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Statistics
Using Statistical Data
MySQL Native Driver contains support for gathering statistics on the
communication between the client and the server. The statistics
gathered are of three main types:
-
Client statistics
-
Connection statistics
-
Zval cache statistics
If you are using the mysqli extension, these
statistics can be obtained through three API calls:
Note:
Statistics are aggregated among all extensions that use MySQL Native
Driver. For example, when compiling both ext/mysql
and ext/mysqli against MySQL Native Driver, both
function calls of ext/mysql and
ext/mysqli will change the statistics. There is no
way to find out how much a certain API call of any extension that has
been compiled against MySQL Native Driver has impacted a certain
statistic. You can configure the PDO MySQL Driver,
ext/mysql and ext/mysqli to
optionally use the MySQL Native Driver. When doing so, all three
extensions will change the statistics.
Accessing Client Statistics
To access client statistics, you need to call
mysqli_get_client_stats. The function call does
not require any parameters.
The function returns an associative array that contains the name of
the statistic as the key and the statistical data as the value.
Client statistics can also be accessed by calling the
phpinfo function.
Accessing Connection Statistics
To access connection statistics call
mysqli_get_connection_stats. This takes the
database connection handle as the parameter.
The function returns an associative array that contains the name of
the statistic as the key and the statistical data as the value.
Accessing Zval Cache Statistics
The MySQL Native Driver also collects statistics from its internal
Zval cache. These statistics can be accessed by calling
mysqli_get_cache_stats.
The Zval cache statistics obtained may lead to a tweaking of
php.ini settings related to the Zval cache,
resulting in better performance.
Buffered and Unbuffered Result Sets
Result sets can be buffered or unbuffered. Using default settings,
ext/mysql and ext/mysqli work
with buffered result sets for normal (non prepared statement) queries.
Buffered result sets are cached on the client. After the query
execution all results are fetched from the MySQL Server and stored in
a cache on the client. The big advantage of buffered result sets is
that they allow the server to free all resources allocated to a result
set, once the results have been fetched by the client.
Unbuffered result sets on the other hand are kept much longer on the
server. If you want to reduce memory consumption on the client, but
increase load on the server, use unbuffered results. If you experience
a high server load and the figures for unbuffered result sets are
high, you should consider moving the load to the clients. Clients
typically scale better than servers. "Load" does not only
refer to memory buffers - the server also needs to keep other
resources open, for example file handles and threads, before a result
set can be freed.
Prepared Statements use unbuffered result sets by default. However,
you can use mysqli_stmt_store_result to enable
buffered result sets.
Statistics returned by MySQL Native
Driver
The following tables show a list of statistics returned by the
mysqli_get_client_stats,
mysqli_get_connection_stats and
mysqli_get_cache_stats functions.
Returned mysqlnd statistics: Network
| Statistic |
Scope |
Description |
Notes |
| bytes_sent |
Connection |
Number of bytes sent from PHP to the MySQL server |
Can be used to check the efficiency of the compression protocol |
| bytes_received |
Connection |
Number of bytes received from MySQL server |
Can be used to check the efficiency of the compression protocol |
| packets_sent |
Connection |
Number of MySQL Client Server protocol packets sent |
Used for debugging Client Server protocol implementation |
| packets_received |
Connection |
Number of MySQL Client Server protocol packets received |
Used for debugging Client Server protocol implementation |
| protocol_overhead_in |
Connection |
MySQL Client Server protocol overhead in bytes for incoming traffic.
Currently only the Packet Header (4 bytes) is considered as
overhead. protocol_overhead_in = packets_received * 4 |
Used for debugging Client Server protocol implementation |
| protocol_overhead_out |
Connection |
MySQL Client Server protocol overhead in bytes for outgoing traffic.
Currently only the Packet Header (4 bytes) is considered as
overhead. protocol_overhead_out = packets_sent * 4 |
Used for debugging Client Server protocol implementation |
| bytes_received_ok_packet |
Connection |
Total size of bytes of MySQL Client Server protocol OK packets received.
OK packets can contain a status message. The length of the status
message can vary and thus the size of an OK packet is not fixed. |
Used for debugging CS protocol implementation. Note that the total size
in bytes includes the size of the header packet (4 bytes, see
protocol overhead). |
| packets_received_ok |
Connection |
Number of MySQL Client Server protocol OK packets received. |
Used for debugging CS protocol implementation. Note that the total size
in bytes includes the size of the header packet (4 bytes, see
protocol overhead). |
| bytes_received_eof_packet |
Connection |
Total size in bytes of MySQL Client Server protocol EOF packets
received. EOF can vary in size depending on the server version.
