query performance - Page 274

Oracle performance report

- by John

Hi, Is there any way of running the $ORACLE_HOME/rdbms/admin/awrrpt.sql so that it doesn't require any input parameters, as in automatically collects a report for the previous hour? /j

performance implications of storing 600,000+ images in the same folder (NTFS)

I need to store about 600,000 images on a web server that using NTFS. Am I better off storing images in 20,000-image chunks in subfolders? (Windows Server 2008) I'm concerned about incurring operating system overhead during image retrieval

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Nhibernate, can i improve my MAPPING or Query

- by dbones

take this simple example A staff class which references other instances of the staff class public class Staff { public Staff() { Team = new List<Staff>(); } public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IList<Staff> Team { get; set; } public virtual Staff Manager { get; set; } } The Fluent Mapping public class StaffMap : ClassMap<Staff> { public StaffMap() { Id(x => x.Id); Map(x => x.Name); References(x => x.Manager).Column("ManagerId"); HasMany(x => x.Team).KeyColumn("ManagerId").Inverse(); } } Now I want to run a query, which will load all the Staff and eager load the manager and Team members. This is what I came up with IList<Staff> resutls = session.CreateCriteria<Staff>() .SetFetchMode("Team", FetchMode.Eager) .SetResultTransformer(Transformers.DistinctRootEntity) .List<Staff>(); however the SQL (does what i want) has duplicate columns, 2 team2_.ManagerId and 2 team2_.Id SELECT this_.Id as Id0_1_, this_.Name as Name0_1_, this_.ManagerId as ManagerId0_1_, team2_.ManagerId as ManagerId3_, team2_.Id as Id3_, team2_.Id as Id0_0_, team2_.Name as Name0_0_, team2_.ManagerId as ManagerId0_0_ FROM [SelfRef].[dbo].[Staff] this_ left outer join [SelfRef].[dbo].[Staff] team2_ on this_.Id=team2_.ManagerId The question is, should this be happening? did i do something wrong in the query or map? or is it a feature of the HHib im using (which is Version 2.1.0.4000)? many thanks in advance

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Using linq2xml to query a single item deep within

- by BrettRobi

I'm wondering if there is a robust and graceful way using linq2xml to query an item deep within an xml hierarchy. For example: <?xml version="1.0" encoding="utf-8" ?> <data> <core id="01234"> <field1>some data</field1> <field2>more data</field2> <metadata> <response> <status code="0">Success</status> <content> <job>f1b5c3f8-e6b1-4ae4-905a-a7c5de3f13c6</job> <id>id of the content</id> </content> </response> </metadata> </core> </data> With this xml how do I query the value of without using something like this: var doc = XElement.Load("file.xml"); string id = (string)doc.Element("core") .Element("metadata") .Element("response") .Element("content") .Element("id"); I don't like the above approach because it is error prone (throws exception if any tag is missing in the hierarchy) and honestly ugly. Is there a more robust and graceful approach, perhaps using the sql-like syntax of linq?

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xpath query to find parent tag

- by cru3l

for example, i have this xml <elements> <a> 6 5 6 </a> <a> 5 5 6 </a> <a> 5 5 5 5 </a> </elements> i need a xpath query, which must return me parent tag, only if all its children are equal to 5 (a[3] in this case). Something like that //b[text()="5"]/.. but with check of all children's tags. Please note that number of children tags can be different from node to node. It's possible with only xpath query? thanks

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query keepalived

- by tdimmig

*Note: I have trouble deciding what should go in serverfault and what should go in superuser, if some kindly admin decides this is in the wrong place please move it for me - many thanks. I am implementing a basic HA system with keepalived. I only want to be notified of the failover in the case of hardware failure. I do, however, have the servers switch roles periodically. I have a track_script running on the backup that will vary it's return between 0 and 1 on an interval (once a week, once a month, whatever). Upon returning 0, the priority is raised above that of the master, upon returning 1 the priority is lowered again. This way they trade places on the configured interval. The question: What can I do to tell the difference between a switch caused by my script, and a switch caused because one of the servers died? I certainly want to be notified when there is an actual problem, but not every time the servers change places because of the script. I see that version 1.2.7 has snmp support and I may be able to use it to get some information that could tell me one way or another, but to be honest I've never used snmp before and I don't know how to get the information I want with it (my Google foo failed me).

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Too many columns to index - use mySQL Partitions?

