Semantic MediaWiki/data/smw di blob

About

• Purpose: specifications for all SMW Objects that are text-blobs (i.e. long text which cannot be associated with a wiki page)
• Refers to: smw_object_ids

Fields

• s_id: ID of wiki page on which the property appears
• p_id: ID of wiki page for the property name
• o_blob: value when text is too long for o_hash; otherwise NULL
• o_hash: exact value of text if o_blob is null; otherwise, truncated value with hash appended (purpose unclear)

SQL

CREATE TABLE `smw_di_blob` (
  `s_id` int(8) unsigned NOT NULL,
  `p_id` int(8) unsigned NOT NULL,
  `o_blob` mediumblob,
  `o_hash` varbinary(255) DEFAULT NULL,
  KEY `s_id` (`s_id`,`p_id`),
  KEY `p_id` (`p_id`,`o_hash`)
) ENGINE=InnoDB DEFAULT CHARSET=binary

Example

titles

SELECT 
    s_id,
    s.smw_namespace AS s_namespace,
    CAST(s.smw_title AS CHAR) AS s_title
FROM
    (smw_di_blob AS r
    LEFT JOIN smw_object_ids AS s ON r.s_id = s.smw_id)

• Filter for p_id to get pages that use a specific property.
• Filter for p_id and o_hash to find pages where a specific property has a specific text value.
• Note that this table only applies to property values that do not link to wiki pages; see smw_di_wikipage for those that do.

relations

SELECT s_id, p_id
  , s.smw_namespace AS s_namespace
  , CAST(s.smw_title AS char) AS s_title
  , p.smw_namespace AS p_namespace
  , CAST(p.smw_title AS char) AS p_title
  , CAST(o_blob AS CHAR) as text
  , CAST(o_hash AS CHAR) as hash
FROM
    (smw_di_blob AS r
    LEFT JOIN smw_object_ids AS s ON r.s_id=s.smw_id)
    LEFT JOIN smw_object_ids AS p ON r.p_id=p.smw_id
ORDER BY s_id

• p_namespace will probably always be the "property:" namespace, which defaults to 102 (unless there's some way to use a page outside that namespace as a property)