DBCacheContrib

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Reusable code that treats TWiki forms as if they were table rows in a database

Summary of Contents

This module supports structured queries over a database built on the fly from the forms in TWiki topics. It does not support any tags, as it is provided as a service for other plugins that want to treat a TWiki web as a simple database; for example, the TWiki:Plugins/FormQueryPlugin, which supports the display of query results.

The plugin encapsulates code that was formerly in the "engine room" of the FormQueryPlugin. It has been abstracted out in the belief that it will be useful to anyone who wants to do simple search operations from a plugin.

Features

Perform complex queries on the TWiki database
Cache TWiki topics for rapid queries

How the database gets built

You can think of the database as an array of all the topics in a web. Each array entry is 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 TWikiMetaData)

name - name of the topic
parent - name of parent topic
_up - reference to the Map of the parent topic, if it exists
attachments - array of Maps, each of which contains:
- _up - reference to the Map for the topic
- 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:
- _up - reference to the Map for the topic
- author - most recent author
- date - date of last change
- format - topic format version
- version - topic version number
moved - Map containing:
- _up - reference to the Map for the topic
- by - who moved it
- date - when they moved it
- from - where they moved it from
- to - where they moved it to
form - form type
form name - e.g. if a "MyForm" is attached, this will be MyForm. 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. The Map will also have an _up reference to the Map for the topic.
text - raw text of the topic)

The sub-Maps created for info, form name, moved, and each row in attachments also have a reference back to the topic Map, called _up.

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

The cache

To achieve best perfomance the plugin caches the database read from the TWiki topics. The cache is stored in the work area for the DBCacheContrib (see {RCS}{WorkAreaDir} in configure). If any topic changes in the web, this cache is automatically rebuilt. The cache file can be deleted at any point with no ill effects.

Extending or customising

Extension or customisation is welcome, as long as all extensions are described and code provided back to the author.

The module is shipped with a perl build file, which should be used for installation and testing. Testing is done using CPAN:Test::Unit, and is invoked using the 'test' build target. Writing tests is a useful way of feeding back bugs as well. I can't encourage you enough to maintain and extend the tests!

Detailed Documentation

Clients use the DBCache by defining a subclass of the TWiki::Contrib::DBCacheContrib class. The following POD documentation describes the methods of this class and the various other classes provided by the plugin..

class DBCacheContrib

General purpose cache that treats TWiki topics as hashes. Useful for rapid read and search of the database. Only works on one web.

Typical usage:

  use TWiki::Contrib::DBCacheContrib;

  $db = new TWiki::Contrib::DBCacheContrib( $web ); # always done
  $db->load(); # may be always done, or only on demand when a tag is parsed that needs it

  # the DB is a hash of topics keyed on their name
  foreach my $topic ($db->getKeys()) {
     my $attachments = $db->get($topic)->get("attachments");
     # attachments is an array
     foreach my $val ($attachments->getValues()) {
       my $aname = $attachments->get("name");
       my $acomment = $attachments->get("comment");
       my $adate = $attachments->get("date");
       ...
     }
  }

As topics are loaded, the readTopicLine method gives subclasses an opportunity to apply special processing to indivual lines, for example to extract special syntax such as %ACTION lines, or embedded tables in the text. See FormQueryPlugin for an example of this.

`new($web, $cacheName)`

$web name of web to create the object for.
$cacheName name of cache file (default "_DBCache")

Construct a new DBCache object.

readTopicLine($topic, $meta, $line, $fh) --> text

$topic - name of the topic being read
$meta - reference to the hash object for this topic
line - the line being read
$fh - the file handle of the file
return text to insert in place of line in the text field of the topic

Called when reading a topic that is being cached, this method is invoked on each line in the topic. It is designed to be overridden by subclasses; the default implementation does nothing. The sort of expected activities will be (for example) reading tables and adding them to the hash for the topic.

onReload($topics)

$topics - perl array of topic names that have just been loaded (or reloaded)

Designed to be overridden by subclasses. Called when one or more topics had to be read from disc rather than from the cache. Passed a list of topic names that have been read.

load( [updateCache] ) -> ($readFromCache, $readFromFile, $removed)

Load the web into the database. Returns a list containing 3 numbers that give the number of topics read from the cache, the number read from file, and the number of previously cached topics that have been removed.

if $TWiki::cfg{DBCache}{AlwaysUpdateCache} is set to FALSE (defaults to TRUE for compatibility) then avoid calling _updateCache unless requested. DBCachePlugin now only asked for it from the afterSaveHandler and from the new REST updateCache handler

package TWiki::Contrib::DBCacheContrib::Search

Search operators work on the fields of a TWiki::Contrib::DBCacheContrib::Map.

