Entity ID Counters

Entity IDs are created based on counters maintained by Wikibase in the md_docs_sql_wb_id_counters table.

• Some extensions also use this table, such as Lexeme.
• Other extensions such as EntitySchema choose not to use the table (instead creating their own).

You can view the table spec at md_docs_sql_wb_id_counters

Code

The IdGenerator interface is generally used when interacting with this storage.

• SqlIdGenerator is the oldest ID generator implementation that works for all DB types.
• UpsertSqlIdGenerator is a newer 'better' generator that only works for MySql.

The IdGenerator implementation to be used can be switched using the idGenerator setting.

Write scaling

A separate db connection can be used for both IdGenerator implementations by setting the [idGeneratorSeparateDbConnection] setting.

Both UpsertSqlIdGenerator and [idGeneratorSeparateDbConnection] may be desired for repositories that have a high number of creates and writes.

$wgWBRepoSettings['idGenerator'] = 'mysql-upsert';
$wgWBRepoSettings['idGeneratorSeparateDbConnection'] = true;