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  • Using MySQL to generate daily sales reports with filled gaps, grouped by currency

    - by Shane O'Grady
    I'm trying to create what I think is a relatively basic report for an online store, using MySQL 5.1.45 The store can receive payment in multiple currencies. I have created some sample tables with data and am trying to generate a straightforward tabular result set grouped by date and currency so that I can graph these figures. I want to see each currency that is available per date, with a 0 in the result if there were no sales in that currency for that day. If I can get that to work I want to do the same but also grouped by product id. In the sample data I have provided there are only 3 currencies and 2 product ids, but in practice there can be any number of each. I can correctly group by date, but then when I add a grouping by currency my query does not return what I want. I based my work off this article. My reporting query, grouped only by date: SELECT calendar.datefield AS date, IFNULL(SUM(orders.order_value),0) AS total_value FROM orders RIGHT JOIN calendar ON (DATE(orders.order_date) = calendar.datefield) WHERE (calendar.datefield BETWEEN (SELECT MIN(DATE(order_date)) FROM orders) AND (SELECT MAX(DATE(order_date)) FROM orders)) GROUP BY date Now grouped by date and currency: SELECT calendar.datefield AS date, orders.currency_id, IFNULL(SUM(orders.order_value),0) AS total_value FROM orders RIGHT JOIN calendar ON (DATE(orders.order_date) = calendar.datefield) WHERE (calendar.datefield BETWEEN (SELECT MIN(DATE(order_date)) FROM orders) AND (SELECT MAX(DATE(order_date)) FROM orders)) GROUP BY date, orders.currency_id The results I am getting (grouped by date and currency): +------------+-------------+-------------+ | date | currency_id | total_value | +------------+-------------+-------------+ | 2009-08-15 | 3 | 81.94 | | 2009-08-15 | 45 | 25.00 | | 2009-08-15 | 49 | 122.60 | | 2009-08-16 | NULL | 0.00 | | 2009-08-17 | 45 | 25.00 | | 2009-08-17 | 49 | 122.60 | | 2009-08-18 | 3 | 81.94 | | 2009-08-18 | 49 | 245.20 | +------------+-------------+-------------+ The results I want: +------------+-------------+-------------+ | date | currency_id | total_value | +------------+-------------+-------------+ | 2009-08-15 | 3 | 81.94 | | 2009-08-15 | 45 | 25.00 | | 2009-08-15 | 49 | 122.60 | | 2009-08-16 | 3 | 0.00 | | 2009-08-16 | 45 | 0.00 | | 2009-08-16 | 49 | 0.00 | | 2009-08-17 | 3 | 0.00 | | 2009-08-17 | 45 | 25.00 | | 2009-08-17 | 49 | 122.60 | | 2009-08-18 | 3 | 81.94 | | 2009-08-18 | 45 | 0.00 | | 2009-08-18 | 49 | 245.20 | +------------+-------------+-------------+ The schema and data I am using in my tests: CREATE TABLE orders ( id INT PRIMARY KEY AUTO_INCREMENT, order_date DATETIME, order_id INT, product_id INT, currency_id INT, order_value DECIMAL(9,2), customer_id INT ); INSERT INTO orders (order_date, order_id, product_id, currency_id, order_value, customer_id) VALUES ('2009-08-15 10:20:20', '123', '1', '45', '12.50', '322'), ('2009-08-15 12:30:20', '124', '1', '49', '122.60', '400'), ('2009-08-15 13:41:20', '125', '1', '3', '40.97', '324'), ('2009-08-15 10:20:20', '126', '2', '45', '12.50', '345'), ('2009-08-15 13:41:20', '131', '2', '3', '40.97', '756'), ('2009-08-17 10:20:20', '3234', '1', '45', '12.50', '1322'), ('2009-08-17 10:20:20', '4642', '2', '45', '12.50', '1345'), ('2009-08-17 12:30:20', '23', '2', '49', '122.60', '3142'), ('2009-08-18 12:30:20', '2131', '1', '49', '122.60', '4700'), ('2009-08-18 13:41:20', '4568', '1', '3', '40.97', '3274'), ('2009-08-18 12:30:20', '956', '2', '49', '122.60', '3542'), ('2009-08-18 13:41:20', '443', '2', '3', '40.97', '7556'); CREATE TABLE currency ( id INT PRIMARY KEY, name VARCHAR(255) ); INSERT INTO currency (id, name) VALUES (3, 'Euro'), (45, 'US Dollar'), (49, 'CA Dollar'); CREATE TABLE calendar (datefield DATE); DELIMITER | CREATE PROCEDURE fill_calendar(start_date DATE, end_date DATE) BEGIN DECLARE crt_date DATE; SET crt_date=start_date; WHILE crt_date < end_date DO INSERT INTO calendar VALUES(crt_date); SET crt_date = ADDDATE(crt_date, INTERVAL 1 DAY); END WHILE; END | DELIMITER ; CALL fill_calendar('2008-01-01', '2011-12-31');

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  • What are the weaknesses of this user authentication method?

    - by byronh
    I'm developing my own PHP framework. It seems all the security articles I have read use vastly different methods for user authentication than I do so I could use some help in finding security holes. Some information that might be useful before I start. I use mod_rewrite for my MVC url's. Passwords are sha1 and md5 encrypted with 24 character salt unique to each user. mysql_real_escape_string and/or variable typecasting on everything going in, and htmlspecialchars on everything coming out. Step-by step process: Top of every page: session_start(); session_regenerate_id(); If user logs in via login form, generate new random token to put in user's MySQL row. Hash is generated based on user's salt (from when they first registered) and the new token. Store the hash and plaintext username in session variables, and duplicate in cookies if 'Remember me' is checked. On every page, check for cookies. If cookies set, copy their values into session variables. Then compare $_SESSION['name'] and $_SESSION['hash'] against MySQL database. Destroy all cookies and session variables if they don't match so they have to log in again. If login is valid, some of the user's information from the MySQL database is stored in an array for easy access. So far, I've assumed that this array is clean so when limiting user access I refer to user.rank and deny access if it's below what's required for that page. I've tried to test all the common attacks like XSS and CSRF, but maybe I'm just not good enough at hacking my own site! My system seems way too simple for it to actually be secure (the security code is only 100 lines long). What am I missing? I've also spent alot of time searching for the vulnerabilities with mysql_real_escape string but I haven't found any information that is up-to-date (everything is from several years ago at least and has apparently been fixed). All I know is that the problem was something to do with encoding. If that problem still exists today, how can I avoid it? Any help will be much appreciated.

