# App/Category/Internals

From XOWA: the free, open-source, offline wiki application

This page will document some of the internals of V2

## Builder commands

For reference, this is the current script to set up the V2 Category system

    app.bldr.pause_at_end_('n');
    app.bldr.cmds
    .add_many('simple.wikipedia.org', 'ctg.hiddencat_sql', 'ctg.hiddencat_ttl', 'ctg.link_sql', 'ctg.link_idx').owner
    ;
    app.bldr.run;

Note that 'ctg.link_sql' and 'ctg.link_idx' are required.

Note that 'ctg.hiddencat_sql' and 'ctg.hiddencat_ttl' can be omitted. However, it is recommended that they be run (for English Wikipedia, it adds less than 5 minutes to the entire process).

### ctg.hiddencat_sql

- This command will look for a file matching *page_props.sql in the wiki directory

  For example: /xowa/wiki/simple.wikipedia.org/simplewiki-latest-page_props.sql. Note this sql will have a format of (page_id, prop_name, prop_val)

- It will then parse the .sql file and look for entries having a prop_name of "hiddencat". For example (1, 'hiddencat', '')

- When it's done, it will generate a Base85 encoded list of all page_ids

  The output directory will be /xowa/wiki/simple.wikipedia.org/tmp/ctg.hiddencat_sql/make/
  An example of a file would be:

    !!!!#
    !!!!$

### ctg.hiddencat_ttl

- This command will look at the output of ctg.hiddencat_sql and find the appropriate title for the given id

  This step is necessary as the category indexes are sorted by title, not by id.

- When it's done, it will generate a sorted list of title|id.

  The output directory will be /xowa/wiki/simple.wikipedia.org/tmp/ctg.hiddencat_ttl/make/
  An example of a file would be:

    A|!!!!#
    B|!!!!$

### ctg.link_sql

- This command will look for a file matching *categorylinks.sql in the wiki directory

  For example: /xowa/wiki/simple.wikipedia.org/simplewiki-latest-categorylinks.sql.

- It will then parse the .sql file and extract the following data: category_name, page_id, page_member_type, page_sortkey, page_member_add_date

- When it's done, it will generate a sorted list of category|type|sortkey|id|date.

  The output directory will be /xowa/wiki/simple.wikipedia.org/tmp/ctg.link_sql/make/
  An example of a file would be:

    A|p|Page_1_sortkey|!!!!%|!!!@!|
    B|p|Page_2_sortkey|!!!!^|!!!@@|

### ctg.link_idx

- This command will generate the /category2/ hive based on the output of the above commands. It uses the following:
  - Category link data as built in /xowa/wiki/simple.wikipedia.org/tmp/ctg.link_sql/make/.
  - Category hidden data as built in /xowa/wiki/simple.wikipedia.org/tmp/ctg.hiddencat_ttl/make/.

- It will then merge the output of the above data and generate the /main/ and /link/ sudirectories in /category2/

## /category2/

### /main/

The main files are located at /xowa/wiki/simple.wikipedia.org/site/category2/main/. They follow the same hive structure as the other directories (a main reg.csv and subdirectories of the format of /00/00/00/00/0123456789.xdat)

Each file contains header information for a category. Presently, this includes the following:

- Category name
- Hidden: "y" means hidden; "n" means not hidden
- Number of subcategories (Base85 encoded)
- Number of files (Base85 encoded)
- Number of pages (Base85 encoded)

  EX: `A|y|!!!!!|!!!!!|!!!!!|`

### /link/

The link files are located at /xowa/wiki/simple.wikipedia.org/site/category2/link/. They also follow the same hive structure as the other directories.

Each file contains members of a category. Presently, this includes the following:

- Category name
- Length of subcategories data
- Length of files data
- Length of pages data
- A series of entries listing category members
  - Note that these entries are broken into subgroups (subcategories / files / pages) depending on the preceding lengths.
  - Each entry is in a semi-colon delimited format
    - page_id (Base85 encoded)
    - page_member_add_date (Base85 encoded)
    - page_sortkey

    EX (for entry): `|!!!!%;!!!@!;Page_1_sortkey|`
  EX (for all): `A|!!!!!|!!!!!|!!!!X|!!!!%;!!!@!;Page_1_sortkey|!!!!^;!!!@@;Page_2_sortkey|`

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