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  • Mapping issue with multi-field primary keys using hibernate/JPA annotations

    - by Derek Clarkson
    Hi all, I'm stuck with a database which is using multi-field primary keys. I have a situation where I have a master and details table, where the details table's primary key contains fields which are also the foreign key's the the master table. Like this: Master primary key fields: master_pk_1 Details primary key fields: master_pk_1 details_pk_2 details_pk_3 In the Master class we define the hibernate/JPA annotations like this: @Id @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "idGenerator") @Column(name = "master_pk_1") private long masterPk1; @OneToMany(cascade=CascadeType.ALL) @JoinColumn(name = "master_pk_1", referencedColumnName = "master_pk_1") private List<Details> details = new ArrayList<Details>(); And in the details class I have defined the id and back reference like this: @EmbeddedId @AttributeOverrides( { @AttributeOverride( name = "masterPk1", column = @Column(name = "master_pk_1")), @AttributeOverride(name = "detailsPk2", column = @Column(name = "details_pk_2")), @AttributeOverride(name = "detailsPk2", column = @Column(name = "details_pk_2")) }) private DetailsPrimaryKey detailsPrimaryKey = new DetailsPrimaryKey(); @ManyToOne @JoinColumn(name = "master_pk_1", referencedColumnName = "master_pk_1", insertable=false) private Master master; The goal of all of this was that I could create a new master, add some details to it, and when saved, JPA/Hibernate would generate the new id for master in the masterPk1 field, and automatically pass it down to the details records, storing it in the matching masterPk1 field in the DetailsPrimaryKey class. At least that's what the documentation I've been looking at implies. What actually happens is that hibernate appears to corectly create and update the records in the database, but not pass the key to the details classes in memory. Instead I have to manually set it myself. I also found that without the insertable=true added to the back reference to master, that hibernate would create sql that had the master_pk_1 field listed twice in the insert statement, resulting in the database throwing an exception. My question is simply is this arrangement of annotations correct? or is there a better way of doing it?

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  • Setting up a multi-site CMS, collecting thoughts about the DB schema

    - by Ben Fransen
    Hello all, I'm collecting some thoughts about creating a multisite CMS. In my opinion there are two major approaches. All data is stored into 1 database, giving me the advantage of single point of updates; Seperated databases, so each client has its own database. Giving me the advantage to measure bandwith. Option 1 gives me the disadvantage of measuring bandwith while option is giving me the disadvantage of a single point of update structure. Are there any generic approaches for creating a sort of update system? So my clients can download a small package (maybe a zip with a conf file to tell the updatescript where to put all the files and how to extend the database??) Do you guys have some thougths about the best solution for a situation like this? I have my own webserver, full access to all resources and I'm developing in PHP with MySQL as DBMS. I hope to hear from you and I surely appreciate any effort you make to help me further! Greets from Holland, Ben Fransen

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  • How do I use Linq-to-sql to iterate db records?

    - by Seth Spearman
    I asked on SO a few days ago what was the simplest quickest way to build a wrapper around a recently completed database. I took the advice and used sqlmetal to build linq classes around my database design. Now I am having two problems. One, I don't know LINQ. And, two, I have been shocked to realize how hard it is to learn. I have a book on LINQ (Linq In Action by Manning) and it has helped some but at the end of the day it is going to take me a couple of weeks to get traction and I need to make some progress on my project today. So, I am looking for some help getting started. Click HERE To see my simple database schema. Click HERE to see the vb class that was generated for the schema. My needs are simple. I have a console app. The main table is the SupplyModel table. Most of the other tables are child tables of the SupplyModel table. I want to iterate through each of Supply Model records. I want to grab the data for a supply model and then DoStuff with the data. And I also need to iterate through the child records, for each supply model, for example the NumberedInventories and DoStuff with that as well. I need help doing this in VB rather than C# if possible. I am not looking for the whole solution...if you can supply a couple of code-snippets to get me on my way that would be great. Thanks for your help. Seth

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  • .NET threading solution for long queries

    - by Eddie
    Senerio We have an application that records incidents. An external database needs to be queried when an incident is approved by a supervisor. The queries to this external database are sometimes taking a while to run. This lag is experienced through the browser. Possible Solution I want to use threading to eliminate the simulated hang to the browser. I have used the Thread class before and heard about ThreadPool. But, I just found BackgroundWorker in this post. MSDN states: The BackgroundWorker class allows you to run an operation on a separate, dedicated thread. Time-consuming operations like downloads and database transactions can cause your user interface (UI) to seem as though it has stopped responding while they are running. When you want a responsive UI and you are faced with long delays associated with such operations, the BackgroundWorker class provides a convenient solution. Is BackgroundWorker the way to go when handling long running queries? What happens when 2 or more BackgroundWorker processes are ran simultaneously? Is it handled like a pool?

