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  • Range partition skip check

    - by user289429
    We have large amount of data partitioned on year value using range partition in oracle. We have used range partition but each partition contains data only for one year. When we write a query targeting a specific year, oracle fetches the information from that partition but still checks if the year is what we have specified. Since this year column is not part of the index it fetches the year from table and compares it. We have seen that any time the query goes to fetch table data it is getting too slow. Can we somehow avoid oracle comparing the year values since we for sure know that the partition contains information for only one year.

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  • Is it OK to re-create many SQL connections (SQL 2008)

    - by Mr. Flibble
    When performing many inserts into a database I would usually have code like this: using (var connection = new SqlConnection(connStr)) { connection.Open(); foreach (var item in items) { var cmd = new SqlCommand("INSERT ...") cmd.ExecuteNonQuery(); } } I now want to shard the database and therefore need to choose the connection string based on the item being inserted. This would make my code run more like this foreach (var item in items) { connStr = GetConnectionString(item); using (var connection = new SqlConnection(connStr)) { connection.Open(); var cmd = new SqlCommand("INSERT ...") cmd.ExecuteNonQuery(); } } Which basically means it's creating a new connection to the database for each item. Will this work or will recreating connections for each insert cause terrible overhead?

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  • Does my TPL partitioner cause a deadlock?

    - by Scott Chamberlain
    I am starting to write my first parallel applications. This partitioner will enumerate over a IDataReader pulling chunkSize records at a time from the data-source. protected class DataSourcePartitioner<object[]> : System.Collections.Concurrent.Partitioner<object[]> { private readonly System.Data.IDataReader _Input; private readonly int _ChunkSize; public DataSourcePartitioner(System.Data.IDataReader input, int chunkSize = 10000) : base() { if (chunkSize < 1) throw new ArgumentOutOfRangeException("chunkSize"); _Input = input; _ChunkSize = chunkSize; } public override bool SupportsDynamicPartitions { get { return true; } } public override IList<IEnumerator<object[]>> GetPartitions(int partitionCount) { var dynamicPartitions = GetDynamicPartitions(); var partitions = new IEnumerator<object[]>[partitionCount]; for (int i = 0; i < partitionCount; i++) { partitions[i] = dynamicPartitions.GetEnumerator(); } return partitions; } public override IEnumerable<object[]> GetDynamicPartitions() { return new ListDynamicPartitions(_Input, _ChunkSize); } private class ListDynamicPartitions : IEnumerable<object[]> { private System.Data.IDataReader _Input; int _ChunkSize; private object _ChunkLock = new object(); public ListDynamicPartitions(System.Data.IDataReader input, int chunkSize) { _Input = input; _ChunkSize = chunkSize; } public IEnumerator<object[]> GetEnumerator() { while (true) { List<object[]> chunk = new List<object[]>(_ChunkSize); lock(_Input) { for (int i = 0; i < _ChunkSize; ++i) { if (!_Input.Read()) break; var values = new object[_Input.FieldCount]; _Input.GetValues(values); chunk.Add(values); } if (chunk.Count == 0) yield break; } var chunkEnumerator = chunk.GetEnumerator(); lock(_ChunkLock) //Will this cause a deadlock? { while (chunkEnumerator.MoveNext()) { yield return chunkEnumerator.Current; } } } } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable<object[]>)this).GetEnumerator(); } } } I wanted IEnumerable object it passed back to be thread safe (the .Net example was so I am assuming PLINQ and TPL could need it) will the lock on _ChunkLock near the bottom help provide thread safety or will it cause a deadlock? From the documentation I could not tell if the lock would be released on the yeld return. Also if there is built in functionality to .net that will do what I am trying to do I would much rather use that. And if you find any other problems with the code I would appreciate it.

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  • Does my GetEnumerator cause a deadlock?

