In my controller, I want to do something like this: def index conditions = {} conditions[:status] = params[:status] if params[:status] and !params[:status].empty? conditions[???] = ["(descr = ? or title = ?)", params[:q], params[:q]] if params[:q] and !params[:q].empty? @items = Item.find(:all, :conditions => conditions) end Unfortunately, it doesn't look like I can mix the two types of conditions (the hash and the paramatized version). Is there a "Rails Way" of doing this or do I simply have to do something awful like this: has_status = params[:status] and !params[:status].empty? has_text = params[:q] and !params[:q].empty? if has_status and !has_text # build paramatized condition with just the status elsif has_text and !has_status # build paramatized condition with just the text query elsif has_text and has_status # build paramatized condition with both else # build paramatized condition with neither end I'm migrating from Hibernate and Criteria so forgive me if I'm not thinking of this correctly... Environment: Rails 2.3.4

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• NHibernate: Using value tables for optimization AND dynamic join

  - by Kostya

  Hi all, My situation is next: there are to entities with many-to-many relation, f.e. Products and Categories. Also, categories has hierachial structure, like a tree. There is need to select all products that depends to some concrete category with all its childs (branch). So, I use following sql statement to do that: SELECT * FROM Products p WHERE p.ID IN ( SELECT DISTINCT pc.ProductID FROM ProductsCategories pc INNER JOIN Categories c ON c.ID = pc.CategoryID WHERE c.TLeft >= 1 AND c.TRight <= 33378 ) But with big set of data this query executes very long and I found some solution to optimize it, look at here: DECLARE @CatProducts TABLE ( ProductID int NOT NULL ) INSERT INTO @CatProducts SELECT DISTINCT pc.ProductID FROM ProductsCategories pc INNER JOIN Categories c ON c.ID = pc.CategoryID WHERE c.TLeft >= 1 AND c.TRight <= 33378 SELECT * FROM Products p INNER JOIN @CatProducts cp ON cp.ProductID = p.ID This query executes very fast but I don't know how to do that with NHIbernate. Note, that I need use only ICriteria because of dynamic filtering\ordering. If some one knows a solution for that, it will be fantastic. But I'll pleasure to any suggestions of course. Thank you ahead, Kostya

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• Please help!! C# Anonymous and returning filtered properties with JSON

  - by Raj Aththanayake

  What is the best way to return only few properties to JSON Result from a collection IEnumerable? Department object has 7properties I only need to 2 of them in client. Can I do this using C# anonymous types? public class Department { public string DeptId { get; set; } public string DeptName { get; set; } public string DeptLoc1 { get; set; } public string DeptLoc2 { get; set; } public string DeptMgr { get; set; } public string DeptEmp { get; set; } public string DeptEmp2 { get; set; } } [HttpGet] public JsonResult DepartmentSearch(string query) { IEnumerable<Department> depts = DeptSearchService.GetDepartments(query); //Department object has 15 properties, I ONLY need 2 (DeptID and DeptName) in the view via returns JSON result) return Json(depts, JsonRequestBehavior.AllowGet); // I don’t want all the properties of a department object }

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• How to first get different related values from diferent SQL tables (PHP)

  - by Ole Jak

  I am triig to fill options list. I have 2 tables USERS and STREAMS I vant to get all streams and get names of users assigned to that streams. Users consists of username and id Streams consists of id, userID, streamID I try such code: <?php global $connection; $query = "SELECT * FROM streams "; $streams_set = mysql_query($query, $connection); confirm_query($streams_set); $streams_count = mysql_num_rows($streams_set); while ($row = mysql_fetch_array($streams_set)){ $userid = $row['userID']; global $connection; $query2 = "SELECT email, username "; $query2 .= "FROM users "; $query2 .= "WHERE id = '{$userid}' "; $qs = mysql_query($query2, $connection); confirm_query($qs); $found_user = mysql_fetch_array($qs); echo ' <option value="'.$row['streamID'].'">'.$row['userID'].$found_user.'</option> '; } ?> But it does not return USER names from DB=( So what shall I do to this code to see usernames as "options" text?

