Oracle 5.0, Reference Manual

Page: 2558 / 3232

MySQL Native Driver (
Mysqlnd
)
2538
Statistic Scope Description Notes
ps_prepared_never_executed
Connection Number of statements prepared but
never executed. Prepared statements occupy server
resources. You should not prepare a
statement if you do not plan to execute
it.
ps_prepared_once_executed
Connection Number of prepared statements
executed only one. One of the ideas behind prepared
statements is that the same query gets
executed over and over again (with
different parameters) and some parsing
and other preparation work can be
saved, if statement execution is split
up in separate prepare and execute
stages. The idea is to prepare once
and “cache” results, for example, the
parse tree to be reused during multiple
statement executions. If you execute
a prepared statement only once the
two stage processing can be inefficient
compared to “normal” queries because
all the caching means extra work and it
takes (limited) server resources to hold
the cached information. Consequently,
prepared statements that are executed
only once may cause performance
hurts.
rows_fetched_from_server_normal
,
rows_fetched_from_server_ps
Connection Total number of result set rows
successfully fetched from MySQL
regardless if the client application has
consumed them or not. Some of the
rows may not have been fetched by the
client application but have been flushed
implicitly. See also
packets_received_rset_row
rows_buffered_from_client_normal
,
rows_buffered_from_client_ps
Connection Total number of successfully buffered
rows originating from a "normal" query
or a prepared statement. This is the
number of rows that have been fetched
from MySQL and buffered on client.
Note that there are two distinct statistics
on rows that have been buffered
(MySQL to mysqlnd internal buffer) and
buffered rows that have been fetched
by the client application (mysqlnd
internal buffer to client application).
If the number of buffered rows is
higher than the number of fetched
buffered rows it can mean that the client
application runs queries that cause
larger result sets than needed resulting
in rows not read by the client. Examples of queries that will
buffer results:
mysqli_query
,
mysqli_store_result
rows_fetched_from_client_normal_buffered
,
rows_fetched_from_client_ps_buffered
Connection Total number of rows fetched by the
client from a buffered result set created
by a normal query or a prepared
statement.
rows_fetched_from_client_normal_unbuffered
,
rows_fetched_from_client_ps_unbuffered
Connection Total number of rows fetched by the
client from a unbuffered result set