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 , ~ 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
`=`	Boolean	LHS exactly matches the regular expression on the RHS. The expression must match the whole string.
`!`	Boolean	Unary NOT
`!=`	Boolean	Inverse of =
`()`	any	Bracketed subexpression
`AND`	Boolean	AND
`EARLIER_THAN`	BOOLEAN	Date is earlier than the given date
`>`	Boolean	Numeric >
`>=`	Boolean	Numeric >=
`LATER_THAN`	Boolean	LHS is later than the given date (string containing a date e.g. '1 Apr 2003')
`lc`	String	Unary lower case
`<`	Boolean	Numeric <
`<=`	Boolean	Numeric <=
`OR`	Boolean	OR
`uc`	String	Unary UPPER CASE
`WITHIN_DAYS`	Boolean	Date (which must be in the future) is within n working days of todays date
`=~`	Boolean	LHS contains RHS i.e. the RHS is found somewhere in the field value.

Dates for EARLIER_THAN, LATER_THAN and WITHIN_DAYS must be dates in the format expected by Time::ParseDate (like the ActionTrackerPlugin). WITHIN_DAYS works out the number of working days (i.e. excluding Saturday and Sunday). Apologies in advance if your weekend is offset ± a day! Integers will automatically be converted to dates, by assuming they represent a number of seconds since midnight GMT on 1st January 1970.

Example

Get a list of attachments that have a date earlier than 1st January 2000

  $db = new TWiki::Contrib::DBCacheContrib::DBCache( $web ); # always done
  $db->load();
  my $search = new TWiki::Contrib::DBCacheContrib::Search("date EARLIER_THAN '1st January 2000'");

  foreach my $topic ($db->getKeys()) {
     my $attachments = $topic->get("attachments");
     foreach my $val ($attachments->getValues()) {
       if ($search->matches($val)) {
          print $val->get("name") . "\n";
       }
     }
  }

A search object implements the "matches" method as its general contract with the rest of the world.

`new($string)`

$string - string containing an expression to parse

Construct a new search node by parsing the passed expression.

`toString()` -> string

Generates a string representation of the object.

--+++ =addOperator(%oper) Add an operator to the parser

%oper is a hash, containing the following fields:

name - operator string
prec - operator precedence, positive non-zero integer. Larger number => higher precedence.
arity - set to 1 if this operator is unary, 2 for binary. Arity 0 is legal, should you ever need it.
exec - the handler to implement the new operator

package TWiki::Contrib::DBCacheContrib::FileTime

Object that handles a file/time tuple for use in Storable and TWiki::Contrib::DBCacheContrib::Archive.

`new($file)`

$file - filename

Construct from a file name

`uptodate()` -> boolean

Check the file time against what is seen on disc. Return 1 if consistent, 0 if inconsistent.

`toString()` -> string

Generates a string representation of the object.

`write()`

TWiki::Contrib::DBCacheContrib::Archive hook

`read()`

TWiki::Contrib::DBCacheContrib::Archive hook

package TWiki::Contrib::DBCacheContrib::Array

Generic array object. This is required because perl arrays are not objects, and cannot be subclassed e.g. for serialisation. To avoid lots of horrid code to handle special cases of the different perl data structures, we use this array object instead.

`new()`

Create a new, empty array object

`add($object)`

$object any perl data type

Add an element to the end of the array

`find($object)` -> integer

$object datum of the same type as the content of the array

Uses "==" to find the given element in the array and return it's index

`remove($index)`

$index - integer index

Remove an entry at an index from the array.

`get($key, $root)` -> datum

$k - key
$root - what # refers to

Subfield syntax

get("9", $r) where $n is a number will get the 9th entry in the array
get("[9]", $r) will also get the 9th entry
get(".9", $r) will also get the 9th entry
get(".X", $r) will return the sum of the subfield X of each entry
get("[?search]", $r) will perform the given search over the entries in the array. Always returns an array result, even when there is only one result. For example: [?name='Sam'] will return an array of all the entries that have their subfield name set to Sam.
# means "reset to root". So get("#[3]", $r) will return the 4th entry of $r (assuming $r is an array!).
get("[*X]", $r) will get a new array made from subfield X of each entry in this array.

