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  • Ridiculously Simple Erlang Question

    - by Aiden Bell
    Read (skimmed enough to get coding) through Erlang Programming and Programming Erlang. One question, which is as simple as it sounds: If you have a process Pid1 on machine m1 and a billion million messages are sent to Pid1, are messages handled in parallel by that process (I get the impression no) and is there any guarantee of order when processing messages? ie. Received in order sent? Coming from the whole C/Thread pools/Shared State background ... I want to get this concrete. I understand distributing an application, but want to ensure the 'raw bones' are what I expect before building processes and distributing workload. Also, am I right in thinking the whole world is currently flicking through Erlang texts ;)

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  • MySQL LEFT OUTER JOIN virtual table

    - by user1707323
    I am working on a pretty complicated query let me try to explain it to you. Here is the tables that I have in my MySQL database: students Table --- `students` --- student_id first_name last_name current_status status_change_date ------------ ------------ ----------- ---------------- -------------------- 1 John Doe Active NULL 2 Jane Doe Retread 2012-02-01 students_have_courses Table --- `students_have_courses` --- students_student_id courses_course_id s_date e_date int_date --------------------- ------------------- ---------- ---------- ----------- 1 1 2012-01-01 2012-01-04 2012-01-05 1 2 2012-01-05 NULL NULL 2 1 2012-01-10 2012-01-11 NULL students_have_optional_courses Table --- `students_have_optional_courses` --- students_student_id optional_courses_opcourse_id s_date e_date --------------------- ------------------------------ ---------- ---------- 1 1 2012-01-02 2012-01-03 1 1 2012-01-06 NULL 1 5 2012-01-07 NULL Here is my query so far SELECT `students_and_courses`.student_id, `students_and_courses`.first_name, `students_and_courses`.last_name, `students_and_courses`.courses_course_id, `students_and_courses`.s_date, `students_and_courses`.e_date, `students_and_courses`.int_date, `students_have_optional_courses`.optional_courses_opcourse_id, `students_have_optional_courses`.s_date, `students_have_optional_courses`.e_date FROM ( SELECT `c_s_a_s`.student_id, `c_s_a_s`.first_name, `c_s_a_s`.last_name, `c_s_a_s`.courses_course_id, `c_s_a_s`.s_date, `c_s_a_s`.e_date, `c_s_a_s`.int_date FROM ( SELECT `students`.student_id, `students`.first_name, `students`.last_name, `students_have_courses`.courses_course_id, `students_have_courses`.s_date, `students_have_courses`.e_date, `students_have_courses`.int_date FROM `students` LEFT OUTER JOIN `students_have_courses` ON ( `students_have_courses`.`students_student_id` = `students`.`student_id` AND (( `students_have_courses`.`s_date` >= `students`.`status_change_date` AND `students`.current_status = 'Retread' ) OR `students`.current_status = 'Active') ) WHERE `students`.current_status = 'Active' OR `students`.current_status = 'Retread' ) `c_s_a_s` ORDER BY `c_s_a_s`.`courses_course_id` DESC ) `students_and_courses` LEFT OUTER JOIN `students_have_optional_courses` ON ( `students_have_optional_courses`.students_student_id = `students_and_courses`.student_id AND `students_have_optional_courses`.s_date >= `students_and_courses`.s_date AND `students_have_optional_courses`.e_date IS NULL ) GROUP BY `students_and_courses`.student_id; What I want to be returned is the student_id, first_name, and last_name for all Active or Retread students and then LEFT JOIN the highest course_id, s_date, e_date, and int_date for the those students where the s_date is since the status_change_date if status is 'Retread'. Then LEFT JOIN the highest optional_courses_opcourse_id, s_date, and e_date from the students_have_optional_courses TABLE where the students_have_optional_courses.s_date is greater or equal to the students_have_courses.s_date and the students_have_optional_courses.e_date IS NULL Here is what is being returned: student_id first_name last_name courses_course_id s_date e_date int_date optional_courses_opcourse_id s_date_1 e_date_1 ------------ ------------ ----------- ------------------- ---------- ---------- ------------ ------------------------------ ---------- ---------- 1 John Doe 2 2012-01-05 NULL NULL 1 2012-01-06 NULL 2 Jane Doe NULL NULL NULL NULL NULL NULL NULL Here is what I want being returned: student_id first_name last_name courses_course_id s_date e_date int_date optional_courses_opcourse_id s_date_1 e_date_1 ------------ ------------ ----------- ------------------- ---------- ---------- ------------ ------------------------------ ---------- ---------- 1 John Doe 2 2012-01-05 NULL NULL 5 2012-01-07 NULL 2 Jane Doe NULL NULL NULL NULL NULL NULL NULL Everything is working except one thing, I cannot seem to get the highest students_have_optional_courses.optional_courses_opcourse_id no matter how I form the query Sorry, I just solved this myself after writing this all out I think it helped me think of the solution. Here is the solution query: SELECT `students_and_courses`.student_id, `students_and_courses`.first_name, `students_and_courses`.last_name, `students_and_courses`.courses_course_id, `students_and_courses`.s_date, `students_and_courses`.e_date, `students_and_courses`.int_date, `students_optional_courses`.optional_courses_opcourse_id, `students_optional_courses`.s_date, `students_optional_courses`.e_date FROM ( SELECT `c_s_a_s`.student_id, `c_s_a_s`.first_name, `c_s_a_s`.last_name, `c_s_a_s`.courses_course_id, `c_s_a_s`.s_date, `c_s_a_s`.e_date, `c_s_a_s`.int_date FROM ( SELECT `students`.student_id, `students`.first_name, `students`.last_name, `students_have_courses`.courses_course_id, `students_have_courses`.s_date, `students_have_courses`.e_date, `students_have_courses`.int_date FROM `students` LEFT OUTER JOIN `students_have_courses` ON ( `students_have_courses`.`students_student_id` = `students`.`student_id` AND (( `students_have_courses`.`s_date` >= `students`.`status_change_date` AND `students`.current_status = 'Retread' ) OR `students`.current_status = 'Active') ) WHERE `students`.current_status = 'Active' OR `students`.current_status = 'Retread' ) `c_s_a_s` ORDER BY `c_s_a_s`.`courses_course_id` DESC ) `students_and_courses` LEFT OUTER JOIN ( SELECT * FROM `students_have_optional_courses` ORDER BY `students_have_optional_courses`.optional_courses_opcourse_id DESC ) `students_optional_courses` ON ( `students_optional_courses`.students_student_id = `students_and_courses`.student_id AND `students_optional_courses`.s_date >= `students_and_courses`.s_date AND `students_optional_courses`.e_date IS NULL ) GROUP BY `students_and_courses`.student_id;

