1.8.6 CQL: Event Processing and History

CQL provides hooks for maintaining detailed history of data in the database.

The hook predicates are:

• cql:cql_event_notification_table(+Schema, +TableName)
• cql:cql_history_attribute(+Schema, +TableName, +ColumnName)
• cql:cql_update_history_hook(+Schema, +TableName, +ColumnName, +PrimaryKeyColumnName, +PrimaryKeyValue, +ApplicationValueBefore, +ApplicationValueAfter, +AccessToken, +TransactionId, +TransactionTimestamp, +ThreadId, +Connection, +Goal).
• cql:process_database_events(+Events)

Event Processing and History recording can be suppressed for a particular update/insert/delete statement by including the _no_state_change_actions_9 directive.

For example

{[],
 update(se_lt_x, [f-'LILAC']
 @ :: [a-'ELSTON_M'],
 no_state_change_actions,   % Don't want history to record this change
 row_count(RowCount)}