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  • Copying metadata over a database link in Oracle 10g

    - by Tunde
    Thanks in advance for your help experts. I want to be able to copy over database objects from database A into database B with a procedure created on database B. I created a database link between the two and have tweaked the get_ddl function of the dbms_metadata to look like this: create or replace function GetDDL ( p_name in MetaDataPkg.t_string p_type in MetaDataPkg.t_string ) return MetaDataPkg.t_longstring is -- clob v_clob clob; -- array of long strings c_SYSPrefix constant char(4) := 'SYS_'; c_doublequote constant char(1) := '"'; v_longstrings metadatapkg.t_arraylongstring; v_schema metadatapkg.t_string; v_fullength pls_integer := 0; v_offset pls_integer := 0; v_length pls_integer := 0; begin SELECT DISTINCT OWNER INTO v_schema FROM all_objects@ENTORA where object_name = upper(p_name); -- get DDL v_clob := dbms_metadata.get_ddl(p_type, upper(p_name), upper(v_schema)); -- get CLOB length v_fullength := dbms_lob.GetLength(v_clob); for nIndex in 1..ceil(v_fullength / 32767) loop v_offset := v_length + 1; v_length := least(v_fullength - (nIndex - 1) * 32767, 32767); dbms_lob.read(v_clob, v_length, v_offset, v_longstrings(nIndex)); -- Remove table’s owner from DDL string: v_longstrings(nIndex) := replace( v_longstrings(nIndex), c_doublequote || user || c_doublequote || '.', '' ); -- Remove the following from DDL string: -- 1) "new line" characters (chr(10)) -- 2) leading and trailing spaces v_longstrings(nIndex) := ltrim(rtrim(replace(v_longstrings(nIndex), chr(10), ''))); end loop; -- close CLOB if (dbms_lob.isOpen(v_clob) > 0) then dbms_lob.close(v_clob); end if; return v_longstrings(1); end GetDDL; so as to remove the schema prefix that usually comes with metadata. I get a null value whenever I run this function over the database link with the following queries. select getddl( 'TABLE', 'TABLE1') from user_tables@ENTORA where table_name = 'TABLE1'; select getddl( 'TABLE', 'TABLE1') from dual@ENTORA; t_string is varchar2(30) t_longstring is varchar2(32767) and type t_ArrayLongString is table of t_longstring I would really appreciate it if any one could help. Many thanks.

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  • functional dependencies vs type families

    - by mhwombat
    I'm developing a framework for running experiments with artificial life, and I'm trying to use type families instead of functional dependencies. Type families seems to be the preferred approach among Haskellers, but I've run into a situation where functional dependencies seem like a better fit. Am I missing a trick? Here's the design using type families. (This code compiles OK.) {-# LANGUAGE TypeFamilies, FlexibleContexts #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u => a -> StateT u IO a -- plus other functions class Universe u where type MyAgent u :: * withAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } defaultWithAgent :: (MyAgent u -> StateT u IO (MyAgent u)) -> String -> StateT u IO () defaultWithAgent = undefined -- stub -- plus default implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- .. and they'll also need to make SimpleUniverse an instance of Universe -- for their agent type. -- instance Universe SimpleUniverse where type MyAgent SimpleUniverse = Bug withAgent = defaultWithAgent -- boilerplate -- plus similar boilerplate for other functions Is there a way to avoid forcing my users to write those last two lines of boilerplate? Compare with the version using fundeps, below, which seems to make things simpler for my users. (The use of UndecideableInstances may be a red flag.) (This code also compiles OK.) {-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, UndecidableInstances #-} import Control.Monad.State (StateT) class Agent a where agentId :: a -> String liveALittle :: Universe u a => a -> StateT u IO a -- plus other functions class Universe u a | u -> a where withAgent :: Agent a => (a -> StateT u IO a) -> String -> StateT u IO () -- plus other functions data SimpleUniverse = SimpleUniverse { mainDir :: FilePath -- plus other fields } instance Universe SimpleUniverse a where withAgent = undefined -- stub -- plus implementations for other functions -- -- In order to use my framework, the user will need to create a typeclass -- that implements the Agent class... -- data Bug = Bug String deriving (Show, Eq) instance Agent Bug where agentId (Bug s) = s liveALittle bug = return bug -- stub -- -- And now my users only have to write stuff like... -- u :: SimpleUniverse u = SimpleUniverse "mydir"

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  • Gotchas INSERTing into SQLite on Android?

    - by paul.meier
    Hi friends, I'm trying to set up a simple SQLite database in Android, handling the schema via a subclass of SQLiteOpenHelper. However, when I query my tables, the columns I think I've inserted are never present. Namely, in SQLiteOpenHelper's onCreate(SQLiteDatabase db) method, I use db.execSQL() to run CREATE TABLE commands, then have tried both db.execSQL and db.insert() to run INSERT commands on the tables I've just created. This appears to run fine, but when I try to query them I always get 0 rows returned (for debugging, the queries I'm running are simple SELECT * FROM table and checking the Cursor's getCount()). Anybody run into anything like this before? These commands seem to run on command-line sqlite3. Are they're gotchas that I'm missing (e.g. INSERTS must/must not be semicolon terminated, or some issue involving multiple tables)? I've attached some of the code below. Thanks for your time, and let me know if I can clarify further. @Override public void onCreate(SQLiteDatabase db) { db.execSQL("CREATE TABLE "+ LEVEL_TABLE +" (" + " "+ _ID +" INTEGER PRIMARY KEY AUTOINCREMENT," + " level TEXT NOT NULL,"+ " rows INTEGER NOT NULL,"+ " cols INTEGER NOT NULL);"); db.execSQL("CREATE TABLE "+ DYNAMICS_TABLE +" (" + " level_id INTEGER NOT NULL," + " row INTEGER NOT NULL,"+ " col INTEGER NOT NULL,"+ " type INTEGER NOT NULL);"); db.execSQL("CREATE TABLE "+ SCORE_TABLE +" (" + " level_id INTEGER NOT NULL," + " score INTEGER NOT NULL,"+ " date_achieved DATE NOT NULL,"+ " name TEXT NOT NULL);"); this.enterFirstLevel(db); } And a sample of the insert code I'm currently using, which gets called in enterFirstLevel() (some values hard-coded just to get it running...): private void insertDynamic(SQLiteDatabase db, int row, int col, int type) { ContentValues values = new ContentValues(); values.put("level_id", "1"); values.put("row", Integer.toString(row)); values.put("col", Integer.toString(col)); values.put("type", Integer.toString(type)); db.insertOrThrow(DYNAMICS_TABLE, "col", values); } Finally, query code looks like this: private Cursor fetchLevelDynamics(int id) { SQLiteDatabase db = this.leveldata.getReadableDatabase(); try { String fetchQuery = "SELECT * FROM " + DYNAMICS_TABLE; String[] queryArgs = new String[0]; Cursor cursor = db.rawQuery(fetchQuery, queryArgs); Activity activity = (Activity) this.context; activity.startManagingCursor(cursor); return cursor; } finally { db.close(); } }

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  • When to call glEnable(GL_FRAMEBUFFER_SRGB)?

    - by Steven Lu
    I have a rendering system where I draw to an FBO with a multisampled renderbuffer, then blit it to another FBO with a texture in order to resolve the samples in order to read off the texture to perform post-processing shading while drawing to the backbuffer (FBO index 0). Now I'd like to get some correct sRGB output... The problem is the behavior of the program is rather inconsistent between when I run it on OS X and Windows and this also changes depending on the machine: On Windows with the Intel HD 3000 it will not apply the sRGB nonlinearity but on my other machine with a Nvidia GTX 670 it does. On the Intel HD 3000 in OS X it will also apply it. So this probably means that I'm not setting my GL_FRAMEBUFFER_SRGB enable state at the right points in the program. However I can't seem to find any tutorials that actually tell me when I ought to enable it, they only ever mention that it's dead easy and comes at no performance cost. I am currently not loading in any textures so I haven't had a need to deal with linearizing their colors yet. To force the program to not simply spit back out the linear color values, what I have tried is simply comment out my glDisable(GL_FRAMEBUFFER_SRGB) line, which effectively means this setting is enabled for the entire pipeline, and I actually redundantly force it back on every frame. I don't know if this is correct or not. It certainly does apply a nonlinearization to the colors but I can't tell if this is getting applied twice (which would be bad). It could apply the gamma as I render to my first FBO. It could do it when I blit the first FBO to the second FBO. Why not? I've gone so far as to take screen shots of my final frame and compare raw pixel color values to the colors I set them to in the program: I set the input color to RGB(1,2,3) and the output is RGB(13,22,28). That seems like quite a lot of color compression at the low end and leads me to question if the gamma is getting applied multiple times. I have just now gone through the sRGB equation and I can verify that the conversion seems to be only applied once as linear 1/255, 2/255, and 3/255 do indeed map to sRGB 13/255, 22/255, and 28/255 using the equation 1.055*C^(1/2.4)+0.055. Given that the expansion is so large for these low color values it really should be obvious if the sRGB color transform is getting applied more than once. So, I still haven't determined what the right thing to do is. does glEnable(GL_FRAMEBUFFER_SRGB) only apply to the final framebuffer values, in which case I can just set this during my GL init routine and forget about it hereafter?