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  • populate object graph from database

    - by Rama
    Hi, I would like to know the best way to populate an object that has a collection of child objects and each child object may inturn have a collection of objects, from database without making multiple calls to the database to get child objects for each object. basically in hierarchical format something like for example a customer has orders and each order has order items. is it best to retrieve the data in xml format (SQL server 2005), or retrieve a dataset by joining the related tables together and then map that the data to the object? thanks in advance for your help.

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  • Grab triangles within a lower triangle

    - by Tyler Rinker
    I have the need to grab all the thee element triangles that make up the lower triangle of a symmetric matrix. I can not think of how to grab all these pieces in the order of far left column working down and then next column to the right and so on. I know that the numbe rof mini triangles inside of the lower triangle is: n = x(x - 1)/2 where: x = nrow(mats[[i]]) Here I've created three matrices with letters (it's easier for me to conceptualize this way) and the elements in the order I'm looking for: FUN <- function(n) { matrix(LETTERS[1:(n*n)], n) } mats <- lapply(3:5, FUN) So this is the output I'd like to get (I put it in code rather than output format) for each of the matrices created above: list(c("B", "C", "F")) list(c("B", "C", "G"), c("C", "D", "H"), c("G", "H", "L")) list(c("B", "C", "H"), c("C", "D", "I"), c("D", "E", "J"), c("H", "I", "N"), c("I", "J", "O"), c("N", "O", "T")) How can I do this task in the fastest manner possible while staying in base R? Not sure if this visual of what I'm after is helpful but it may be:

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  • Android Extend BaseExpandableListAdapter

