Extension:Cargo/Storing data

The creation of data structures, and storage of data, is done in Cargo exclusively via templates. Any template that makes use of Cargo needs to contain calls to the parser functions #cargo_declare and #cargo_store; or, more rarely, calls to #cargo_attach and #cargo_store. #cargo_declare defines the fields for a table of data, #cargo_store stores data within that table, and #cargo_attach specifies that a template stores its data in a table that has been defined elsewhere.

Declaring a table

A template that stores data in a table needs to also either declare that table, or "attach" itself to a table that is declared elsewhere. Since there is usually one table per template and vice versa, most templates that make use of Cargo will declare their own table. Declaring is done via the parser function #cargo_declare.

This function is called with the following syntax:

{{#cargo_declare:
_table = table_name
|field_1 = field description 1
|field_2 = field description 2
...etc.
}}

Neither the table name nor field names can contain spaces or dashes; instead, you can use underscores, CamelCase, etc. Underscores cannot be used at the beginning or end of table and field names.

The field description must start with the type of the field, and in many cases it will simply be the type. The following types are predefined in Cargo:

Field Type	Description	Unindexed?
Page	Holds the name of a page in the wiki (default max size: 300 characters)
String	Holds standard, non-wikitext text (default max size: 300 characters)
Text	Holds standard, non-wikitext text; intended for longer values	✔
Integer	Holds an integer
Float	Holds a real, i.e., non-integer, number
Date	Holds a date without time
Start date, End date	Similar to Date, but are meant to hold the beginning and end of some duration. A table can hold either no Start date and no End date field, or exactly one of both.
Datetime	Holds a date and time
Start datetime, End datetime	Work like Start date or End date, but include a time.
Boolean	Holds a Boolean value, whose value should be 1 or 0, or 'yes' or 'no' (see this section for Cargo-specific information on querying Boolean values)
Wikitext string	Holds a short text that is meant to be parsed by the MediaWiki parser (default max size: 300 characters)
Wikitext	Holds longer text that is meant to be parsed by the MediaWiki parser	✔
Searchtext	Holds text that can be searched on, using the MATCHES command (requires MySQL 5.6+ or MariaDB 5.6+)
File	Holds the name of an uploaded file or image in the wiki (similar to Page, but does not require specifying the "File:" namespace) (default max size: 300 characters)
URL	Holds a URL (default max size: 300 characters)
Email	Holds an email address (default max size: 300 characters)
Rating	Holds a "rating" value, i.e., usually an integer from 1 to 5

Any other type specified will be treated as type "String". Fields of types that are unindexed are significantly slower to query on or join on.

A field can also hold a list of any such type. To define such a list, the type value needs to look like "List (delimiter) of type". For example, to have a field called "Authors" that holds a list of string values separated by commas, you would have the following parameter in the #cargo_declare call:

|Authors=List (,) of String

Caveat: fields set to List of type must have a different name than the table. If they're identical, cargo queries that include the "list" field return errors.

Field parameters

The description string can also have additional parameters; these all are enclosed within parentheses after the type identifier, and separated by semicolons. The current allowed parameters are:

Parameter	Description
size=	For fields of type "Page", "String", "Wikitext string", "File", "URL" and "Email", sets the size of this field, i.e., the number of characters; the default is set by the global variable $wgCargoDefaultStringBytes, which in turn has a default value of 300 (although it can be modified in LocalSettings.php).
hierarchy	Specifies that the field holds a hierarchy of values, as defined in the "allowed values" parameter (see next item).
allowed values=	A set of allowed values that a field can have. (This is usually only done for fields of type "String" or "Page".) If "hierarchy" is not specified, this should simply be a set of comma-separated values. If "hierarchy" is specified, the values should be defined using the syntax of a bulleted list. In brief: every value should be on its own line, each line should start with at least one "*", the first line should start with exactly one "*", and the number of "*" should increase by no more than one at a time.

