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  • Developing Schema Compare for Oracle (Part 6): 9i Query Performance

    - by Simon Cooper
    All throughout the EAP and beta versions of Schema Compare for Oracle, our main request was support for Oracle 9i. After releasing version 1.0 with support for 10g and 11g, our next step was then to get version 1.1 of SCfO out with support for 9i. However, there were some significant problems that we had to overcome first. This post will concentrate on query execution time. When we first tested SCfO on a 9i server, after accounting for various changes to the data dictionary, we found that database registration was taking a long time. And I mean a looooooong time. The same database that on 10g or 11g would take a couple of minutes to register would be taking upwards of 30 mins on 9i. Obviously, this is not ideal, so a poke around the query execution plans was required. As an example, let's take the table population query - the one that reads ALL_TABLES and joins it with a few other dictionary views to get us back our list of tables. On 10g, this query takes 5.6 seconds. On 9i, it takes 89.47 seconds. The difference in execution plan is even more dramatic - here's the (edited) execution plan on 10g: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 108K| 939 || 1 | SORT ORDER BY | | 108K| 939 || 2 | NESTED LOOPS OUTER | | 108K| 938 ||* 3 | HASH JOIN RIGHT OUTER | | 103K| 762 || 4 | VIEW | ALL_EXTERNAL_LOCATIONS | 2058 | 3 ||* 20 | HASH JOIN RIGHT OUTER | | 73472 | 759 || 21 | VIEW | ALL_EXTERNAL_TABLES | 2097 | 3 ||* 34 | HASH JOIN RIGHT OUTER | | 39920 | 755 || 35 | VIEW | ALL_MVIEWS | 51 | 7 || 58 | NESTED LOOPS OUTER | | 39104 | 748 || 59 | VIEW | ALL_TABLES | 6704 | 668 || 89 | VIEW PUSHED PREDICATE | ALL_TAB_COMMENTS | 2025 | 5 || 106 | VIEW | ALL_PART_TABLES | 277 | 11 |------------------------------------------------------------------------------- And the same query on 9i: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 16P| 55G|| 1 | SORT ORDER BY | | 16P| 55G|| 2 | NESTED LOOPS OUTER | | 16P| 862M|| 3 | NESTED LOOPS OUTER | | 5251G| 992K|| 4 | NESTED LOOPS OUTER | | 4243M| 2578 || 5 | NESTED LOOPS OUTER | | 2669K| 1440 ||* 6 | HASH JOIN OUTER | | 398K| 302 || 7 | VIEW | ALL_TABLES | 342K| 276 || 29 | VIEW | ALL_MVIEWS | 51 | 20 ||* 50 | VIEW PUSHED PREDICATE | ALL_TAB_COMMENTS | 2043 | ||* 66 | VIEW PUSHED PREDICATE | ALL_EXTERNAL_TABLES | 1777K| ||* 80 | VIEW PUSHED PREDICATE | ALL_EXTERNAL_LOCATIONS | 1744K| ||* 96 | VIEW | ALL_PART_TABLES | 852K| |------------------------------------------------------------------------------- Have a look at the cost column. 10g's overall query cost is 939, and 9i is 55,000,000,000 (or more precisely, 55,496,472,769). It's also having to process far more data. What on earth could be causing this huge difference in query cost? After trawling through the '10g New Features' documentation, we found item 1.9.2.21. Before 10g, Oracle advised that you do not collect statistics on data dictionary objects. From 10g, it advised that you do collect statistics on the data dictionary; for our queries, Oracle therefore knows what sort of data is in the dictionary tables, and so can generate an efficient execution plan. On 9i, no statistics are present on the system tables, so Oracle has to use the Rule Based Optimizer, which turns most LEFT JOINs into nested loops. If we force 9i to use hash joins, like 10g, we get a much better plan: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 7587K| 3704 || 1 | SORT ORDER BY | | 7587K| 3704 ||* 2 | HASH JOIN OUTER | | 7587K| 822 ||* 3 | HASH JOIN OUTER | | 5262K| 616 ||* 4 | HASH JOIN OUTER | | 2980K| 465 ||* 5 | HASH JOIN OUTER | | 710K| 432 ||* 6 | HASH JOIN OUTER | | 398K| 302 || 7 | VIEW | ALL_TABLES | 342K| 276 || 29 | VIEW | ALL_MVIEWS | 51 | 20 || 50 | VIEW | ALL_PART_TABLES | 852K| 104 || 78 | VIEW | ALL_TAB_COMMENTS | 2043 | 14 || 93 | VIEW | ALL_EXTERNAL_LOCATIONS | 1744K| 31 || 106 | VIEW | ALL_EXTERNAL_TABLES | 1777K| 28 |------------------------------------------------------------------------------- That's much more like it. This drops the execution time down to 24 seconds. Not as good as 10g, but still an improvement. There are still several problems with this, however. 10g introduced a new join method - a right outer hash join (used in the first execution plan). The 9i query optimizer doesn't have this option available, so forcing a hash join means it has to hash the ALL_TABLES table, and furthermore re-hash it for every hash join in the execution plan; this could be thousands and thousands of rows. And although forcing hash joins somewhat alleviates this problem on our test systems, there's no guarantee that this will improve the execution time on customers' systems; it may even increase the time it takes (say, if all their tables are partitioned, or they've got a lot of materialized views). Ideally, we would want a solution that provides a speedup whatever the input. To try and get some ideas, we asked some oracle performance specialists to see if they had any ideas or tips. Their recommendation was to add a hidden hook into the product that allowed users to specify their own query hints, or even rewrite the queries entirely. However, we would prefer not to take that approach; as well as a lot of new infrastructure & a rewrite of the population code, it would have meant that any users of 9i would have to spend some time optimizing it to get it working on their system before they could use the product. Another approach was needed. All our population queries have a very specific pattern - a base table provides most of the information we need (ALL_TABLES for tables, or ALL_TAB_COLS for columns) and we do a left join to extra subsidiary tables that fill in gaps (for instance, ALL_PART_TABLES for partition information). All the left joins use the same set of columns to join on (typically the object owner & name), so we could re-use the hash information for each join, rather than re-hashing the same columns for every join. To allow us to do this, along with various other performance improvements that could be done for the specific query pattern we were using, we read all the tables individually and do a hash join on the client. Fortunately, this 'pure' algorithmic problem is the kind that can be very well optimized for expected real-world situations; as well as storing row data we're not using in the hash key on disk, we use very specific memory-efficient data structures to store all the information we need. This allows us to achieve a database population time that is as fast as on 10g, and even (in some situations) slightly faster, and a memory overhead of roughly 150 bytes per row of data in the result set (for schemas with 10,000 tables in that means an extra 1.4MB memory being used during population). Next: fun with the 9i dictionary views.

