7 calls to db_add_primary_key()

system_update_6001 in drupal-6.x/modules/system/system.install
Add version id column to {term_node} to allow taxonomy module to use revisions.
system_update_6002 in drupal-6.x/modules/system/system.install
Increase the maximum length of variable names from 48 to 128.
system_update_6019 in drupal-6.x/modules/system/system.install
Reconcile small differences in the previous, manually created mysql and pgsql schemas so they are the same and can be represented by a single schema structure.
system_update_6022 in drupal-6.x/modules/system/system.install
Update files tables to associate files to a uid by default instead of a nid. Rename file_revisions to upload since it should only be used by the upload module used by upload to link files to nodes.
system_update_6033 in drupal-6.x/modules/system/system.install
Change node_comment_statistics to be not autoincrement.
system_update_6043 in drupal-6.x/modules/system/system.install
Update table indices to make them more rational and useful.
_db_create_keys in drupal-6.x/includes/database.pgsql.inc