For example, to define a field called "Color" that has three allowed values, you could have the following declaration:

|Color=String (size=10;allowed values=Red,Blue,Yellow)

Meanwhile, to define a field called "Main ingredient" that is a hierarchy, you could have the following declaration:

|Main_ingredient = String (hierarchy;allowed values=*Fruits
**Mangoes
**Apples
*Vegetables
**Root vegetables
***Carrots
***Turnips
**Peppers)

Parameter	Description
link text=	For fields of type "URL", sets text that would be displayed as a link to that URL. By default, the entire URL is shown.
hidden	Takes no value. If set, the field is not listed in Special:Drilldown, although it is still queryable.
mandatory	Takes no value. If set, the field is declared as mandatory, i.e., blank values are not allowed.
unique	Takes no value. If set, all values for the field must be unique – a value that already exists for that field in the table will not be saved.
regex=	Sets a regular expression for this field, which all values must match. For example, if "regex=T\d+" is set, values for that field must consist of the letter "T" followed by one or more numerals.
dependent on=	Takes in the name of another field in this table, to specify that this field should only be displayed in Special:Drilldown once the user has selected a value for that field.

Other #cargo_declare parameters

Other than the table's name and fields, the following parameters can also be added to #cargo_declare:

• _parentTables - for setting one or more other Cargo tables as the "parent tables" of this table. This is used within Special:Drilldown, to let the user filter on fields from additional Cargo tables that are tied in some way to this one. It takes the following syntax:

|_parentTables= tableName1(_localField=localFieldName, _remoteField=remoteFieldName, _alias=tableAlias); tableName2(...); ...

Here, 'tableName1' is the name of the table you want to declare as the parent table. '_localField' and '_remoteField' specify the fields in the two tables that need to be joined on (the default values for both are "_pageName"). If '_alias' is defined, then that will be displayed in the drilldown instead of the parent table's name.

Example: This drilldown display shows additional drilldown fields from a parent table, "Items" (listed as "Item) (template here)

• _drilldownTabs - for setting custom drilldown tabs in Special:Drilldown page. It can be declared like this:

|_drilldownTabs= Tab1(format=list;delimiter=\;;fields=A,B,C), Tab2(format=table; fields=A,C,D)

where 'Tab1' is the display name of the tab, 'format' parameter takes the desired format name and thereafter, you can add all the parameters needed for that format and then 'fields' holds the set of fields to be displayed.

Example: This drilldown display also shows custom tabs (template here)

#cargo_declare also displays a link to the Special:CargoTables page for viewing the contents of this database table.

Attaching to a table

In some cases, you may want more than one template to store their data to the same Cargo table. In that case, only one of the templates should declare the table, while the others should simply "attach" themselves to that table, using the parser function #cargo_attach.

This function is called with the following syntax:

{{#cargo_attach:
_table = table_name
}}

A template should have no more than one call to #cargo_attach (and no more than one call to #cargo_declare, for that matter). Any template that contains a call to #cargo_store should also call either #cargo_declare or #cargo_attach.

Storing data in a table

A template that declares a table or attaches itself to one should also store data in that table. This is done with the parser function #cargo_store. Unlike #cargo_declare and #cargo_attach, which apply to the template page itself and thus should go into the template's <noinclude> section, #cargo_store applies to each page that calls that template, and thus should go into the template's <includeonly> section.

This function is called with the following syntax:

{{#cargo_store:
_table = table_name
|field_1 = value 1
|field_2 = value 2
...etc.
}}

The field names must match those in the #cargo_declare call elsewhere in the template.

The values will usually, but not always, be template parameters; but in theory they could hold anything.

If $wgCargoStoreUseTemplateArgsFallback is enabled, for fields whose value is one of your template's parameters (i.e. you are writing |paramName={{{paramName}}}), and where the name of the template parameter is the same as the name of the Cargo field (apart from the presence of underscores instead of spaces), the field can be left out of the #cargo_store call; so, in many cases, the call could instead simply look like:

{{#cargo_store:
_table = table_name
}}

In fact, not even the table name really needs to specified; so in many cases the call could even look like:

{{#cargo_store:}}

However, this is slightly less efficient (and maybe more confusing to readers) than specifying the table name. Please note, $wgCargoStoreUseTemplateArgsFallback is disabled on some wiki farms, including wiki.gg.