- by Christopher Padfield

We have an application with a table with 20+ columns that are all searchable. Building indexes for all these columns would make write queries very slow; and any really useful index would often have to be across multiple columns increasing the number of indexes needed. However, for 95% of these searches, only a small subset of those rows need to be searched upon, and quite a small number - say 50,000 rows. So, we have considered using mySQL Partition tables - having a column that is basically isActive which is what we divide the two partitions by. Most search queries would be run with isActive=1. Most queries would then be run against the small 50,000 row partition and be quick without other indexes. Only issue is the rows where isActive=1 is not fixed; i.e. it's not based on the date of the row or anything fixed like that; we will need to update isActive based on use of the data in that row. As I understand it that is no problem though; the data would just be moved from one partition to another during the UPDATE query. We do have a PK on id for the row though; and I am not sure if this is a problem; the manual seemed to suggest the partition had to be based on any primary keys. This would be a huge problem for us because the primary key ID has no basis on whether the row isActive.

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Query specific nameserver for a particular domain upon VPN connect

- by MT

Some background: I have a work laptop with Ubuntu 9.10 on it. I have a small network at home where I've been running some basic services (for myself/my family) for 10 some years. In my home network there is a nameserver (Fedora) running Bind 9 with two "views". One view is the "outside" view and it provides name resolution (to the Internet at large) for email, a wiki, and a couple of blogs. The "inside" view provides name resolution (to the internal RFC1918 addresses of theses servers) as well as all the inside hosts, network equipment, ...etc. I connect with an openvpn client to my home network from outside (such as work). What I'd like to be able to do is resolve names on my internal network across this VPN (so I get the RFC1918 "inside" responses) without fully changing my resolver to the DNS server at my hose. For example, if I connect to the VPN from work, I can change my resolver (by editing resolv.conf) to the DNS server at my house (across the VPN) and then successfully resolve all of the inside DNS names on my home network. The issue I have with this is that now I'm no longer able to resolve "inside" names provided by my work's DNS servers (because I'm using my home DNS server). Alternatively, I can connect to the VPN and access my home severs via IP addresses directly, but this is inconvenient and causes issues with Apache name-based hosting (among other things). In the end, the effect I'm trying to achieve is as follows: When I connect to the VPN I automatically start sending DNS requests for *.myhomedomain.com to my home nameserver, but any other requests continue to go the the nameserver I was using before (the one I received on my company LAN via DHCP). When I disconnect the VPN, requests for *.myhomedomain.com go back to the local LAN DNS server (e.g. all requests are going there now). I'm looking for suggestion at to how this can be accomplished.

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.NET IsValidXml Extension Method Performance

- by tyndall

I have a legacy application that I inherited that passes a lot of XML around as Strings. I often need the ability to check if a String will be valid XML. What is the fastest and least expensive way to check if a string is valid XML in .NET? I'm working in .NET 3.5 and would most likely use this as an extension method (off of string) in this one project within the solution.

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Performance issue finding weekdays over a given period

- by Oysio

I have some methods that return the number of weekdays between two given dates. Since calling these methods become very expensive to call when the two dates lie years apart, I'm wondering how these methods could be refactored in a more efficient way. The returned result is correct but I feel that the iphone processor is struggling to keep up and consequently freezes up the application when I would call these methods over a period of say 10years. Any suggestions ? //daysList contains all weekdays that need to be found between the two dates -(NSInteger) numberOfWeekdaysFromDaysList:(NSMutableArray*) daysList startingFromDate:(NSDate*)startDate toDate:(NSDate*)endDate { NSInteger retNumdays = 0; for (Day *dayObject in [daysList objectEnumerator]) { if ([dayObject isChecked]) { retNumdays += [self numberOfWeekday:[dayObject weekdayNr] startingFromDate:startDate toDate:endDate]; } } return retNumdays; } -(NSInteger) numberOfWeekday:(NSInteger)day startingFromDate:(NSDate*)startDate toDate:(NSDate*)endDate { NSInteger numWeekdays = 0; NSDate *nextDate = startDate; NSComparisonResult result = [endDate compare:nextDate]; //Do while nextDate is in the past while (result == NSOrderedDescending || result == NSOrderedSame) { if ([NSDate weekdayFromDate:nextDate] == day) { numWeekdays++; } nextDate = [nextDate dateByAddingDays:1]; result = [endDate compare:nextDate]; } return numWeekdays; }

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Suggestions for performance improvement surrounding sending email notifications?

