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  • Oracle - Parameterized Query has EXECUTIONS = PARSE_CALLS

    - by Cory Grimster
    We have a .NET application talking to Oracle 10g. Our DBA recently pulled a list of queries where executions is equal to parse_calls. We assumed that this would help us find all of the unparameterized queries in our code. Unexpectedly, the following query showed up near the top of this list, with 1,436,169 executions and 1,436,151 parses: SELECT bar.foocolumn FROM bartable bar, baztable baz WHERE bar.some_id = :someId AND baz.another_id = :anotherId AND baz.some_date BETWEEN bar.start_date AND (nvl(bar.end_date, baz.some_date + (1/84600)) - (1/84600)) Why is executions equal to parse_calls for this query?

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  • Combine static files or load in parallel

    - by Niall Collins
    I am at present introducing code to my site to combine css and javascript files. Is there a way without having to include an external library to load javascript asynchronously or in parallel? I have read on some blogs that combining of files can be counter productive as the load of the http request can be large and its better to load multiple files in parallel. Opinions on this? I am caching my javascript/css. And would have thought it was better to combine rather than have multiple http requests.

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  • DBnull in Linq query causing problems

    - by nat
    hi there i am doing a query thus: int numberInInterval = (from dsStatistics.J2RespondentRow item in jStats.J2Respondent where item.EndTime > dtIntervalLower && item.EndTime <= dtIntervalUpper select item).count(); there appear to be some dbnulls in the endtime column.. any way i can avoid these? tried adding && where item.endtime != null.. and even != dbnull.value do i have to do a second (first) query to grab all that arent null then run the above one? im sure its super simple fix, but im still missing it.. as per thanks nat

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  • Improving the speed of php

    - by cast01
    I'm currently working on a website in PHP, and I'm wondering what the best practices/methods are to reduce the time requests take. I've build the site in a modular way, so a page would consist of a number of modules, and each of these would need to request information. For example, I have a cart module, that (if a cart is set) will fetch the cart with the id (stored in a session variable) from the database and return its contents. I have another module that lists categories and this needs to fetch the categories from the database. My system is built with models, and each model might also make a request, for example a category model will make a request to get products in that category.

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  • Function-Local Static Const variable Initialization semantics.

    - by Hassan Syed
    The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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  • Multiple ParticleSystems in cocos2d

    - by Mattias Akerman
    I wonder about what road I should go with ParticleSystem. In this particular case I want to create 1-20 small explosions at the same time but with different positions. Right now I'm creating a new ParticleSystem for each explosion and then release it, but of course this is very punishing to the performance. My question is: Is there a way to create one ParticleSystem with multiple emitting sources. If not should I create an array of ParticleSystem in init and then use a free one when an explosion is needed? Or is there another approach I haven't thought of?

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  • Custom View - Avoid redrawing when non-interactive

    - by MasterGaurav
    I have a complex custom view - photo collage. What is observed is whenever any UI interaction happens, the view is redrawn. How can I avoid complete redrawing (for example, use a cached UI) of the view specially when I click the "back" button to go back to previous activity because that also causes redrawing of the view. While exploring the API and web, I found a method - getDrawingCache() - but don't know how to use it effectively. How do I use it effectively? I've had other issues with Custom Views that I outline here.

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  • Get multiple records with one query

    - by Lewy
    User table: name lastname Bob Presley Jamie Cox Lucy Bush Find users q = Query.new("Bob Presley, Cox, Lucy") q.find_users => {0=>{:name=>"Bob", :lastname=>"Presley"}, 1=>{:lastname=>"Cox"}, 2=>{:name=>"Lucy"}} Question: I've got hash with few names and lastnames. I need to build Activerecord query to fetch all users from that hash. I can do object = [] hash = q.find_users hash.each do |data| #check if data[:lastname] and data[:name] exist # object << User.where(:name => ..., :lastname => ...) end But I think it is higly inefficient. How should I do this ?