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  • Is the recent trend toward widescreen (16:9) computer monitors a plus or minus for programmers?

    - by DanM
    It's almost gotten to the point where you can't buy a conventional (4:3) monitor anymore. Pretty much everything is widescreen. This is fine for watching movies or TV, but is it good or bad for programming? My initial thoughts on the issue are that widescreens are a net negative for programmers. Here are some of the disadvantages I see: Poor space utiliziation One disadvantage of widescreens you can't argue with is that they offer poor space utilization for the amount of total pixels you get. For example, my Thinkpad, which I bought just before the widescreen craze, has a 15" monitor with a native resolution of 1600 x 1200. The newer 15.4" Thinkpads run at most 1680 x 1050. So (if you do the math) you get fewer pixels in a wider (but not shorter) package. With desktop monitors, you pay a price in terms of desk space used. Two 1680 x 1050 monitors will simply take up more of your desk than two 1600 x 1200 monitors (assuming equal dot pitch). More scrolling If you compare a 1680 x 1050 monitor to a 1600 x 1200 monitor, you get 80 extra pixels of width but 150 fewer pixels of height. The height reduction means you lose approximately 11 lines of code. That's less you can see on the screen at one time and more scrolling you have to do. This harms productivity, maybe not dramatically, but insidiously. Less room for wide panels Widescreens also mean you lose space for wide but short panels common in programming environments. If you use Visual Studio, for example, your code window will be that much shorter when viewing the Find Results, Task List, or Error List (all of which I use frequently). This isn't to say the 80 pixels of extra width you get with widescreen would never be useful, but I tend to keep my lines of code short, so seeing more lines would be more valuable to me than seeing fewer, longer lines. What do you think? Do you agree/disagree? Are you now using one or more widescreen monitors for development? What resolution are you running on each? Do you ever miss the height of the traditional 4:3 monitor? Would you complain if your monitors were one inch narrower but two inches taller?

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  • Postgresql count+sort performance

    - by invictus
    I have built a small inventory system using postgresql and psycopg2. Everything works great, except, when I want to create aggregated summaries/reports of the content, I get really bad performance due to count()'ing and sorting. The DB schema is as follows: CREATE TABLE hosts ( id SERIAL PRIMARY KEY, name VARCHAR(255) ); CREATE TABLE items ( id SERIAL PRIMARY KEY, description TEXT ); CREATE TABLE host_item ( id SERIAL PRIMARY KEY, host INTEGER REFERENCES hosts(id) ON DELETE CASCADE ON UPDATE CASCADE, item INTEGER REFERENCES items(id) ON DELETE CASCADE ON UPDATE CASCADE ); There are some other fields as well, but those are not relevant. I want to extract 2 different reports: - List of all hosts with the number of items per, ordered from highest to lowest count - List of all items with the number of hosts per, ordered from highest to lowest count I have used 2 queries for the purpose: Items with host count: SELECT i.id, i.description, COUNT(hi.id) AS count FROM items AS i LEFT JOIN host_item AS hi ON (i.id=hi.item) GROUP BY i.id ORDER BY count DESC LIMIT 10; Hosts with item count: SELECT h.id, h.name, COUNT(hi.id) AS count FROM hosts AS h LEFT JOIN host_item AS hi ON (h.id=hi.host) GROUP BY h.id ORDER BY count DESC LIMIT 10; Problem is: the queries runs for 5-6 seconds before returning any data. As this is a web based application, 6 seconds are just not acceptable. The database is heavily populated with approximately 50k hosts, 1000 items and 400 000 host/items relations, and will likely increase significantly when (or perhaps if) the application will be used. After playing around, I found that by removing the "ORDER BY count DESC" part, both queries would execute instantly without any delay whatsoever (less than 20ms to finish the queries). Is there any way I can optimize these queries so that I can get the result sorted without the delay? I was trying different indexes, but seeing as the count is computed it is possible to utilize an index for this. I have read that count()'ing in postgresql is slow, but its the sorting that are causing me problems... My current workaround is to run the queries above as an hourly job, putting the result into a new table with an index on the count column for quick lookup. I use Postgresql 9.2.

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  • how to change color of text following function in javascript

    - by OVERTONE
    Ok before i make spaghetti of this code i thought id ask around here. ive made a quiz for an online site. The answers are stored in an array, and ive a function that checks the answers array to what youve clicked. then it counts them and gives you your score. but i want to change the clor of the right answer wen the user clicks the score button. so the correct answers are highlighted. something like this https://www.shutterpoint.com/Home-Quiz.cfm (just hit submit at the bottom, no need to do the quiz). the little answer icon at the side looks flashy but id rather just have the text change color. heres how my questions are formatted <p>Depth of field is controlled by :?</p> <p id = "question2"><input type="radio" name="question2" id="Answer1" value = "a" onClick ="recordAnswer(2,this.value)"/> The focal length of the lens. <br/> <input type="radio" name="question2" id="Answer2" value = "b" onClick = "recordAnswer(2,this.value)"/> The size of the aperture opening. <br/> <input type="radio" name="question2" id="Answer3" value = "c" onClick = "recordAnswer(2,this.value)"/> The distance between the camera and lens. <br/> <input type="radio" name="question2" id="Answer4" value = "d" onClick = "recordAnswer(2,this.value)"/> All of these. <br/></p> and these are the two functions that are called throughout. record answer is called every time the user clicks a button function recordAnswer(question,answer) { answers[question-1] = answer; } this is the final button which calculates the score function scoreQuiz() { var totalCorrect = 0; for(var count = 0; count<correctAnswers.length;count++) { if(answers[count]== correctAnswers[count]) totalCorrect++; } <!-- alert("You scored " + totalCorrect + " out of 12 correct!"); --> } another function is best i think. ive already made attemots at it and know i have to set the color using document.getElementById('question2').style.color = '#0000ff'; question2 being the p id i think if i take in the value part of (input type....) ill be able to compare it to the answers array. but im not quite sure how to do this. any helpers? maybe something like this document.getElementById("Answer1").style.color = '#0000ff'; using the id part of the (input type line) i think i got it actually. ill post my answer in a sec

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  • JPA Database strcture for internationalisation