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  • Insert a Row with a sorted DataGridView

    - by Ruben Trancoso
    My DataGridView is bound to the same BindingSource as the Insert Form, and the Name column is sorted. After insert is done, the groupBindingSource.Current is not returning the new inserted DataRowView but the last row in the sort order what makes the Update do nothing. FormGroup formGroup = new FormGroup(); formGroup .Source = groupBindingSource; formGroup .setMode(FormGroup.Mode.Insert); if (formGroup .ShowDialog() == DialogResult.OK) { DataRowView drv = (DataRowView)groupBindingSource.Current; grupoTableAdapter.Update(drv.Row); }

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  • Sorted directory size display in Unix

    - by Srikanth M
    How do i display directory sizes in a sorted manner in Unix while listing only innermost sub-directories? For example, I don't want to something like this - 100270480 /a/b/BP/b/bat/qc3 100270416 /a/b/BP/b/bat/qc3/logs 99020464 /a/b/BP/b/bat/qc3/logs/i 99005456 /a/b/BP/b/bat/qc5 99005408 /a/b/BP/b/bat/qc5/logs 97726832 /a/b/BP/b/bat/qc5/logs/i I just want - 99020464 /a/b/BP/b/bat/qc3/logs/i 97726832 /a/b/BP/b/bat/qc5/logs/i

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  • Merging some sorted lists with unknown order sequence

    - by Gabriel
    I've some sorted lists with variable number of elements. I wold like to merge the lists into one big list which contains all other lists in same order, without duplicates. Example: 1. XS,M,L,XL 2. S,M,XXL 3. XXS,XS,S,L Result: XXS,XS,S,M,L,XL,XXL The function should notify, if there are elements which have ambiguous positions. Here, it would be XXL and I need to specify its position after XL.