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  • ZIP Numerous Blob Files

    - by Michael
    I have a database table that contains numerous PDF blob files. I am attempting to combine all of the files into a single ZIP file that I can download and then print. Please help! <?php include 'config.php'; include 'connect.php'; $session= $_GET[session]; $query = " SELECT $tbl_uploads.username, $tbl_uploads.description, $tbl_uploads.type, $tbl_uploads.size, $tbl_uploads.content, $tbl_members.session FROM $tbl_uploads LEFT JOIN $tbl_members ON $tbl_uploads.username = $tbl_members.username WHERE $tbl_members.session= '$session'"; $result = mysql_query($query) or die('Error, query failed'); while(list($username, $description, $type, $size, $content) = mysql_fetch_array($result)) { header("Content-length: $size"); header("Content-type: $type"); header("Content-Disposition: inline; filename=$username-$description.pdf"); echo $content; } $files = array('File 1 from database', 'File 2 from database'); $zip = new ZipArchive; $zip->open('file.zip', ZipArchive::CREATE); foreach ($files as $file) { $zip->addFile($file); } $zip->close(); header('Content-Type: application/zip'); header('Content-disposition: attachment; filename=filename.zip'); header('Content-Length: ' . filesize($zipfilename)); readfile($zipname); mysql_close($link); exit; ?>

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  • Rails : fighting long http response times with ajax. Is it a good idea? Please, help with implementa

    - by baranov
    Hi, everybody! I've googled some tutorials, browsed some SO answers, and was unable to find a recipe for my problem. I'm writing a web site which is supposed to display almost realtime stock chart. Data is stored in constantly updating MySQL database, I wrote a find_by_sql query code which fetches all the data I need to get my chart drawn. Everything is ok, except performance - it takes from one second to one minute for different queries to fetch all the data from the database, this time includes necessary (My)SQL-server side calculations. This is simply unacceptable. I got the following idea: if the data is queried from the MySQL server one point a time instead of entire dataset, it takes only about 1-100ms to get an individual point. I imagine the data fetch process might be browser-driven. After the user presses the button in order to get a chart drawn, controller makes one request to the database and renders, say, a progress bar, say 1% ready. When the browser gets the response, it immediately makes an (ajax) request, and the server fetches the next piece of data and renders "2%". And so on, until all the data is ready and the server displays the requested chart. Could this be implemented in rails+js, is there a tutorial for solving a similar problem on the Web? I suppose if the thing is feasible at all, somebody should have already done this before. I have read several articles about ajax, I believe I do understand general principles, but never did nontrivial ajax programming myself. Thanks for your time!

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  • Combining multiple rows into one row, Oracle

    - by Torbjørn
    Hi. I'm working with a database which is created in Oracle and used in a GIS-software through SDE. One of my colleuges is going to make some statistics out of this database and I'm not capable of finding a reasonable SQL-query for getting the data. I have two tables, one with registrations and one with registrationdetails. It's a one to many relationship, so the registration can have one or more details connected to it (no maximum number). table: Registration RegistrationID Date TotLenght 1 01.01.2010 5 2 01.02.2010 15 3 05.02.2009 10 2.table: RegistrationDetail DetailID RegistrationID Owner Type Distance 1 1 TD UB 1,5 2 1 AB US 2 3 1 TD UQ 4 4 2 AB UQ 13 5 2 AB UR 13,1 6 3 TD US 5 I want the resulting selection to be something like this: RegistrationID Date TotLenght DetailID RegistrationID Owner Type Distance DetailID RegistrationID Owner Type Distance DetailID RegistrationID Owner Type Distance 1 01.01.2010 5 1 1 TD UB 1,5 2 1 AB US 2 3 1 TD UQ 4 2 01.02.2010 15 4 2 AB UQ 13 5 2 AB UR 13,1 3 05.02.2009 10 6 3 TD US 5 With a normal join I get one row per each registration and detail. Can anyone help me with this? I don't have administrator-rights for the database, so I can't create any tables or variables. If it's possible, I could copy the tables into Access.

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  • How to deal with "partial" dates (2010-00-00) from MySQL in Django?

    - by Etienne
    In one of my Django projects that use MySQL as the database, I need to have a date fields that accept also "partial" dates like only year (YYYY) and year and month (YYYY-MM) plus normal date (YYYY-MM-DD). The date field in MySQL can deal with that by accepting 00 for the month and the day. So 2010-00-00 is valid in MySQL and it represent 2010. Same thing for 2010-05-00 that represent May 2010. So I started to create a PartialDateField to support this feature. But I hit a wall because, by default, and Django use the default, MySQLdb, the python driver to MySQL, return a datetime.date object for a date field AND datetime.date() support only real date. So it's possible to modify the converter for the date field used by MySQLdb and return only a string in this format 'YYYY-MM-DD'. Unfortunately the converter use by MySQLdb is set at the connection level so it's use for all MySQL date fields. But Django DateField rely on the fact that the database return a datetime.date object, so if I change the converter to return a string, Django is not happy at all. Someone have an idea or advice to solve this problem? How to create a PartialDateField in Django ? EDIT Also I should add that I already thought of 2 solutions, create 3 integer fields for year, month and day (as mention by Alison R.) or use a varchar field to keep date as string in this format YYYY-MM-DD. But in both solutions, if I'm not wrong, I will loose the special properties of a date field like doing query of this kind on them: Get all entries after this date. I can probably re-implement this functionality on the client side but that will not be a valid solution in my case because the database can be query from other systems (mysql client, MS Access, etc.)