    - by IrishDubGuy
    I am trying to get a JPA implementation of a simple approach to internationalisation. I want to have a table of translated strings that I can reference in multiple fields in multiple tables. So all text occurrences in all tables will be replaced by a reference to the translated strings table. In combination with a language id, this would give a unique row in the translated strings table for that particular field. For example, consider a schema that has entities Course and Module as follows :- Course int course_id, int name, int description Module int module_id, int name The course.name, course.description and module.name are all referencing the id field of the translated strings table :- TranslatedString int id, String lang, String content That all seems simple enough. I get one table for all strings that could be internationalised and that table is used across all the other tables. How might I do this in JPA, using eclipselink 2.4? I've looked at embedded ElementCollection, ala this... JPA 2.0: Mapping a Map - it isn't exactly what i'm after cos it looks like it is relating the translated strings table to the pk of the owning table. This means I can only have one translatable string field per entity (unless I add new join columns into the translatable strings table, which defeats the point, its the opposite of what I am trying to do). I'm also not clear on how this would work across entites, presumably the id of each entity would have to use a database wide sequence to ensure uniqueness of the translatable strings table. BTW, I tried the example as laid out in that link and it didn't work for me - as soon as the entity had a localizedString map added, persisting it caused the client side to bomb but no obvious error on the server side and nothing persisted in the DB :S I been around the houses on this about 9 hours so far, I've looked at this Internationalization with Hibernate which appears to be trying to do the same thing as the link above (without the table definitions it hard to see what he achieved). Any help would be gratefully achieved at this point... Edit 1 - re AMS anwser below, I'm not sure that really addresses the issue. In his example it leaves the storing of the description text to some other process. The idea of this type of approach is that the entity object takes the text and locale and this (somehow!) ends up in the translatable strings table. In the first link I gave, the guy is attempting to do this by using an embedded map, which I feel is the right approach. His way though has two issues - one it doesn't seem to work! and two if it did work, it is storing the FK in the embedded table instead of the other way round (I think, I can't get it to run so I can't see exactly how it persists). I suspect the correct approach ends up with a map reference in place of each text that needs translating (the map being locale-content), but I can't see how to do this in a way that allows for multiple maps in one entity (without having corresponding multiple columns in the translatable strings table)...

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  • Embedded "Smart" character LCD driver. Is this a good idea?

    - by chris12892
    I have an embedded project that I am working on, and I am currently coding the character LCD driver. At the moment, the LCD driver only supports "dumb" writing. For example, let's say line 1 has some text on it, and I make a call to the function that writes to the line. The function will simply seek to the beginning of the line and write the text (plus enough whitespace to erase whatever was last written). This is well and good, but I get the feeling it is horribly inefficient sometimes, since some lines are simply: "Some-reading: some-Value" Rather than "brute force" replacing the entire line, I wanted to develop some code that would figure out the best way to update the information on the LCD. (just as background, it takes 2 bytes to seek to any char position. I can then begin writing the string) My idea was to first have a loop. This loop would compare the input to the last write, and in doing so, it would cover two things: A: Collect all the differences between the last write and the input. For every contiguous segment (be it same or different) add two bytes to the byte count. This is referenced in B to determine if we are wasting serial bandwidth. B: The loop would determine if this is really a smart thing to do. If we end up using more bytes to update the line than to "brute force" the line, then we should just return and let the brute force method take over. We should exit the smart write function as soon as this condition is met to avoid wasting time. The next part of the function would take all the differences, seek to the required char on the LCD, and write them. Thus, if we have a string like this already on the LCD: "Current Temp: 80F" and we want to update it to "Current Temp: 79F" The function will go through and see that it would take less bandwidth to simply seek to the "8" and write "79". The "7" will cover the "8" and the "9" will cover the "0". That way, we don't waste time writing out the entire string. Does this seem like a practical idea?

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  • How do I find the Next Closest Date to today from a list of dates in a Plist on iOS?

    - by user1173823
    Situation: In short, I have a football schedule. I would like to use a custom cell which provides more info for only the next game date in the schedule. Issue: How do I find only the next closest game in the schedule (for iOS)? I've watched the WWDC 2013 video for "Solutions to Common Date and Time Issues" however this primarily applies to the Mac. I've searched numerous posts here and some are close but not what I need to find ONLY the next date from my list of dates in the schedule. From other posts I see where I can compare two specific dates, but this is not what I want to do. I want to find the next closest date that is equal to or after today from a list of dates. This is where I am now. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { //Populate the table from the plist NSDictionary *season = _schedContentArray[indexPath.section]; NSArray *schedule = season[@"Schedule"]; NSDictionary *game = schedule[indexPath.row]; //find the closest game date after today's date ?? NSString *gameDateStr = game[@"GameDate"]; NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar]; NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; dateFormatter.calendar=calendar; [dateFormatter setDateFormat:@"MM/dd/yy"]; NSDate *today = [NSDate date]; NSDate *gameDate = [dateFormatter dateFromString:gameDateStr]; //NSString *nextGame = NSLog(@"game date is %@",gameDate); The NSLog returns the game dates (except for the open date): 2013-11-11 16:10:05.979 Clemson Football[24060:70b] game date is 2013-08-31 04:00:00 +0000 2013-11-11 16:10:05.982 Clemson Football[24060:70b] game date is 2013-09-07 04:00:00 +0000 2013-11-11 16:10:05.985 Clemson Football[24060:70b] game date is (null) 2013-11-11 16:10:05.987 Clemson Football[24060:70b] game date is 2013-09-19 04:00:00 +0000 2013-11-11 16:10:05.988 Clemson Football[24060:70b] game date is 2013-09-28 04:00:00 +0000 2013-11-11 16:10:05.990 Clemson Football[24060:70b] game date is 2013-10-05 04:00:00 +0000 2013-11-11 16:10:05.992 Clemson Football[24060:70b] game date is 2013-10-12 04:00:00 +0000 2013-11-11 16:10:05.993 Clemson Football[24060:70b] game date is 2013-10-19 04:00:00 +0000 2013-11-11 16:10:05.995 Clemson Football[24060:70b] game date is 2013-10-26 04:00:00 +0000 2013-11-11 16:10:05.996 Clemson Football[24060:70b] game date is 2013-11-02 04:00:00 +0000 2013-11-11 16:10:05.998 Clemson Football[24060:70b] game date is 2013-11-09 05:00:00 +0000 2013-11-11 16:10:06.000 Clemson Football[24060:70b] game date is 2013-11-14 05:00:00 +0000 2013-11-11 16:10:06.001 Clemson Football[24060:70b] game date is 2013-11-23 05:00:00 +0000 2013-11-11 16:10:06.003 Clemson Football[24060:70b] game date is 2013-11-30 05:00:00 +0000 2013-11-11 16:10:06.005 Clemson Football[24060:70b] game date is 2013-12-07 05:00:00 +0000 Thanks in advance for any assistance you can provide. This seems like it should be simple but has been fairly frustrating. Let me know if you need additional info.