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  • Position of least significant bit that is set

    - by peterchen
    I am looking for an efficient way to determine the position of the least significant bit that is set in an integer, e.g. for 0x0FF0 it would be 4. A trivial implementation is this: unsigned GetLowestBitPos(unsigned value) { assert(value != 0); // handled separately unsigned pos = 0; while (!(value & 1)) { value >>= 1; ++pos; } return pos; } Any ideas how to squeeze some cycles out of it? (Note: this question is for people that enjoy such things, not for people to tell me xyzoptimization is evil.) [edit] Thanks everyone for the ideas! I've learnt a few other things, too. Cool!

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  • HSQLDB Constraint Violation & SQL Query Log for an HSQLDB in-memory setup

    - by shipmaster
    We have a setup where we are using an embedded HSQLDB for backing Hibernate/JPA unit tests in java, and we are using the in-memory database mode since we simply want the database thrown away after the test run. My problem is that one of the tests is failing due to a constraint violation and HSQLDB lists the column as SYS_CT_286, and the query that appears in the log is the prepared statement where I cant see what the actual parameter values are (they are replaced by '?'). My questions are: 1- Is there a way in which I can see the actual SQL being executed? (like the mysql query log for example?). 2- What exactly is SYS_CT_286? it is not one of my columns, is it a generated column? is there something obvious that may be wrong with it? Thanks.

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  • Optimizing spacing of mesh containing a given set of points

    - by Feynman
    I tried to summarize the this as best as possible in the title. I am writing an initial value problem solver in the most general way possible. I start with an arbitrary number of initial values at arbitrary locations (inside a boundary.) The first part of my program creates a mesh/grid (I am not sure which is the correct nuance), with N points total, that contains all the initial values. My goal is to optimize the mesh such that the spacing is as uniform as possible. My solver seems to work half decently (it needs some more obscure debugging that is not relevant here.) I am starting with one dimension. I intend to generalize the algorithm to an arbitrary number of dimensions once I get it working consistently. I am writing my code in fortran, but feel free to reply with pseudocode or the language of your choice. Allow me to elaborate with an example: Say I am working on a closed interval [1,10] xmin=1 xmax=10 Say I have 3 initial points: xmin, 5 and xmax num_ivc=3 known(num_ivc)=[xmin,5,xmax] //my arrays start at 1. Assume "known" starts sorted I store my mesh/grid points in an array called coord. Say I want 10 points total in my mesh/grid. N=10 coord(10) Remember, all this is arbitrary--except the variable names of course. The algorithm should set coord to {1,2,3,4,5,6,7,8,9,10} Now for a less trivial example: num_ivc=3 known(num_ivc)=[xmin,5.5,xmax or just num_ivc=1 known(num_ivc)=[5.5] Now, would you have 5 evenly spaced points on the interval [1, 5.5] and 5 evenly spaced points on the interval (5.5, 10]? But there is more space between 1 and 5.5 than between 5.5 and 10. So would you have 6 points on [1, 5.5] followed by 4 on (5.5 to 10]. The key is to minimize the difference in spacing. I have been working on this for 2 days straight and I can assure you it is a lot trickier than it sounds. I have written code that only works if N is large only works if N is small only works if it the known points are close together only works if it the known points are far apart only works if at least one of the known points is near a boundary only works if none of the known points are near a boundary So as you can see, I have coded the gamut of almost-solutions. I cannot figure out a way to get it to perform equally well in all possible scenarios (that is, create the optimum spacing.)

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  • Django: query with ManyToManyField count?