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  • Binary search in rotated sorted list

    - by Algorist
    I am having a sorted list which is rotated and I would like to do a binary search on that list to find the minimum element. Lets suppose initial list is {1,2,3,4,5,6,7,8} rotated list can be like {5,6,7,8,1,2,3,4} Normal binary search doesn't work in this case. Any idea how to do this.

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  • Keeping DB Table sorted using multi-field formula (Microsoft SQL Server)

    - by user298167
    I have a JOB table, with two interesting columns: Creation Date Importance (high - 3, medium 2, low - 1). A JOB record's priority calculated like this: Priority = Importance * (time passed since creation) The problem is, every time I would like to pick 200 jobs with highest priority, and I don't want to resort the table. Is there a way to keep rows sorted? I was also thinking about having three tables one for High, Medium and Low and then sort those by Creation Date.

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  • data from few MySQL tables sorted by ASC

    - by Andrew
    In the dbase I 've few tables named as aaa_9xxx, aaa_9yyy, aaa_9zzz. I want to find all data with a specified DATE and show it with the TIME ASC. First, I must find a tables in the dbase: $STH_1a = $DBH->query("SELECT table_name FROM information_schema.tables WHERE table_name LIKE 'aaa\_9%' "); foreach($STH_1a as $row) { $table_name_s1[] = $row['table_name']; } Second, I must find a data wit a concrete date and show it with TIME ASC: foreach($table_name_s1 as $table_name_1) { $STH_1a2 = $DBH->query("SELECT * FROM `$table_name_1` WHERE date = '2011-11-11' ORDER BY time ASC "); while ($row = $STH_1a2->fetch(PDO::FETCH_ASSOC)) { echo " ".$table_name_1."-".$row['time']."-".$row['ei_name']." <br>"; } } .. but it shows the data sorted by tables name, then by TIME ASC. I must to have all this data (from all tables) sorted by TIME ASC. Thank You dev-null-dweller, Andrew Stubbs and Jaison Erick for your help. I test the Erick solution : foreach($STH_1a as $row) { $stmts[] = sprintf('SELECT * FROM %s WHERE date="%s"', $row['table_name'], '2011-11-11'); } $stmt = implode("\nUNION\n", $stmts); $stmt .= "\nORDER BY time ASC"; $STH_1a2 = $DBH->query($stmt); while ($row_1a2 = $STH_1a2->fetch(PDO::FETCH_ASSOC)) { echo " ".$row['table_name']."-".$row_1a2['time']."-".$row_1a2['ei_name']." <br>"; } it's working but I've problem with 'table_name' - it's always the LAST table name. //---------------------------------------------------------------------- end the ending solution with all fixes, thanks all for your help, :)) foreach($STH_1a as $row) { $stmts[] = sprintf("SELECT *, '%s' AS table_name FROM %s WHERE date='%s'", $row['table_name'], $row['table_name'], '2011-11- 11'); } $stmt = implode("\nUNION\n", $stmts); $stmt .= "\nORDER BY time ASC"; $STH_1a2 = $DBH->query($stmt); while ($row_1a2 = $STH_1a2->fetch(PDO::FETCH_ASSOC)) { echo " ".$row_1a2['table_name']."-".$row_1a2['time']."-".$row_1a2['ei_name']." <br>"; }

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  • How can I set view preferences to sorted by reverse date modified?

    - by Statwonk
    I'd like to permanently set Nautilus's view preferences to show files sorted in reverse by date modified (newest first). Similar questions have been asked before: How can I sort files in Nautilus by modified date? Can I view my files sorted by date? However, they don't address making the preference permanent. Nautilus's preferences allow you to set sort by date modified (oldest first), but not reverse date modified (newest first). Does anyone have suggestions on setting sorted by reverse date modified as default?

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  • Puppet&Hiera: $variable is not an hash or array when accessing it

    - by txworking
    I wrote a puppet module and the content of init.pp was: class install( $common_instanceconfig = hiera_hash('common_instanceconfig'), $common_instances = hiera('common_instances') ) { define instances { common { $title: name => $title, path => $common_instanceconfig[$title]['path'], version => $common_instanceconfig[$title]['version'], files => $common_instanceconfig[$title]['files'], pre => $common_instanceconfig[$title]['pre'], after => $common_instanceconfig[$title]['after'], properties => $common_instanceconfig[$title]['properties'], require => $common_instanceconfig[$title]['require'] , } } instances {$common_instances:} } And the hieradata file was: classes: - install common_instances: - common_instance_1 - common_instance_2 common_instanceconfig: common_instance_1 path : '/opt/common_instance_1' version : 1.0 files : software-1.bin pre : pre_install.sh after : after_install.sh properties: "properties" common_instance_2: path : '/opt/common_instance_2' version : 2.0 files : software-2.bin pre : pre_install.sh after : after_install.sh properties: "properties" I always got a error message When puppet agent run Error: common_instanceconfig String is not an hash or array when accessing it with common_instance_1 at /etc/puppet/modules/install/manifests/init.pp:16 on node puppet.agent1.tmp It seems $common_instances can be got correctly, but $commono_instanceconfig always be treated as a string. I used YAML.load_file to load the hieradata file, and got a correct hash object. Can anybody help?

