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  • Joining different models in Django

    - by Andrew Roberts
    Let's say I have this data model: class Workflow(models.Model): ... class Command(models.Model): workflow = models.ForeignKey(Workflow) ... class Job(models.Model): command = models.ForeignKey(Command) ... Suppose somewhere I want to loop through all the Workflow objects, and for each workflow I want to loop through its Commands, and for each Command I want to loop through each Job. Is there a way to structure this with a single query? That is, I'd like Workflow.objects.all() to join in its dependent models, so I get a collection that has dependent objects already cached, so workflows[0].command_set.get() doesn't produce an additional query. Is this possible?

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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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  • Lucene neo4j sort with boolean fields

    - by Daniele
    I have indexed some documents (nodes of neo4j) with a boolean property which not always is present. Eg. Node1 label : "label A" Node2: label : "label A" (note, same label of node1) special : true The goal is to get Node2 higher than node 1 for query "label A". Here the code: Index<Node> fulltextLucene = graphDb.index().forNodes( "my-index" ); Sort sort = new Sort(new SortField[] {SortField.FIELD_SCORE, new SortField("special", SortField.????, true) }); IndexHits<Node> results = fulltextLucene.query( "label", new QueryContext( "label A").sort(sort)); How can I accomplish that? Thanks

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  • iPhone SDK Nested For Loop performance

    - by Skeep
    Hi All, I have a NSArray of string id and a NSDictionary of NSDictionary objects. I am currently looping through the string id array to match the id value in the NSDictionary. There are around 200 NSDictionary objects and only 5 or so string ID. My current code is such: for (NSString *Str in aArr) { for (NSDictionary *a in apArr) { if ([a objectForKey:@"id"] == Str) { NSLog(@"Found!"); } } } The performance of the above code is really slow and I was wondering if there is a better way to do this?

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  • Increasing speed of webservice - howto

    - by Koran
    Hi, Our client-server product has the protocol between them as XML over HTTP. Here, the client asks a GET/POST query to the web server and the server responds with XML. The server is written using django. The server has to be on the web because there are many clients across the world using this. The server code uses extensive memoization and also there is very less db queries - most queries dont have any db queries, some of them has max 1. The biggest problem is the speed. Every query takes close to 5 seconds for the reply. The data replied is also very less - in the range of 4-6 Kb. What are the mechanisms to improve speed of the web service? Is this the usual way of writing a client-server? Are there other technologies and are we missing out on it? Thank you K

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  • Getting mysql row that doesn't conflict with another row

    - by user939951
    I have two tables that link together through an id one is "submit_moderate" and one is "submit_post" The "submit_moderate" table looks like this id moderated_by post 1 James 60 2 Alice 32 3 Tim 18 4 Michael 60 Im using a simple query to get data from the "submit_post" table according to the "submit_moderate" table. $get_posts = mysql_query("SELECT * FROM submit_moderate WHERE moderated_by!='$user'"); $user is the person who is signed in. Now my problem is when I run this query, with the user 'Michael' it will retrieve this 1 James 60 2 Alice 32 3 Tim 18 Now technically this is correct however I don't want to retrieve the first row because 60 is associated with Michael as well as James. Basically I don't want to retrieve that value '60'. I know why this is happening however I can't figure out how to do this. I appreciate any hints or advice I can get.

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  • c# - pull records from database without timeout

    - by BhejaFry
    Hi folks, i have a sql query with multiple joins & it pulls data from a database for processing. This is supposed to be running on some scheduled basis. So day 1, it might pull 500, day 2 say 400. Now, if the service is stopped for some reason & the data not processed, then on day3 there could be as much as 1000 records to process. This is causing timeout on the sql query. How best to handle this situation without causing timeout & gradually reducing workload to process? TIA

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  • Can this MySQL subquery be optimised?

