Wikibase/Schema/wbs propertypairs

The  table stores statistics on property usage. It has statistics for 1) properties used for a given class/subclass, 2) properties used as qualifiers for a given property and 3) properties used as references for a given property. The statistics include a count and percentage of items/subclasses/qualifiers/references that have the given property pair.

row_id
auto-increment row ID for internal use. Primary key.

pid1

 * : 31 (instance of) or 279 (subclass of)
 * : Property that has a qualifier or reference

qid1

 * : QID of class
 * : Not used

pid2
Property that counts are for.

count
Count of instances/subclasses that have pid2.

probability
Percentage of instances/subclasses that have pid2.

context
What type of pair is this ( (class/subclass -> property),   (property -> qualifier property) or   (property -> reference property).

Schema
mysql> describe wbs_propertypairs; +-+-+--+-+-++ +-+-+--+-+-++ +-+-+--+-+-++ 7 rows in set (0.01 sec)
 * Field      | Type                | Null | Key | Default | Extra          |
 * row_id     | bigint(20) unsigned | NO   | PRI | 0       | auto_increment |
 * pid1       | int(10) unsigned    | NO   | MUL | NULL    |                |
 * qid1       | int(10) unsigned    | YES  |     | NULL    |                |
 * pid2       | int(10) unsigned    | NO   |     | NULL    |                |
 * count      | int(10) unsigned    | NO   |     | NULL    |                |
 * probability | float              | NO   |     | NULL    |                |
 * context    | varbinary(32)       | NO   |     | NULL    |                |