The index probes are triggered each time a a row is read using one of the indexes for the specified table. The probe is triggered within the corresponding storage engine for the table.
index-read-row-start(database, table) index-read-row-done(status)
index-read-row-start: Triggered when a
row is read by the storage engine from the specified
index-read-row-done: Triggered when an
indexed row read operation within a storage engine
status returns 0 on
success, or a positive value on failure.