    - by Scott Chamberlain
    I am starting to write my first parallel applications. This partitioner will enumerate over a IDataReader pulling chunkSize records at a time from the data-source. TLDR; version private object _Lock = new object(); public IEnumerator GetEnumerator() { var infoSource = myInforSource.GetEnumerator(); //Will this cause a deadlock if two threads lock (_Lock) //use the enumator at the same time? { while (infoSource.MoveNext()) { yield return infoSource.Current; } } } full code protected class DataSourcePartitioner<object[]> : System.Collections.Concurrent.Partitioner<object[]> { private readonly System.Data.IDataReader _Input; private readonly int _ChunkSize; public DataSourcePartitioner(System.Data.IDataReader input, int chunkSize = 10000) : base() { if (chunkSize < 1) throw new ArgumentOutOfRangeException("chunkSize"); _Input = input; _ChunkSize = chunkSize; } public override bool SupportsDynamicPartitions { get { return true; } } public override IList<IEnumerator<object[]>> GetPartitions(int partitionCount) { var dynamicPartitions = GetDynamicPartitions(); var partitions = new IEnumerator<object[]>[partitionCount]; for (int i = 0; i < partitionCount; i++) { partitions[i] = dynamicPartitions.GetEnumerator(); } return partitions; } public override IEnumerable<object[]> GetDynamicPartitions() { return new ListDynamicPartitions(_Input, _ChunkSize); } private class ListDynamicPartitions : IEnumerable<object[]> { private System.Data.IDataReader _Input; int _ChunkSize; private object _ChunkLock = new object(); public ListDynamicPartitions(System.Data.IDataReader input, int chunkSize) { _Input = input; _ChunkSize = chunkSize; } public IEnumerator<object[]> GetEnumerator() { while (true) { List<object[]> chunk = new List<object[]>(_ChunkSize); lock(_Input) { for (int i = 0; i < _ChunkSize; ++i) { if (!_Input.Read()) break; var values = new object[_Input.FieldCount]; _Input.GetValues(values); chunk.Add(values); } if (chunk.Count == 0) yield break; } var chunkEnumerator = chunk.GetEnumerator(); lock(_ChunkLock) //Will this cause a deadlock? { while (chunkEnumerator.MoveNext()) { yield return chunkEnumerator.Current; } } } } IEnumerator IEnumerable.GetEnumerator() { return ((IEnumerable<object[]>)this).GetEnumerator(); } } } I wanted IEnumerable object it passed back to be thread safe (the MSDN example was so I am assuming PLINQ and TPL could need it) will the lock on _ChunkLock near the bottom help provide thread safety or will it cause a deadlock? From the documentation I could not tell if the lock would be released on the yeld return. Also if there is built in functionality to .net that will do what I am trying to do I would much rather use that. And if you find any other problems with the code I would appreciate it.

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  • How to make ActiveRecord work with legacy partitioned/sharded databases/tables?

    - by Utensil
    thanks for your time first...after all the searching on google, github and here, and got more confused about the big words(partition/shard/fedorate),I figure that I have to describe the specific problem I met and ask around. My company's databases deals with massive users and orders, so we split databases and tables in various ways, some are described below: way database and table name shard by (maybe it's should be called partitioned by?) YZ.X db_YZ.tb_X order serial number last three digits YYYYMMDD. db_YYYYMMDD.tb date YYYYMM.DD db_YYYYMM.tb_ DD date too The basic concept is that databases and tables are seperated acording to a field(not nessissarily the primary key), and there are too many databases and too many tables, so that writing or magically generate one database.yml config for each database and one model for each table isn't possible or at least not the best solution. I looked into drnic's magic solutions, and datafabric, and even the source code of active record, maybe I could use ERB to generate database.yml and do database connection in around filter, and maybe I could use named_scope to dynamically decide the table name for find, but update/create opertions are bounded to "self.class.quoted_table_name" so that I couldn't easily get my problem solved. And even I could generate one model for each table, because its amount is up to 30 most. But this is just not DRY! What I need is a clean solution like the following DSL: class Order < ActiveRecord::Base shard_by :order_serialno do |key| [get_db_config_by(key), #because some or all of the databaes might share the same machine in a regular way or can be configed by a hash of regex, and it can also be a const get_db_name_by(key), get_tb_name_by(key), ] end end Can anybody enlight me? Any help would be greatly appreciated~~~~

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  • Database(Partitions) related query.... Please suggest..........

