18.104.22.168 Read Row Probes
The read row probes are triggered at a storage engine level each time a row read operation occurs. These probes are specified within each storage engine (as opposed to the
*row-start probes which are in the storage engine interface). These probes can therefore be used to monitor individual storage engine row-level operations and performance. Because these probes are triggered around the storage engine row read interface, they may be hit a significant number of times during a basic query.
read-row-start(database, table, scan_flag) read-row-done(status)
read-row-start: Triggered when a row is read by the storage engine from the specified
scan_flagis set to 1 (true) when the read is part of a table scan (that is, a sequential read), or 0 (false) when the read is of a specific record.
read-row-done: Triggered when a row read operation within a storage engine completes. The
statusreturns 0 on success, or a positive value on failure.