Where the result of a subfield expansion is another object (a Map or an Array) then further subfield expansions can be used. For example,

get("parent.UserTable[?SubTopic='ThisTopic'].UserName", $web);

See also TWiki::Contrib::DBCacheContrib::Map for syntax that applies to maps.

`size()` -> integer

Get the size of the array

`sum($field)` -> number

$field - name of a field in the class of objects stored by this array

Returns the sum of values of the given field in the objects stored in this array.

`search($search)` -> search result

$search - TWiki::Contrib::DBCacheContrib::Search object to use in the search

Search the array for matches with the given object. values. Return a TWiki::Contrib::DBCacheContrib::Array of matching entries.

`getValues()` -> perl array

Get a "perl" array of the values in the array, suitable for use with foreach

`toString($limit, $level, $strung)` -> string

$limit - recursion limit for expansion of elements
$level - currentl recursion level

Generates an HTML string representation of the object.

write($archive)

$archive - the TWiki::Contrib::DBCacheContrib::Archive being written to

Writes this object to the archive. Archives are used only if Storable is not available. This method must be overridden by subclasses is serialisation of their data fields is required.

read($archive)

$archive - the TWiki::Contrib::DBCacheContrib::Archive being read from

Reads this object from the archive. Archives are used only if Storable is not available. This method must be overridden by subclasses is serialisation of their data fields is required.

package TWiki::Contrib::DBCacheContrib::Map

Generic map object for mapping names to things. A name is defined as name = \w+ | \w+ "." name The . indicates a field reference in a sub-map. Objects in the map are either strings, or other objects that must support toString.

`new($string)`

$string - optional attribute string in standard TWiki syntax

Create a new, empty array object. Optionally parse a standard attribute string containing name=value pairs. The value may be a word or a quoted string (no escapes!)

`fastget($k)` -> datum

$k - key

Get the value for a key, but without any subfield field expansion

`get($k, $root)` -> datum

$k - key
$root what # refers to

Get the value corresponding to key $k; return undef if not set.

Subfield syntax

get("X",$r) will get the subfield named X.
get("X.Y",$r) will get the subfield Y of the subfield named X.
get("[X]",$r) = will get the subfield named =X (so X[Y] and X.Y are synonymous)..
# means "reset to root". So get("#.Y", $r) will return the subfield =Y of $r (assuming $r is a map!), as will get("#[Y]".

Where the result of a subfield expansion is another object (a Map or an Array) then further subfield expansions can be used. For example,

get("UserTable[0].Surname", $web);

See also TWiki::Contrib::DBCacheContrib::Array for syntax that applies to arrays.

`set($k, $v)`

$k - key
$v - value

Set the given key, value pair in the map.

`size()` -> integer

Get the size of the map

`remove($index)` -> old value

$index - integer index

Remove an entry at an index from the array. Return the old value.

`getKeys()` -> perl array

Get a "perl" array of the keys in the map, suitable for use with foreach

`getValues()` -> perl array

Get a "perl" array of the values in the Map, suitable for use with foreach

`search($search)` -> search result

$search - TWiki::Contrib::DBCacheContrib::Search object to use in the search

Search the map for keys that match with the given object. values. Return a TWiki::Contrib::DBCacheContrib::Array of matching keys.

`toString($limit, $level, $strung)` -> string

$limit - recursion limit for expansion of elements
$level - currentl recursion level

Generates an HTML string representation of the object.

write($archive)

$archive - the TWiki::Contrib::DBCacheContrib::Archive being written to

Writes this object to the archive. Archives are used only if Storable is not available. This method must be overridden by subclasses is serialisation of their data fields is required.

read($archive)

$archive - the TWiki::Contrib::DBCacheContrib::Archive being read from

Reads this object from the archive. Archives are used only if Storable is not available. This method must be overridden by subclasses is serialisation of their data fields is required.

Installation Instructions

{DBCache}{AlwaysUpdateCache}

If $TWiki::cfg{DBCache}{AlwaysUpdateCache} is set to FALSE (defaults to TRUE for compatibility) then DBCacheContrib will avoid calling _updateCache unless requested. _updateCache accesses every topic file in the web, so its an unnecessary performance hit. DBCacePlugin now only requests _updateCache from the afterSaveHandler and from the new REST updateCache handler.

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 where TWiki is running.

Like many other TWiki extensions, this module is shipped with a fully automatic installer script written using the BuildContrib.