    - by AGeek
    The Query is as follows:- We have an oracle schema, with tables partitioned. -- Need to make one of the partition offline. (How to achieve this,, or have thought of assigning each partition, a different tablespace, and then making that tablespace offline) any other way out possible so as to avoid making so many tablespaces???? -- Then, copy the data files/ logs related to that partition to the temporary storage..... how to achieve this thing... any docs related to the same.... -- Then We make this partition / related tablespace online... -- Then we create a second schema with the same tables as above..... -- Copy the partition data from temporary storage to this table. (How this can be achieved,,, any specific doc??? -- Then verifying to the data is accessible in all respects..... If possible, let's discuss to find out the solution........ Thanks....

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  • Is there a way to split the results of a select query into two equal halfs?

    - by Matthias
    I'd like to have a query returning two ResultSets each of which holding exactly half of all records matching a certain criteria. I tried using TOP 50 PERCENT in conjunction with an Order By but if the number of records in the table is odd, one record will show up in both resultsets. Example: I've got a simple table with TheID (PK) and TheValue fields (varchar(10)) and 5 records. Skip the where clause for now. SELECT TOP 50 PERCENT * FROM TheTable ORDER BY TheID asc results in the selected id's 1,2,3 SELECT TOP 50 PERCENT * FROM TheTable ORDER BY TheID desc results in the selected id's 3,4,5 3 is a dup. In real life of course the queries are fairly complicated with a ton of where clauses and subqueries.

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  • I tried installing Ubuntu 10.04 and I got this message - any ideas on what to do?

    - by vette982
    No root file system defined. Please correct this from the partition menu. This message shows up when I first boot into Ubuntu after the installation. I installed it by mounting the ISO with Daemon Tools, and I just did the default Wubi installation. I keep reading everywhere that I need to choose my installation directory, but I don't get any option to do that. These are all the options I get for installation directory. I have a C and D partition on my drive, and I tried installing it on both and no luck either way. Any ideas?

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  • Difference between std::result_of and decltype

    - by Luc Touraille
    I have some trouble understanding the need for std::result_of in C++0x. If I understood correctly, result_of is used to obtain the resulting type of invoking a function object with certain types of parameters. For example: template <typename F, typename Arg> typename std::result_of<F(Arg)> invoke(F f, Arg a) { return f(a); } I don't really see the difference with the following code: template <typename F, typename Arg> auto invoke(F f, Arg a) -> decltype(f(a)) //uses the f parameter { return f(a); } or template <typename F, typename Arg> auto invoke(F f, Arg a) -> decltype(F()(a)); //"constructs" an F { return f(a); } The only problem I can see with these two solutions is that we need to either: have an instance of the functor to use it in the expression passed to decltype. know a defined constructor for the functor. Am I right in thinking that the only difference between decltype and result_of is that the first one needs an expression whereas the second does not?

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  • What is the best way to partition large tables in SQL Server?

    - by RyanFetz
    In a recent project the "lead" developer designed a database schema where "larger" tables would be split across two seperate databases with a view on the main database which unioned the two seperate database-tables together. The main database is what the application was driven off of so these tables looked and felt like ordinary tables (except some quirkly things around updating). This seemed like a HUGE performance problem. We do see problems with performance around these tables but nothing to make him change his mind about his design. Just wondering what is the best way to do this, or if it is even worth doing?

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  • Validating result of JsonConvert.DeserializeObject (think "try parse") using JSON.Net

    - by Riri
    I have incoming messages that I need to try and parse in my own objects structure. SOme of these are well formed JSON obejcts and some are just nonsense. I use JsonConvert.DeserializeObject<MyObject>(incmoingString); to do this. This however sometimes gives me a exception when the incoming is total garbage. Other times I get a non-complete object structure when the incoming string is kind of OK - and finally it sometimes work. I've wrapped the conversion in a try/catch and than manually validate that I've gotten the properties I need to the deserialized result. Is there a better way to do this?

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  • Using LINQ to fetch result from nested SQL queries

    - by Shantanu Gupta
    This is my first question and first day in Linq so bit difficult day for me to understand. I want to fetch some records from database i.e. select * from tblDepartment where department_id in ( select department_id from tblMap where Guest_Id = @GuestId ) I have taken two DataTable. i.e. tblDepartment, tblMap Now I want to fetch this result and want to store it in third DataTable. How can I do this. I have been able to construct this query up till now after googling. var query = from myrow in _dtDepartment.AsEnumerable() where myrow.Field<int>("Department_Id") == _departmentId select myrow; Please provide me some link for learning Linq mainly for DataTables and DataSets. EDIT: I have got a very similar example here but i m still not able to understand how it is working. Please put some torch on it.