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• login script in php using session variables

  - by kracekumar

  ? username: '; } else { $user=$_POST['user']; $query="select name from login where name='$user'"; $result=mysql_query($query) or die(mysql_error()); $rows=mysql_num_rows($result)or die(mysql_error()); session_start(); //echo "results"; $username=mysql_fetch_array($result) or die(mysql_error()); $fields=mysql_num_fields($result) or die(mysql_error()); echo "username:$username[0]"; $_SESSION['username']=$username[0]; $sesion_username=$_SESSION['username']; //echo "rows:$rows"." "."fields:$fields"; echo""."username:$sesion_username"; } ? i wanted to create a site where user can login and upload their details depending on their user name have stored their details in a database,the problem i am facing is two people 'a' and 'b' login one after other session_variable $_SESSION['username'] will have 'b's' username ,so i can't display 'a's' details now. . . . what i want to achieve is when a user logins in i want to store his name and other details in session variable and navigate him according and display his details

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• MySql: Is it reasonable to use 'view' or I would better denormalize my DB?

  - by Budda

  There is 'team_sector' table with following fields: Id, team_id, sect_id, size, level It contains few records for each 'team' entity (referenced with 'team_id' field). Each record represent sector of team's stadium (totally 8 sectors). Now it is necessary to implement few searches: by overall stadium size (SUM(size)); the best quality (SUM(level)/COUNT(*)). I could create query something like this: SELECT TS.team_id, SUM(TS.size) as OverallSize, SUM(TS.Level)/COUNT(TS.Id) AS QualityLevel FROM team_sector GROUP BY team_id ORDER BY OverallSize DESC / ORDER BY QualityLevel DESC But my concern here is that calculation for each team will be done each time on query performed. It is not too big overhead (at least now), but I would like to avoid performance issues later. I see 2 options here. The 1st one is to create 2 additional fields in 'team' table (for example) and store there OverallSize and QualityLevel fields. If information if 'sector' table is changed - update those table too (probably would be good to do that with triggers, as sector table doesn't change too often). The 2nd option is to create a view that will provide required data. The 2nd option seems much easier for me, but I don't have a lot of experience/knowledge of work with views. Q1: What is the best option from your perspective here and why? Probably you could suggest other options? Q2: Can I create view in such way that it will do calculations rarely (at least once per day)? If yes - how? Q3: Is it reasonable to use triggers for such purpose (1st option). P.S. MySql 5.1 is used, overall number of teams is around 1-2 thousand, overall number of records in sector table - overall 6-8 thousand. I understand, those numbers are pretty small, but I would like to implement the best practice here.

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• Very weird jquery/json problem...

  - by Scarface

  Hey guys I have finally located the cause of this problem...I just have no idea how to fix it and why it is happening. I have a jquery getjson function and it returns 0 results every 2-5 clicks on new topics or refreshes. For some reason if I change my query to sort results by ASC it always returns results and much quicker, but this poses a problem since I need results by DESC. If anyone has any ideas, I would greatly appreciate it because I am dumbfounded at this point. Here is my query but I need it by DESC SELECT time, user, message FROM comments WHERE topic_id='$topic_id' ORDER BY time ASC LIMIT 10 $.getJSON(files+"comments.php?action=view&load=initial&topic_id="+topic_id+"&t=" + (new Date()), function(json) { if(json.length) { for(i=0; i < json.length; i++) { $('#comment-list').prepend(prepare(json[i])); $('#list-' + count).fadeIn(1500); } } }); I return results like so while($row = mysql_fetch_array($res)){ $data[] = $row; } $out = json_encode($data); print $out;

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• Hive performance increase

  - by Sagar Nikam

  I am dealing with a database (2.5 GB) having some tables only 40 row to some having 9 million rows data. when I am doing any query for large table it takes more time. I want results in less time small query on table which have 90 rows only-- hive> select count(*) from cidade; Time taken: 50.172 seconds hdfs-site.xml <configuration> <property> <name>dfs.replication</name> <value>3</value> <description>Default block replication. The actual number of replications can be specified when the file is created. The default is used if replication is not specified in create time. </description> </property> <property> <name>dfs.block.size</name> <value>131072</value> <description>Default block replication. The actual number of replications can be specified when the file is created. The default is used if replication is not specified in create time. </description> </property> </configuration> does these setting affects performance of hive? dfs.replication=3 dfs.block.size=131072 can i set it from hive prompt as hive>set dfs.replication=5 Is this value remains for a perticular session only ? or Is it better to change it in .xml file ?

