Development:XML database schema - Revision history

Stronk7 at 16:53, 28 February 2007

2007-02-28T16:53:39Z

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	~~__NOTOC__~~		#redirect [[Development:XMLDB Documentation]]
	One of the main upcoming features in Moodle 1.7 will be its ability to work with some more [[wikipedia:RDBMS\|RDBMS]] ([[wikipedia:MSSQL\|MSSQL]] and [[wikipedia:Oracle database\|Oracle]]) while maintaining everything working properly with both [[MySQL]] and [[PostgreSQL]]. As Moodle core uses [http://adodb.sourceforge.net/ ADOdb] internally, this possibility has been present since the beginning and, with the current maturity of the project (5 years old baby!), this can be a good moment to sort all this out.

	Initially, all our tests and preliminary work was to inspect how [http://adodb.sourceforge.net/ ADOdb] was doing its work, and how we could mix together all those 4 RDBMS, whose SQL dialects, although pretty similar, have some differences and idiosyncrasies that force us to do some important changes to our current database code (formerly '''datalib.php''') and how it's used by the rest of Moodle.

	~~All the changes to be performed, which primary objective is to enable Moodle to work with more RDBMS must be be filled following the next non-functional requirements:~~

	* '''Provide one layer (new) for DB creation/upgrade''' ([[wikipedia:Data_Definition_Language\|DDL]]): With this, developers will create their structures in one neutral form, independent of the exact implementation to be used by each RDBMS.

	* '''Provide one layer (existing) for DB handling''' ([[wikipedia:Data_Manipulation_Language\|DML]]): With this, developers will request/store information also in one nuetral form, independent of the RDBMS being used.

	* '''Easy migration path from previous versions''': The current installation/upgrade system will work until, at least, Moodle 2.0, allowing 3rd part developers to migrate along the time to the new system.

	* '''Simple, usable and effective''': Until now, the way to upgrade Moodle has been really cool and it has worked pretty fine since the beginning, but it has forced developers to maintain at least two installation and two upgrade scripts for each module/plugin. The new alternative will have only one file to install and one file to upgrade (per modude/plugin too), reducing the possibility of mistakes in an high degree.

	* '''Conditional code usage must be minimised''': Database libraries must accept 99% of potential SQL sentences, building/transforming them as necessary to work properly under any RDBMS. The number of places using custom (per DB) code should be minimum.

	* '''Well documented''': All the functions defined, both at DML and DDL level must be well documented, helping the developer to find and use the correct one in each situation.

	~~== The Stack ==~~

	The next stack shows how Moodle 1.7 code will interact with underlying RDBMS. It will help us to understand a bit more what we are trying to do and will explain some of the points related in the Roadmap (below in this page).

	~~[[Image:MoodleDBStack.png\|center]]~~

	~~Moodle code will use two ''languages'' to perform its DB actions:~~

	* '''XMLDB neutral description files''': To create, modify and delete database objects (DDL: create/alter/drop tables, fields, indexes, constraints...). It consists in a collection of validated, standard, XML files. They will be used to define all the DB objects. New for 1.7.
	* '''Moodle SQL neutral statements''': To add, modify, delete and select database information (DML: insert/update/delete/select records). To modify for 1.7.

	Please note the '''neutral''' keyword used in the expressions above. It means that both '''languages''' will be 100% the same, independently of the underlying RDBMS being used. And this must be particularly true for the XMLDB part. Point.

	Obviously it's possible that in the SQL part we found some specialised queries (using complex joins, regular expressions...) that will force us to do some '''Exceptions'''. Well, they can exist (in fact, they exist), but we always must try to provide an alternate path to minimise them using neutral statements and standard libraries.

	~~Each one of the '''languages''' above will use its own library to do the work:~~

	* '''Moodle DDL Library''' ([[DDL functions\|ddllib.php]]): Where all the functions needed to handle DB objects will exist. This library in new for 1.7 and will provide developers with an high level of abstraction. As input it will accept some well defined objects and actions and it will execute the proper commands for the RDBMS being used.
	* '''Moodle DML Library''' ([[DML functions\|dmllib.php]]): Where all the functions needed to handle DB contents will exist. This library is new for 1.7, although its contents are, basically, functions currently present in '''datalib.php''' (moved from there). All those DML functions will offer cross-db support for insert/update/delete/select statements using a common behaviour.

	Also note that '''datalib.php''' continues present in the schema above. It will contain all the functions that haven't been moved to the new '''ddllib.php''' and '''dmllib.php''' libraries. Only some common functions will remain there, and this situation will disappear (it's considered a legacy library) in upcoming '''Moodle''' releases (after 1.7) by moving all those functions to their proper library (course/lib.php, user/lib.php....).

