How many is too many columns in a composite index

hi all, (using 10g r2)
i do realize that there is not an exact right answer, but im more curious to find out how others have handled this situation, for better or for worse...
i know the literal upper bound on the number of columns that can be part of a composite index but i was wondering if any of you had come up with what you feel to be practical or upper bounds on the number of columns in a composite index? Also, can anyone share info on what might be strategy to figure out at what point the number of columns in the index creates a situation where updating/maintaining the index outweighs any performance gain you get from the composite index? Thanks in advance! -- jp

user12241698 wrote:
i was wondering if any of you had come up with what you feel to be practical or upper bounds on the number of columns in a composite >index? Also, can anyone share info on what might be strategy to figure out at what point the number of columns in the index creates a >situation where updating/maintaining the index outweighs any performance gain you get from the composite index? sb92075 pointed out the practical limit can only be obtained by testing. This is situational - like everything else, it "depends".
Testing can be done by timing the results of the index variations you want to check. Time multiple uses of the index for DML and query operations involving the index. I like to track the numbers in seconds and put the values in spreadsheets for later reference and easy summation; you can put the data in tables to and use SQL for analysis if you want. I use dbms_utiltiy.get_time in pl/sql (get first time before run, get second time after run, time in fractiions of a second is second time minus first time) or set timing on in sql*plus (hour-minute-second) to obtain run times.
Efficiency depends on what the compsite index is for. Are you trying to enforce uniqueness? Use the composite for data retrieval? Adding exra columns to avoid table access?
Due to maintenance considerations indexes should not have more columns than needed. "duplicate" indexes with the same columns (like "id" vs "id, name") are usually redundant and one index (the one with the fewer columns) can usually be removed.

Similar Messages

  • How to Handle Too Many js Files?

    I making a website and i want to know how to handle too many js in one page.
    And i want to add news ticker but js is conflict with someone
    <script src="js/ticker/1.8.jquery.min.js"></script>
    <script src="js/ticker/all.js"></script>
    <script src="js/ticker/jquery.li-scroller.1.0.js"></script>
    <script src="js/jquery.slicknav.js"></script>
    <script type="text/javascript" src="js/modernizr.custom.js"></script>
    <script type='text/javascript' src='js/scrollIt.min.js'></script>
    <script type="text/javascript" src="js/jquery.simple-text-rotator.js"></script>
    <script type="text/javascript" src="js/jquery.nicescroll.min.js"></script>
    <script type="text/javascript" src="js/jquery.appear.js"></script>
    <script type="text/javascript" src="js/jquery.bxslider.min.js"></script>
    <script type="text/javascript" src="js/jquery.fitvids.js"></script>
    <script type="text/javascript" src="js/owl.carousel.min.js"></script>
    <script type="text/javascript" src="js/jquery.colorbox.js"></script>
    <script type="text/javascript" src="js/jquery.parallax-1.1.3.js"></script>
    <script type="text/javascript" src="js/jquery.localscroll-1.2.7-min.js"></script>
    <script type="text/javascript" src="js/jquery.scrollTo-1.4.2-min.js"></script>
    <script type="text/javascript" src="js/classie.js"></script>
    <script type="text/javascript" src="js/cbpAnimatedHeader.min.js"></script>
    <script type="text/javascript" src="js/template.js"></script>

    I trying ti use your code but that's not working,
    i want to add one news ticker but that's not work
    <script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"></script>
    <script type="text/javascript" src="js/jquery.js"></script>
    <script type='text/javascript' src='js/scrollIt.min.js'></script>
    <script type="text/javascript" src="js/jquery.simple-text-rotator.js"></script>
    <script type="text/javascript" src="js/jquery.nicescroll.min.js"></script>
    <script type="text/javascript" src="js/jquery.appear.js"></script>
    <script type="text/javascript" src="js/jquery.fitvids.js"></script>
    <script type="text/javascript" src="js/owl.carousel.min.js"></script>
    <script type="text/javascript" src="js/template.js"></script>

  • How much is too many?