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• Questions about shifting from mysql to PDO

  - by Scarface

  Hey guys I have recently decided to switch all my current plain mysql queries performed with php mysql_query to PDO style queries to improve performance, portability and security. I just have some quick questions for any experts in this database interaction tool Will it prevent injection if all statements are prepared? (I noticed on php.net it wrote 'however, if other portions of the query are being built up with unescaped input, SQL injection is still possible' I was not exactly sure what this meant). Does this just mean that if all variables are run through a prepare function it is safe, and if some are directly inserted then it is not? Currently I have a connection at the top of my page and queries performed during the rest of the page. I took a look at PDO in more detail and noticed that there is a try and catch procedure for every query involving a connection and the closing of that connection. Is there a straightforward way to connecting and then reusing that connection without having to put everything in a try or constantly repeat the procedure by connecting, querying and closing? Can anyone briefly explain in layman's terms what purpose a set_exception_handler serves? I appreciate any advice from any more experienced individuals.

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• Can't seem to get my like/dislike to work in PHP

  - by user300371

  My table is comment_likedislike. It has the comment_counterid, comment_counter, comment_id(which is from another table) fields. And I have an url (LIKE) that when clicked would link to this code and get the comment_id and like_id. I want to do a count where if it is the first 'like', it would store a new comment_counter in the comment_likedislike table. But if there is already a 'like' for the comment in the table, it would just update the comment_counter to +1. Problem: When I run this code, it doesn't UPDATE(1st statement) but INSERT(2nd if statement) no matter if there is a like for the comment or not. I don't think the code is checking if the comment_id is in the table already. I am a novice php programmer. Thanks! if (isset($_GET['comment_id']) && isset($_GET['like_id'])) { $query5="SELECT * FROM comment_likedislike "; $data5=mysqli_query ($dbc, $query5); while ($row5= mysqli_fetch_array($data5)){ $comment_id2=$row5['comment_id']; } if ($comment_id2 == $_GET['comment_id']){ $counter=$row5['comment_counter']; $counter++; $query= "UPDATE comment_likedislike SET comment_counter ='$counter' WHERE comment_id= '".$_GET['comment_id']."' "; mysqli_query($dbc, $query); } if ($comment_id2 != $_GET['comment_id']) { $counter2=1; $query9 = "INSERT INTO comment_likedislike (comment_counter, comment_id) VALUES ('$counter2', '".$_GET['comment_id']."' )"; mysqli_query($dbc, $query9); } }

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• Why does this sql statement keep saying it is a boolean and not a parameter? (php/Mysql)

  - by ggfan

  In this statement, I am trying to see if there if the latest posting in the database that has the exact same title, price, city, state, detail. If there is, then it would say to the user that the exact post has been already made; if not then insert the posting into the dbc. (This is one type of check so that users can't accidentally post twice. This may not be the best check, but this statement error is annoying me, so I want it to work :)) Why won't this sql work? I think it's not letting the title=$title and not getting the value in the $title... ERROR: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in postad.php on line 365 //there is a form that users fill out that has title, price, city, etc <form> blah blah </form> //if users click submit, then does all the checks and if all okay, insert to dbc if (isset($_POST['submit'])) { // Grab the pposting data from the POST and gets rid of any funny stuff $title = mysqli_real_escape_string($dbc, trim($_POST['title'])); $price = mysqli_real_escape_string($dbc, trim($_POST['price'])); $city = mysqli_real_escape_string($dbc, trim($_POST['city'])); $state = mysqli_real_escape_string($dbc, trim($_POST['state'])); $detail = mysqli_real_escape_string($dbc, trim($_POST['detail'])); if (!is_numeric($price) && !empty($price)) { echo "<p class='error'>The price can only be numbers. No special characters, etc</p>"; } //Error problem...won't let me set title=$title, detail=$detail, etc. //this statement after all the checks so that none of the variables are empty $query="Select * FROM posting WHERE user_id={$_SESSION['user_id']} AND title=$title AND price=$price AND city=$city AND state=$state AND detail=$detail"; $data = mysqli_query($dbc, $query); if(mysqli_num_rows($data)==1) { echo "You already posted this ad. Most likely caused by refreshing too many times."; } }

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