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  • ASP.NET Membership C# - How to compare existing password/hash

    - by Steve
    I have been on this problem for a while. I need to compare a paasword that the user enters to a password that is in the membership DB. The password is hashed and has a salt. Because of the lack of documentation I do not know if the salt is append to the password and then hashed how how it is created. I am unable to get this to match. The hash returned from the function never matches the hash in the DB and I know for fact it is the same password. Microsoft seems to hash the password in a different way then I am. I hope someone has some insights please. Here is my code: protected void Button1_Click(object sender, EventArgs e) { //HERE IS THE PASSWORD I USE, SAME ONE IS HASHED IN THE DB string pwd = "Letmein44"; //HERE IS THE SALT FROM THE DB string saltVar = "SuY4cf8wJXJAVEr3xjz4Dg=="; //HERE IS THE PASSWORD THE WAY IT STORED IN THE DB AS HASH string bdPwd = "mPrDArrWt1+tybrjA0OZuEG1P5w="; // FOR COMPARISON I DISPLAY IT TextBox1.Text = bdPwd; // HERE IS WHERE I DISPLAY THE return from THE FUNCTION, IT SHOULD MATCH THE PASSWORD FROM THE DB. TextBox2.Text = getHashedPassUsingUserIdAsSalt(pwd, saltVar); } private string getHashedPassUsingUserIdAsSalt(string vPass, string vSalt) { string vSourceText = vPass + vSalt; System.Text.UnicodeEncoding vUe = new System.Text.UnicodeEncoding(); byte[] vSourceBytes = vUe.GetBytes(vSourceText); System.Security.Cryptography.SHA1CryptoServiceProvider vSHA = new System.Security.Cryptography.SHA1CryptoServiceProvider(); byte[] vHashBytes = vSHA.ComputeHash(vSourceBytes); return Convert.ToBase64String(vHashBytes); }

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  • Is this a safe/valid hash method implementation?

    - by Sean
    I have a set of classes to represent some objects loaded from a database. There are a couple variations of these objects, so I have a common base class and two subclasses to represent the differences. One of the key fields they have in common is an id field. Unfortunately, the id of an object is not unique across all variations, but within a single variation. What I mean is, a single object of type A could have an id between, say, 0 and 1,000,000. An object of type B could have an id between, 25,000 and 1,025,000. This means there's some overlap of id numbers. The objects are just variations of the same kind of thing, though, so I want to think of them as such in my code. (They were assigned ids from different sets for legacy reasons.) So I have classes like this: @class BaseClass @class TypeAClass : BaseClass @class TypeBClass : BaseClass BaseClass has a method (NSNumber *)objectId. However instances of TypeA and TypeB could have overlapping ids as discussed above, so when it comes to equality and putting these into sets, I cannot just use the id alone to check it. The unique key of these instances is, essentially, (class + objectId). So I figured that I could do this by making the following hash function on the BaseClass: -(NSUInteger)hash { return (NSUInteger)[self class] ^ [self.objectId hash]; } I also implemented isEqual like so: - (BOOL)isEqual:(id)object { return (self == object) || ([object class] == [self class] && [self.objectId isEqual:[object objectId]]); } This seems to be working, but I guess I'm just asking here to make sure I'm not overlooking something - especially with the generation of the hash by using the class pointer in that way. Is this safe or is there a better way to do this?

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  • .NET SortedDictionary But Sorted By Values

    - by Michael Covelli
    I need a data structure that acts like a SortedDictionary<int, double> but is sorted based on the values rather than the keys. I need it to take about 1-2 microseconds to add and remove items when we have about 3000 items in the dictionary. My first thought was simply to switch the keys and values in my code. This very nearly works. I can add and remove elements in about 1.2 microseconds in my testing by doing this. But the keys have to be unique in a SortedDictionary so that means that values in my inverse dictionary would have to be unique. And there are some cases where they may not be. Any ideas of something in the .NET libraries already that would work for me?