    Have an iPad 16gb.
    Curious - At what point and how many Apps does it take for the device to be affected and slow down?

    Ask 300 people, get 300 answers .....
    I rarely have more than 4 or 5 apps in my recents tray at any one time. But you can bet your bottom dollar that my browser - and it doesn't matter which of the five that I have I am using at the time - will crash on me every day - day after day - 3 or 4 times a day. I seem to have particularly bad luck with the iPad internet experience. When I use the Mercury browser - and it has done this since day one - I constantly get the low memory warning - even if I have closed all apps and have just restarted the iPad.
    That's kind of a bummer for me because my iPad has become more of an mobile internet toy and email reader than a work machine. That's OK - I had no problem spending the money and taking the chance to see what I would get out of it because I wasn't quite sure what I would be using it for but I knew I really wanted one.
    There really is a point to this and it is that no one has any way of knowing for certain how many is too many. As I have told you - I can run one solitary app and crash with great frequency. It's just something that only you can find out on your own as you continue to use the device.

  • How much can too many imports slow inititialization down?

    How much can too many imports slow applet inititialization down?
    I have seen our company's sorce code for some huge applets they have written. In many, many cases, the imports at the beginning of each file are written something like this...
    import java.awt.*;
    import java.awt.event.*;
    import java.util.*;
    import javax.swing.*;
    import javax.swing.border.*; 
    import javax.swing.event.*;Only certain portion of these imports are actually used. Does this sort of thing really impact the applets loading speed? I know it will obviously take at least a little longer but will the user even notice?

    You are not actually importing the classes, but rather making the names of the classes available.

  • How to fix: Too many Primary Partitions ? G770

    Hello,
    I am trying to install PuppyLinuxSlacko.5.4 from a LiveUsb to a unallocated-Partition in my Lenovo-G770 Laptop, Win7 . 
    My G770 shows that I have two disks: C:\  and  D:\ .
    But the Using (Linux) GParted program shows there are 4-Primary Partitions already (see pic GParted01.png below) . 
    http://www.vmars316.com/ShowMe/GParted01.png
    And when I try to Format the Unallocated Partition, I get an Error Msg (GParted02.png below) .  
    http://www.vmars316.com/ShowMe/GParted02.png 
    Pls, How to fix: Too many Primary Partitions ? 
    Thanks...vmars316...Vernon

    * Questions added to original Post: 
    I am trying to install PuppyLinuxSlacko.5.4 from a LiveUsb to an unallocated-Partition in my Lenovo-G770 Laptop, Win7 .
    My G770 shows that I have two disks: C:\ and D:\ .
    But the Using (Linux) GParted program shows there are 4-Primary Partitions already (see pic GParted01.png below) .
    http://www.vmars316.com/ShowMe/GParted01.png
    And when I try to Format the Unallocated Partition, I get an Error Msg (GParted02.png below) .
    http://www.vmars316.com/ShowMe/GParted02.png
    Pls, How to fix: Too many Primary Partitions ?
    I've been told that to try and fix it in Linux is too risky .
    I set up the unallocated 20gb partition.
    Can I just merge it into the 29gb Extended Partition ?
    If I did merge, How would I access it ? Which Partition is it an extension of ?
    I am on thin ice here, and would rather fix the prob in Window7 , because I am brand new to Linux .
    Here is the PartitionsDetail using AomeiPartitionAssistant -note the differences:
    http://www.vmars316.com/ShowMe/AoemiPartitionWindows.png
    Is there a way to tell what's in the partitions , especially the two 29gb partitions and the 14gb partition ?
    Worst case: Is there a way to reset my 'Lenovo G770' computer back to factory settings under win7 ? 
    I think I'll add this Post to the Win7 Forum, since I hope to fix it via Win7 .
    Thanks...vmars316...Vernon

  • Airport Express--How many is too many?