Storing a recurring event

Special handling exists for storing recurring events, which are events that happen regularly, like birthdays or weekly meetings. For these, the parser function #recurring_event exists. It takes in a set of parameters for a recurring event (representing the start date, frequency etc.), and simply prints out a string holding a list of the dates for that event. It is meant to be called within #cargo_store (for a field defined as holding a list of dates), and #cargo_store will then store the data appropriately. #recurring_event is called with the following syntax:

{{#recurring_event:
start=start date
|end=end date
|unit=day, week, month, or year
|period=some number, representing the number of "units" between event instances (default is 1)
|include=list of dates, to be included in the list
|exclude=list of dates to exclude
|delimiter=delimiter for dates (default is ';')
}}

Of these parameters, only "start=" and "unit=" are required.

By default, if no end date is set, or if the end date is too far in the future, #recurring_event stores 50 instances of the event. To change this, you can add a setting for $wgCargoRecurringEventMaxInstances in LocalSettings.php, under the inclusion of Cargo. For instance, to set the number to 100, you would add the following:

$wgCargoRecurringEventMaxInstances = 100;

If working with recurring events, declare the type of the field of the field to be List (;) of Date.

Example

You can see two templates that make use of #cargo_declare and #cargo_store here and here.

Creating or recreating a table

No data is actually generated or modified when a template page containing a #cargo_declare call is saved. Instead, the data must be created or recreated in a separate process. There are two ways to do this:

Web-based tab

File:Cargo recreate data interface.png

The form displayed at "?action=recreatedata" if an existing table is being recreated

From the template page, select the tab action called either "Create data" or "Recreate data". This will bring up an interface that may contain a checkbox reading "Recreate data into a replacement table, keeping the old one for querying". (That checkbox will only appear if the Cargo table in question already exists.)

Once you hit "OK", one of the following will happen:

1. If the checkbox was selected, a "replacement table" will be created, while the current table remains unaffected. This replacement table can be viewed by anyone, but its data will not be used in queries. (In the database, the actual table will have a name like "cargo__tableName__NEXT".) If/when you think this replacement table is ready to be used, you can click on the "Switch in table" link at Special:CargoTables. This link will delete the current Cargo table and rename the replacement table so that it becomes the official table. Conversely, if you would rather not use the replacement table, you can click on the "Delete" link for it.
2. If the checkbox was not selected, the current table will be deleted immediately, and a new version will get created.
3. If the checkbox was not there, it means that this is a new table. In that case, the table will be created.

In all three cases, MediaWiki jobs are used to cycle through all the relevant pages and recreate the data - a separate job is created for each page. This can be a lengthy process for large tables, which is why using the "replacement table" approach is recommended for large tables - it avoids a "downtime" period when the table is mostly empty.

Depending on the MediaWiki configuration, a call to MediaWiki's runJobs.php script may be useful or even necessary for these jobs to actually start.

If any templates contain #cargo_attach, they too will get a "Create data" or "Recreate data" tab. If this tab is selected and activated, it will not drop and recreate the database table itself; instead, it will only recreate those rows in the table that came from pages that call that template.

Permissions

The ability to create/recreate data is available to users with the 'recreatecargodata' permission, which by default is given to sysops. You can give this permission to other users; for instance, to have a new user group, 'cargoadmin', with this ability, you would just need to add the following to LocalSettings.php:

$wgGroupPermissions['cargoadmin']['recreatecargodata'] = true;

Once a table exists for a template, any page that contains one or more calls to that template will have its data in that table refreshed whenever it is resaved, and new pages that contain call(s) to that template will get their data added in when the pages are created.

Command-line script

If you have access to the command line, you can also recreate the data by calling the script cargoRecreateData.php, located in Cargo's /maintenance directory. It can be called in one of two ways:

Command	Description
php cargoRecreateData.php	Recreates the data for all Cargo tables in the system
php cargoRecreateData.php --table tableName	Recreates the data for the one specified Cargo table.

In addition, the script can be called with the --quiet flag, which turns off all printouts. For full usage information, call it with --help.

Storing page data

You can create an additional Cargo table that holds "page data": data specific to each page in the wiki, not related to infobox data. This data can then be queried either on its own or joined with one or more "regular" Cargo tables. The table is named "_pageData", and it holds one row for every page in the wiki. You must specify the set of fields you want the table to store; by default it will only hold the five standard Cargo fields (_pageName, _pageTitle, _pageNamespace, _pageID and _ID: see Database storage details). To include additional fields, add to the array $wgCargoPageDataColumns in LocalSettings.php, below the line that installs Cargo.