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  • php - sort the unsorted text file and rewrite to same text file in sorted order

    - by arrgggg
    Hi, I have a question. I am in process of learning how to read/write files, but having little trouble trying to do both at the same time in same php script. I have a text file with words like this, Richmond,Virginia Seattle,Washington Los Angeles,California Dallas,Texas Jacksonville,Florida I wrote a code to sort them in order and this will display in sort order by City. <?php $file = file("states.txt"); sort($file); for($i=0; $i<count($file); $i++) { $states = explode(",", $file[$i]); echo $states[0], $states[1],"<br />"; } ?> From this, how can I rewrite those sorted information back into the states.txt file? Thanks for your help.

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  • How to move an element in a sorted list and keep the CouchDb write "atomic"

    - by karlthorwald
    I have elements of a list in couchdb documents. Let's say these are 3 elements in 3 documents: { "id" : "783587346", "type" : "aList", "content" : "joey", "sort" : 100.0 } { "id" : "358734ff6", "type" : "aList", "content" : "jill", "sort" : 110.0 } { "id" : "abf587346", "type" : "aList", "content" : "jack", "sort" : 120.0 } A view retrieves all "aList" documents and displays them sorted by "sort". Now I want to move the elements, when I want to move "jack" to the middle, I could do this atomic in one write and change it's sort key to 105.0. The view now returns the documents in the new sort order. After a lot of sorting I could end up with sort keys like 50.99999 and 50.99998 after some years and in extreme situations run out of digits? What can you recommend, is there a better way to do this? I'd rather keep the elements in seperate documents. Different users might edit different elements in parallel (which also can get tricky). Maybe there is a much better way?

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  • sqL table is sorted by default

    - by Pramodtech
    I have simple SSIS package where I import data from flat file into sql table(MS sql 2005). File contains 70k rows and table has no primary key. Importing is sucessful but when I open sql table the order of rwos is different from the that of file. After observing closely I see that data in table is sorted by default by first column. Why this is happening? and how I can avoid default sort? Thanks.

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  • Make Map Key Sorted According To Insert Sequence

    - by Yan Cheng CHEOK
    Without help from additional container (like vector), is it possible that I can make map's key sorted same sequence as insertion sequence? #include <map> #include <iostream> using namespace std; int main() { map<const char*, int> m; m["c"] = 2; m["b"] = 2; m["a"] = 2; m["d"] = 2; for (map<const char*, int>::iterator begin = m.begin(); begin != m.end(); begin++) { // How can I get the loop sequence same as my insert sequence. // c, b, a, d std::cout << begin->first << std::endl; } getchar(); }

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  • An Efficient data structure for Sorted List

    - by holydiver
    I want to save my objects according to a key in the attributes of my object in a sorted fashion. Later on I'll access these objects sequentially from max key to min key. I'll do some search tasks as well. I consider to use either AVL tree or RB Tree. As far as i know they are nearly equivalent in theory(Both have O(logn)). But in practice which one might be better in performance in my situation. And is there a better alternative than those, considering that I'll mostly do insert and sequentially access to the ds.

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  • Need sorted dictionary designed to find values with keys less or greater than search value

    - by Captain Comic
    Hi I need to have objects sorted by price (decimal) value for fast access. I need to be able to find all objects with price more then A or less than B. I was thinkg about SortedList, but it does not provide a way to find ascending or descending enumerator starting from given key value (say give me all objects with price less than $120). Think of a system that accepts items for sell from users and stores them into that collection. Another users want to find items cheaper than $120. Basically what i need is tree-based collection and functionality to find node that is smaller\greater\equal to provided key. Please advice.

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  • Keeping DB Table sorted using multi-field formula (Microsoft SQL)

    - by user298167
    Hello Everybody. I have a Job Table which has two interesting columns: Creation Date and Importance (high - 3, medium 2, low - 1). Job's priority calculated like this: Priority = Importance * (time passed since creation). The problem is, Every time I would like to pick 200 jobs with highest priority, I dont want to resort the table. Is there a way to keep rows sorted? I was also thinking about having three tables one for High, Medium and Low and then sort those by Creation Date. Thanks

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