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  • Select latest group by in nhibernate

    - by Kendrick
    I have Canine and CanineHandler objects in my application. The CanineHandler object has a PersonID (which references a completely different database), an EffectiveDate (which specifies when a handler started with the canine), and a FK reference to the Canine (CanineID). Given a specific PersonID, I want to find all canines they're currently responsible for. The (simplified) query I'd use in SQL would be: Select Canine.* from Canine inner join CanineHandler on(CanineHandler.CanineID=Canine.CanineID) inner join (select CanineID,Max(EffectiveDate) MaxEffectiveDate from caninehandler group by CanineID) as CurrentHandler on(CurrentHandler.CanineID=CanineHandler.CanineID and CurrentHandler.MaxEffectiveDate=CanineHandler.EffectiveDate) where CanineHandler.HandlerPersonID=@PersonID Edit: Added mapping files below: <class name="CanineHandler" table="CanineHandler" schema="dbo"> <id name="CanineHandlerID" type="Int32"> <generator class="identity" /> </id> <property name="EffectiveDate" type="DateTime" precision="16" not-null="true" /> <property name="HandlerPersonID" type="Int64" precision="19" not-null="true" /> <many-to-one name="Canine" class="Canine" column="CanineID" not-null="true" access="field.camelcase-underscore" /> </class> <class name="Canine" table="Canine"> <id name="CanineID" type="Int32"> <generator class="identity" /> </id> <property name="Name" type="String" length="64" not-null="true" /> ... <set name="CanineHandlers" table="CanineHandler" inverse="true" order-by="EffectiveDate desc" cascade="save-update" access="field.camelcase-underscore"> <key column="CanineID" /> <one-to-many class="CanineHandler" /> </set> <property name="IsDeleted" type="Boolean" not-null="true" /> </class> I haven't tried yet, but I'm guessing I could do this in HQL. I haven't had to write anything in HQL yet, so I'll have to tackle that eventually anyway, but my question is whether/how I can do this sub-query with the criterion/subqueries objects. I got as far as creating the following detached criteria: DetachedCriteria effectiveHandlers = DetachedCriteria.For<Canine>() .SetProjection(Projections.ProjectionList() .Add(Projections.Max("EffectiveDate"),"MaxEffectiveDate") .Add(Projections.GroupProperty("CanineID"),"handledCanineID") ); but I can't figure out how to do the inner join. If I do this: Session.CreateCriteria<Canine>() .CreateCriteria("CanineHandler", "handler", NHibernate.SqlCommand.JoinType.InnerJoin) .List<Canine>(); I get an error "could not resolve property: CanineHandler of: OPS.CanineApp.Model.Canine". Obviously I'm missing something(s) but from the documentation I got the impression that should return a list of Canines that have handlers (possibly with duplicates). Until I can make this work, adding the subquery isn't going to work... I've found similar questions, such as http://stackoverflow.com/questions/747382/only-get-latest-results-using-nhibernate but none of the answers really seem to apply with the kind of direct result I'm looking for. Any help or suggestion is greatly appreciated.

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  • How to implement best matching logic in TSQL (SQL Server 2000)

    - by sanjay-kumar1911
    I have two tables X and Y: Table X C1 C2 C3 1 A 13 2 B 16 3 C 8 Table Y C1 C2 C3 C4 1 A 2 N 2 A 8 N 3 A 12 N 4 A 5 N 5 B 7 N 6 B 16 N 7 B 9 N 8 B 5 N 9 C 8 N 10 C 2 N 11 C 8 N 12 C 6 N Records in Table Y can be n number CREATE TABLE X(C1 INT, C2 CHAR(1), C3 INT); CREATE TABLE Y(C1 INT, C2 CHAR(1), C3 INT, C4 CHAR(1)); with following data: INSERT INTO X VALUES (1 'A',13 ); INSERT INTO X VALUES (2 'B',16 ); INSERT INTO X VALUES (3 'C',8 ); INSERT INTO Y VALUES (1,'A', 2,'N'); INSERT INTO Y VALUES (2,'A', 8,'N'); INSERT INTO Y VALUES (3,'A', 12,'N'); INSERT INTO Y VALUES (4,'A', 5,'N'); INSERT INTO Y VALUES (5,'B', 7,'N'); INSERT INTO Y VALUES (6,'B', 16,'N'); INSERT INTO Y VALUES (7,'B', 9,'N'); INSERT INTO Y VALUES (8,'B', 5,'N'); INSERT INTO Y VALUES (9,'C', 8,'N'); INSERT INTO Y VALUES (10,'C', 2,'N'); INSERT INTO Y VALUES (11,'C', 8,'N'); INSERT INTO Y VALUES (12,'C', 6,'N'); EXPECTED RESULT Table Y C1 C2 C3 C4 1 A 2 N 2 A 8 Y 3 A 12 N 4 A 5 Y 5 B 7 N 6 B 16 Y 7 B 9 N 8 B 5 N 9 C 8 Y 10 C 2 N 11 C 8 N 12 C 6 N How do I compare value of column C3 in Table X with all possible matches of column C3 of Table Y and to mark records as matched and unmatched in column C4 of Table Y? Possible matches for A (i.e. value of column C2 in Table X) would be (where R is row number i.e. value of column C1 in Table Y): R1, R2, R3, R4, R1+R2, R1+R3, R1+R4, R2+R3, R2+R4, R3+R4, R4+R5, R1+R2+R3, R1+R2+R4, R2+R3+R4, R1+R2+R3+R4

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  • Good design of mapping Java Domain objects to Tables (using Hibernate)

    - by M. McKenzie
    Hey guys, I have a question that is more in the realm of design, than implementation. I'm also happy for anyone to point out resources for the answer and I'll gladly, research for myself. Highly simplified Java and SQL: Say I have a business domain POJO called 'Picture' with three attributes. class Picture int idPicture String fileName long size Say I have another business domain POJO called "Item" with 3 attributes Class Item int idItem String itemName ArrayList itemPictures These would be a normal simple relationship. You could say that 'Picture' object, will never exist outside an 'Item' object. Assume a picture belongs only to a specific item, but that an item can have multiple pictures Now - using good database design (3rd Normal Form), we know that we should put items and pictures in their own tables. Here is what I assume would be correct. table Item int idItem (primary key) String itemName table Picture int idPicture (primary key) varchar(45) fileName long size int idItem (foreign key) Here is my question: If you are making Hibernate mapping files for these objects. In the data design, your Picture table needs a column to refer to the Item, so that a foreign key relation can be maintained. However,in your business domain objects - your Picture does not hold a reference/attribute to the idItem - and does not need to know it. A java Picture instance is always instantiated inside an Item instance. If you want to know the Item that the Picture belongs to you are already in the correct scope. Call myItem.getIdItem() and myItem.getItemPictures(),and you have the two pieces of information you need. I know that Hibernate tools have a generator that can auto make your POJO's from looking at your database. My problem stems from the fact that I planned out the data design for this experiment/project first. Then when I went to make the domain java objects, I realized that good design dictated that the objects hold other objects in a nested way. This is obviously different from the way that a database schema is - where all objects(tables) are flat and hold no other complex types within them. What is a good way to reconcile this? Would you: (A) Make the hibernate mapping files so that Picture.hbm.xml has a mapping to the POJO parent's idItem Field (if it's even possible) (B) Add an int attribute in the Picture class to refer to the idItem and set it at instantiation, thus simplifying the hbm.xml mapping file by having all table fields as local attributes in the class (C) Fix the database design because it is wrong, dork. I'd truly appreciate any feedback

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  • using dictionaries with WebServices

