6.8 Handler Activity Metrics

Lists the Handler Activity metrics and provides a brief description of each.

Table 6.8 Handler Activity Metrics

Name	Description
Commit (Delta)	The number of internal COMMIT statements.
Delete (Delta)	The number of times that rows have been deleted from tables.
Discover (Delta)	A counter for the prepare phase of two-phase commit operations.
External Lock (Delta)	The server increments this variable for each call to its external_lock() function, which generally occurs at the beginning and end of access to a table instance.
Mrr Init (Delta)	The number of times the server uses a storage engine's own Multi-Range Read implementation for table access.
Prepare (Delta)	The number of times the first entry in an index was read.
Read First (Delta)	The number of requests to read a row based on a index key value. If this value is high, it suggests that the server is doing a lot of full index scans.
Read Key (Delta)	The number of requests to read the last key in an index. If this value is high, it is a good indication that your tables are properly indexed for your queries.
Read Last (Delta)	The number of requests to read the last key in an index.
Read Next (Delta)	The number of requests to read the next row in key order. This value is incremented if you are querying an index column with a range constraint or if you are doing an index scan.
Read Prev (Delta)	The number of requests to read the previous row in key order. This read method is mainly used to optimize ORDER BY ... DESC.
Read Rnd (Delta)	The number of requests to read a row based on a fixed position. This value is high if you are doing a lot of queries that require sorting of the result.
Read Rnd Next (Delta)	The number of requests to read the next row in the data file. This value is high if you are doing a lot of table scans.
Rollback (Delta)	The number of requests for a storage engine to perform a rollback operation.
Savepoint (Delta)	The number of requests for a storage engine to place a savepoint.
Savepoint Rollback (Delta)	The number of requests for a storage engine to rollback to a savepoint.
Update (Delta)	The number of requests to update a row in a table.
Write (Delta)	The number of requests to insert a row in a table.
Indexes Not Being Used Efficiently (Rate)	The target server does not appear to be using indexes efficiently. The values of Handler_read_rnd_next and Handler_read_rnd together - which reflect the number of rows read via full table scans - are high compared to the Handler variables which denote index accesses - such as Handler_read_key, Handler_read_next etc. Examine your tables and queries for proper use of indexes.
Rows Read Via Indexes (Delta)	Rows read via the storage engine handler layer that used indexes in the last interval.
Rows Read Via Indexes (Per Sec Avg)	Average of rows read per second via the storage engine handler layer that used indexes in the last interval.
Rows Read Via Scan (Delta)	Rows read via the storage engine handler layer that used a table scan in the last interval.
Rows Read Via Scan (Per Sec Avg)	Average of rows read per second via the storage engine handler layer that used a table scan.
Index Usage Ratio (Delta)	The ratio of rows read via indexes vs rows read via table scan in the last interval.