	Both this libraries (plus the small '''Exceptions''' bar) will perform all their actions using the '''ADOdb Database Abstraction Library for PHP''' that will receive all the request from them, communicate with the DB ('''MySQL''', '''PostgreSQL''', '''Oracle''' or '''SQL*Server'''), retrieve results and forward them back to originator library.

	~~== The process ==~~

	~~This section points to the main areas of information about the '''process of design and implementation''' of the new XMLDB layer:~~

	* [[XMLDB Roadmap\|Roadmap]]: Where the whole process is defined. It has been splitted in small chuncks to be performed and tested easily. Also, such documents should be used to track what's done and what's pending following some easy nomenclature.

	* [[XMLDB Problems\|Problems]]: A comprensive list of issues that need to be determined/solved prior to incorporate them to the [[XMLDB Roadmap\|roadmap]].

	~~== The documentation ==~~

	~~This section points to the '''main documentation index''' about the implemented XMLDB:~~

	* [[Development:XMLDB Documentation~~\|Documentation]]: Where you'll find quick links to different parts of the XMLDB documentation.~~

	~~==See also==~~

	~~=== XMLDB related ===~~

	* [[XMLDB preliminary links]] - A collection of links about general info, searched and analysed at the initial stages of the project
	* [[XMLDB preliminary notes]] - A collection of notes collected in the early stages of this project, pointing both to some changes required and some problems to solve.

	~~=== Database related ===~~

	* [[DDL functions]] - Documentation for all the Data Definition Language (DDL) functions available inside Moodle.
	* [[DML functions]] - Documentation for all the Data Manipulation Language (DML) functions available inside Moodle.

	~~[[Category:Developer]]~~
	~~[[Category:XMLDB]]~~
	~~[[Category:Future]]~~

	~~[[zh:开发:XML数据库计划~~]]

Stronk7 at 16:42, 28 February 2007

2007-02-28T16:42:12Z

← Older revision		Revision as of 16:42, 28 February 2007
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	~~__TOC__~~		__NOTOC__
	One of the main upcoming features in Moodle 1.7 will be its ability to work with some more [[wikipedia:RDBMS\|RDBMS]] ([[wikipedia:MSSQL\|MSSQL]] and [[wikipedia:Oracle database\|Oracle]]) while maintaining everything working properly with both [[MySQL]] and [[PostgreSQL]]. As Moodle core uses [http://adodb.sourceforge.net/ ADOdb] internally, this possibility has been present since the beginning and, with the current maturity of the project (5 years old baby!), this can be a good moment to sort all this out.		One of the main upcoming features in Moodle 1.7 will be its ability to work with some more [[wikipedia:RDBMS\|RDBMS]] ([[wikipedia:MSSQL\|MSSQL]] and [[wikipedia:Oracle database\|Oracle]]) while maintaining everything working properly with both [[MySQL]] and [[PostgreSQL]]. As Moodle core uses [http://adodb.sourceforge.net/ ADOdb] internally, this possibility has been present since the beginning and, with the current maturity of the project (5 years old baby!), this can be a good moment to sort all this out.

Stronk7 at 16:41, 28 February 2007

2007-02-28T16:41:19Z

← Older revision		Revision as of 16:41, 28 February 2007
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			__TOC__
	One of the main upcoming features in Moodle 1.7 will be its ability to work with some more [[wikipedia:RDBMS\|RDBMS]] ([[wikipedia:MSSQL\|MSSQL]] and [[wikipedia:Oracle database\|Oracle]]) while maintaining everything working properly with both [[MySQL]] and [[PostgreSQL]]. As Moodle core uses [http://adodb.sourceforge.net/ ADOdb] internally, this possibility has been present since the beginning and, with the current maturity of the project (5 years old baby!), this can be a good moment to sort all this out.		One of the main upcoming features in Moodle 1.7 will be its ability to work with some more [[wikipedia:RDBMS\|RDBMS]] ([[wikipedia:MSSQL\|MSSQL]] and [[wikipedia:Oracle database\|Oracle]]) while maintaining everything working properly with both [[MySQL]] and [[PostgreSQL]]. As Moodle core uses [http://adodb.sourceforge.net/ ADOdb] internally, this possibility has been present since the beginning and, with the current maturity of the project (5 years old baby!), this can be a good moment to sort all this out.