    - by AP257
    In Django, how do I construct a COUNT query for a ManyToManyField? My models are as follows, and I want to get all the people whose name starts with A and who are the lord or overlord of at least one Place, and order the results by name. class Manor(models.Model): lord = models.ManyToManyField(Person, null=True, related_name="lord") overlord = models.ManyToManyField(Person, null=True, related_name="overlord") class Person(models.Model): name = models.CharField(max_length=100) So my query should look something like this... but how do I construct the third line? people = Person.objects.filter( Q(name__istartswith='a'), Q(lord.count > 0) | Q(overlord.count > 0) # pseudocode ).order_by('name'))

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  • MySQL slow query

    - by andrhamm
    SELECT items.item_id, items.category_id, items.title, items.description, items.quality, items.type, items.status, items.price, items.posted, items.modified, zip_code.state_prefix, zip_code.city, books.isbn13, books.isbn10, books.authors, books.publisher FROM ( ( items LEFT JOIN bookitems ON items.item_id = bookitems.item_id ) LEFT JOIN books ON books.isbn13 = bookitems.isbn13 ) LEFT JOIN zip_code ON zip_code.zip_code = items.item_zip WHERE items.rid = $rid` I am running this query to get the list of a user's items and their location. The zip_code table has over 40k records and this might be the issue. It currently takes up to 15 seconds to return a list of about 20 items! What can I do to make this query more efficient?

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  • Nhibernate criteria query inserts an extra order by expression when using JoinType.LeftOuterJoin and Projections

    - by Aaron Palmer
    Why would this nhibernate criteria query produce the sql query below? return Session.CreateCriteria(typeof(FundingCategory), "fc") .CreateCriteria("FundingPrograms", "fp") .CreateCriteria("Projects", "p", JoinType.LeftOuterJoin) .Add(Restrictions.Disjunction() .Add(Restrictions.Eq("fp.Recipient.Id", recipientId)) .Add(Restrictions.Eq("p.Recipient.Id", recipientId)) ) .SetProjection(Projections.ProjectionList() .Add(Projections.GroupProperty("fc.Name"), "fcn") .Add(Projections.Sum("fp.ObligatedAmount"), "fpo") .Add(Projections.Sum("p.ObligatedAmount"), "po") ) .AddOrder(Order.Desc("fpo")) .AddOrder(Order.Desc("po")) .AddOrder(Order.Asc("fcn")) .List<object[]>(); SELECT this_.Name as y0_, sum(fp1_.ObligatedAmount) as y1_, sum(p2_.ObligatedAmount) as y2_ FROM fundingCategories this_ inner join fundingPrograms fp1_ on this_.fundingCategoryId = fp1_.fundingCategoryId left outer join projects p2_ on fp1_.fundingProgramId = p2_.fundingProgramId WHERE (fp1_.recipientId = 6 /* @p0 */ or p2_.recipientId = 6 /* @p1 */) GROUP BY this_.Name ORDER BY p2_.name asc, y1_ desc, y2_ desc, y0_ asc It is incorrectly putting the p2_name asc into the ORDER BY statement, and causing it to crash. This only happens when I use JoinType.LeftOuterJoin on my Projects criteria. Is this a known nhibernate bug? I'm using nhibernate 2.0.1.4000. Thanks for any insight.

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  • MySQL efficiency as it relates to the database/table size

    - by mlissner
    I'm building a system using django, Sphinx and MySQL that's very quickly becoming quite large. The database currently has about 2000 rows, and I've written a program that's going to populate it with another 40,000 rows in a couple days. Since the database is live right now, and since I've never had a database with this much information in it, I'm worried about some things: Is adding all these rows going to seriously degrade the efficiency of my django app? Will I need to go back through it and optimize all my database calls so they're doing things more cleverly? Or will this make the database slow all around to the extent that I can't do anything about it at all? If you scoff at my 40k rows, then, my next question is, at what point SHOULD I be concerned? I will likely be adding another couple hundred thousand soon, so I worry, and I fret. How is sphinx going to feel about all this? Is it going to freak out when it realizes it has to index all this data? Or will it be fine? Is this normal for it? If it is, at what point should I be concerned that it's too much data for Sphinx? Thanks for any thoughts.

