DBCacheContrib < System

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---+!! %TOPIC%

Reusable code that caches Foswiki topics, and provides fast
searches of the content.

%TOC%

---++ Summary of Contents

This module supports fast structured queries over topics in an
arbitrarily-sized web. It uses a database to cache topic data to
deliver much more scaleable search performance. Different back-end
techologies can be used to implement the cache, to allow simple
tradeoffs between scaling and raw performance.

Historically this module was designed to be used with a
companion plugin, such as Foswiki:Extensions.FormQueryPlugin or
Foswiki:Extensions.DBCachePlugin, which support queries and the display of
query results. When used this way, the %TOPIC% supports queries made using
a simple [[%TOPIC%#QueryLanguage][query language]].

The module can also be used in "standard schema mode" to support plugins
that accelerate core functions, such as the !QueryAcceleratorPlugin.

---++ Features
   * Perform efficient structured queries on data in forms

---++ Using the built-in query language
The query language supported by !DBCacheContrib is very similar to the query language used with %SEARCH, which was derived from it. The contrib can be used in two modes; compatible schema mode (as used by FormQueryPlugin and DBCachePlugin) and standard schema mode (as described in QuerySearch).

In standard schema mode the schema of the DB is as described in QuerySearch.
In compatible schema mode, the underlying schema is somewhat different, to
support the extended requirements of the plugins that use it.

---+++ The Compatible Schema
You can think of the database as an map of all the topics in a web. Each
entry is itself a map (or hash, in perl terms) that maps a set of field
names to values.

Each topic in the web automatically gets a number of standard fields, generated
by reading the metadata from the topic (see %SYSTEMWEB%.MetaData)
   * =name=        - name of the topic
   * =parent=      - *name* of parent topic
   * =attachments= - array of maps, each of which contains:
      * =name= - attachment name
      * =attr= - e.g hidden
      * =comment= - attachment comment
      * =path= - client path used to upload attachment
      * =size= - size in Kb
      * =user= - who uploaded the attachment
      * =version= - e.g. 1.3
   * =info= - map containing:
      * =author= - most recent author
      * =date= - date of last change
      * =format= - topic format version
      * =version= - topic version number
   * =moved= - map containing:
      * =by= - who moved it
      * =date= - when they moved it
      * =from= - where they moved it from
      * =to= - where they moved it to
   * =preferences= - array of maps, each of which contains:
      * =name= - preference name
      * =type= - either Set or Local
      * =value= - the value of the named preference 
   * =form= - form type
   *  _form name_ - e.g. if a "My<nop>Form" is attached, this will be
          =My<nop>Form=. This is a reference to a map containing a key for each
          field in the form. Each key maps to the value in the form data for
          that key. 
   * =text= - raw text of the topic)

Other fields may be added by subclasses. Refer to the documentation for the
plugin that is using the DBCache for more details.

---++ Query operators
%STARTSECTION{"searchoperators"}%
Fields are given by name, and values by strings or numbers. Strings should always be surrounded by 'single-quotes'. Strings which are regular expressions (RHS of <nop>=, !<nop>= <nop>=~ operators) use 'perl' regular expression syntax (google for =perlre= for help). Numbers can be signed integers or decimals. Single quotes in values may be escaped using backslash (\).

The following operators are available:
| *Operator* | *Result* | *Meaning* |
| <code>=</code> | Boolean | LHS exactly matches the regular expression on the RHS. The expression must match the whole string. |
| <code>!=</code> | Boolean | Inverse of = |
| <code>=~</code> | Boolean | LHS contains RHS i.e. the RHS is found somewhere in the field value. |
| <code>&lt;</code> | Boolean | Numeric < |
| <code>&gt;</code> | Boolean | Numeric > |
| <code>&gt;=</code> | Boolean | Numeric >= |
| <code>&lt;=</code> | Boolean | Numeric <= |
| =lc= | String | Unary lower case |
| =uc= | String | Unary UPPER CASE |
| =IS_DATE= | Boolean | Compare two dates e.g. '1 Apr 2003' IS_DATE '1 Apr 2004' |
| =EARLIER_THAN= | Boolean | Date is earlier than the given date |
| =EARLIER_THAN_OR_ON= | Boolean | Date is earlier than, or on, the given date |
| =LATER_THAN= | Boolean | LHS is later than the given date |
| =LATER_THAN_OR_ON= | Boolean | LHS is later than the given date |
| =WITHIN_DAYS= | Boolean | Date (which must be in the future) is within n _working_ days of todays date |
| <code>!</code> | Boolean | Unary NOT |
| =AND= | Boolean | AND |
| =OR= | Boolean | OR |
| <code>()</code> | any | Bracketed subexpression |