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  • Is there anyway to carry a value in php forward to a second page?

    - by Henry Aspden
    I have created a php site, and previously it was listing only products with defined values. I have now changed it to include an array of products for example all products WHERE id = "spotlights" and this works great so it means I can add new products just to the database, but I still have to add the second page manually. e.g going from the product div on the main page, through to www.example.com/spotlight_1.php Is there anyway in PHP to carry the data from my index.php e.g. the ID through to the next page? so that I can have a template product.php page, and I can use a database pull to echo the product information required. So on index.php i click on the product with ID="1" and on the product.php page, it loads the relevant data for product 1. I can write the php SQL/mySQL calls myself, its just the way to carry accross a value from the previous page which I dont understand Regards Henry p.s. all the IDs and things are stored in the database already as 1 to 3digit values e.g. 3 or or 93 or 254 Any advice as always is greatly appreciated Regards Henry

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  • SQLite for personal use

    - by ALife
    What are the applications for your personal use that needs a small database like SQLite? I am thinking of trying a few popular databases and SQLite is surely the first one I am planning to try since I know barely nothing about database except some simple programming years ago. I learned that SQLite is good for personal use. But embarrassingly I do not see any application except maybe managing my list of phone numbers/contact info, which has probably a few hundred items. What's your experience? FYI, I use EndNote for my reference and softcopy of books, and I feel iTunes' music/media management is ok since I am not a frequent user anyway. And others? I do lots of coding, but I just use some simple etags tools for that. And I pretty much use .txt file (sometimes in the asciidoc style) for my notes. I have quite a bunch of notes, but not that many either. So, really, what are your personal applications that need a small database instead of existing tools and plain text files?

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  • How to publish internal data to the internet - as simple as possible

    - by mlarsen
    We have a .net 2-tier application where a desktop program is talking to a database. We support MS SQL Server 2000, 2005, 2008 and Oracle 9, 10 and 11. The application is sold, not as shrink-wrap, but pretty close. It is quite important for us that the installation and configuration is as easy as possible as installation instructions are usually supplied in written form to the customers internal IT-department. Our application is usually not seen as mission critical for the IT-department, so we need to keep their work down to a minimum. Now we are starting to get wishes for a web application build on top of the same data. The web application will be hosted by us and delivered as a SaaS application. Now the challenge is how to move data back and forth between the web application and the customers internal database. as I see it we have some requirements: We must be ready to handle the situation where the customers database is not accessible from the DMZ. I guess the easiest solution is that all communication is initiated from inside the customers lan. As little firewall configuration as possible. The best is if we can run without any special configuration as long as outgoing traffic from the customers lan are not blocked. If we need something changed in the firewall, we must be able to document that the change is secure. It doesn't have to be real time. Moving data in batches every ten minutes or so is OK. Data moves both ways, but not the same tables, so we don't have to support merges. It would be nice if we don't have to roll our own framework completely. Looking forward to hear your suggestions.

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  • how do simple SQLAlchemy relationships work?

    - by Carson Myers
    I'm no database expert -- I just know the basics, really. I've picked up SQLAlchemy for a small project, and I'm using the declarative base configuration rather than the "normal" way. This way seems a lot simpler. However, while setting up my database schema, I realized I don't understand some database relationship concepts. If I had a many-to-one relationship before, for example, articles by authors (where each article could be written by only a single author), I would put an author_id field in my articles column. But SQLAlchemy has this ForeignKey object, and a relationship function with a backref kwarg, and I have no idea what any of it MEANS. I'm scared to find out what a many-to-many relationship with an intermediate table looks like (when I need additional data about each relationship). Can someone demystify this for me? Right now I'm setting up to allow openID auth for my application. So I've got this: from __init__ import Base from sqlalchemy.schema import Column from sqlalchemy.types import Integer, String class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) username = Column(String, unique=True) email = Column(String) password = Column(String) salt = Column(String) class OpenID(Base): __tablename__ = 'openid' url = Column(String, primary_key=True) user_id = #? I think the ? should be replaced by Column(Integer, ForeignKey('users.id')), but I'm not sure -- and do I need to put openids = relationship("OpenID", backref="users") in the Users class? Why? What does it do? What is a backref?

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  • Is it wise to use temporary tables?