    - by umit-alba
    Hi! I tried to pass a dictionary via WebServices. However it is not serializeable. So i wrote an Own Class that makes it serializeable: using System; using System.Net; using System.Windows; using System.Collections.Generic; using System.Xml.Serialization; using System.Xml; using System.Xml.Schema; namespace Platform { public class SaDictionary<TKey, TValue> : Dictionary<TKey, TValue>, IXmlSerializable { #region Constructors public SaDictionary() : base() { } public SaDictionary(IDictionary<TKey, TValue> dictionary) : base(dictionary) { } public SaDictionary(IEqualityComparer<TKey> comparer) : base(comparer) { } public SaDictionary(int capacity) : base(capacity) { } public SaDictionary(IDictionary<TKey, TValue> dictionary, IEqualityComparer<TKey> comparer) : base(dictionary, comparer) { } public SaDictionary(int capacity, IEqualityComparer<TKey> comparer) : base(capacity, comparer) { } //protected SaDictionary(SerializationInfo info, StreamingContext context) // : base(info, context) //{ //} #endregion public XmlSchema GetSchema() { return null; } public void ReadXml(XmlReader reader) { XmlSerializer keySerializer = new XmlSerializer(typeof(TKey)); XmlSerializer valueSerializer = new XmlSerializer(typeof(TValue)); bool wasEmpty = reader.IsEmptyElement; reader.Read(); if (wasEmpty) return; while (reader.NodeType != XmlNodeType.EndElement) { reader.ReadStartElement("item"); reader.ReadStartElement("key"); TKey key = (TKey)keySerializer.Deserialize(reader); reader.ReadEndElement(); //key reader.ReadStartElement("value"); TValue value = (TValue)valueSerializer.Deserialize(reader); reader.ReadEndElement(); //value this.Add(key, value); reader.ReadEndElement(); //item // reader.MoveToContent(); } reader.ReadEndElement(); } public void WriteXml(XmlWriter writer) { XmlSerializer keySerializer = new XmlSerializer(typeof(TKey)); XmlSerializer valueSerializer = new XmlSerializer(typeof(TValue)); foreach (TKey key in this.Keys) { writer.WriteStartElement("item"); writer.WriteStartElement("key"); keySerializer.Serialize(writer, key); writer.WriteEndElement(); //key writer.WriteStartElement("value"); TValue value = this[key]; valueSerializer.Serialize(writer, value); writer.WriteEndElement(); //value writer.WriteEndElement(); //item } } } } However i get an ArrayOfXElement back. Is there a way to cast it back to a Dictionary? greets

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  • using a Singleton to pass credentials in a multi-tenant application a code smell?

    - by Hans Gruber
    Currently working on a multi-tenant application that employs Shared DB/Shared Schema approach. IOW, we enforce tenant data segregation by defining a TenantID column on all tables. By convention, all SQL reads/writes must include a Where TenantID = '?' clause. Not an ideal solution, but hindsight is 20/20. Anyway, since virtually every page/workflow in our app must display tenant specific data, I made the (poor) decision at the project's outset to employ a Singleton to encapsulate the current user credentials (i.e. TenantID and UserID). My thinking at the time was that I didn't want to add a TenantID parameter to each and every method signature in my Data layer. Here's what the basic pseudo-code looks like: public class UserIdentity { public UserIdentity(int tenantID, int userID) { TenantID = tenantID; UserID = userID; } public int TenantID { get; private set; } public int UserID { get; private set; } } public class AuthenticationModule : IHttpModule { public void Init(HttpApplication context) { context.AuthenticateRequest += new EventHandler(context_AuthenticateRequest); } private void context_AuthenticateRequest(object sender, EventArgs e) { var userIdentity = _authenticationService.AuthenticateUser(sender); if (userIdentity == null) { //authentication failed, so redirect to login page, etc } else { //put the userIdentity into the HttpContext object so that //its only valid for the lifetime of a single request HttpContext.Current.Items["UserIdentity"] = userIdentity; } } } public static class CurrentUser { public static UserIdentity Instance { get { return HttpContext.Current.Items["UserIdentity"]; } } } public class WidgetRepository: IWidgetRepository{ public IEnumerable<Widget> ListWidgets(){ var tenantId = CurrentUser.Instance.TenantID; //call sproc with tenantId parameter } } As you can see, there are several code smells here. This is a singleton, so it's already not unit test friendly. On top of that you have a very tight-coupling between CurrentUser and the HttpContext object. By extension, this also means that I have a reference to System.Web in my Data layer (shudder). I want to pay down some technical debt this sprint by getting rid of this singleton for the reasons mentioned above. I have a few thoughts on what an better implementation might be, but if anyone has any guidance or lessons learned they could share, I would be much obliged.

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  • Spring's JdbcDaoSupport (using MySQL Connector/J) fails after executing sql that adds FK

    - by John
    I am using Spring's JdbcDaoSupport class with a DriverManagerDataSource using the MySQL Connector/J 5.0 driver (driverClassName=com.mysql.jdbc.driver). allowMultiQueries is set to true in the url. My application is an in-house tool we recently developed that executes sql scripts in a directory one-by-one (allows us to re-create our schema and reference table data for a given date, etc, but I digress). The sql scripts sometime contain multiple statements (hence allowMultiQueries), so one script can create a table, add indexes for that table, etc. The problem happens when including a statement to add a foreign key constraint in one of these files. If I have a file that looks like... --(column/constraint names are examples) CREATE TABLE myTable ( fk1 BIGINT(19) NOT NULL, fk2 BIGINT(19) NOT NULL, PRIMARY KEY (fk1, fk2) ); ALTER TABLE myTable ADD CONSTRAINT myTable_fk1 FOREIGN KEY (fk1) REFERENCES myOtherTable (id) ; ALTER TABLE myTable ADD CONSTRAINT myTable_fk2 FOREIGN KEY (fk2) REFERENCES myOtherOtherTable (id) ; then JdbcTemplate.execute throws an UncategorizedSqlException with the following error message and stack trace: Exception in thread "main" org.springframework.jdbc.UncategorizedSQLException: StatementCallback; uncategorized SQLException for SQL [ THE SQL YOU SEE ABOVE LISTED HERE ]; SQL state [HY000]; error code [1005]; Can't create table 'myDatabase.myTable' (errno: 150); nested exception is java.sql.SQLException: Can't create table 'myDatabase.myTable' (errno: 150) at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:83) at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:80) at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:80) and the table and foreign keys are not inserted. Also, especially weird: if I take the foreign key statements out of the script I showed above and then place them in their own script that executes after (so I now have 1 script with just the create table statement, and 1 script with the add foreign key statements that executes after that) then what happens is: tool executes create table script, works fine, table is created tool executes add fk script, throws the same exception as seen above (except errno=121 this time), but the FKs actually get added (!!!) In other words, when the create table/FK statements are in the same script then the exception is thrown and nothing is created, but when they are different scripts a nearly identical exception is thrown but both things get created. Any help on this would be greatly appreciated. Please let me know if you'd like me to clarify anything more.

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  • MATLAB image corner coordinates & referncing to cell arrays