    - by Dan
    I have two tables, news and news_views. Every time an article is viewed, the news id, IP address and date is recorded in news_views. I'm using a query with a subquery to fetch the most viewed titles from news, by getting the total count of views in the last 24 hours for each one. It works fine except that it takes between 5-10 seconds to run, presumably because there's hundreds of thousands of rows in news_views and it has to go through the entire table before it can finish. The query is as follows, is there any way at all it can be improved? SELECT n.title , nv.views FROM news n LEFT JOIN ( SELECT news_id , count( DISTINCT ip ) AS views FROM news_views WHERE datetime >= SUBDATE(now(), INTERVAL 24 HOUR) GROUP BY news_id ) AS nv ON nv.news_id = n.id ORDER BY views DESC LIMIT 15

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  • Counting the most tagged tag with MySQL

    - by Jack W-H
    Hi folks My problem is that I'm trying to count which tag has been used most in a table of user-submitted code. But the problem is with the database structure. The current query I'm using is this: SELECT tag1, COUNT(tag1) AS counttag FROM code GROUP BY tag1 ORDER BY counttag DESC LIMIT 1 This is fine, except, it only counts the most often occurence of tag1 - and my database has 5 tags per post - so there's columns tag1, tag2, tag3, tag4, tag5. How do I get the highest occurring tag value from all 5 columns in one query? Jack

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  • MySQL: Insert row on table2 if row in table1 exists

    - by Andrew M
    I'm trying to set up a MySQL query that will insert a row into table2 if a row in table1 exist already, otherwise it will just insert the row into table1. I need to find a way to adapt the following query into inserting a row into table2 with the existing row's id. INSERT INTO table1 (host, path) VALUES ('youtube.com', '/watch') IF NOT EXISTS ( SELECT * FROM table1 WHERE host='youtube.com' AND path='/watch' LIMIT 1); Something kind of like this: INSERT ... IF NOT EXISTS(..) ELSE INSERT INTO table2 (table1_id) VALUES(row.id); Except I don't know the syntax for this.

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  • SqlServer2008 + expensive union

    - by Tim Mahy
    Hi al, we have 5 tables over which we should query with user search input throughout a stored procedure. We do a union of the similar data inside a view. Because of this the view can not be materialized. We are not able to change these 5 tables drastically (like creating a 6th table that contains the similar data of the 5 tables and reference that new one from the 5 tables). The query is rather expensive / slow what are our other options? It's allowed to think outside the box. Unfortunately I cannot give more information like the table/view/SP definition because of customer confidentiality... greetings, Tim

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  • How to select only the first rows for each unique value of a column

    - by nuit9
    Let's say I have a table of customer addresses: CName | AddressLine ------------------------------- John Smith | 123 Nowheresville Jane Doe | 456 Evergreen Terrace John Smith | 999 Somewhereelse Joe Bloggs | 1 Second Ave In the table, one customer like John Smith can have multiple addresses. I need the select query for this table to return only first row found where there are duplicates in 'CName'. For this table it should return all rows except the 3rd (or 1st - any of those two addresses are okay but only one can be returned). Is there a keyword I can add to the SELECT query to filter based on whether the server has already seen the column value before?

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  • performance of parameterized queries for different db's

    - by tuinstoel
    A lot of people know that it is important to use parameterized queries to prevent sql injection attacks. Parameterized queries are also much faster in sqlite and oracle when doing online transaction processing because the query optimizer doesn't have to reparse every parameterized sql statement before executing. I've seen sqlite becoming 3 times faster when you use parameterized queries, oracle can become 10 times faster when you use parameterized queries in some extreme cases with a lot of concurrency. How about other db's like mysql, ms sql, db2 and postgresql? Is there an equal difference in performance between parameterized queries and literal queries?