    - by Industrial
    Hi guys, We have a mySQL database table for products. We are utilizing a cache layer to reduce database load, but we think that it's a good idea to minimize the actual data needed to be stored in the cache layer to speed up the application further. All the products in the database, that is visible to visitors have a price attached to them: The prices are stored in a different table, called prices . There are multiple price categories depending on which discount level each visitor (customer) applies to. From time to time, there are campaigns which means that a special price for each product is available. The special prices are stored in a table called specials. Is it a bad to make a temp table that binds the tables together? It would only have the neccessary information and would ofcourse be cached. -------------|-------------|------------ | productId | hasPrice | hasSpecial -------------|-------------|------------ 1 | 1 | 0 2 | 1 | 1 By doing such, it would be super easy to know if the specific product really has a price, without having to iterate through the complete prices or specials table each time a product should be listed or presented. Are temp tables a common thing for web applications or is it just bad design?

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  • Understanding MongoDB(and NoSQL in general) and How to make the best use of it

    - by Earlz
    Hello, I am beginning to think that my next project I am wanting to do would work better with a NoSQL solution. The project would either involve a ton of 2-column tables or a ton of dynamic queries with dynamically generated columns in a traditional SQL database. So I feel a NoSQL database would be much cleaner. I'm looking at MongoDB and it looks pretty promising. Anyway, I'm attempting to make sense of it all. Also, I will be using MongoMapper in Ruby. Anyway though, I'm confused as to how to layout things in such a freeform database. I've read http://stackoverflow.com/questions/2170152/nosql-best-practices and the answer there says that normalization is usually bad in a NoSQL DB. So how would be the best way of laying out say a simple blog with users, posts, and comments? My natural thought was to have 3 collections for each and then link them by a unique ID. But this apparently is wrong? So, what are some of the ways to lay out such a thing? My concern with the answer given in the other question is what if the author's name changed. You'd have to go through updating a ton of posts and comments. But is this an ok thing to do with NoSQL?

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  • Understanding MongoDB (and NoSQL in general) and how to make the best use of it

    - by Earlz
    Hello, I am beginning to think that my next project I am wanting to do would work better with a NoSQL solution. The project would either involve a ton of 2-column tables or a ton of dynamic queries with dynamically generated columns in a traditional SQL database. So I feel a NoSQL database would be much cleaner. I'm looking at MongoDB and it looks pretty promising. Anyway, I'm attempting to make sense of it all. Also, I will be using MongoMapper in Ruby. Anyway though, I'm confused as to how to layout things in such a freeform database. I've read http://stackoverflow.com/questions/2170152/nosql-best-practices and the answer there says that normalization is usually bad in a NoSQL DB. So how would be the best way of laying out say a simple blog with users, posts, and comments? My natural thought was to have three collections for each and then link them by a unique ID. But this apparently is wrong? So, what are some of the ways to lay out such a thing? My concern with the answer given in the other question is, what if the author's name changed? You'd have to go through updating a ton of posts and comments. But is this an okay thing to do with NoSQL?

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  • How do I get PHP variables from this MySQL query?

    - by CT
    I am working on an Asset Database problem using PHP / MySQL. In this script I would like to search my assets by an asset id and have it return all related fields. First I query the database asset table and find the asset's type. Then depending on the type I run 1 of 3 queries. <?php //make database connect mysql_connect("localhost", "asset_db", "asset_db") or die(mysql_error()); mysql_select_db("asset_db") or die(mysql_error()); //get type of asset $type = mysql_query(" SELECT asset.type From asset WHERE asset.id = 93120 ") or die(mysql_error()); switch ($type){ case "Server": //do some stuff that involves a mysql query mysql_query(" SELECT asset.id ,asset.company ,asset.location ,asset.purchase_date ,asset.purchase_order ,asset.value ,asset.type ,asset.notes ,server.manufacturer ,server.model ,server.serial_number ,server.esc ,server.user ,server.prev_user ,server.warranty FROM asset LEFT JOIN server ON server.id = asset.id WHERE asset.id = 93120 "); break; case "Laptop": //do some stuff that involves a mysql query mysql_query(" SELECT asset.id ,asset.company ,asset.location ,asset.purchase_date ,asset.purchase_order ,asset.value ,asset.type ,asset.notes ,laptop.manufacturer ,laptop.model ,laptop.serial_number ,laptop.esc ,laptop.user ,laptop.prev_user ,laptop.warranty FROM asset LEFT JOIN laptop ON laptop.id = asset.id WHERE asset.id = 93120 "); break; case "Desktop": //do some stuff that involves a mysql query mysql_query(" SELECT asset.id ,asset.company ,asset.location ,asset.purchase_date ,asset.purchase_order ,asset.value ,asset.type ,asset.notes ,desktop.manufacturer ,desktop.model ,desktop.serial_number ,desktop.esc ,desktop.user ,desktop.prev_user ,desktop.warranty FROM asset LEFT JOIN desktop ON desktop.id = asset.id WHERE asset.id = 93120 "); break; } ?> So far I am able to get asset.type into $type. How would I go about getting the rest of the variables (laptop.model to $model, asset.notes to $notes and so on)? Thank you.