Dates for the date operators (=IS_DATE=, =EARLIER_THAN= etc) must be dates in the format expected by =Time::ParseDate= (like the [[Foswiki:Extensions/ActionTrackerPlugin][ActionTrackerPlugin]]). =WITHIN_DAYS= works out the number of _working_ days assuming a 5 day week (i.e. excluding Saturday and Sunday). Apologies in advance if your weekend is offset &plusmn; a day! Integers will automatically be converted to dates, by assuming they represent a number of seconds since midnight GMT on 1st January 1970. You can also use the =d2n= operator to convert a date string to such an integer.

%ENDSECTION{"searchoperators"}%

---++ The cache
To achieve best perfomance the plugin caches the data read from topics in a
database. The database is stored in the work area for the DBCacheContrib (see
={WorkAreaDir}= in =configure=). If any topic changes in the web, this
cache is automatically updated.

---++ Detailed Documentation
Clients use the DBCache by defining a subclass of the
=Foswiki::Contrib::DBCacheContrib= class. Implementors are stongly recommended to read the POD documentation in the code:

<!--
   * Set SHORTDESCRIPTION = Reusable code that treats forms as if they were table rows in a database
-->

---++ 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.


---++ Contrib Info
|  Author: | Foswiki:Main/CrawfordCurrie http://c-dot.co.uk, Foswiki:Main/MichaelDaum http://michaeldaumconsulting.com |
|  Copyright &copy;: | This code is based on an original development of Motorola Inc. and is protected by the following copyrights: <br>Copyright @copy 2002-2003 Motorola Inc. All Rights Reserved. %BR%\
                       Portions copyright &copy; 2004 Crawford Currie http://www.c-dot.co.uk. %BR%\
                       Portions copyright &copy; 2013 Michael Daum http://michaeldaumconsulting.com |
|  License: | GPL |
|  Release: | 30 Jun 2013 |
|  Version: | v3.0.0 |
|  Change History: | |
|  10 Jul 2013 | Foswikitask:Item12542: cache non-standard %META data and make it searchable |
|  28 Mar 2013 | Foswikitask:Item12458: fix op_ref in search queries |
|  14 Mar 2013 | Foswikitask:Item12425: make preferences searchable by caching them into a map instead of an array |
|  25 Jan 2013 | Foswikitask:Item12369: fixed loading cache from disk on a change |
|  07 Jan 2013 | Foswikitask:Item8195: extract and cache preference settings; \
                 Foswikitask:Item12333: implement an archivist caching a web in segments; |
|  01 Oct 2012 | Foswiktask:Item11752: don't fail to build the cache for formfield names with dots in it |
|  10 Jan 2012 | Foswikitask:Item11406: remove redundant reference to archivist from all stored values |
|  25 Aug 2011 | Foswikitask:Item11070: working around odd defaults of =normalizeWebTopicName= |
|  28 Mar 2011 | Foswikitask:Item9375: disabling {AlwaysUpdateCache} by default and making an expert option with appropriate warnings |
|  17 Nov 2009 | Foswikitask:Item8327: series of robustness fixes (Foswiki:Main.MichaelDaum) |
|  30 Jun 2009 | Foswikitask:Item8153: make dirs for path to cache; Foswikitask:Item8194: incoporated patch from Foswiki:Main.MichaelDaum Foswikitask:Item8195: extract and cache permissions settings |
|  18 Jun 2009 | Foswikitask:Item8183: fixed problem with Scalar::Util::weaken that was causing !DBCachePlugin problems |
|  6 Jun 2009 | Foswikitask:Item1691: changes to support Foswiki:Extensions.QueryAcceleratorPlugin |