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  • Performance - User defined query / filter to search data

    - by Cagatay Kalan
    What is the best way to design a system where users can create their own criterias to search data ? By "design" i mean, data storage, data access layer and search structure. We will actually refactor an existing application which is written in C# and ASP .NET and we don't want to change the infrastructure. Our main issue is performance and we use MSSQL and DevExpress to build queries. Some queries run in 4-5 minutes and all the columns included in the queries have indexes. When i check queries, i see that DevExpress builds too many "exists" clauses and i'm not happy with that because i have doubts that some of these queries skip some indexes. What may be the alternatives to DevExpress? NHibernate or Entity Framework? Can we build dynamic criteria system and store these to database in both of them ? And also do we need any alternative storage like a lucene index or OLAP database?

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  • SQL SELECT across two tables

    - by Brett Spurrier
    Hi there, I am a little confused as to how to approach this SQL query. I have two takes (equal number of records), and I would like to return a column with which is the division between the two. In other words, here is my not-working-correctly query: SELECT( (SELECT v FROM Table1) / (SELECT DotProduct FROM Table2) ); How would I do this? All I want it a column where each row equals the same row in Table1 divided by the same row in Table2. The resulting table should have the same number of rows, but I am getting something with a lot more rows than the original two tables. I am at a complete loss. Any advice?

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  • MySQL slow queries

    - by jack
    The MySQL slow query log often shows a bunch of following entries in sequence. SET timestamp=1268999330; commit; # User@Host: username[username] @ localhost [] # Query_time: 4.172700 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0 SET timestamp=1268999330; commit; # User@Host: username[username] @ localhost [] # Query_time: 3.628924 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0 SET timestamp=1268999330; commit; # User@Host: username[username] @ localhost [] # Query_time: 3.116018 Lock_time: 0.000000 Rows_sent: 0 Rows_examined: 0 ... Usually 6-7 "commit" queries in sequence. Anyone what they are and what's the preceding query of each of them? Thanks in advance.

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  • SqlServer2008 + expensive union all

    - by Tim Mahy
    Hi al, we have 5 tables over which we should query with user search input throughout a stored procedure. We do a union all of the similar data inside a view. Because of this the view can not be materialized. We are not able to change these 5 tables drastically (like creating a 6th table that contains the similar data of the 5 tables and reference that new one from the 5 tables). The query is rather expensive / slow what are our other options? It's allowed to think outside the box. Unfortunately I cannot give more information like the table/view/SP definition because of customer confidentiality... greetings, Tim

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  • Possible Performance Considerations using Linq to SQL Repositories

    - by Robert Harvey
    I have an ASP.NET MVC application that uses Linq to SQL repositories for all interactions with the database. To deal with data security, I do trimming to filter data to only those items to which the user has access. This occurs in several places: Data in list views Links in a menu bar A treeview on the left hand side containing links to content Role-based security A special security attribute, inheriting from AuthorizeAttribute, that implements content-based authorization on every controller method. Each of these places instantiates a repository, which opens a Linq to Sql DataContext and accesses the database. So, by my count, each request for a page access opens at least six separate Linq to SQL DataContexts. Should I be concerned about this from a performance perspective, and if so, what can be done to mitigate it?

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  • SQLite table creation date

    - by legr3c
    Is there a way to query the creation date of a table in SQLite? I am new to SQL, overall. I just found this http://stackoverflow.com/questions/1171019/sql-server-table-creation-date-query. I am assuming that sqlite_master is the equivalent to sys.tables in SQLite. Is that correct? But then my sqlite_master table only has the columns "type", "name", "tbl_name", "rootpage" and "sql". If this is not possible in SQLite, what would be the best way to implement this functionality by myself?