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  • Online ALTER TABLE in MySQL 5.6

    - by Marko Mäkelä
    This is the low-level view of data dictionary language (DDL) operations in the InnoDB storage engine in MySQL 5.6. John Russell gave a more high-level view in his blog post April 2012 Labs Release – Online DDL Improvements. MySQL before the InnoDB Plugin Traditionally, the MySQL storage engine interface has taken a minimalistic approach to data definition language. The only natively supported operations were CREATE TABLE, DROP TABLE and RENAME TABLE. Consider the following example: CREATE TABLE t(a INT); INSERT INTO t VALUES (1),(2),(3); CREATE INDEX a ON t(a); DROP TABLE t; The CREATE INDEX statement would be executed roughly as follows: CREATE TABLE temp(a INT, INDEX(a)); INSERT INTO temp SELECT * FROM t; RENAME TABLE t TO temp2; RENAME TABLE temp TO t; DROP TABLE temp2; You could imagine that the database could crash when copying all rows from the original table to the new one. For example, it could run out of file space. Then, on restart, InnoDB would roll back the huge INSERT transaction. To fix things a little, a hack was added to ha_innobase::write_row for committing the transaction every 10,000 rows. Still, it was frustrating that even a simple DROP INDEX would make the table unavailable for modifications for a long time. Fast Index Creation in the InnoDB Plugin of MySQL 5.1 MySQL 5.1 introduced a new interface for CREATE INDEX and DROP INDEX. The old table-copying approach can still be forced by SET old_alter_table=0. This interface is used in MySQL 5.5 and in the InnoDB Plugin for MySQL 5.1. Apart from the ability to do a quick DROP INDEX, the main advantage is that InnoDB will execute a merge-sort algorithm before inserting the index records into each index that is being created. This should speed up the insert into the secondary index B-trees and potentially result in a better B-tree fill factor. The 5.1 ALTER TABLE interface was not perfect. For example, DROP FOREIGN KEY still invoked the table copy. Renaming columns could conflict with InnoDB foreign key constraints. Combining ADD KEY and DROP KEY in ALTER TABLE was problematic and not atomic inside the storage engine. The ALTER TABLE interface in MySQL 5.6 The ALTER TABLE storage engine interface was completely rewritten in MySQL 5.6. Instead of introducing a method call for every conceivable operation, MySQL 5.6 introduced a handful of methods, and data structures that keep track of the requested changes. In MySQL 5.6, online ALTER TABLE operation can be requested by specifying LOCK=NONE. Also LOCK=SHARED and LOCK=EXCLUSIVE are available. The old-style table copying can be requested by ALGORITHM=COPY. That one will require at least LOCK=SHARED. From the InnoDB point of view, anything that is possible with LOCK=EXCLUSIVE is also possible with LOCK=SHARED. Most ALGORITHM=INPLACE operations inside InnoDB can be executed online (LOCK=NONE). InnoDB will always require an exclusive table lock in two phases of the operation. The execution phases are tied to a number of methods: handler::check_if_supported_inplace_alter Checks if the storage engine can perform all requested operations, and if so, what kind of locking is needed. handler::prepare_inplace_alter_table InnoDB uses this method to set up the data dictionary cache for upcoming CREATE INDEX operation. We need stubs for the new indexes, so that we can keep track of changes to the table during online index creation. Also, crash recovery would drop any indexes that were incomplete at the time of the crash. handler::inplace_alter_table In InnoDB, this method is used for creating secondary indexes or for rebuilding the table. This is the ‘main’ phase that can be executed online (with concurrent writes to the table). handler::commit_inplace_alter_table This is where the operation is committed or rolled back. Here, InnoDB would drop any indexes, rename any columns, drop or add foreign keys, and finalize a table rebuild or index creation. It would also discard any logs that were set up for online index creation or table rebuild. The prepare and commit phases require an exclusive lock, blocking all access to the table. If MySQL times out while upgrading the table meta-data lock for the commit phase, it will roll back the ALTER TABLE operation. In MySQL 5.6, data definition language operations are still not fully atomic, because the data dictionary is split. Part of it is inside InnoDB data dictionary tables. Part of the information is only available in the *.frm file, which is not covered by any crash recovery log. But, there is a single commit phase inside the storage engine. Online Secondary Index Creation It may occur that an index needs to be created on a new column to speed up queries. But, it may be unacceptable to block modifications on the table while creating the index. It turns out that it is conceptually not so hard to support online index creation. All we need is some more execution phases: Set up a stub for the index, for logging changes. Scan the table for index records. Sort the index records. Bulk load the index records. Apply the logged changes. Replace the stub with the actual index. Threads that modify the table will log the operations to the logs of each index that is being created. Errors, such as log overflow or uniqueness violations, will only be flagged by the ALTER TABLE thread. The log is conceptually similar to the InnoDB change buffer. The bulk load of index records will bypass record locking. We still generate redo log for writing the index pages. It would suffice to log page allocations only, and to flush the index pages from the buffer pool to the file system upon completion. Native ALTER TABLE Starting with MySQL 5.6, InnoDB supports most ALTER TABLE operations natively. The notable exceptions are changes to the column type, ADD FOREIGN KEY except when foreign_key_checks=0, and changes to tables that contain FULLTEXT indexes. The keyword ALGORITHM=INPLACE is somewhat misleading, because certain operations cannot be performed in-place. For example, changing the ROW_FORMAT of a table requires a rebuild. Online operation (LOCK=NONE) is not allowed in the following cases: when adding an AUTO_INCREMENT column, when the table contains FULLTEXT indexes or a hidden FTS_DOC_ID column, or when there are FOREIGN KEY constraints referring to the table, with ON…CASCADE or ON…SET NULL option. The FOREIGN KEY limitations are needed, because MySQL does not acquire meta-data locks on the child or parent tables when executing SQL statements. Theoretically, InnoDB could support operations like ADD COLUMN and DROP COLUMN in-place, by lazily converting the table to a newer format. This would require that the data dictionary keep multiple versions of the table definition. For simplicity, we will copy the entire table, even for DROP COLUMN. The bulk copying of the table will bypass record locking and undo logging. For facilitating online operation, a temporary log will be associated with the clustered index of table. Threads that modify the table will also write the changes to the log. When altering the table, we skip all records that have been marked for deletion. In this way, we can simply discard any undo log records that were not yet purged from the original table. Off-page columns, or BLOBs, are an important consideration. We suspend the purge of delete-marked records if it would free any off-page columns from the old table. This is because the BLOBs can be needed when applying changes from the log. We have special logging for handling the ROLLBACK of an INSERT that inserted new off-page columns. This is because the columns will be freed at rollback.