- by jcmoney

It takes around a couple of seconds for my app to execute the code to send an email right now on a test server with nothing much else running. Not sure if this is typical/expected. I'm also using the php framework Kohana's email helper and not php's mail directly out of convenience if that matters. Is it always just better to schedule a cron job to send emails every 5 min or so? Or should I be able to send emails immediately and I'm just not doing something right? What the script does is insert a row into the db and notifies the relevant group that the row was created. The groups are usually < 20 people so I just do a loop calling Kohana's email helper each time for each member of the group.

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Lucene raise document score if sibling entity matches query

- by Pitagoras

I have the following design situation. I use hibernate search (lucene in the back). Tha application manages ITEMs which have title, description and tags. These are full text indexed. On the other hand, we have COLLECTION of ITEMs. The user can create a COLLECTION and add as many ITEMs as she wants. ITEMs can also belong to many COLLECTIONs. I have a boosted query so that search terms that appear in the tags are more important than in the title, and lastly in the description. But I need an additional matching criteria: for a given ITEM, it whould rank better if other documents in some COLLECTION where the ITEM belongs, also match the query. This is like to say: the title/tags/description of "fellow" items (i.e. items in some shared collection) make the item rank better. I was thinking that adding an ITEM to a COLLECTION would add something like "extra tags" to every other ITEM in the collection, being these extra tags the elements to match in the added ITEM. I feel a more clever solution lucene-wise should exists. Any ideas/pointers are welcome. Thanks.

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Compact Framework Remote Performance Monitor Error connecting to a device

- by Big Endian

Hello *, I am trying to do a memory profile on a .Net CF app. It was originally compiled in 2.0, but I converted it to 3.5 so I can use the 3.5 CF PowerToys Remote Perf Mon. I am getting the following error message when trying to connect: ActiveSync device: transport incompatible. I am connecting via DMA through ActiveSync, should I be doing something differently? Thanks!

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SQL Query to separate data into two fields

- by Phillip

I have data in one column that I want to separate into two columns. The data is separated by a comma if present. This field can have no data, only one set of data or two sets of data saperated by the comma. Currently I pull the data and save as a comma delimited file then use an FoxPro to load the data into a table then process the data as needed then I re-insert the data back into a different SQL table for my use. I would like to drop the FoxPro portion and have the SQL query saperate the data for me. Below is a sample of what the data looks like. Store Amount Discount 1 5.95 1 5.95 PO^-479^2 1 5.95 PO^-479^2 2 5.95 2 5.95 PO^-479^2 2 5.95 +CA8A09^-240^4,CORDRC^-239^7 3 5.95 3 5.95 +CA8A09^-240^4,CORDRC^-239^7 3 5.95 +CA8A09^-240^4,CORDRC^-239^7 In the data above I want to sum the data in the amount field to get a gross amount. Then pull out the specific discount amount which is located between the carat characters and sum it to get the total discount amount. Then add the two together and get the total net amount. The query I want to write will separate the discount field as needed, see store 2 line 3 for two discounts being applied, then pull out the value between carat characters.

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MySQL Data Truncation: Out of range value in Performance test

- by Khaledez

on a test for Java-MySQL-Restlet application, I write to database at 4reqs/second for 120 seconds. In this write I insert a row that has foreign key which has the same value for all rows, and this exception occurs: Could not recover transaction. Original exception follows. com.mysql.jdbc.MysqlDataTruncation: Data truncation: Out of range value for column 'idPxxx' at row 1 Only 5% of requests fails to this exceptions, others works. Regards

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checking is username exists on two tables PHP PDO?

- by PHPLOVER

Me again. I have a users table and a users_banlist table. On my registration form i want to check all in one query whether the username someone entered on form exists in the users table and see if it also exists on the users_banlist table. I can do them on there own in individual queries but would rather do it all in one. Here is what i got, but even thou i enter a username that is taken it does not tell me its already taken. $stmt = $dbh->prepare(" SELECT users.user_login, users_banlist.user_banlist FROM users , users_banlist WHERE users.user_login = ? OR users_banlist.user_banlist = ?"); // checker if username exists in users table or users_banlist table $stmt->execute(array($username, $username)); if ( $stmt->rowCount() > 0 ) { $error[] = 'Username already taken'; } Basically i think it is something to do with the execute or rowCount(), could anyone tell me where i am going wrong ? being new to pdo im finding it a little confusing at the moment until i get my pdo book delivered to learn pdo. Thank you as always, phplover