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  • Question about joins and table with Millions of rows

    - by xRobot
    I have to create 2 tables: Magazine ( 10 millions of rows with these columns: id, title, genres, printing, price ) Author ( 180 millions of rows with these columns: id, name, magazine_id ) . Every author can write on ONLY ONE magazine and every magazine has more authors. So if I want to know all authors of Motors Magazine, I have to use this query: SELECT * FROM Author, Magazine WHERE ( Author.id = Magazine.id ) AND ( genres = 'Motors' ) The same applies to Printing and Price column. To avoid these joins with tables of millions of rows, I thought to use this tables: Magazine ( 10 millions of rows with this column: id, title, genres, printing, price ) Author ( 180 millions of rows with this column: id, name, magazine_id, genres, printing, price ) . and this query: SELECT * FROM Author WHERE genres = 'Motors' Is it a good approach ? I can use Postgresql or Mysql.

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  • what is a performance way to 'tree-walking' through my Entity Framework data

    - by Greg
    Hi, I have a Entity Framework design with a few tables that define a "graph". So there can be a large chain of relationships between objects in the few tables via concept of parent/child relationships. What is a performance way to 'tree-walking' through my Entity Framework data? That is I assume I wouldn't want to load the full set of all NODES and RELATIONSHIPS from the database for the purpose of walking the tree, where the end result may only be identifying leaf nodes? Or would this be OK with the way lazy loading may work at the column/parameter level? Else how could I load just the skeleton of the objects and then when needing to refer to any attributes have them lazy load then?

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  • SQL to get friends AND friends of friends of a user

    - by Enrique
    My MySQL tables structure is like this. USER int id varchar username FRIEND_LIST int user_id int friend_id For each friend relationship I insert 2 records in FRIEND_LIST. If user 1 is friend of user 2 then the next rows are inserted into FRIEND_LIST 1,2 2,1 I want to get the friends and friends of friends of an specific user. The select should return columns a, b, c. a: user_id b: friend_id c: username (username of friend_id ) If 1 is friend of 2 and 3. 2 is friend of 3, 4 and 5 3 is friend of 5,6,7 Then the query to get 1's friends and friends of friends should return: 1 2 two 1 3 three 2 1 one 2 3 three 2 4 four 2 5 five 3 1 one 3 5 five 3 6 six 3 7 seven Can I get this rows with a single query?

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  • Performance impact of rewrite conditions?

    - by makeee
    My web framework (cakephp) uses the following rewrite conditions and rule: RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.*)$ index.php?url=$1 [QSA,L] I serve up a lot of image files (~10 a second). I'm wondering if it would improve performance to have a rewrite rule that exempted requests for files in my images directory from even trying those rewrite conditions (checking whether the file exists). My traffic is constantly fluctuating, so this would be hard to benchmark, which is why I thought I'd ask here. If that would be beneficial, how might I exclude files in "/images" directory from trying those conditions and rewrite rule?

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  • Appengine (python) returns empty for valid queries

    - by Grant
    I've got an app with around half a million 'records', each of which only stores three fields. I'd like to look up records by a string field with a query, but I'm running into problems. If I visit the console page, manually view a record and save it (without making changes) it shows up in a query: SELECT * FROM wordEntry WHERE wordStr = 'SomeString' If I don't do this, I get 'no results'. Does appengine need time to update? If so, how much? (I was also having trouble batch deleting and modifying data, but I was able to break the problem up into smaller chunks.)

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  • How to dynamically modify NHibernate load queries at runtime? EventListeners? Interceptors?

    - by snicker
    I need to modify the query used to load many-to-one references in my model. Specifically, I need to be able to further filter this data. Unfortunately, NH will not allow me to filter many-to-one relationships using the built in filtering system (?). I could just be doing something incorrect. Is there a hook where I can manually and dynamically modify the query used to load the data? Or an alternative to filters that will allow me to specify parameters? Background: I am working with a database that is using a form of revision control, with each entity having a natural ID PK, an EntityId, a RevisionValidTo and RevisionValidFrom field. There may be many rows using the same EntityId, which is the reference for other tables to join on, but the Revision ranges are mutually exclusive. Thus, the relationship is only many-to-one IIF the filter is applied. However, NH offers no way to specify a filter on many-to-one references (they do for collections...)

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