    - by James
    Hi, I am having some problems comparing the elements in different cell arrays. The context of this problem is that I am using the bwboundaries function in MATLAB to trace the outline of an image. The image is of a structural cross section and I am trying to find if there is continuity throughout the section (i.e. there is only one outline produced by the bwboundaries command). Having done this and found where the is more than one section traced (i.e. it is not continuous), I have used the cornermetric command to find the corners of each section. The code I have is: %% Define the structural section as a binary matrix (Image is an I-section with the web broken) bw(20:40,50:150) = 1; bw(160:180,50:150) = 1; bw(20:60,95:105) = 1; bw(140:180,95:105) = 1; Trace = bw; [B] = bwboundaries(Trace,'noholes'); %Traces the outer boundary of each section L = length(B); % Finds number of boundaries if L > 1 disp('Multiple boundaries') % States whether more than one boundary found end %% Obtain perimeter coordinates for k=1:length(B) %For all the boundaries perim = B{k}; %Obtains perimeter coordinates (as a 2D matrix) from the cell array end %% Find the corner positions C = cornermetric(bw); Areacorners = find(C == max(max(C))) % Finds the corner coordinates of each boundary [rowindexcorners,colindexcorners] = ind2sub(size(Newgeometry),Areacorners) % Convert corner coordinate indexes into subcripts, to give x & y coordinates (i.e. the same format as B gives) %% Put these corner coordinates into a cell array Cornerscellarray = cell(length(rowindexcorners),1); % Initialises cell array of zeros for i =1:numel(rowindexcorners) Cornerscellarray(i) = {[rowindexcorners(i) colindexcorners(i)]}; %Assigns the corner indicies into the cell array %This is done so the cell arrays can be compared end for k=1:length(B) %For all the boundaries found perim = B{k}; %Obtains coordinates for each perimeter Z = perim; % Initialise the matrix containing the perimeter corners Sectioncellmatrix = cell(length(rowindexcorners),1); for i =1:length(perim) Sectioncellmatrix(i) = {[perim(i,1) perim(i,2)]}; end for i = 1:length(perim) if Sectioncellmatrix(i) ~= Cornerscellarray Sectioncellmatrix(i) = []; %Gets rid of the elements that are not corners, but keeps them associated with the relevent section end end end This creates an error in the last for loop. Is there a way I can check whether each cell of the array (containing an x and y coordinate) is equal to any pair of coordinates in cornercellarray? I know it is possible with matrices to compare whether a certain element matches any of the elements in another matrix. I want to be able to do the same here, but for the pair of coordinates within the cell array. The reason I don't just use the cornercellarray cell array itself, is because this lists all the corner coordinates and does not associate them with a specific traced boundary.

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  • (mySQL) Unable to query 2 tables properly for data

    - by Devner
    I have 2 tables. One is 'page_links' and the other is 'rpp'. Table page_links is the superset of table rpp. The following is the schema of my tables: -- Table structure for table `page_links` -- CREATE TABLE IF NOT EXISTS `page_links` ( `page` varchar(255) NOT NULL, `page_link` varchar(100) NOT NULL, `heading_id` tinyint(3) unsigned NOT NULL, PRIMARY KEY (`page`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; -- -- Dumping data for table `page_links` -- INSERT INTO `page_links` (`page`, `page_link`, `heading_id`) VALUES ('a1.php', 'A1', 8), ('b1.php', 'B1', 8), ('c1.php', 'C1', 5), ('d1.php', 'D1', 5), ('e1.php', 'E1', 8), ('f1.php', 'F1', 8), ('g1.php', 'G1', 8), ('h1.php', 'H1', 1), ('i1.php', 'I1', 1), ('j1.php', 'J1', 8), ('k1.php', 'K1', 8), ('l1.php', 'L1', 8), ('m1.php', 'M1', 8), ('n1.php', 'N1', 8), ('o1.php', 'O1', 8), ('p1.php', 'P1', 4), ('q1.php', 'Q1', 5), ('r1.php', 'R1', 4); -- Table structure for table `rpp` -- CREATE TABLE IF NOT EXISTS `rpp` ( `role_id` tinyint(3) unsigned NOT NULL, `page` varchar(255) NOT NULL, `is_allowed` tinyint(1) NOT NULL, PRIMARY KEY (`role_id`,`page`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; -- -- Dumping data for table `rpp` -- INSERT INTO `rpp` (`role_id`, `page`, `is_allowed`) VALUES (3, 'a1.php', 1), (3, 'b1.php', 1), (3, 'c1.php', 1), (3, 'd1.php', 1), (3, 'e1.php', 1), (3, 'f1.php', 1), (3, 'h1.php', 1), (3, 'i1.php', 1), (3, 'l1.php', 1), (3, 'm1.php', 1), (3, 'n1.php', 1), (4, 'a1.php', 1), (4, 'b1.php', 1), (4, 'q1.php', 1), (5, 'r1.php', 1); WHAT I AM TRYING TO DO: I am trying to query both the above tables (in a single query) in such a way that all the pages from page_links are displayed along with the is_allowed value from rpp for a particular role. For example, I want to get the is_allowed value of all the pages from rpp for role_id = 3 and at the same time, list all the available pages from page_links. A clear example of my expected result would be: page is_allowed role_id ---------------------------------------- a1.php 1 3 b1.php 1 3 c1.php 1 3 d1.php 1 3 e1.php 1 3 f1.php 1 3 g1.php NULL NULL h1.php 1 3 i1.php 1 3 j1.php NULL NULL k1.php NULL NULL l1.php 1 3 m1.php 1 3 n1.php 1 3 o1.php NULL NULL p1.php NULL NULL q1.php NULL NULL r1.php NULL NULL One more example of my desired result could be achieved by doing a LEFT JOIN rpp ON page_links.page = rpp.page but we need to omit using role_id = 3 (or any value) to be able to get that. But I do want to specify the role_id as well and get the results. I need the query to be able to get this result. I would appreciate any replies that could help me with this. If you can suggest me any changes as well to the table(s) design to be able to achieve the desired result, that's good as well. Thanks in advance.

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  • Is there a way to make PHP's SplHeap recalculate? (aka: add up-heap to SplHeap?)

    - by md2k7
    I am using an SplHeap to hold graph nodes of a tree with directed edges that will be traversed from the leaves to the root. For this, I precalculate the "fan-in" of nodes and put them into the heap so that I can always retrieve the node with the smallest fan-in (0) from it. After visiting a node, I reduce the fan-in of its successor by 1. Then obviously, the heap needs to be recalculated because the successor is now in the wrong place there. I have tried recoverFromCorruption(), but it doesn't do anything and keeps the heap in the wrong order (node with larger fanIn stays in front of smaller fanIn). As a workaround, I'm now creating a new heap after each visit, amounting to a full O(N*log(N)) sort each time. It should be possible, however, to make up-heap operations on the changed heap entry until it's in the right position in O(log(N)). The API for SplHeap doesn't mention an up-heap (or deletion of an arbitrary element - it could then be re-added). Can I somehow derive a class from SplHeap to do this or do I have to create a pure PHP heap from scratch? EDIT: Code example: class VoteGraph { private $nodes = array(); private function calculateFanIn() { /* ... */ } // ... private function calculateWeights() { $this->calculateFanIn(); $fnodes = new GraphNodeHeap(); // heap by fan-in ascending (leaves are first) foreach($this->nodes as $n) { // omitted: filter loops $fnodes->insert($n); } // traversal from leaves to root while($fnodes->valid()) { $node = $fnodes->extract(); // fetch a leaf from the heap $successor = $this->nodes[$node->successor]; // omitted: actual job of traversal $successor->fanIn--; // will need to fix heap (sift up successor) because of this //$fnodes->recoverFromCorruption(); // doesn't work for what I want // workaround: rebuild $fnodes from scratch $fixedHeap = new GraphNodeHeap(); foreach($fnodes as $e) $fixedHeap->insert($e); $fnodes = $fixedHeap; } } } class GraphNodeHeap extends SplHeap { public function compare($a, $b) { if($a->fanIn === $b->fanIn) return 0; else return $a->fanIn < $b->fanIn ? 1 : -1; } }

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  • gcc optimization? bug? and its practial implication to project