    - by Robert Mills
    I am trying to extend the BaseExpandableListAdapter, however when once I view the list and I select one of the elements to expand, the order of the list gets reversed. For example, if I have a list with 4 elements and select the 1st element, the order (from top to bottom) is now 4, 3, 2, 1 with the 4th element (now at the top) expanded. If I unexpand the 4th element the order reverts to 1, 2, 3, 4 with no expanded elements. Here is my implementation:`public class SensorExpandableAdapter extends BaseExpandableListAdapter { private static final int FILTER_POSITION = 0; private static final int FUNCTION_POSITION = 1; private static final int NUMBER_OF_CHILDREN = 2; ArrayList mParentGroups; private Context mContext; private LayoutInflater mInflater; public SensorExpandableAdapter(ArrayList<SensorType> parentGroup, Context context) { mParentGroups = parentGroup; mContext = context; mInflater = LayoutInflater.from(mContext); } @Override public Object getChild(int groupPosition, int childPosition) { // TODO Auto-generated method stub if(childPosition == FILTER_POSITION) return "filter"; else return "function"; } @Override public long getChildId(int groupPosition, int childPosition) { return childPosition; } @Override public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) { if(convertView == null) { //do something convertView = (RelativeLayout)mInflater.inflate(R.layout.sensor_row_list_item, parent, false); if(childPosition == FILTER_POSITION) { ((CheckBox)convertView.findViewById(R.id.chkTextAddFilter)).setText("Add Filter"); } else { ((CheckBox)convertView.findViewById(R.id.chkTextAddFilter)).setText("Add Function"); ((CheckBox)convertView.findViewById(R.id.chkTextAddFilter)).setEnabled(false); } } return convertView; } @Override public int getChildrenCount(int groupPosition) { // TODO Auto-generated method stub return NUMBER_OF_CHILDREN; } @Override public Object getGroup(int groupPosition) { return mParentGroups.get(groupPosition); } @Override public int getGroupCount() { // TODO Auto-generated method stub return mParentGroups.size(); } @Override public long getGroupId(int groupPosition) { // TODO Auto-generated method stub return groupPosition; } @Override public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) { if(convertView == null) { convertView = mInflater.inflate(android.R.layout.simple_expandable_list_item_1, parent, false); TextView tv = ((TextView)convertView.findViewById(android.R.id.text1)); tv.setText(mParentGroups.get(groupPosition).toString()); } return convertView; } @Override public boolean hasStableIds() { // TODO Auto-generated method stub return true; } @Override public boolean isChildSelectable(int groupPosition, int childPosition) { // TODO Auto-generated method stub return true; } } ` I just need to take a simple ArrayList of my own SensorType class. The children are the same for all classes, just two. Also, how do I go about making the parent in each group LongClickable? I have tried in my ExpandableListActivity with this getExpandableListView().setOnLongClickableListener() ... and on the parent TextView set its OnLongClickableListener but neither works. Any help on either of these is greatly appreciated!

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  • SQL query duration is longer for smaller dataset?

    - by entens
    I received reports that a my report generating application was not working. After my initial investigation, I found that the SQL transaction was timing out. I'm mystified as to why the query for a smaller selection of items would take so much longer to return results. Quick query (averages 4 seconds to return): SELECT * FROM Payroll WHERE LINEDATE >= '04-17-2010'AND LINEDATE <= '04-24-2010' ORDER BY 'EMPLYEE_NUM' ASC, 'OP_CODE' ASC, 'LINEDATE' ASC Long query (averages 1 minute 20 seconds to return): SELECT * FROM Payroll WHERE LINEDATE >= '04-18-2010'AND LINEDATE <= '04-24-2010' ORDER BY 'EMPLYEE_NUM' ASC, 'OP_CODE' ASC, 'LINEDATE' ASC I could simply increase the timeout on the SqlCommand, but it doesn't change the fact the query is taking longer than it should. Why would requesting a subset of the items take longer than the query that returns more data? How can I optimize this query?

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  • Java accessing variables using extends

    - by delo
    So here I have two classes: Customer Order Class and Confirmation Class. I want to access the data stored in LastNameTextField (Customer Order Class) and set it as the text for UserLastNameLabel (Confirmation Class) after clicking a "Submit" button. For some reason however, the output displays nothing. Snippet of my code: package customer_order; public class customer_order extends Frame{ private static final long serialVersionUID = 1L; private JPanel jPanel = null; private JLabel LastNameLabel = null; protected JTextField LastNameTextField = null; private JButton SubmitButton = null; public String s; public customer_order() { super(); initialize(); } private void initialize() { this.setSize(729, 400); this.setTitle("Customer Order"); this.add(getJPanel(), BorderLayout.CENTER); } /** * This method initializes LastNameTextField * * @return javax.swing.JTextField */ public JTextField getLastNameTextField() { if (LastNameTextField == null) { LastNameTextField = new JTextField(); LastNameTextField.setBounds(new Rectangle(120, 100, 164, 28)); LastNameTextField.setName("LastNameTextField"); } return LastNameTextField; } /** * This method initializes SubmitButton * * @return javax.swing.JButton */ private JButton getSubmitButton() { if (SubmitButton == null) { SubmitButton = new JButton(); SubmitButton.setBounds(new Rectangle(501, 225, 96, 29)); SubmitButton.setName("SubmitButton"); SubmitButton.setText("Submit"); SubmitButton.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent e) { System.out.println("actionPerformed()"); // TODO Auto-generated Event stub actionPerformed() //THE STRING I WANT s = LastNameTextField.getText(); java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new confirmation().setVisible(true); } }); } }); } return SubmitButton; } package customer_order; public class confirmation extends customer_order{ private static final long serialVersionUID = 1L; private JPanel jPanel = null; // @jve:decl-index=0:visual-constraint="58,9" private JLabel LastNameLabel = null; private JLabel UserLastNameLabel = null; // @jve:decl-index=0: /** * This method initializes frame * * @return java.awt.Frame */ public confirmation() { super(); initialize(); } private void initialize() { this.setSize(729, 400); this.setTitle("Confirmation"); this.add(getJPanel(), BorderLayout.CENTER); } /** * This method initializes jPanel * * @return javax.swing.JPanel */ private JPanel getJPanel() { if (jPanel == null) { UserLastNameLabel = new JLabel(); UserLastNameLabel.setBounds(new Rectangle(121, 60, 167, 26)); //THE PROBLEM? UserLastNameLabel.setText(s); } return jPanel; }