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  • Filtering MySQL query result according to a interval of timestamp

    - by celalo
    Let's say I have a very large MySQL table with a timestamp field. So I want to filter out some of the results not to have too many rows because I am going to print them. Let's say the timestamps are increasing as the number of rows increase and they are like every one minute on average. (Does not necessarily to be exactly once every minute, ex: 2010-06-07 03:55:14, 2010-06-07 03:56:23, 2010-06-07 03:57:01, 2010-06-07 03:57:51, 2010-06-07 03:59:21 ...) As I mentioned earlier I want to filter out some of the records, I do not have specific rule to do that, but I was thinking to filter out the rows according to the timestamp interval. After I achieve filtering I want to have a result set which has a certain amount of minutes between timestamps on average (ex: 2010-06-07 03:20:14, 2010-06-07 03:29:23, 2010-06-07 03:38:01, 2010-06-07 03:49:51, 2010-06-07 03:59:21 ...) Last but not least, the operation should not take incredible amount of time, I need this functionality to be almost fast as a normal select operation. Do you have any suggestions?

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  • Linq-to-sql Compiled Query is returning result from different DataContext

    - by Vladimir Kojic
    Compiled query: public static Func<OperationalDataContext, short, Machine> QueryMachineById = CompiledQuery.Compile((OperationalDataContext db, short machineID) => db.Machines.Where(m => m.MachineID == machineID).SingleOrDefault()); It looks like compiled query is caching Machine object and returning the same object even if query is called from new DataContext (I’m disposing DataContext in the service but I’m getting Machine from previous DataContext). I use POCOs and XML mapping. Revised: It looks like compiled query is returning result from new data context and it is not using the one that I passed in compiled-query. Therefore I can not reuse returned object and link it to another object obtained from datacontext thru non compiled queries. I’m using unit of work pattern : // First Call Using(new DataContext) { Machine from DataContext.Table == machine from cached query } // Do some work // Second Call is failing Using(new DataContext) { Machine from DataContext.Table <> machine from cached query }

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  • Different result with reverse proxy apache and lighttpd.

    - by Danny
    I have an Apache server running in reverse proxy mode in front of a Tomcat java server. It handle HTTP and HTTPS and send those request back and forth to the Tomcat server on an internal HTTP port. I'm trying to replace the reverse proxy with Lighttpd. Here's the problem: while asking for the same HTTPS url, while using Apache as the reverse proxy, the Tomcat server redirect (302) to an HTTPS page but with Lighttpd it redirect to the same page in HTTP (not HTTPS). What does Lighttpd could do different in order to have a different result from the backend server? In theory, using Apache or Lighttpd server as a reverse proxy should not change anything... but it does. Any idea? I'll try to find something by sniffing the traffic on the backend tomcat server.

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  • call by value-result in Pascal

    - by Luciano Lorenti
    How can i simulate calling by value-result in this example. Without adding variables and without change a variable name.? Program one; var x:integer; Function two():integer; begin x:=x+1; dos:=x; end; Procedure three(x:integer); begin x:=x+5; x:=two(); end; begin x:=8; trhee(x); write(x); end.

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  • oracle pl sql dump result into file

    - by CC
    Hi. I'm working on a pl sql stored procedure. What I need is to do a select, use a cursor and for every record build a string using values. At the end I need to write this into a file. I try to use dbms_output.put_line("toto") but the buffer size is to small because I have about 14 millions lines. I call my procedure from a unix ksh. I'm thinking at something like using "spool on" (on the ksh side) to dump the result of my procedure, but I don' know how to do it (if this is possible) Anyone has any idea? Thank alot. C.C.

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  • In cakePHP, how to retrieve joined result from multiple tables

    - by Manish Sharma
    Hi, can anyone tell me, how to retrieve joined result from multiple tables in cakePHP ( using cakePHP mvc architecture). For example, I have three tables to join (tbl_topics, tbl_items, tbl_votes. Their relationship is defined as following: a topic can have many items and an item can have many votes. Now I want to retrieve a list of topics with the count of all votes on all items for each topic. The SQL query for this is written below: SELECT Topic.*, count(Vote.id) voteCount FROM tbl_topics AS Topic LEFT OUTER JOIN tbl_items AS Item ON (Topic.id = Item.topic_id) LEFT OUTER JOIN tbl_votes AS Vote ON (Item.id = Vote.item_id); My problem is I can do it easily using $this-><Model Name>->query function, but this requires sql code to be written in the controller which I don't want. I'm trying to find out any other way to do this (like find()).