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Performance implications of using a variable versus a magic number

- by Nathan

I'm often confused by this. I've always been taught to name numbers I use often using variables or constants, but if it reduces the efficiency of the program, should I still do it? Heres an example: private int CenterText(Font font, PrintPageEventArgs e, string text) { int recieptCenter = 125; int stringLength = Convert.ToInt32(e.Graphics.MeasureString(text, font)); return recieptCenter - stringLength / 2; } The above code is using named variables, but runs slower then this code: private int CenterText(Font font, PrintPageEventArgs e, string text) { return 125 - Convert.ToInt32(e.Graphics.MeasureString(text, font) / 2); } In this example, the difference in execution time is minimal, but what about in larger blocks of code?

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need a library to get performance counters data under Win CE, c++ code

- by Oleg Ivanov

Under WindowsCE, C++ project, I'd like to get CPU utilization and memory allocation data real time - for logging and troubleshooting. Is there a library or activeX available that i could include in my code and use [without bringing my process to a halt, preferably], anyone knows? thanks much for any insight! O.

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Multiple/nested "select where" with Zend_Db_Select

- by DJRayon

Hi there I need to create something like this: select name from table where active = 1 AND (name LIKE 'bla' OR description LIKE 'bla') The first part is easy: $sqlcmd = $db->select() ->from("table", "name") ->where("active = ?", 1) Now comes the tricky part. How can I nest? I know that I can just write ->orWhere("name LIKE ? OR description LIKE ?", "bla") But thats wron, because I need to dynamically change all the parts. The query will be built all the time the script runs. Some parts get deleted, some altered. In this example I need to add those OR-s because sometimes I need to search wider. "My Zend Logic" tells me that the correct way is like this: $sqlcmd = $db->select() ->from("table", "name") ->where("active = ?", 1) ->where(array( $db->select->where("name LIKE ?", "bla"), $db->select->orWhere("description LIKE ?", "bla") )) But that doesn't work (atleast I dont remember it working). Please. Can someone help me to find a object oriented way for nesting "where"-s

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Why Swift is 100 times slower than C in this image processing test?

- by xiaobai

Like many other developers I have been very excited at the new Swift language from Apple. Apple has boasted its speed is faster than Objective C and can be used to write operating system. And from what I learned so far, it's a very type-safe language and able to have precisely control over the exact data type (like integer length). So it does look like having good potential handling performance critical tasks, like image processing, right? That's what I thought before I carried out a quick test. The result really surprised me. Here is a much simplified image alpha blending code snippet in C: test.c: #include <stdio.h> #include <stdint.h> #include <string.h> uint8_t pixels[640*480]; uint8_t alpha[640*480]; uint8_t blended[640*480]; void blend(uint8_t* px, uint8_t* al, uint8_t* result, int size) { for(int i=0; i<size; i++) { result[i] = (uint8_t)(((uint16_t)px[i]) *al[i] /255); } } int main(void) { memset(pixels, 128, 640*480); memset(alpha, 128, 640*480); memset(blended, 255, 640*480); // Test 10 frames for(int i=0; i<10; i++) { blend(pixels, alpha, blended, 640*480); } return 0; } I compiled it on my Macbook Air 2011 with the following command: gcc -O3 test.c -o test The 10 frame processing time is about 0.01s. In other words, it takes the C code 1ms to process one frame: $ time ./test real 0m0.010s user 0m0.006s sys 0m0.003s Then I have a Swift version of the same code: test.swift: let pixels = UInt8[](count: 640*480, repeatedValue: 128) let alpha = UInt8[](count: 640*480, repeatedValue: 128) let blended = UInt8[](count: 640*480, repeatedValue: 255) func blend(px: UInt8[], al: UInt8[], result: UInt8[], size: Int) { for(var i=0; i<size; i++) { var b = (UInt16)(px[i]) * (UInt16)(al[i]) result[i] = (UInt8)(b/255) } } for i in 0..10 { blend(pixels, alpha, blended, 640*480) } The build command line is: xcrun swift -O3 test.swift -o test Here I use the same O3 level optimization flag to make the comparison hopefully fair. However, the resulting speed is 100 time slower: $ time ./test real 0m1.172s user 0m1.146s sys 0m0.006s In other words, it takes Swift ~120ms to processing one frame which takes C just 1 ms. I also verified the memory initialization time in both test code are very small compared to the blend processing function time. What happened?