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  • Next and Previous MySQL row based on name

    - by NightMICU
    Hi everyone, I have a table with details on personnel. I would like to create a Next/Previous link based on the individual's last name. Since personnel were not added in alphabetical order, selecting the next or previous row based on its ID does not work. It is a hefty table - the pertinent fields are id, name_l, and name_f. I would like to order by name_l, the individuals' last name. How would I go about accomplishing this task? Thanks!

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  • top-k selection/merge

    - by tcurdt
    I have n sorted lists. These lists are quite long (300000+ tuples). Selecting the top 10 of the individual lists is of course trivial - they are right at the head of the lists. Where it gets more interesting is when I want the top 10 of all the sorted lists. The question is whether there is an algorithm to calculate the combined top 10 having the correct order while cutting off the long tail of the lists. The goal is to reduce the required space. And if there is: How does one find the limit where is is safe to cut? Note: The actual counts are not important. Only the order is.

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  • Calculate minimum moves to solve a puzzle

    - by Luke
    I'm in the process of creating a game where the user will be presented with 2 sets of colored tiles. In order to ensure that the puzzle is solvable, I start with one set, copy it to a second set, then swap tiles from one set to another. Currently, (and this is where my issue lies) the number of swaps is determined by the level the user is playing - 1 swap for level 1, 2 swaps for level 2, etc. This same number of swaps is used as a goal in the game. The user must complete the puzzle by swapping a tile from one set to the other to make the 2 sets match (by color). The order of the tiles in the (user) solved puzzle doesn't matter as long as the 2 sets match. The problem I have is that as the number of swaps I used to generate the puzzle approaches the number of tiles in each set, the puzzle becomes easier to solve. Basically, you can just drag from one set in whatever order you need for the second set and solve the puzzle with plenty of moves left. What I am looking to do is after I finish building the puzzle, calculate the minimum number of moves required to solve the puzzle. Again, this is almost always less than the number of swaps used to create the puzzle, especially as the number of swaps approaches the number of tiles in each set. My goal is to calculate the best case scenario and then give the user a "fudge factor" (i.e. 1.2 times the minimum number of moves). Solving the puzzle in under this number of moves will result in passing the level. A little background as to how I currently have the game configured: Levels 1 to 10: 9 tiles in each set. 5 different color tiles. Levels 11 to 20: 12 tiles in each set. 7 different color tiles. Levels 21 to 25: 15 tiles in each set. 10 different color tiles. Swapping within a set is not allowed. For each level, there will be at least 2 tiles of a given color (one for each set in the solved puzzle). Is there any type of algorithm anyone could recommend to calculate the minimum number of moves to solve a given puzzle?

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  • Advanced search functionality

    - by Chris
    I have a website with a jQuery based autocomplete search functionality which works great. Currently though I have just one search box for all categories, what I want is for someone to be able to type in, say for example, dorian gray dvd (in any order) which will search for dorian gray within the dvd category. What this will require then is a bit of magic on the server side to figure out if any of the words are category keywords, and then limit the search by that. What is the best (and quickest) way to do this in PHP / MySQL? I currently have a few trains of thought Search the category table for matches and perhaps order the results by that. Or split up the search terms into an array and separately search the categories for that for a match. Another thought I just had is to concat the category title to the dvd title in the database and match against that, or something similar... but this sounds computationally expensive? Any advice?