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  • rename an html page according to an image within it

    - by Jake
    Hi, firstly I'll give some background regarding the situation. I have a website containing approximately 56k pages each page contain a mapped sketch of a machine part. this machine part is made out of smaller parts which are outlined in the image and hold a certain number. when you hover over the numbers a box with the part item code shows up. I order parts according to this item codes but recently a lot of the items codes have changed, therefore I am looking for a solution. now I own a database with data on all the 56k parts and I want to link the relevant webpage to each record according to the name of the part(a column in my database), the problem is that the webpages names has no logic name that could connect with the part name in any way but the image that is displayed in the page has the exact name of the part. I want to rename all the html files I has according to the Images displayed within them. how can I achieve that without renaming all the 56k pages manually? additionally how can I add the links to all the 56k pages automatically to my database after all the above is done? Thank you for your patience I know it was long.

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  • Populating a foreign key table with variable user input

    - by Vincent
    I'm working on a website that will be based on user contributed data, submitted using a regular HTML form. To simplify my question, let's say that there will be two fields in the form: "User Name" and "Country" (this is just an example, not the actual site). There will be two tables in the database : "countries" and "users," with "users.country_id" being a foreign key to the "countries" table (one-to-many). The initial database will be empty. Users from all over the world will submit their names and the countries they live in and eventually the "countries" table will get filled out with all of the country names in the world. Since one country can have several alternative names, input like Chile, Chili, Chilli will generate 3 different records in the countries table, but in fact there is only one country. When I search for records from Chile, Chili and Chilli will not be included. So my question is - what would be the best way to deal with a situation like this, with conditions such that the initial database is empty, no other resources are available and everything is based on user input? How can I organize it in such way that Chile, Chili and Chilli would be treated as one country, with minimum manual interference. What are the best practices when it comes to normalizing user submitted data and is there a scientific term for this? I'm sure this is a common problem. Again, I used country names just to simplify my question, it can be anything that has possible different spellings.

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  • Are document-oriented databases any more suitable than relational ones for persisting objects?

    - by Owen Fraser-Green
    In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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  • Making a simple searchable directory of people and their skills in a day - Which technologies?

    - by gav
    Hi All, I am working with a small theatre company. Currently they have a list of people on paper with notes about their skills next to each one. I want to create a database / directory for them so that they can add, delete, update and search for people. It is a very simple and common scenario I know but the issue here is that I only have a day to build a working solution. The search has to be very simple At first I was thinking LAMP but I'd rather not have to create it all from scratch and host it myself. That lead me to Google Spreadsheet as a database, this has the advantage that they already use google docs for everything and if my front end goes tits up they can still get to the data. Presuming none of you can think of some existing software which does exactly what I want the next step is to make a front end for the database. You can create forms for Google Spreadsheets but they only let you add new entries, I can make a Google Gadget but that will only let me implement the search as the Google Visualisation API provides read only access. It's at this point I'm stuck, should I just create a Java Servlet front end for the Google Spreadsheet and use the Java API to add, search and update? I know this is a broad question but I'm just asking 'What would you do?' to implement this system with a day's development time? Gav

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  • Alternative or succesor to GDBM