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Image creation performance / image caching

- by Kilnr

Hello, I'm writing an application that has a scrollable image (used to display a map). The map background consists of several tiles (premade from a big JPG file), that I draw on a Graphics object. I also use a cache (Hashtable), to prevent from having to create every image when I need it. I don't keep everything in memory, because that would be too much. The problem is that when I'm scrolling through the map, and I need an image that wasn't cached, it takes about 60-80 ms to create it. Depending on screen resolution, tile size and scroll direction, this can occur multiple times in one scroll operation (for different tiles). In my case, it often happens that this needs to be done 4 times, which introduces a delay of more than 300 ms, which is extremely noticeable. The easiest thing for me would be that there's some way to speed up the creation of Images, but I guess that's just wishful thinking... Besides that, I suppose the most obvious thing to do is to load the tiles predictively (e.g. when scrolling to the right, precache the tiles to the right), but then I'm faced with the rather difficult task of thinking up a halfway decent algorithm for this. My actual question then is: how can I best do this predictive loading? Maybe I could offload the creation of images to a separate thread? Other things to consider? Thanks in advance.

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High performance distributed asynchronous RPC in java

- by unludo

I would like to do RPC to a list of clients with the following requirements: the server does not know the clients (implies a kind of broker?) and the cleints do not know the server there may be several clients - they share the load to treat the RPC The RPC is asynchronous very fast (round-trip < 1ms) optional : offers a fail-over mechanism. It can be done with underlying tools which are not really intended for that (Hazelcast is an example). What would you use for such requirements? Thanks!

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JQuery performance issue (Or just bad CODING!)

- by ferronrsmith

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Cannot locate record in delphi ADO query

- by Danatela

I can't locate any record in TADOQuery using PK. First, I was trying to use standard Locate method: PPUQuery.Locate('ID', SpPlansQuery['PPONREC'], []); It always returns False, but manual search (passing the whole query matching ID with given PPONREC which is really slow) finds the desired row. I tried using loPartialKey and switched CursorLocation of query to clUseServer, but it didn't help. Next, I tried to filter my PPUQuery: PPUQuery.Filter := 'ID = ' + VarToStr(SpPlansQuery['PPONREC']); PPUQuery.Filtered := True; PPUQuery.First; But after that the PPUQuery.Eof is True and PPUQuery.RecordCount equals 0. Underlying database is Oracle 9 and the ID is of type INTEGER and is PK of table TPORDER_CMK. PPUQuery.SQL is: SELECT tp.*, la.*, lm.*, ld.*, ld1.*, to_cmk.* FROM ppu_plan.tporder_cmk tp JOIN PPU_PLAN.LARTICLES la ON TP.ARTICLE = LA.ID JOIN PPU_PLAN.LMATERIAL lm ON TP.MATERIAL = lm.id JOIN PPU_PLAN.LCADEP ld ON TP.CADEP = LD.ID JOIN PPU_PLAN.LCADEP ld1 ON TP.PRODUCER = LD1.ID JOIN PPU_PLAN.TORDER_CMK to_cmk ON TP.order_id=TO_cmk.ID WHERE TP.PLAN_ID = :pplan_id What should I try next and how to solve this problem?

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XPath Query - Select relative top level nodes

- by John

I'm trying to iterate over some elements in an XML document that may be nested, but as I iterate over them I may be removing some from the tree. I'm thinking the best way is to do this recursively, so I'm trying to come up with an XPath Query that will select all the top-level nodes relative to the current node. //foo[not(ancestor::foo)] works great at the document level, but I'm trying to figure out how to do this from a relative query. <foo id="1"> <foo id="2" /> <foo id="3"> <foo id="4"> <bar> <foo id="5"> <foo id="6" /> </foo> <foo id="7" /> </bar> </foo> </foo> </foo> If the current node is foo#3, I only want to select foo#4. When the current node is foo#4, I only want to select foo#5 and foo#7. I think I'm trying to select any descendant foo nodes of the current node, but without any ancestor foo nodes between the current node and the node I'm selecting. My conundrum is if we're already inside a foo node, not(ancestor::foo) doesn't help.

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