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  • Optimize code performance when odd/even threads are doing different things in CUDA

    - by Orion Nebula
    Hi all! I have two large vectors, I am trying to do some sort of element multiplication, where an even-numbered element in the first vector is multiplied by the next odd-numbered element in the second vector .... and where the odd-numbered element in the first vector is multiplied by the preceding even-numbered element in the second vector Ex. vector 1 is V1(1) V1(2) V1(3) V1(4) vector 2 is V2(1) V2(2) V2(3) V2(4) V1(1) * V2(2) V1(3) * V2(4) V1(2) * V2(1) V1(4) * V2(3) I have written a Cuda code to do this: (Pds has the elements of the first vector in shared memory, Nds the second Vector) //instead of using %2 .. i check for the first bit to decide if number is odd/even -- faster if ((tx & 0x0001) == 0x0000) Nds[tx+1] = Pds[tx] * Nds[tx+1]; else Nds[tx-1] = Pds[tx] * Nds[tx-1]; __syncthreads(); Is there anyway to further accelerate this code or avoid divergence ? Thanks

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  • What is the Fastest Way to Check for a Keyword in a List of Keywords in Delphi?

    - by lkessler
    I have a small list of keywords. What I'd really like to do is akin to: case MyKeyword of 'CHIL': (code for CHIL); 'HUSB': (code for HUSB); 'WIFE': (code for WIFE); 'SEX': (code for SEX); else (code for everything else); end; Unfortunately the CASE statement can't be used like that for strings. I could use the straight IF THEN ELSE IF construct, e.g.: if MyKeyword = 'CHIL' then (code for CHIL) else if MyKeyword = 'HUSB' then (code for HUSB) else if MyKeyword = 'WIFE' then (code for WIFE) else if MyKeyword = 'SEX' then (code for SEX) else (code for everything else); but I've heard this is relatively inefficient. What I had been doing instead is: P := pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX '); case P of 1: (code for CHIL); 6: (code for HUSB); 11: (code for WIFE); 17: (code for SEX); else (code for everything else); end; This, of course is not the best programming style, but it works fine for me and up to now didn't make a difference. So what is the best way to rewrite this in Delphi so that it is both simple, understandable but also fast? (For reference, I am using Delphi 2009 with Unicode strings.) Followup: Toby recommended I simply use the If Then Else construct. Looking back at my examples that used a CASE statement, I can see how that is a viable answer. Unfortunately, my inclusion of the CASE inadvertently hid my real question. I actually don't care which keyword it is. That is just a bonus if the particular method can identify it like the POS method can. What I need is to know whether or not the keyword is in the set of keywords. So really I want to know if there is anything better than: if pos(' ' + MyKeyword + ' ', ' CHIL HUSB WIFE SEX ') > 0 then The If Then Else equivalent does not seem better in this case being: if (MyKeyword = 'CHIL') or (MyKeyword = 'HUSB') or (MyKeyword = 'WIFE') or (MyKeyword = 'SEX') then In Barry's comment to Kornel's question, he mentions the TDictionary Generic. I've not yet picked up on the new Generic collections and it looks like I should delve into them. My question here would be whether they are built for efficiency and how would using TDictionary compare in looks and in speed to the above two lines? In later profiling, I have found that the concatenation of strings as in: (' ' + MyKeyword + ' ') is VERY expensive time-wise and should be avoided whenever possible. Almost any other solution is better than doing this.

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  • Optimizing processing and management of large Java data arrays

    - by mikera
    I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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  • FxCop giving a warning on private constructor CA1823 and CA1053

    - by Luis Sánchez
    I have a class that looks like the following: Public Class Utilities Public Shared Function blah(userCode As String) As String 'doing some stuff End Function End Class I'm running FxCop 10 on it and it says: "Because type 'Utilities' contains only 'static' ( 'Shared' in Visual Basic) members, add a default private constructor to prevent the compiler from adding a default public constructor." Ok, you're right Mr. FxCop, I'll add a private constructor: Private Utilities() Now I'm having: "It appears that field 'Utilities.Utilities' is never used or is only ever assigned to. Use this field or remove it." Any ideas of what should I do to get rid of both warnings?