|  7 Apr 2009 | Foswikitask:Item5440: fixed negative values in SUMFIELD Foswikitask:Item8106: add back in the Map methods to the main class, as they are used by subclasses Foswikitask:Item8063: fix the accidental encoding of field values in the cache |
|  28 Jan 2009 | Foswikitask:Item453: Foswiki version; added Berkeley DB support, dropped plain-file support. Added Michael Daum's EARLIER_THAN_OR_ON and LATER_THAN_OR_ON ops. Fixed a number of bugs. |
|  12346 | fixing uptodate() for Andrew File Systems; fixed memory leak on persistent perl |   
|  16347 | remove META data from text hash; include META data in all hash. Foswiki:Main.MichaelDaum |
|  16346 | caching all topic elements to an =all= field to allow th search in all of the text and the formfields like \
           the normal grep-based SEARCH does. Foswiki:Main.MichaelDaum |
|  15868 | fixed WITHIN_DAYS and EARLIER_THAN. Foswiki:Main.MichaelDaum |
|  15583 | made query parser pluggable so that other plugins can implement their own predicates. Foswiki:Main.MichaelDaum |
|  15019 | added {DBCacheContrib}{AlwaysUpdateCache} to remove the updateCache from every operation. Foswiki:Main.SvenDowideit |
|  13562 | Bugs:Item3985 - fixed failures with hierarchical webs |
|  13527 | Moved the cache into the extensions work areas, instead of the web directory |
|  12943 | Bugs:Item3659: added automatic conversion of integers to dates |
|  12923 | added REF operator; \
           added link to web object to hashes; \
           fixed parent relation to end in WebHome; \
           added "web" property to topic hashes; \
           caching META:PREFERENCES now |
|  11537 | Added lc and uc operators for case-insensitive searches |
|  9303 | TWikibug:Item1844 - don't die on broken symlinks |
|  8682 | TWikibug:Item1580 - one-char fix that makes the difference |
|  8110 | TWikibug:Item663 - formatting and text fixes |
|  7552 | TWikibug:Item997 - test update |
|  7274 | TWikibug:Item719 - onReload() is not a static method. |
|  7262 | TWikibug:Item719 - Foswiki:Main.MichaelDaum's patch (almost) to correct parameters to onReload |
|  7260 | TWikibug:Item727 - made it clean the form name using normaliseWebTopicName |
|  6353 | TWikibug:Item380 - do as the man says; make all $/ local |
|  5720 | Updated tests |
|  5719 | Fix for correct handling of parent relations |
|  5229 | Small improvement to the way it handles errors from Storable and Archive |
|  5223 | Documentation fixes, adding gifs. |
|  5048 | Cairo readiness |
|  5036 | Split from <nop>SharedCode |
|  5031 | Moving to new name |
|  5030 | About to rename |
|  5019 | Improved topic data model, cleaned up tests |
|  5008 | Added extended access syntax, [?], [*] etc. |
|  5006 | Doc fixes |
|  5005 | Poddified documentation |
|  5003 | Initial version |
|  8 Jul 2004 | Initial version, split out from <nop>FormQueryPlugin |
|  Dependencies: | <table class="foswikiTable" border="1"><tr><th>Name</th><th>Version</th><th>Description</th></tr><tr><td align="left">Time::ParseDate</td><td align="left">&gt;=2003.0211</td><td align="left">Required. </td></tr><tr><td align="left">Storable</td><td align="left">&gt;=2.07</td><td align="left">Required. </td></tr><tr><td align="left">BerkeleyDB</td><td align="left">&gt;=0</td><td align="left">Optional, still experimental.</td></tr></table> |
|  Home: | http://foswiki.org/Extensions/%TOPIC% |
|  Support: | http://foswiki.org/Support/%TOPIC% |
Topic revision: r4 - 30 Oct 2013, AdminUser
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