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DBIStoreContrib

Use DBI to implement a store using an SQL database.

This extension supports the storing of wiki data in an SQL database. Works with Foswiki 1.1.9 and later.

At this point in time, it works as a mirror of an existing store (e.g. PlainFile, RCS)
  1. With all searching operations performed using SQL or
  2. With just structured queries performed using the store or
  3. Simply to support other clients querying data using SQL.
However it may be extended to be a full store implementation at some point in the future.

The extension has been designed to be fully compatible with existing %SEARCH expressions, and is useable with all well-written extensions (those that have been written to use the Foswiki::Func API, and do not perform direct-to-disk file operations).

It has been tested with SQLite, MySQL, Postgresql, and Microsoft SQL Server.

Note however that there are many different versions of these databases and campatibility with any given version cannot be guaranteed.

Database Schema

The database schema reflects 1:1 the schema of Foswiki topics. The following tables exist by default:

web
Contains full hierarchical names of all webs
  • name - web name

topic
Contains all wiki topics.
  • tid - this column contains a numeric identifier that uniquely identifies the topic
  • web - the web name
  • name - the topic name
  • text - the full text of the topic, without embedded meta-data
  • raw - the full text of the topic including embedded meta-data

metatypes
Contains the names of all meta-tables.
  • name - table name, e.g. TOPICINFO, FORM etc

The full schema, including the types used to represent different data can be found in configure under the settings for the Extension.

Search Limitations

Regular Expressions

Regular expression searches are mapped to whatever regular expression support exists in the database. Most SQL databases support sophisticated regular expression matching; however there are features of the default Perl syntax supported by Foswiki that cannot be mapped to the databases. Regular expressions written using this extended syntax may fail.

Numeric comparison

Foswiki "knows" when two values in the database can be compared using numeric, as against lexical, comparison (the , <, >, < and >= operators). SQL doesn't have this kind of support, and has to be explicitly told whether a the values being compared are numeric or lexical.

If one of the things being compared is explicitly a number, then numeric comparison will be used by default.

If the query expression isn't explicit about the type to be used, you can use the is_number() operator to indicate when one side represents a number or is_string() when it is a string. You only need to use number / string on one side of an expression. For example,

  • %SEARCH{"info.version<'1.1'"}% will always use lexical comparison
  • %SEARCH{"info.version<1.1"}% will always use numeric comparison
  • %SEARCH{"info.version<is_number('1.1')"}% will use numeric comparison
  • %SEARCH{"info.version<is_string(1.1)"}% will use lexical comparison

Date comparison

Date conversion using the d2n operator is not supported.

Row indexes

Integer indexes are not supported. Use queries instead.

Representational types

The type defined in the schema must be long enough to store any possible value for the given field, but be as short as possible to maximise the DB's chance of building a decent index for it.

length of an array

The length() operator only works on string data, not on tables.

Installation Instructions

You do not need to install anything in the browser to use this extension. The following instructions are for the administrator who installs the extension on the server.

Open configure, and open the "Extensions" section. Use "Find More Extensions" to get a list of available extensions. Select "Install".

If you have any problems, or if the extension isn't available in configure, then you can still install manually from the command-line. See http://foswiki.org/Support/ManuallyInstallingExtensions for more help.

  • Go to configure and:
    1. Set a DSN etc. for the contrib in the 'Extensions' section (the default is for sqlite3),
    2. Select Foswiki::Store::QueryAlgorithms::DBIStoreContrib for the {Store}{QueryAlgorithm} EXPERT setting
    3. For Foswiki > 1.1 only
      • Set {Store}{ImplementationClasses}{Foswiki::Contrib::DBIStoreContrib::DBIStore} EXPERT setting in LocalSite.cfg to $TRUE.
      • select Foswiki::Store::SearchAlgorithms::DBIStoreContrib for the {Store}{SearchAlgorithm} setting
    4. For Foswiki 1.1 only
      • Select Foswiki::Store::QueryAlgorithms::DBIStoreContrib for the {Store}{QueryAlgorithm} configuration setting
      • enable the integrated DBIStorePlugin

Testing

Basic tests for queries can be found in the DBIStoreTest topic.

Reloading the database

It may become necessary to reload the DBI database - for example, because changes to topics have been made outside of Foswiki.

Foswiki <1.20

Click on the following link to clear down and re-load the entire database. WARNING on a large site this may take a very long time. You may prefer to run it from the command-line, using a command like this:
./view topic=System.DBIStoreTest skin=text dbistore_reset=1
You can also update an individual topic by passing dbistore_update to a view of the topic. For example,
./view topic=System.DBIStoreTest skin=text dbistore_update=1
will update the DB for DBIStoreTest only.