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  • error CS0133: Assigning the result of a function to a const in C#.net

    - by Greg
    Trying to tidy up scope and avoid possible multiple calls to RegisterWindowMessage. Currently have a class used once with the following member [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)] static extern int RegisterWindowMessage(string lpString); private int m_message = RegisterWindowMessage("MY_MSG"); As we only have one instance this seems ok, but think it would be more tidy to use. With my basic C# understanding this should call RegisterWindowMessage and assign the result to int and not allow it to change. private const int message = RegisterWindowMessage("MY_MSG"); however attempting to do so leads to a error CS0133: The expression being assigned to 'someclass.messageEvent' must be constant so now I'm confused, does this mean the function was being assigned and called each time m_message was used previously, is there something else missing?

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  • Getting empty result within PHP when in browser I get the JSON exception

    - by Pentium10
    I have this code: $url="https://graph.facebook.com/me/friends?access_token=".$access_token."&fields=id,first_name,last_name&limit=10"; $content=file_get_contents($url); Whenever I use this on a non authenticated user I should get feedback of OAuthException, which doesn't show up in the PHP the $content is empty. While if I copy the URL to the browser I get the result and I see the exception. I want to detect if the user is logged in and the session data is valid. What might be wrong?

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  • Iterating result of Select Query

    - by user294146
    Hi experts, I have a question related to select query. here i am explaining down below. i have a table with the following data **Column1(Primary Key) Column2 Column3** ------ --------- -------------- 1 C 2 C 3 Null 4 H 5 L 6 H my problem is i have to replace the value of Column3 with the corresponding value of Column1 for every occurrence of data "C", "H" and "L". Please provide me query related to this problem. how can i solve this using query or stored procedure. please elaborate the same. I need final select query result as follows **Column1(Primary Key) Column2 Column3** ------ --------- -------------- 1 C 1 2 C 2 3 Null 4 H 4 5 L 5 6 H 6 Thanks & Regards, Murali

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  • Filtering A MySQL Result Set Based On The Return Value Of A Function

    - by Joshua
    I'm a SQL noob, and I need a little bit of help understanding the big picture of if it is possible, and if so how to go about filtering a result set based on the return value of a function which is passed one of the fields of the record. Let's say I have a table called "Numbers" with just one field: "Value". How could I correctly specify the following "pseudo-sql"?: SELECT Value FROM numbers WHERE IsPrime(Value)=true Can I accomplish such a thing, and if so, where/how do I put/store "IsPrime"? I'm using MySQL.

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  • Check if hydrated doctrine result is NULL

    - by iggnition
    Hi, I'm trying to check if a result in my DQL is NULL. I got the following DQL query: $q = self::createQuery("l") ->select('i.*, s.aantal, m.naam, c.cat_naam, a.app_id') ->from('InstalledBase i, i.Spare s, i.Apparaat a, a.Categorie c, a.Merk m') ->execute(); return $q; Now i want to check if the s.aantal is NULL so i do: if(is_null($installedbase->Spare->spare_id)) when the variable is NOT null everything works, but when it is actually NULL i get a E notice message: Notice: Trying to get property of non-object in \installedbase\templates\_index.php on line 29 It does see that it is null though because the if condition is executed. Weird thing is i'm doing the exact same thing on another page where it works no problem. But i must be doing something wrong or stupid since those messages generally don't show for nothing. So can anybody explain this to me? :)

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  • Will this Java regex return a single result or multiple

    - by Blankman
    If my HTML is: <tr><td>....</td><hr></tr> <tr><td>....</td><hr></tr> <tr><td>....</td><hr></tr> <tr><td>....</td><hr></tr> <tr><td>....</td><hr></tr> <tr><td>....</td><hr></tr> If my regex is: Patterp p = Pattern.compile("<tr>(.*)<hr></tr>"); Should this get 1 result or all the individual rows? Is there a way to force it to get all the rows and not just the entire html from the top <tr> to the last instance of <hr></tr> ?

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