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  • Create a SQL query to retrieve most recent records

    - by mattruma
    I am creating a status board module for my project team. The status board allows the user to to set their status as in or out and they can also provide a note. I was planning on storing all the information in a single table ... and example of the data follows: Date User Status Notes ------------------------------------------------------- 1/8/2009 12:00pm B.Sisko In Out to lunch 1/8/2009 8:00am B.Sisko In 1/7/2009 5:00pm B.Sisko In 1/7/2009 8:00am B.Sisko In 1/7/2009 8:00am K.Janeway In 1/5/2009 8:00am K.Janeway In 1/1/2009 8:00am J.Picard Out Vacation I would like to query the data and return the most recent status for each user, in this case, my query would return the following results: Date User Status Notes ------------------------------------------------------- 1/8/2009 12:00pm B.Sisko In Out to lunch 1/7/2009 8:00am K.Janeway In 1/1/2009 8:00am J.Picard Out Vacation I am try to figure out the TRANSACT-SQL to make this happen? Any help would be appreciated.

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  • cheapest way to draw a fullscreen quad

    - by Soubok
    I wondering if there is a faster way to draw a full-screen quad in OpenGL: NewList(); PushMatrix(); LoadIdentity(); MatrixMode(PROJECTION); PushMatrix(); LoadIdentity(); Begin(QUADS); Vertex(-1,-1,0); Vertex(1,-1,0); Vertex(1,1,0); Vertex(-1,1,0); End(); PopMatrix(); MatrixMode(MODELVIEW); PopMatrix(); EndList();

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  • HQL query for entity with max value

    - by Rob
    I have a Hibernate entity that looks like this (accessors ommitted for brevity): @Entity @Table(name="FeatureList_Version") @SecondaryTable(name="FeatureList", pkJoinColumns=@PrimaryKeyJoinColumn(name="FeatureList_Key")) public class FeatureList implements Serializable { @Id @Column(name="FeatureList_Version_Key") private String key; @Column(name="Name",table="FeatureList") private String name; @Column(name="VERSION") private Integer version; } I want to craft an HQL query that retrieves the most up to date version of a FeatureList. The following query sort of works: Select f.name, max(f.version) from FeatureList f group by f.name The trouble is that won't populate the key field, which I need to contain the key of the record with the highest version number for the given FeatureList. If I add f.key in the select it won't work because it's not in the group by or an aggregate and if I put it in the group by the whole thing stops working and it just gives me every version as a separate entity. So, can anybody help?

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  • Optimizing a Soundex Query for finding similar names

    - by xkingpin
    My application will offer a list of suggestions for English names that "sound like" a given typed name. The query will need to be optimized and return results as quick as possible. Which option would be most optimal for returning results quickly. (Or your own suggestion if you have one) A. Generate the Soundex Hash and store it in the "Names" table then do something like the following: (This saves generating the soundex hash for at least every row in my db per query right?) select name from names where NameSoundex = Soundex('Ann') B. Use the Difference function (This must generate the soundex for every name in the table?) select name from names where Difference(name, 'Ann') = 3 C. Simple comparison select name from names where Soundex(name) = Soundex('Ann') Option A seems like to me it would be the fastest to return results because it only generates the Soundex for one string then compares to an indexed column "NameSoundex" Option B should give more results than option A because the name does not have to be an exact match of the soundex, but could be slower Assuming my table could contain millions of rows, what would yield the best results?

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  • explicit copy constructor or implicit parameter by value

    - by R Samuel Klatchko
    I recently read (and unfortunately forgot where), that the best way to write operator= is like this: foo &operator=(foo other) { swap(*this, other); return *this; } instead of this: foo &operator=(const foo &other) { foo copy(other); swap(*this, copy); return *this; } The idea is that if operator= is called with an rvalue, the first version can optimize away construction of a copy. So when called with a rvalue, the first version is faster and when called with an lvalue the two are equivalent. I'm curious as to what other people think about this? Would people avoid the first version because of lack of explicitness? Am I correct that the first version can be better and can never be worse?

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