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  • habtm multiple times with the same model

    - by Ermin
    I am trying to model a publications. A publication can have multiple authors and editors. Since it is possible that one person is an author of one publication and an editor of another, no separate models for Authors and Editors: class Publication < ActiveRecord::Base has_and_belongs_to_many :authors, :class_name=>'Person' has_and_belongs_to_many :editors, :class_name=>'Person' end The above code doesn't work, because it uses the same join table. Now I now that I can specify the name of the join table, but there is a warning in the API documentation is a warning about that which I don't understand: :join_table: Specify the name of the join table if the default based on lexical order isn’t what you want. WARNING: If you’re overwriting the table name of either class, the table_name method MUST be declared underneath any has_and_belongs_to_many declaration in order to work.

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  • How to retrieve the ordered list of best articles having a minimum number of votes by using HSQL ?

    - by fabien7474
    I have a Vote domain class from my grails application containing properties like article_id and note I want to HQL query the Vote domain class in order to retrieve the 5 best rated articles having at least 10 votes. I tried : SELECT v.article_id, avg(v.note), count(*) FROM vote v where count(*) >= 10 group by v.article_id order by avg(v.note) desc limit 5; But unfortunately the insertion of where count(*) >= 10 throws an error. How can I do that in a simple way? Thank you for your help.

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  • Sharing some info with all DLLs pulled into a process

    - by JBRWilkinson
    Hi all, We've got an Enterprise system which has many processes (EXEs, services, DCOM servers, COM+ apps, ISAPI, MMC snapins) all of which make use of many COM components. We've recently seen failures in some of the customer deployments, but are finding it hard to troubleshoot the cause. In order to track down the problem, we've augmented the entire source with logging statements where errors occur. In order to identify which logs came from what processes, the C++ logging code (compiled into all components) uses the EXE name to name the log. This is good for some cases, but not all - COM+ apps, ISAPI and MMC snapins all have system EXE names and the logs end up interleaved. I saw this post about shared data sections which might help, but what I don't understand is who decides what goes in the shared section. Is there any way I can guarantee that a particular piece of code writes into the shared section before anyone else reads it? Or is there a better solution to this problem?

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  • How to use JQuery to truncate the contents of option tags?

    - by George
    Hello! Please take a look here: http://www.binarymark.com/Products/FLVDownloader/order.aspx What I am trying to do is to get rid of the prices inside the option tag. On that page you can see a drop-down box under Order Information, Product. I want to remove the prices from all the options that contain them in that box, so get rid of " - $75.98" for example. I am not used to JQuery, but I realize it would be possible - just not sure how to do it, so your help would be greatly appreciated. Thanks. George

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  • Finding rank of the student -Sql Compact

    - by Jankhana
    I have a table like this : Name Mar1 Mar2 Mar3 Total xxx 80 80 80 240 yyy 60 70 50 180 aaa 85 65 75 225 I wanted to find the rank of the student based on total. I using SQL Compact 3.5 . As we have rank() function in sql server do we have something with which we can find the students rank??? When I used "select Total,rank() over (order by total desc) i1 from stmarks " it's giving error as " Major Error 0x80040E14, Minor Error 25501 select Total,rank() over (order by total desc) i1 from stmarks There was an error parsing the query. [ Token line number = 1,Token line offset = 21,Token in error = over ] " Do Sql Compact support rank() over or is there any another way???

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  • How to compute a unicode string which bidirectional representation is specified?

    - by valdo
    Hello, fellows. I have a rather pervert question. Please forgive me :) There's an official algorithm that describes how bidirectional unicode text should be presented. http://www.unicode.org/reports/tr9/tr9-15.html I receive a string (from some 3rd-party source), which contains latin/hebrew characters, as well as digits, white-spaces, punctuation symbols and etc. The problem is that the string that I receive is already in the representation form. I.e. - the sequence of characters that I receive should just be presented from left to right. Now, my goal is to find the unicode string which representation is exactly the same. Means - I need to pass that string to another entity; it would then render this string according to the official algorithm, and the result should be the same. Assuming the following: The default text direction (of the rendering entity) is RTL. I don't want to inject "special unicode characters" that explicitly override the text direction (such as RLO, RLE, etc.) I suspect there may exist several solutions. If so - I'd like to preserve the RTL-looking of the string as much as possible. The string usually consists of hebrew words mostly. I'd like to preserve the correct order of those words, and characters inside those words. Whereas other character sequences may (and should) be transposed. One naive way to solve this is just to swap the whole string (this takes care of the hebrew words), and then swap inside it sequences of non-hebrew characters. This however doesn't always produce correct results, because actual rules of representation are rather complex. The only comprehensive algorithm that I see so far is brute-force check. The string can be divided into sequences of same-class characters. Those sequences may be joined in random order, plus any of them may be reversed. I can check all those combinations to obtain the correct result. Plus this technique may be optimized. For instance the order of hebrew words is known, so we only have to check different combinations of their "joining" sequences. Any better ideas? If you have an idea, not necessarily the whole solution - it's ok. I'll appreciate any idea. Thanks in advance.