Below are the fields that can be added to the _pageData table, along with the call to add each one:

Field	Description	LocalSettings.php call
_creationDate	The date/time the page was created	$wgCargoPageDataColumns[] = 'creationDate';
_modificationDate	The date/time the page was last modified	$wgCargoPageDataColumns[] = 'modificationDate';
_creator	The username of the user who created the page	$wgCargoPageDataColumns[] = 'creator';
_lastEditor	The username of the user who last modified the page	$wgCargoPageDataColumns[] = 'lastEditor';
_fullText	The (searchable) full text of the page	$wgCargoPageDataColumns[] = 'fullText';
_categories	The categories of the page (a list, queryable using "HOLDS"). Note that spaces are stored as underscores.	$wgCargoPageDataColumns[] = 'categories';
_numRevisions	The number of edits this page has had	$wgCargoPageDataColumns[] = 'numRevisions';
_isRedirect	Whether this page is a redirect	$wgCargoPageDataColumns[] = 'isRedirect';
_pageNameOrRedirect	The target of the page if it's a redirect, otherwise the page name	$wgCargoPageDataColumns[] = 'pageNameOrRedirect';
_pageIDOrRedirect	The ID of the target of the page if it's a redirect, otherwise the page ID	$wgCargoPageDataColumns[] = 'pageIDOrRedirect';

Once you have specified which fields you want the table to hold, go to the Cargo /maintenance directory, and make the following call to create, or recreate, the _pageData table:

php setCargoPageData.php

To recreate with replacement, add a --replacement flag:

php setCargoPageData.php --replacement

The replacement table can then be switched in normally using the Special:CargoTables interface.

If you want to get rid of this table, call the following instead:

php setCargoPageData.php --delete

You do not need to call the "--delete" option if you are planning to recreate the table; simply calling setCargoPageData.php will delete the previous version.

Storing file data

Similarly to page data, you can also automatically store data for each uploaded file. This data gets put in a table called "_fileData", which holds one row for each file. This table again has its own settings array, to specify which columns should be stored, called $wgCargoFileDataColumns.

There are currently five columns that can be set:

Field	Description	LocalSettings.php call
_mediaType	The media type, or MIME type, of each file, like "image/png"	$wgCargoFileDataColumns[] = 'mediaType';
_path	The directory path of the file on the wiki's server	$wgCargoFileDataColumns[] = 'path';
_lastUploadDate	The date/time at which the file was last uploaded	$wgCargoFileDataColumns[] = 'lastUploadDate';
_fullText	The full text of the file; this is only stored for PDF files	$wgCargoFileDataColumns[] = 'fullText';
_numPages	The number of pages in the file; this is only stored for PDF files	$wgCargoFileDataColumns[] = 'numPages';

To store the full text of PDF files, you need to have the pdftotext utility installed on the server, and then add the following to LocalSettings.php:

$wgCargoPDFToText = '...path to file.../pdftotext';

pdftotext is available as part of several packages. if you have the PdfHandler extension installed (and working), you may have pdftotext installed already.

To store the number of pages, you need to have the pdfinfo utility installed on the server, and then add the following to LocalSettings.php:

$wgCargoPDFInfo = '...path to file.../pdfinfo';

Once you have specified which fields you want the table to hold, go to the Cargo /maintenance directory, and make the following call to create, or recreate, the _fileData table:

php setCargoFileData.php

Database storage details

When the data for a template is created or recreated, a database table is created in the Cargo database that (usually) has one column for each specified field. This table will additionally hold the following columns:

Field	Description
_pageName	Holds the name of the page from which this row of values was stored.
_pageTitle	Similar to _pageName, but omits the namespace, if there is one.
_pageNamespace	Holds the numerical ID of the namespace of the page from which this row of values was stored.
_pageID	Holds the internal MediaWiki ID for that page.
_ID	Holds a unique ID for this row.