    - by kumar_m_kiran
    Hi All, My questions are divided into three parts Question 1 Consider the below code, #include <iostream> using namespace std; int main( int argc, char *argv[]) { const int v = 50; int i = 0X7FFFFFFF; cout<<(i + v)<<endl; if ( i + v < i ) { cout<<"Number is negative"<<endl; } else { cout<<"Number is positive"<<endl; } return 0; } No specific compiler optimisation options are used or the O's flag is used. It is basic compilation command g++ -o test main.cpp is used to form the executable. The seemingly very simple code, has odd behaviour in SUSE 64 bit OS, gcc version 4.1.2. The expected output is "Number is negative", instead only in SUSE 64 bit OS, the output would be "Number is positive". After some amount of analysis and doing a 'disass' of the code, I find that the compiler optimises in the below format - Since i is same on both sides of comparison, it cannot be changed in the same expression, remove 'i' from the equation. Now, the comparison leads to if ( v < 0 ), where v is a constant positive, So during compilation itself, the else part cout function address is added to the register. No cmp/jmp instructions can be found. I see that the behaviour is only in gcc 4.1.2 SUSE 10. When tried in AIX 5.1/5.3 and HP IA64, the result is as expected. Is the above optimisation valid? Or, is using the overflow mechanism for int not a valid use case? Question 2 Now when I change the conditional statement from if (i + v < i) to if ( (i + v) < i ) even then, the behaviour is same, this atleast I would personally disagree, since additional braces are provided, I expect the compiler to create a temporary built-in type variable and them compare, thus nullify the optimisation. Question 3 Suppose I have a huge code base, an I migrate my compiler version, such bug/optimisation can cause havoc in my system behaviour. Ofcourse from business perspective, it is very ineffective to test all lines of code again just because of compiler upgradation. I think for all practical purpose, these kinds of error are very difficult to catch (during upgradation) and invariably will be leaked to production site. Can anyone suggest any possible way to ensure to ensure that these kind of bug/optimization does not have any impact on my existing system/code base? PS : When the const for v is removed from the code, then optimization is not done by the compiler. I believe, it is perfectly fine to use overflow mechanism to find if the variable is from MAX - 50 value (in my case).

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  • NHibernate and objects with value-semantics

    - by Groo
    Problem: If I pass a class with value semantics (Equals method overridden) to NHibernate, NHibernate tries to save it to db even though it just saved an entity equal by value (but not by reference) to the database. What am I doing wrong? Here is a simplified example model for my problem: Let's say I have a Person entity and a City entity. One thread (producer) is creating new Person objects which belong to a specific existing City, and another thread (consumer) is saving them to a repository (using NHibernate as DAL). Since there is lot of objects being flushed at a time, I am using Guid.Comb id's to ensure that each insert is made using a single SQL command. City is an object with value-type semantics (equal by name only -- for this example purposes only): public class City : IEquatable<City> { public virtual Guid Id { get; private set; } public virtual string Name { get; set; } public virtual bool Equals(City other) { if (other == null) return false; return this.Name == other.Name; } public override bool Equals(object obj) { return Equals(obj as City); } public override int GetHashCode() { return this.Name.GetHashCode(); } } Fluent NH mapping is something like: public class PersonMap : ClassMap<Person> { public PersonMap() { Id(x => x.Id) .GeneratedBy.GuidComb(); References(x => x.City) .Cascade.SaveUpdate(); } } public class CityMap : ClassMap<City> { public CityMap() { Id(x => x.Id) .GeneratedBy.GuidComb(); Map(x => x.Name); } } Right now (with my current NHibernate mapping config), my consumer thread maintains a dictionary of cities and replaces their references in incoming person objects (otherwise NHibernate will see a new, non-cached City object and try to save it as well), and I need to do it for every produced Person object. Since I have implemented City class to behave like a value type, I hoped that NHibernate would compare Cities by value and not try to save them each time -- i.e. I would only need to do a lookup once per session and not care about them anymore. Is this possible, and if yes, what am I doing wrong here?

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  • What does Apache need to support both mysqli and PDO?

    - by Nathan Long
    I'm considering changing some PHP code to use PDO for database access instead of mysqli (because the PDO syntax makes more sense to me and is database-agnostic). To do that, I'd need both methods to work while I'm making the changeover. My problem is this: so far, either one or the other method will crash Apache. Right now I'm using XAMPP in Windows XP, and PHP Version 5.2.8. Mysqli works fine, and so does this: $dbc = new PDO("mysql:host=$hostname;dbname=$dbname", $username, $password); echo 'Connected to database'; $sql = "SELECT * FROM `employee`"; But this line makes Apache crash: $dbc->query($sql); I don't want to redo my entire Apache or XAMPP installation, but I'd like for PDO to work. So I tried updating libmysql.dll from here, as oddvibes recommended here. That made my simple PDO query work, but then mysqli queries crashed Apache. (I also tried the suggestion after that one, to update php_pdo_mysql.dll and php_pdo.dll, to no effect.) Test Case I created this test script to compare PDO vs mysqli. With the old copy of libmysql.dll, it crashes if $use_pdo is true and doesn't if it's false. With the new copy of libmysql.dll, it's the opposite. if ($use_pdo){ $dbc = new PDO("mysql:host=$hostname;dbname=$dbname", $username, $password); echo 'Connected to database<br />'; $sql = "SELECT * FROM `employee`"; $dbc->query($sql); foreach ($dbc->query($sql) as $row){ echo $row['firstname'] . ' ' . $row['lastname'] . "<br>\n"; } } else { $dbc = @mysqli_connect($hostname, $username, $password, $dbname) OR die('Could not connect to MySQL: ' . mysqli_connect_error()); $sql = "SELECT * FROM `employee`"; $result = @mysqli_query($dbc, $sql) or die(mysqli_error($dbc)); while ($row = mysqli_fetch_array($result,MYSQLI_ASSOC)) { echo $row['firstname'] . ' ' . $row['lastname'] . "<br>\n"; } } What does Apache need in order to support both methods of database query?

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  • Approaches for Content-based Item Recommendations

    - by PartlyCloudy
    Hello, I'm currently developing an application where I want to group similar items. Items (like videos) can be created by users and also their attributes can be altered or extended later (like new tags). Instead of relying on users' preferences as most collaborative filtering mechanisms do, I want to compare item similarity based on the items' attributes (like similar length, similar colors, similar set of tags, etc.). The computation is necessary for two main purposes: Suggesting x similar items for a given item and for clustering into groups of similar items. My application so far is follows an asynchronous design and I want to decouple this clustering component as far as possible. The creation of new items or the addition of new attributes for an existing item will be advertised by publishing events the component can then consume. Computations can be provided best-effort and "snapshotted", which means that I'm okay with the best result possible at a given point in time, although result quality will eventually increase. So I am now searching for appropriate algorithms to compute both similar items and clusters. At important constraint is scalability. Initially the application has to handle a few thousand items, but later million items might be possible as well. Of course, computations will then be executed on additional nodes, but the algorithm itself should scale. It would also be nice if the algorithm supports some kind of incremental mode on partial changes of the data. My initial thought of comparing each item with each other and storing the numerical similarity sounds a little bit crude. Also, it requires n*(n-1)/2 entries for storing all similarities and any change or new item will eventually cause n similarity computations. Thanks in advance! UPDATE tl;dr To clarify what I want, here is my targeted scenario: User generate entries (think of documents) User edit entry meta data (think of tags) And here is what my system should provide: List of similar entries to a given item as recommendation Clusters of similar entries Both calculations should be based on: The meta data/attributes of entries (i.e. usage of similar tags) Thus, the distance of two entries using appropriate metrics NOT based on user votings, preferences or actions (unlike collaborative filtering). Although users may create entries and change attributes, the computation should only take into account the items and their attributes, and not the users associated with (just like a system where only items and no users exist). Ideally, the algorithm should support: permanent changes of attributes of an entry incrementally compute similar entries/clusters on changes scale something better than a simple distance table, if possible (because of the O(n²) space complexity)

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