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  • Problem with updating multiple rows which are in conflict with unique index

    - by GUZ
    I am using Microsoft SQL Server and I have a master-detail scenario where I need to store the order of details. So in the Detail table I have ID, MasterID, Position and some other columns. There is also a unique index on MasterID and Position. It works OK except one case: when I have some existing details and I change their order. For example when I change a detail on position 3 with a detail on position 2. When I save the detail on position 2 (which in the database has Position equal to 3) SQL Server protests, because the index uniqueness constraint. How to solve this problem in a reasonable way? Thank you in advance Lukasz Glaz

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  • how to add column in SQL Query that incl. LEFT OUTER JOIN

    - by radbyx
    I have this Query: SELECT p.ProductName, dt.MaxTimeStamp, p.Responsible FROM Product p LEFT JOIN (SELECT ProductID, MAX(TimeStamp) AS MaxTimeStamp FROM StateLog WHERE State = 0 GROUP BY ProductID, Status) dt ON p.ProductID = dt.ProductID ORDER BY p.ProductName; It works like it should, but now I need to SELECT "State" out too. The tricky part is, that I only want the lastest "TimeStamp" where "State" was false. But now I also need the "State" for the lastest "TimeStamp". I tried this: SELECT p.ProductName, dt.State, dt.MaxTimeStamp, p.Responsible FROM Product p LEFT JOIN (SELECT ProductID, MAX(TimeStamp) AS MaxTimeStamp, State FROM StateLog WHERE State = 0 GROUP BY ProductID, Status) dt ON p.ProductID =dt.ProductID ORDER BY p.ProductName; But it didn't work, because it gave me the "State" for the lastest "TimeStamp". So I hope there is some clever heads out there that can help me. I'm guessing that this is either very simple or very hard to solve.

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  • FOUR questions to ask if you are implementing DATABASE-AS-A-SERVICE