    I am running a new Airport Extreme base station with 3 Airport Express units to extend the range over about a 6200 sq ft house. My wife set up her office at the far extreme from the base station and, although her signal was somewhat intermittent, it worked well enough to allow her to connect to the internet with adequate functionality (although her signal strength was generally at or below 5 Mbps). After I successfully installed a 4th Express using Airport Utility, and located it in her office, her PC connectivity to the network suffered, and a printer connected to the Express in her office was not recognized on the network and wouldn't print. Do I have too many Expresses on the base station such that the signal is degrading performance for the whole network? Thanks.

    If using the "Extend" option instead of a WDS with all the stations being of band type "n", is there a limit to how many Express "n" I can use to extend an Extreme "n".
    I currently have one Express "n" extending (not WDS) my Extreme "n", and I would like to add one more. Is there a limit to how many can be used to extend the wireless network wirelessly?
    Thanks,
    Frank

  • How to resolve "too many HTTP redirects"?

    Hi, anyone who knows how to solve the error every time I open the App store in my iPad? It says "too many HTTP redirects". Thanks.

    There have been many discussions about this - some of which are listed in the box on the right >>>>> More Like This. Take a look at some of those.
    Some users restored from backups, reset all settings and there were a couple of other fixes that worked. Just take a look at those. When you open some of the those discussions you will see additional discussions in the More Like This boxes in those threads.

  • How many is too many pictures on iphoto

    will having a couple thousand pictures on iphoto slow down my macbook pro? It seems to run slow getting pictures to come up and even on other safari web pages?

    I would consider an external drive to store your photos at this point, you are getting up there. It will free up space on your internal drive, then you get to have another go-round:)
    By the way my wife killed 2 MBP's by ot clearing her drive of too many photos.
    Drives are cheap, but some photos are priceless.
    Just my thoughts;)

  • Conditional Build Tags - How Many is Too Many?

    Has anyone ever run into problems generating a project because of too many conditional build tags? I'm new to this and considering using quite a few in a particular project - unless I find that overuse will compromise the project on the backend. I'd really like to find that out before I put the work in. Thanks!

    Hi there
    From the simple standpoint of ease of use, I'd say you want to limit the number to as few as you can.
    Can you tell us more about why you are using them? I ask because later versions of RoboHelp offer things that help us out in this area. You may well discover you don't need build tags at all. But we will reserve that judgment until after we know more.
    What version of RoboHelp are you using? What RoboFlavor?
    You may wish to give the link below a once over.
    Click here to view
    Cheers... Rick
    Helpful and Handy Links
    RoboHelp Wish Form/Bug Reporting Form
    Begin learning RoboHelp HTML 7, 8 or 9 within the day!
    Adobe Certified RoboHelp HTML Training
    SorcerStone Blog
    RoboHelp eBooks

  • I get a "Too many recipients" Thunderbird error msg when trying to send a group email -- how many is too many ? does Thunderbird have a limit?

    My ISP says it doesn't impose a limit on the number of recipients in a group email, BUT still I get a Thunderbird error msg. Why?

    Well, no, because 4 or 5 times a year, someone writes in with pretty much exactly your question because they too have had a message refused with the "too many recipients" warning. We suggest they use a Mailing List and all is well.

  • How to handle too many custom UITableViewCells in UITableView?

    In my iphone app, I need to display many custom rows (maybe thousands or even more) in the UITableView. I add one custom UIView onto each UITableViewCell in "- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath" function, so there will be allocate much memory for the all my custom UIViews. When I add 500 rows into the UITableView, the memory ran out, then the app crashed. I think maybe there is something wrong with my code or design, I don't know how to handle this (thousands custom rows in UITableView). Please help me.... Thanks very much..
    Below is the my code:(if I have thousands of rows, the following code will allocate thousands of CustomViews), is there any way that not allocate so many CustomViews?
    // Customize the appearance of table view cells.
    - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
    **cell = [[[UITableViewCell alloc] initWithFrame:CGRectMake(0, 0, 110, 25) reuseIdentifier:CellIdentifier] autorelease] ;
    // Set up the cell...
    CustomView *cellView = [[CustomView alloc]initWithFrame:CGRectMake(1, 1, 108, 24)];
    [cell addSubview: cellView];
    [cellView release];
    return cell;
    }