    - by Anon Guy
    We a have a GDBM key-value database as the backend to a load-balanced web-facing application that is in implemented in C++. The data served by the application has grown very large, so our admins have moved the GDBM files from "local" storage (on the webservers, or very close by) to a large, shared, remote, NFS-mounted filesystem. This has affected performance. Our performance tests (in a test environment) show page load times jumping from hundreds of milliseconds (for local disk) to several seconds (over NFS, local network), and sometimes getting as high as 30 seconds. I believe a large part of the problem is that the application makes lots of random reads from the GDBM files, and that these are slow over NFS, and this will be even worse in production (where the front-end and back-end have even more network hardware between them) and as our database gets even bigger. While this is not a critical application, I would like to improve performance, and have some resources available, including the application developer time and Unix admins. My main constraint is time only have the resources for a few weeks. As I see it, my options are: Improve NFS performance by tuning parameters. My instinct is we wont get much out of this, but I have been wrong before, and I don't really know very much about NFS tuning. Move to a different key-value database, such as memcachedb or Tokyo Cabinet. Replace NFS with some other protocol (iSCSI has been mentioned, but i am not familiar with it). How should I approach this problem?

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  • Moving information between databases

    - by williamjones
    I'm on Postgres, and have two databases on the same machine, and I'd like to move some data from database Source to database Dest. Database Source: Table User has a primary key Table Comments has a primary key Table UserComments is a join table with two foreign keys for User and Comments Dest looks just like Source in structure, but already has information in User and Comments tables that needs to be retained. I'm thinking I'll probably have to do this in a few steps. Step 1, I would dump Source using the Postgres Copy command. Step 2, In Dest I would add a temporary second_key column to both User and Comments, and a new SecondUserComments join table. Step 3, I would import the dumped file into Dest using Copy again, with the keys input into the second_key columns. Step 4, I would add rows to UserComments in Dest based on the contents of SecondUserComments, only using the real primary keys this time. Could this be done with a SQL command or would I need a script? Step 5, delete the SecondUserComments table and remove the second_key columns. Does this sound like the best way to do this, or is there a better way I'm overlooking?

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  • PHP/MySQL allowing current user to edit there account information