    - by Sudip Datta
    During my ongoing tenure at Oracle, I have met all types of DBAs. Happy DBAs, unhappy DBAs, proud DBAs, risk-loving DBAs, cautious DBAs. These days, as Database-as-a-Service (DBaaS) becomes more mainstream, I find some complacent DBAs who are basking in their achievement of having implemented DBaaS. Some others, however, are not that happy. They grudgingly complain that they did not have much of a say in the implementation, they simply had to follow what their cloud architects (mostly infrastructure admins) offered them. In most cases it would be a database wrapped inside a VM that would be labeled as “Database as a Service”. In other cases, it would be existing brute-force automation simply exposed in a portal. As much as I think that there is more to DBaaS than those approaches and often get tempted to propose Enterprise Manager 12c, I try to be objective. Neither do I want to dampen the spirit of the happy ones, nor do I want to stoke the pain of the unhappy ones. As I mentioned in my previous post, I don’t deny vanilla automation could be useful. I like virtualization too for what it has helped us accomplish in terms of resource management, but we need to scrutinize its merit on a case-by-case basis and apply it meaningfully. For DBAs who either claim to have implemented DBaaS or are planning to do so, I simply want to provide four key questions to ponder about: 1. Does it make life easier for your end users? Database-as-a-Service can have several types of end users. Junior DBAs, QA Engineers, Developers- each having their own skillset. The objective of DBaaS is to make their life simple, so that they can focus on their core responsibilities without having to worry about additional stuff. For example, if you are a Developer using Oracle Application Express (APEX), you want to deal with schema, objects and PL/SQL code and not with datafiles or listener configuration. If you are a QA Engineer needing database copies for functional testing, you do not want to deal with underlying operating system patching and compliance issues. The question to ask, therefore, is, whether DBaaS makes life easier for those users. It is often convenient to give them VM shells to deal with a la Amazon EC2 IaaS, but is that what they really want? Is it a productive use of a developer's time if he needs to apply RPM errata to his Linux operating system. Asking him to keep the underlying operating system current is like making a guest responsible for a restaurant's decor. 2. Does it make life easier for your administrators? Cloud, in general, is supposed to free administrators from attending to mundane tasks like provisioning services for every single end user request. It is supposed to enable a readily consumable platform and enforce standardization in the process. For example, if a Service Catalog exposes DBaaS of specific database versions and configurations, it, by its very nature, enforces certain discipline and standardization within the IT environment. What if, instead of specific database configurations, cloud allowed each end user to create databases of their liking resulting in hundreds of version and patch levels and thousands of individual databases. Therefore the right question to ask is whether the unwanted consequence of DBaaS is OS and database sprawl. And if so, who is responsible for tracking them, backing them up, administering them? Studies have shown that these administrative overheads increase exponentially with new targets, and it could result in a management nightmare. That leads us to our next question. 3. Does it satisfy your Security Officers and Compliance Auditors? Compliance Auditors need to know who did what and when. They also want the cloud platform to be secure, so that end users have little freedom in tampering with it. Dealing with VM sprawl is not the easiest of challenges, let alone dealing with them as they keep getting reconfigured and moved around. This leads to the proverbial needle in the haystack problem, and all it needs is one needle to cause a serious compliance issue in the enterprise. Bottomline is, flexibility and agility should not come at the expense of compliance and it is very important to get the balance right. Can we have security and isolation without creating compliance challenges? Instead of a ‘one size fits all approach’ i.e. OS level isolation, can we think smartly about database isolation or schema based isolation? This is where the appropriate resource modeling needs to be applied. The usual systems management vendors out there with heterogeneous common-denominator approach have compromised on these semantics. If you follow Enterprise Manager’s DBaaS solution, you will see that we have considered different models, not precluding virtualization, for different customer use cases. The judgment to use virtual assemblies versus databases on physical RAC versus Schema-as-a-Service in a single database, should be governed by the need of the applications and not by putting compliance considerations in the backburner. 4. Does it satisfy your CIO? Finally, does it satisfy your higher ups? As the sponsor of cloud initiative, the CIO is expected to lead an IT transformation project, not merely a run-of-the-mill IT operations. Simply virtualizing server resources and delivering them through self-service is a good start, but hardly transformational. CIOs may appreciate the instant benefit from server consolidation, but studies have revealed that the ROI from consolidation would flatten out at 20-25%. The question would be: what next? As we go higher up in the stack, the need to virtualize, segregate and optimize shifts to those layers that are more palpable to the business users. As Sushil Kumar noted in his blog post, " the most important thing to note here is the enterprise private cloud is not just an IT project, rather it is a business initiative to create an IT setup that is more aligned with the needs of today's dynamic and highly competitive business environment." Business users could not care less about infrastructure consolidation or virtualization - they care about business agility and service level assurance. Last but not the least, lot of CIOs get miffed if we ask them to throw away their existing hardware investments for implementing DBaaS. In Oracle, we always emphasize on freedom of choosing a platform; hence Enterprise Manager’s DBaaS solution is platform neutral. It can work on any Operating System (that the agent is certified on) Oracle’s hardware as well as 3rd party hardware. As a parting note, I urge you to remember these 4 questions. Remember that your satisfaction as an implementer lies in the satisfaction of others.

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  • Potential problems porting to different architectures

    - by Brendan Long
    I'm writing a Linux program that currently compiles and works fine on x86 and x86_64, and now I'm wondering if there's anything special I'll need to do to make it work on other architectures. What I've heard is that for cross platform code I should: Don't assume anything about the size of a pointer, int or size_t Don't make assumptions about byte order (I don't do any bit shifting -- I assume gcc will optimize my power of two multiplication/division for me) Don't use assembly blocks (obvious) Make sure your libraries work (I'm using SQLite, libcurl and Boost, which all seem pretty cross-platform) Is there anything else I need to worry about? I'm not currently targeting any other architectures, but I expect to support ARM at some point, and I figure I might as well make it work on any architecture if I can. Also, regarding my second point about byte order, do I need to do anything special with text input? I read files with getline(), so it seems like that should be done automatically as well.