    Hi,
    well you should add the customView if you need to create a new cell only. Any reused cell will contain this customview allready since you've added it when the cell was created.
    static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
    cell = [[UITableViewCell alloc] initWithFrame:CGRectMake(0, 0, 110, 25) reuseIdentifier:CellIdentifier] autorelease];
    // Add customView to new cell's only
    CustomView *cellView = [CustomView alloc] initWithFrame:CGRectMake(1, 1, 108, 24)];
    [cell addSubview: cellView];
    [cellView release];
    // Set up the cell...
    return cell;

  • How to handle too many songs for disk space?

    I have a limited collection of fongs on my primary hard drive; most of my collection - about 500GB - is kept on network attached storage. When I install iTunes it copies the music files in My Music to its iTunes Media folder. That's OK for the limited size of My Music - I have enough room on the primary hard drive for the copies. But there is no way I can store a copy of all the files on the NAS. So how do I 'catalog' those files, as well as those on my primary hard drive?

    OK, I follow this - except that I read elsewhere (in this forum if memory serves me correctly) that one reason to use the option to copy media to iTunes was so that iTunes would not create duplicate entries - which it seems very fond of doing, no matter how many times I delete them.
    If this is not the purpose of the Media folder, then what purpose does it have?
    Assuming that I elect to stop this copying, what is the recommended way of removing all the files in the media folder: blunt force with Windows Explorer, or is there an implicit/explicit command somewhere in iTunes that I haven't understood?
    And is iTunes limited to just the 1 location for 'sources' of music - or is that what the 'add folder to Library' is meant to do?

  • AI CS5 Font handling, how many are too many fonts.  I have 14000 fonts

    Since I installed a font pack that I purchased, Adobe is sluggish...opening, saving files, closing files...getting a lot of "not responding" and then it returns to working condition.  I can select text, right click, but clicking Fonts does nothing.  Is there a setting I can change or am I stuck having to unistall fonts.

    I like to have lots of choices.
    So do I. But I still don't like having to plunder through every piece of fabric in the house in order to find a matching pair of socks. I also can never seem to have enough motorcycle tools, but I sure don't throw them all into a single tool bag, either.
    Anyone who likes to collect a ridiculous number of fonts (as do I) should organize them so it doesn't take three forevers to find a suitable one. Regardless of performance, you should be using a font manager that lets you organize them into stylistic groups, and/or groups for particluar projects.
    I've been using Bitstream Font Navigator (comes bundled with Corel Draw) on Windows for many years without much trouble. I do sometimes find it more reliable to quit and restart Illustrator when using BFN, but it's usually not necessary.
    JET

  • HT1918 im new to the iphone charges, how can i stop my credit card from been billed so many times. too many charges for updates and down loading apps

    why so many charges on the apple I phone? I'm I been charge for updates each time there comes up an update or what is really been charged for?

    Welcome to the Apple Community.
    Select the content which is causing a problem and use the 'Report a problem' button in Your Purchase History on your computer.

  • Kernel Panic's:  How many is too many?

    I have had everything replaced in my MBP over the past 6 months. There is nothing inside that came with the computer. My last trip to the Genius Bar was in July where the memory was replaced. I was told that the next problem would get me a replacement MBP.
    I have had 4 kernel panics with the grey screen telling me to restart my computer. Don't know if that is excessive or not.
    I have no clue how to read the logs so I don't have a clue what is causing them. They all seem to occur when I have Firefox open or opening.
    Any assistance is appreciated. Thanks much.

    Well, I took my MBP back to the Apple Store due to the Kernel Panics. The previous visit they had replaced the RAM and told me if any further issues they would replace the machine. So, two weeks later I now have my second replacement machine. The first one lasted 12 months, the second one also 12 months. Now I have the really nice new MBP 15" with Snow Leopard and all the bells and whistles.
    Hope this one lasts more than 12 months. All have been within warranty and replaced with no questions. I did purchase Applecare which I would HIGHLY recommend to all, especially if you have a notebook computer.

Maybe you are looking for