Storage of lists

For fields that have lists of values, the handling is more complex: a whole separate database table is created to hold all the individual values for this field. This table will get the name "MainTableName__FieldName" (e.g., "Books__Authors"), and it will have the following fields:

Field	Description
_rowID	Holds the ID of the row (i.e., _ID) in the main table that this value corresponds to.
_value	Holds the actual, individual value.
_position	Holds the position of this value in the list (can be 1, 2, etc.)

So if an "Authors" field contained three values, the "Books__Authors" table would have three rows corresponding to that one page.

There's one more complication for list fields: the corresponding field for a list field in the database table will not actually be given that name, but will rather be called "FieldName__full", e.g., "Authors__full". This is to enable the "true" field name to serve as a "virtual" field within the #cargo_query call, to make querying on the field values table easier (see 'The "HOLDS" command').

Storage of hierarchies

For fields that have a set of allowed values that is defined as being a hierarchy, a separate database table is created to store the whole set of allowed values. This table will get the name "MainTableName__FieldName__hierarchy" (e.g. "Books__Genre__hierarchy"), and it will have the following fields:

Field	Description
_value	The allowed value.
_left	The number of the leftmost node represented by this value.
_right	The number of the rightmost node represented by this value.

For an explanation of this method of storage, see the Wikipedia article "Nested set model".

Storage of file names

If a table has one or more fields of type "File", an additional table is created - for use in searching on files within Special:Drilldown - with the name "MainTableName__files" (e.g., "Books__files"), with the following fields:

Field	Description
_pageName	The name of the page from which this row of values was stored.
_pageID	The internal MediaWiki ID for the page.
_fieldName	The name of the relevant field of type "File".
_fileName	The value of the field, i.e., the name of an uploaded file.

Storage of coordinates

For fields of type 'Coordinates', like for fields that hold a list of values, no database field is created with the actual specified field name. Instead, the following three fields are created:

Field	Description
fieldName__full	Holds the coordinates as written on the page
fieldName__lat	Holds the latitude from the coordinates, as a float
fieldName__lon	Holds the longitude from the coordinates, as a float

If the coordinates cannot be parsed, the "__full" field still gets the value, but the "__lat" and "__lon" fields are set to null.

Storage of dates

For fields of type 'Date' or 'Datetime', an extra field is created that is named "fieldName__precision". It holds an integer value representing the "precision" of each date value, i.e., whether it holds a full date, only a year, etc. The possible values are:

Value	Description
0	Date and time (can only occur for 'Datetime' fields)
1	Date only
2	Year and month only
3	Year only

Storing Flex Diagrams data

The Flex Diagrams extension lets users define (and display) diagrams within wiki pages. If both Cargo and Flex Diagrams are installed on a wiki, you can store some data from those diagrams within special Cargo tables so that the data can be browsed and queried. Two diagram types can have their data stored: BPMN diagrams and Gantt charts. Unlike with Cargo's standard special tables, _pageData and _fileData, you cannot dictate which columns get set - they all are.

BPMN diagrams

Data about BPMN diagrams is stored in the table _bpmnData. This table can be generated by calling the following in the Cargo /maintenance directory:

php setCargoBPMNData.php

This table holds the following columns:

Field	Description
_BPMNID	The internal ID of a component
_name	The external name assigned to the component
_type	The type of the component; one of 'task', 'exclusiveGateway', 'sequenceFlow', or 'startEvent'
_connectsTo	The IDs of the components this component connects to
_annotation	The annotation of this component.

Gantt charts

Data about Gantt charts is stored in the table _ganttData. This table can be generated by calling the following in the Cargo /maintenance directory:

php setCargoGanttData.php

This table holds the following columns:

Field	Description
_localID	The internal ID of a task
_name	The name of the task
_startDate	The start date of the task
_endDate	The end date of the task
_progress	A decimal value (between 0 and 1) representing the progress of the task
_parent	The ID of the parent task, if any
_linksToBB	A list of IDs of tasks whose beginnings are connected to this task's beginning
_linksToBF	A list of IDs of tasks whose ends are connected to this task's beginning
_linksToFB	A list of IDs of tasks whose beginnings are connected to this task's end
_linksToFF	A list of IDs of tasks whose ends are connected to this task's end