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  • MySQL - get all unique values of a column, check if has a specific value

    - by gamers2000
    First off - apologies for the poor title, I have no idea how to describe it in a one-liner. I have a table - snippet is below. mysql> select * from playlistfiles; +-----------------------+--------------+-----------+ | FileName | PlaylistName | FileIndex | +-----------------------+--------------+-----------+ | File1 | Image1 | 0 | | File1 | Video1 | 2 | | File2 | Video1 | 0 | | File3 | Video1 | 1 | | File4 | Image1 | 1 | | File4 | Video1 | 3 | +-----------------------+--------------+-----------+ 6 rows in set (0.00 sec) What I need to do is to get all the FileNames and whether the file is in a playlist or not, as well as order them by FileIndex i.e. for the Image1 playlist, the output should be +-----------------------+------------+-----------+ | FileName | InPlaylist | FileIndex | +-----------------------+------------+-----------+ | File1 | 1 | 0 | | File2 | 0 | Null | | File3 | 0 | Null | | File4 | 1 | 1 | +-----------------------+------------+-----------+ and Video1 would be +-----------------------+------------+-----------+ | FileName | InPlaylist | FileIndex | +-----------------------+------------+-----------+ | File2 | 1 | 0 | | File3 | 1 | 1 | | File1 | 1 | 2 | | File4 | 1 | 3 | +-----------------------+------------+-----------+ In short, I need to be able to get all the unique FileNames from the table, and check if it is in a given table and if so, order it by FileIndex.

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  • Process for beginning a Ruby on Rails project

    - by Daniel Beardsley
    I'm about to begin a Ruby on Rails project and I'd love to hear how others go through the process of starting an application design. I have quite a bit of experience with RoR, but don't have that many starting from scratch with only a vision experiences and would appreciate the wisdom of others who've been there. I'm looking for an order of events, reasons for the order, and maybe why each part is important. I can think of a few starting points, but I'm not sure where it's best to begin Model design and relationships (entities, how they relate, and their attributes) Think of user use-cases (or story-boards) and implement the minimum to get these done Create Model unit-tests then create the necessary migrations and AR models to get the tests to pass Hack out the most basic version of the simplest part of your application and go from there Start with a template for a rails app (like http://github.com/thoughtbot/suspenders) Do the boring gruntwork first (User auth, session management, ...) ...

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  • mod_rewrite not working for a specific directory

    - by punkish
    This has got me completely foxed for a couple of days now, and I am convinced that I will look stupid once I solve it, but will be even stupider if I don't ask for help now. I have mod_rewrite working successfully on my localhost (no vhosts involved; this is my laptop, my development machine), and I use .htaccess in various directories to help rewrite crufty URLs to clean ones. EXCEPT... it doesn't work in one directory. Since it is impossible to reproduce my entire laptop in this question, I provide the following details. In my httpd.conf, I have mod_rewrite.so loaded. LoadModule rewrite_module modules/mod_rewrite.so In my httpd.conf, I have included another conf file like so Include /usr/local/apache2/conf/other/punkish.conf In my punkish.conf, I have directories defined like so DocumentRoot "/Users/punkish/Sites" <Directory "/Users/punkish/Sites"> Options ExecCGI AllowOverride None Order allow,deny Allow from all </Directory> <Directory "/Users/punkish/Sites/one"> Options FollowSymLinks AllowOverride All Order allow,deny Allow from all </Directory> <Directory "/Users/punkish/Sites/two"> Options FollowSymLinks AllowOverride All Order allow,deny Allow from all </Directory> In ~/Sites/one I have the following .htaccess file RewriteEngine On RewriteBase /one/ # If an actual file or directory is requested, serve directly RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d # Otherwise, pass everything through to the dispatcher RewriteRule ^(.*)$ index.cgi/$1 [L,QSA] and, everything works just fine. However, in my directory ~/Sites/two I have the following .htaccess file RewriteEngine On RewriteBase /two/ # If an actual file or directory is requested, serve directly RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d # Otherwise, pass everything through to the dispatcher RewriteRule ^(.*)$ index.cgi/$1 [L,QSA] and, nothing works. Nada. Zip. Zilch. I just get a 404. I have determined that mod_rewrite is not even looking at my ~/Sites/two/.htaccess by putting spurious commands in it and not getting any error other than 404. Another confounding issue -- I have turned on RewriteLog in my httpd.conf with RewriteLogLevel 3, but my rewrite_log is completely empty. I know this is hard to trouble shoot unless sitting physically at the computer in question, but I hope someone can give me some indication as to what is going on. **Update: ** There are no aliases involved anywhere. This is my laptop, and everything is under the above stated Document Root, so I just access each directory as http://localhost/. Yes, typos are a big possibility (I did say that I will look stupid once I solve it, however, for now, I have not discovered a single typo anywhere, and yes, I have restarted Apache about a dozen times now. I even thought that perhaps I had two different Apaches running, but no, I have only one, the one under /usr/local/apache2, and I installed it myself a while back.

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