WikiDB/Tables

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Revision as of 17:14, 15 January 2014 by HappyDog (Talk | contribs) (Updated introductory text, as it was quite out of date.)

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There are three additional tables that WikiDB will add to the database in order to store the data required by the extension. In all cases, the data stored in these tables is derived from data elsewhere on your wiki, therefore it is always safe to delete and rebuild these tables, if necessary.

If you have any suggestions about how these tables could be further optimised, please discuss them on the talk page.



IMPORTANT NOTES - READ THESE BEFORE YOU CONTINUE!

  1. WikiDB comes with scripts to add these tables to the database, and to populate them with data (or to reset/re-populate them if necessary, e.g. because your configuration has changed). The scripts will also allow you to upgrade existing installations if the schema has changed. Therefore, so long as you have command-line access to run the maintenance scripts then you should never need to manually modify the database.
  2. The schema may change as the extension develops and changes may be incompatible with the current version. It may not be obvious how to change from one version to another, and if the incorrect version is used, the behaviour is undefined. Therefore, take care if you are unable to run the command-line scripts, and so need to modify the tables manually.
  3. If a new release makes changes to the schema, then the major version of the WikiDB software will be incremented, so it should be easy to tell if you need to update your schema. See WikiDB/Versioning for more details.
  4. The table definitions on this page are live, and are pulled from the DB that is powering this wiki. Any changes made to the live DB will automatically be reflected here (which is achieved using my Debugging tools extension). This has two implications. Occasionally I upgrade the wiki before a stable release is made available, for testing purposes. In this case the schema shown here may be more recent than the latest released version. Check Special:Version to see what version of WikiDB this wiki is running. Secondly, because these are updated live and are not shown in the page history, there is no easy way to view the schema for old versions of WikiDB. If this is a problem, you should check the SQL in ~/maintenance/sql/tables.sql, though this is not in a format that is ready to be run directly on your database.
  5. I cannot be held responsible for any problems or damage that may arise from using the software, deploying with the wrong schema or running the SQL on this page... standard disclaimer, etc. :)


wikidb_tables

Live Table Definition: wikidb_tables

CREATE TABLE IF NOT EXISTS `wikidb_tables` (
  `table_namespace` int(11) NOT NULL,
  `table_title` varchar(255) NOT NULL,
  `table_def` mediumblob NOT NULL,
  `redirect_namespace` int(11) DEFAULT NULL,
  `redirect_title` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`table_namespace`,`table_title`),
  KEY `wikidb_tables_redirect_ns_title` (`redirect_namespace`,`redirect_title`)
) ENGINE=InnoDB;

Contains information about all tables defined in the wiki.

Purpose:

  • To stop us having to parse the article text whenever data is requested.

Needs to be updated:

  • Whenever a page in a DB namespace is created/saved.
  • Whenever a page in a DB namespace is moved.
  • Whenever a page in a DB namespace is deleted/undeleted.

Considerations:

  • If you remove a table namespace redundant records will be left in this table. This may affect data display.
  • If you convert an existing namespace to a table namespace, this table will not be updated. The workaround is to go to each page in the namespace and to save a NULL edit.
  • A maintenance script needs to be written to fix-up both the above situations.

wikidb_rowdata

Live Table Definition: wikidb_rowdata

CREATE TABLE IF NOT EXISTS `wikidb_rowdata` (
  `row_id` int(8) unsigned NOT NULL AUTO_INCREMENT,
  `page_namespace` int(11) NOT NULL,
  `page_title` varchar(255) NOT NULL,
  `table_namespace` int(11) NOT NULL,
  `table_title` varchar(255) NOT NULL,
  `parsed_data` mediumblob NOT NULL,
  `is_stale` tinyint(1) unsigned NOT NULL DEFAULT '0',
  PRIMARY KEY (`row_id`),
  KEY `wikidb_rowdata_table_ns_title` (`table_namespace`,`table_title`),
  KEY `wikidb_rowdata_ns_title` (`page_namespace`,`page_title`),
  KEY `wikidb_rowdata_is_stale` (`is_stale`)
) ENGINE=InnoDB;

Contains a record for each row in each database. These may defined anywhere in the wiki.

Purpose:

  • To avoid having to parse all articles whenever data is required.

Needs to be updated:

  • Whenever any page is created/saved.
  • Whenever any page is moved.
  • Whenever any page is deleted/undeleted.
  • If we decide to cache formatted versions of the field data, whenever wikidb_tables is updated.


wikidb_fielddata

Live Table Definition: wikidb_fielddata

CREATE TABLE IF NOT EXISTS `wikidb_fielddata` (
  `row_id` int(8) unsigned NOT NULL,
  `field_name` varchar(255) NOT NULL DEFAULT '',
  `field_value` varchar(255) NOT NULL DEFAULT '',
  KEY `wikidb_fielddata_row_id` (`row_id`),
  KEY `wikidb_fielddata_field_name` (`field_name`(75),`field_value`(75))
) ENGINE=InnoDB;

Contains a record for each field in each row in each database.

Purpose:

  • To be searchable and sortable.
  • Actual data for display is pulled from the row data.

Needs to be updated:

  • Whenever wikidb_rowdata is updated.
  • If we need to cache formatted versions of the fields (which we probably do), whenever wikidb_tables is updated.

Considerations:

  • All values are in the same text field.
  • Sorting via this field should always give the correct order (whether the values are numeric or alphabetic).
    • One solution is for numeric values to be stored zero-padded. E.g. 9.5 becomes 00000009.50000000. This would mean updating this table whenever the table format changes... may need to use the job queue for this!
    • Another solution is to cast the data in the query, based on the type of the field. However this may not be possible in all cases.