Foswiki 1.2 and later

To be completed

Unknown meta-data EXPERT

Normally the module will only record recognised meta-data in the database, and so make it accessible for searching. "Recognised" meta-data is meta-data created by the core and by plugins that use the Foswiki::Func::registerMETA method to announce meta-data to the system. In exceptional circumstances you can override this behaviour by setting the {Extensions}{DBIStoreContrib}{AutoloadUnknownMETA} control in configure. This will cause all meta-data being recorded in the database, even if the plugin which is supposed to register it is missing, broken, or simply too old to do the right thing.

MySQL Notes

The MySQL database user needs at least the following privileges: SELECT, INSERT, CREATE, and DROP.

Postgresql Notes

Microsoft SQL Server Notes

If you are using Windows authentication for users on SQL Server, then the simplest thing to do is to use the ODBC driver with DBIStoreContrib and create a data source for SQL Server in the ODBC Administrator which uses Windows authentication. Then set an empty username and password for DBIStoreContrib.

SQL Server does not come equipped with regular expression matching, which is required for Foswiki, so you wil need to install a regular expression library. The default personality module included in this module requires the user function dbo.fn_RegExIsMatch to stub the .NET RegEx class. Instructions for building and installing this user function can be found at http://www.codeproject.com/Articles/19502/A-T-SQL-Regular-Expression-Library-for-SQL-Server

SQLite Notes

SQLite requires the pcre module to be installed to support regular expression searches. The path to this module is set up in configure.

How it works

Searches and Queries

Foswiki has two internal interfaces, "search algorithm" and "query algorithm", that are selected from configure. These two interfaces are implemented in a variety of ways in the Foswiki core, but the typical solution is to implement the query interface in terms of the search interface i.e. map queries to regular expression searches. This is done by "hoisting" those parts of a query that can be mapped to regular expressions and using those hoisted expressions as a filter to reduce the set of matching topics. The "unhoistable" parts of the query are then applied to the remaining topics using "brute force" to give a final set of matching topics.

The DBIStoreContrib turns this process on its head by mapping searches to SQL queries. Most modern RDBMS support regular expression searches, so a text search can be expressed as a regular expression match on a "raw text" field in the DB. Structured queries, on the other hand, are hoisted to extract SQL from the Foswiki query statement.

Note that you don't have to use the mapping search algorithm for text searches - if you have a caching full text search implementation (such as Foswiki:Extensions.SolrPlugin) you should be able to continue using that.

The Database

The database is used simply as a cache, to accelerate searches. The contrib is designed to work with the standard Foswiki RCS-based store, but can also work with any post 1.2.0 store implementation. It can also hook into the standard plugin handlers for a slightly reduced capability.

The database is interfaced to via the standard Perl DBI interface, so any RDBMS that has an adapter can be used for the cache. This includes most standard SQL RDBMS.

The schema used to represent Foswiki topics is (currently) a 1:1 mapping of the schema described in QuerySearch. The same schema could be used to store Foswiki topics in the actual store, and this is one of the longer term goals. Among other things, this would allow us to search topic histories.

The Code

Here's an overview of the important bits of the contrib:
  • lib/Foswiki/Contrib/DBIStoreContrib/HoistSQL.pm - code that hoists SQL statements from Foswiki queries
  • lib/Foswiki/Contrib/DBIStoreContrib/DBIStore.pm - a partial Foswiki::Store implementation that eveavesdrops on Store::recordChange events (Foswiki >1.1 only)
  • lib/Foswiki/Plugins/DBIStorePlugin.pm - plugin handlers (Foswiki <=1.1 only)
  • lib/Foswiki/Store/QueryAlgorithms/DBIStoreContrib.pm - the query algorithm
  • lib/Foswiki/Store/SearchAlgorithms/DBIStoreContrib.pm - the search algorithm

The subversion repository (but not the official release) contains a fixed version of DBI::Shell from CPAN. This can be useful when debugging SQL server, or for simply understanding the tables. Run it using:

perl -I <path to DBIStoreContrib checkout>/lib -MDBI::Shell <dsn from configure> <username> <password>

Info

Author(s): Crawford Currie http://c-dot.co.uk
Copyright: © 2010-2014 C-Dot Consultants
License: GPL (Gnu General Public License)
Release: 12 Aug 2014
Version: 1.1
Change History:  
1.1 (12 Aug 2014) Fixes for Foswikitask:Item12989 and Foswikitask:Item12990:
1.0 (8 May 2014) First version
Dependencies:
NameVersionDescription
DBI>=0.1Required.
DBD::Pg>=1.49Optional,Required for PostgreSQL.
DBD::MySql>=0Optional,Required for MySQL.
DBD::SQLite3>=0Optional,Required for SQLite, and for testing.
Home page: http://foswiki.org/bin/view/Extensions/DBIStoreContrib
Support: http://foswiki.org/bin/view/Support/DBIStoreContrib

Topic revision: r3 - 13 Aug 2014, CrawfordCurrie - This page was cached on 28 Jul 2016 - 14:31.

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