    - by user1837896
    i have created 2 pages update.php edit.php we start on edit.php so here is edit.php's script <?php session_start(); $id = $_SESSION["id"]; $username = $_POST["username"]; $fname = $_POST["fname"]; $password = $_POST["password"]; $email = $_POST["email"]; mysql_connect('mysql13.000webhost.com', 'a2670376_Users', 'Password') or die(mysql_error()); echo "MySQL Connection Established! <br>"; mysql_select_db("a2670376_Pass") or die(mysql_error()); echo "Database Found! <br>"; $query = "UPDATE members SET username = '$username', fname = '$fname', password = '$password' WHERE id = '$id'"; $res = mysql_query($query); if ($res) echo "<p>Record Updated<p>"; else echo "Problem updating record. MySQL Error: " . mysql_error(); ?> <form action="update.php" method="post"> <input type="hidden" name="id" value="<?=$id;?>"> ScreenName:<br> <input type='text' name='username' id='username' maxlength='25' style='width:247px' name="username" value="<?=$username;?>"/><br> FullName:<br> <input type='text' name='fname' id='fname' maxlength='20' style='width:248px' name="ud_img" value="<?=$fname;?>"/><br> Email:<br> <input type='text' name='email' id='email' maxlength='50' style='width:250px' name="ud_img" value="<?=$email;?>"/><br> Password:<br> <input type='text' name='password' id='password' maxlength='25' style='width:251px' value="<?=$password;?>"/><br> <input type="Submit"> </form> now here is the update.php page where i am having the MAJOR problem <?php session_start(); mysql_connect('mysql13.000webhost.com', 'a2670376_Users', 'Password') or die(mysql_error()); mysql_select_db("a2670376_Pass") or die(mysql_error()); $id = (int)$_SESSION["id"]; $username = mysql_real_escape_string($_POST["username"]); $fname = mysql_real_escape_string($_POST["fname"]); $email = mysql_real_escape_string($_POST["email"]); $password = mysql_real_escape_string($_POST["password"]); $query="UPDATE members SET username = '$username', fname = '$fname', email = '$email', password = '$password' WHERE id='$id'"; mysql_query($query)or die(mysql_error()); if(mysql_affected_rows()>=1){ echo "<p>($id) Record Updated<p>"; }else{ echo "<p>($id) Not Updated<p>"; } ?> now on edit.php i fill out the form to edit the account "test" while i am logged into it now once the form if filled out i click on |Submit!| button and it takes me to update.php and it returns this (0) Not Updated (0) <= id of user logged in Not Updated <= MySql Error from mysql_query($query)or die(mysql_error()); if(mysql_affected_rows()>=1){ i want it to update the user logged in and if i am not mistaken in this script it says $id = (int)$_SESSION["id"]; witch updates the user with the id of the person who is logged in but it isnt updating its saying that no tables were effected if it helps heres my MySql Database picture just click here http://i50.tinypic.com/21juqfq.png if this could possibly be any help to find the solution i have 2 more files delete.php and delete_ac.php they have can remove users from my sql database and they show the user id and it works there are no bugs in this script at all PLEASE DO NOT MAKE SUGGESTIONS FOR THE SCRIPTS BELOW delete.php first <?php $host="mysql13.000webhost.com"; // Host name $username="a2670376_Users"; // Mysql username $password="PASSWORD"; // Mysql password $db_name="a2670376_Pass"; // Database name $tbl_name="members"; // Table name // Connect to server and select database. mysql_connect("$host", "$username", "$password")or die("cannot connect"); mysql_select_db("$db_name")or die("cannot select DB"); // select record from mysql $sql="SELECT * FROM $tbl_name"; $result=mysql_query($sql); ?> <table border="0" cellpadding="3" cellspacing="1" bgcolor="#CCCCCC"> <tr> <td colspan="8" style="bgcolor: #FFFFFF"><strong><img src="http://i47.tinypic.com/u6ihk.png" height="30" widht="30">Delete data in mysql</strong> </td> </tr> <tr> <td align="center" bgcolor="#FFFFFF"><strong>Id</strong></td> <td align="center" bgcolor="#FFFFFF"><strong>UserName</strong></td> <td align="center" bgcolor="#FFFFFF"><strong>FullName</strong></td> <td align="center" bgcolor="#FFFFFF"><strong>Password</strong></td> <td align="center" bgcolor="#FFFFFF"><strong>Email</strong></td> <td align="center" bgcolor="#FFFFFF"><strong>Date</strong></td> <td align="center" bgcolor="#FFFFFF"><strong>Ip</strong></td> <td align="center" bgcolor="#FFFFFF">&nbsp;</td> </tr> <?php while($rows=mysql_fetch_array($result)){ ?> <tr> <td bgcolor="#FFFFFF"><? echo $rows['id']; ?></td> <td bgcolor="#FFFFFF"><? echo $rows['username']; ?></td> <td bgcolor="#FFFFFF"><? echo $rows['fname']; ?></td> <td bgcolor="#FFFFFF"><? echo $rows['password']; ?></td> <td bgcolor="#FFFFFF"><? echo $rows['email']; ?></td> <td bgcolor="#FFFFFF"><? echo $rows['date']; ?></td> <td bgcolor="#FFFFFF"><? echo $rows['ip']; ?></td> <td bgcolor="#FFFFFF"><a href="delete_ac.php?id=<? echo $rows['id']; ?>">delete</a></td> </tr> <?php // close while loop } ?> </table> <?php // close connection; sql_close(); ?> and now delete_ac.php <table width="500" border="0" cellpadding="3" cellspacing="1" bgcolor="#CCCCCC"> <tr> <td colspan="8" bgcolor="#FFFFFF"><strong><img src="http://t2.gstatic.com/images? q=tbn:ANd9GcS_kwpNSSt3UuBHxq5zhkJQAlPnaXyePaw07R652f4StmvIQAAf6g" height="30" widht="30">Removal Of Account</strong> </td> </tr> <tr> <td align="center" bgcolor="#FFFFFF"> <?php $host="mysql13.000webhost.com"; // Host name $username="a2670376_Users"; // Mysql username $password="javascript00"; // Mysql password $db_name="a2670376_Pass"; // Database name $tbl_name="members"; // Table name // Connect to server and select databse. mysql_connect("$host", "$username", "$password")or die("cannot connect"); mysql_select_db("$db_name")or die("cannot select DB"); // get value of id that sent from address bar $id=$_GET['id']; // Delete data in mysql from row that has this id $sql="DELETE FROM $tbl_name WHERE id='$id'"; $result=mysql_query($sql); // if successfully deleted if($result){ echo "Deleted Successfully"; echo "<BR>"; echo "<a href='delete.php'>Back to main page</a>"; } else { echo "ERROR"; } ?> <?php // close connection mysql_close(); ?> </td> </tr> </table>

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  • Validating Login / Changing User settings / Php Mysql

    - by Marcelo
    Hi everyone, my questions are about login, and changing already saved data. (Q1) 'Till now I've only saved input in the tables of the database (registration steps), now I need to check if the input (login steps), are the same of my table in database, in fact I have 3 types of users, then I'll have to check 3 kind of tables. Then if the input data matches with one of those 3 tables I will redirect the user to his specific area. I'm thinking about saved the submitted data $login=$_REQUEST['login']; and $password=$_REQUEST['password']; and compare with the login column in the database. Then if the login matches, I'll compare the password submitted with the one in the row, not in the column. But I don't know how to do this search and comparison,neither what to use. Then if both matches I'll redirect the user. Else I'll send an login error message. (this I know how to do) (Q2) What if need to change an already saved user ? For example to change an email address. My changing user's data web page is exactly the same like the registration user web page. Can I load the already saved options and values of registration (table user for example). Then the user will change whatever he thinks it's necessary, and then when he submits the new information, they would not create a new row in my table, but just be overwritten the old information? How can I do this? Sorry for any mistake in English, and Thanks for the attention.

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