If you have TWiki 4.2 or later, you can install from the configure interface (Go to Plugins->Find More Extensions)
- See the installation supplement on TWiki.org for more information.
If you have any problems, then you can still install manually from the command-line:
1. Download one of the .zip or .tgz archives
2. Unpack the archive in the root directory of your TWiki installation.
3. Run the installer script ( perl <module>_installer )
4. Run configure and enable the module, if it is a plugin.
5. Repeat for any missing dependencies.
If you are still having problems, then instead of running the installer script:
1. Make sure that the file permissions allow the webserver user to access all files.
2. Check in any installed files that have existing ,v files in your existing install (take care not to lock the files when you check in)
3. Manually edit LocalSite.cfg to set any configuration variables.

Contrib Info

Author: TWiki:Main.CrawfordCurrie

Copyright: This code is based on an original development of Motorola Inc. and is protected by the following copyrights:
© 2002-2003 Motorola Inc. All Rights Reserved.
Portions copyright © 2004. Crawford Currie http://www.c-dot.co.uk
© 2004-2011, TWiki:TWiki.TWikiContributor

License: As required for the publication of all extensions to TWiki, this software is published under the terms of the GNU General Public License. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Version: 21578 (2011-07-07)

Change History:

2011-07-07: TWikibug:Item6711: Small doc fix in Config.spec

2010-04-29: TWikibug:Item6433: Doc improvements

16347 remove META data from text hash; include META data in all hash. TWiki: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. TWiki:Main/MichaelDaum

15868 fixed WITHIN_DAYS and EARLIER_THAN. TWiki:Main/MichaelDaum

15583 made query parser pluggable so that other plugins can implement their own predicates. TWiki:Main/MichaelDaum

15019 added {DBCache}{AlwaysUpdateCache} to remove the updateCache from every operation. TWiki: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 - 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 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 FormQueryPlugin

Dependencies:

Name	Version	Description
Time::ParseDate	>=2003.0211	Required. Available from CPAN.
Storable	>=2.07	Recommended; accelerates cache handling. Available from CPAN

Perl Version: 5.0

Plugin Home: http://TWiki.org/cgi-bin/view/Plugins/DBCacheContrib

Feedback: http://TWiki.org/cgi-bin/view/Plugins/DBCacheContribDev

Appraisal: http://TWiki.org/cgi-bin/view/Plugins/DBCacheContribAppraisal

DBCacheContrib

Summary of Contents

Features

How the database gets built

The cache

Extending or customising

Detailed Documentation

class DBCacheContrib

new($web, $cacheName)

readTopicLine($topic, $meta, $line, $fh) --> text

onReload($topics)

load( [updateCache] ) -> ($readFromCache, $readFromFile, $removed)

package TWiki::Contrib::DBCacheContrib::Search

Example

new($string)

toString() -> string

package TWiki::Contrib::DBCacheContrib::FileTime

new($file)

uptodate() -> boolean

toString() -> string

write()

read()

package TWiki::Contrib::DBCacheContrib::Array

new()

add($object)

find($object) -> integer

remove($index)

get($key, $root) -> datum

size() -> integer

sum($field) -> number

search($search) -> search result

getValues() -> perl array

toString($limit, $level, $strung) -> string

write($archive)

read($archive)

package TWiki::Contrib::DBCacheContrib::Map

new($string)

fastget($k) -> datum

get($k, $root) -> datum

set($k, $v)

size() -> integer

remove($index) -> old value

getKeys() -> perl array

getValues() -> perl array

search($search) -> search result

toString($limit, $level, $strung) -> string

write($archive)

read($archive)

Installation Instructions

{DBCache}{AlwaysUpdateCache}

Contrib Info

Menu

TopicActions

WebActions

Webs

Over deze site

`new($web, $cacheName)`

`new($string)`

`toString()` -> string

`new($file)`

`uptodate()` -> boolean

`toString()` -> string

`write()`

`read()`

`new()`

`add($object)`

`find($object)` -> integer

`remove($index)`

`get($key, $root)` -> datum

`size()` -> integer

`sum($field)` -> number

`search($search)` -> search result

`getValues()` -> perl array

`toString($limit, $level, $strung)` -> string

`new($string)`

`fastget($k)` -> datum

`get($k, $root)` -> datum

`set($k, $v)`

`size()` -> integer

`remove($index)` -> old value

`getKeys()` -> perl array

`getValues()` -> perl array

`search($search)` -> search result

`toString($limit, $level, $strung)` -> string