Stronk7 at 16:40, 28 February 2007

2007-02-28T16:40:37Z

← Older revision		Revision as of 16:40, 28 February 2007
Line 1:		Line 1:
	~~__NOTOC__~~
	One of the main upcoming features in Moodle 1.7 will be its ability to work with some more [[wikipedia:RDBMS\|RDBMS]] ([[wikipedia:MSSQL\|MSSQL]] and [[wikipedia:Oracle database\|Oracle]]) while maintaining everything working properly with both [[MySQL]] and [[PostgreSQL]]. As Moodle core uses [http://adodb.sourceforge.net/ ADOdb] internally, this possibility has been present since the beginning and, with the current maturity of the project (5 years old baby!), this can be a good moment to sort all this out.		One of the main upcoming features in Moodle 1.7 will be its ability to work with some more [[wikipedia:RDBMS\|RDBMS]] ([[wikipedia:MSSQL\|MSSQL]] and [[wikipedia:Oracle database\|Oracle]]) while maintaining everything working properly with both [[MySQL]] and [[PostgreSQL]]. As Moodle core uses [http://adodb.sourceforge.net/ ADOdb] internally, this possibility has been present since the beginning and, with the current maturity of the project (5 years old baby!), this can be a good moment to sort all this out.

Stronk7: /* XMLDB related */

2007-02-28T16:33:26Z

XMLDB related

← Older revision		Revision as of 16:33, 28 February 2007
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	* [[XMLDB preliminary links]] - A collection of links about general info, searched and analysed at the initial stages of the project		* [[XMLDB preliminary links]] - A collection of links about general info, searched and analysed at the initial stages of the project
	* [[XMLDB preliminary notes]] - A collection of notes collected in the early stages of this project, pointing both to some changes required and some problems to solve.		* [[XMLDB preliminary notes]] - A collection of notes collected in the early stages of this project, pointing both to some changes required and some problems to solve.
	* [[XMLDB column types]] - Some links about column types inside every RDBMS and their characteristics
	* [[XMLDB key and index naming]] - Some info about automatic naming of keys/indexes and other objects.
	* [[XMLDB reserved words]] - A collection of reserver words inside each RDBMS

	=== Database related ===		=== Database related ===

Stronk7: /* The documentation */

2007-02-28T16:25:46Z

The documentation

← Older revision		Revision as of 16:25, 28 February 2007
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	This section points to the '''main documentation index''' about the implemented XMLDB:		This section points to the '''main documentation index''' about the implemented XMLDB:

	* [[Development:XMLDB ~~Documenting everything~~\|Documentation]]: Where you'll find quick links to different parts of the XMLDB documentation.		* [[Development:XMLDB Documentation\|Documentation]]: Where you'll find quick links to different parts of the XMLDB documentation.

	==See also==		==See also==

Stronk7: /* The process */

2007-02-28T16:11:00Z

The process

← Older revision		Revision as of 16:11, 28 February 2007
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	== The process ==		== The process ==

	This section ~~of the documentation~~ points to the main areas of information about the process of design and implementation of the new XMLDB layer:		This section points to the main areas of information about the '''process of design and implementation''' of the new XMLDB layer:

	* [[XMLDB Roadmap\|Roadmap]]: Where the whole process is defined. It has been splitted in small chuncks to be performed and tested easily. Also, such documents should be used to track what's done and what's pending following some easy nomenclature.		* [[XMLDB Roadmap\|Roadmap]]: Where the whole process is defined. It has been splitted in small chuncks to be performed and tested easily. Also, such documents should be used to track what's done and what's pending following some easy nomenclature.

	* [[XMLDB Problems\|Problems]]: A comprensive list of issues that need to be determined/solved prior to incorporate them to the [[XMLDB Roadmap\|roadmap]].		* [[XMLDB Problems\|Problems]]: A comprensive list of issues that need to be determined/solved prior to incorporate them to the [[XMLDB Roadmap\|roadmap]].

			== The documentation ==

			This section points to the '''main documentation index''' about the implemented XMLDB:

			* [[Development:XMLDB Documenting everything\|Documentation]]: Where you'll find quick links to different parts of the XMLDB documentation.

	==See also==		==See also==

Stronk7: /* The process */

2007-02-28T16:06:45Z

The process

← Older revision		Revision as of 16:06, 28 February 2007
Line 43:		Line 43:

	== The process ==		== The process ==

			This section of the documentation points to the main areas of information about the process of design and implementation of the new XMLDB layer:

	* [[XMLDB Roadmap\|Roadmap]]: Where the whole process is defined. It has been splitted in small chuncks to be performed and tested easily. Also, such documents should be used to track what's done and what's pending following some easy nomenclature.		* [[XMLDB Roadmap\|Roadmap]]: Where the whole process is defined. It has been splitted in small chuncks to be performed and tested easily. Also, such documents should be used to track what's done and what's pending following some easy nomenclature.

Sunner: Add chinese interlang link

2006-10-02T13:34:25Z

Add chinese interlang link

← Older revision		Revision as of 13:34, 2 October 2006
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	[[Category:XMLDB]]		[[Category:XMLDB]]
	[[Category:Future]]		[[Category:Future]]

			[[zh:开发:XML数据库计划]]

Tsala: XML database schema moved to Development:XML database schema

2006-09-19T18:46:13Z

XML database schema moved to Development:XML database schema

← Older revision	Revision as of 18:46, 19 September 2006
(No difference)