Also, EOF can transport an error message. |
Used for debugging CS protocol implementation. Note that the total size
in bytes includes the size of the header packet (4 bytes, see
protocol overhead). |
| packets_received_eof |
Connection |
Number of MySQL Client Server protocol EOF packets. Like with other
packet statistics the number of packets will be increased even if
PHP does not receive the expected packet but, for example, an
error message. |
Used for debugging CS protocol implementation. Note that the total size
in bytes includes the size of the header packet (4 bytes, see
protocol overhead). |
| bytes_received_rset_header_packet |
Connection |
Total size in bytes of MySQL Client Server protocol result set header
packets. The size of the packets varies depending on the payload
(LOAD LOCAL INFILE, INSERT,
UPDATE, SELECT, error
message). |
Used for debugging CS protocol implementation. Note that the total size
in bytes includes the size of the header packet (4 bytes, see
protocol overhead). |
| packets_received_rset_header |
Connection |
Number of MySQL Client Server protocol result set header packets. |
Used for debugging CS protocol implementation. Note that the total size
in bytes includes the size of the header packet (4 bytes, see
protocol overhead). |
| bytes_received_rset_field_meta_packet |
Connection |
Total size in bytes of MySQL Client Server protocol result set meta data
(field information) packets. Of course the size varies with the
fields in the result set. The packet may also transport an error
or an EOF packet in case of COM_LIST_FIELDS. |
Only useful for debugging CS protocol implementation. Note that the
total size in bytes includes the size of the header packet (4
bytes, see protocol overhead). |
| packets_received_rset_field_meta |
Connection |
Number of MySQL Client Server protocol result set meta data (field
information) packets. |
Only useful for debugging CS protocol implementation. Note that the
total size in bytes includes the size of the header packet (4
bytes, see protocol overhead). |
| bytes_received_rset_row_packet |
Connection |
Total size in bytes of MySQL Client Server protocol result set row data
packets. The packet may also transport an error or an EOF packet.
You can reverse engineer the number of error and EOF packets by
subtracting rows_fetched_from_server_normal
and rows_fetched_from_server_ps from
bytes_received_rset_row_packet. |
Only useful for debugging CS protocol implementation. Note that the
total size in bytes includes the size of the header packet (4
bytes, see protocol overhead). |
| packets_received_rset_row |
Connection |
Number of MySQL Client Server protocol result set row data packets and
their total size in bytes. |
Only useful for debugging CS protocol implementation. Note that the
total size in bytes includes the size of the header packet (4
bytes, see protocol overhead). |
| bytes_received_prepare_response_packet |
Connection |
Total size in bytes of MySQL Client Server protocol OK for Prepared
Statement Initialization packets (prepared statement init
packets). The packet may also transport an error. The packet size
depends on the MySQL version: 9 bytes with MySQL 4.1 and 12 bytes
from MySQL 5.0 on. There is no safe way to know how many errors
happened. You may be able to guess that an error has occurred if,
for example, you always connect to MySQL 5.0 or newer and,
bytes_received_prepare_response_packet !=
packets_received_prepare_response * 12. See
also ps_prepared_never_executed,
ps_prepared_once_executed. |
Only useful for debugging CS protocol implementation. Note that the
total size in bytes includes the size of the header packet (4
bytes, see protocol overhead). |
| packets_received_prepare_response |
Connection |
Number of MySQL Client Server protocol OK for Prepared Statement
Initialization packets (prepared statement init packets). |
Only useful for debugging CS protocol implementation. Note that the
total size in bytes includes the size of the header packet (4
bytes, see protocol overhead). |
| bytes_received_change_user_packet |
Connection |
Total size in bytes of MySQL Client Server protocol COM_CHANGE_USER
packets. The packet may also transport an error or EOF. |
Only useful for debugging CS protocol implementation. Note that the
total size in bytes includes the size of the header packet (4
bytes, see protocol overhead). |
| packets_received_change_user |
Connection |
Number of MySQL Client Server protocol COM_CHANGE_USER packets |
Only useful for debugging CS protocol implementation. Note that the
total size in bytes includes the size of the header packet (4
bytes, see protocol overhead). |
| packets_sent_command |
Connection |
Number of MySQL Client Server protocol commands sent from PHP to MySQL.
There is no way to know which specific commands and how many of
them have been sent. At its best you can use it to check if PHP
has sent any commands to MySQL to know if you can consider to
disable MySQL support in your PHP binary. There is also no way to
reverse engineer the number of errors that may have occurred while
sending data to MySQL. The only error that is recorded is
command_buffer_too_small (see below). |
Only useful for debugging CS protocol implementation. |
| bytes_received_real_data_normal |
Connection |
Number of bytes of payload fetched by the PHP client from
mysqlnd using the text protocol. |
This is the size of the actual data contained in result sets that do not
originate from prepared statements and which have been fetched by
the PHP client. Note that although a full result set may have been
pulled from MySQL by mysqlnd, this statistic
only counts actual data pulled from mysqlnd by
the PHP client. An example of a code sequence that will increase
the value is as follows:
$mysqli = new mysqli();
$res = $mysqli->query("SELECT 'abc'");
$res->fetch_assoc();
$res->close();
Every fetch operation will increase the value.
The statistic will not be increased if the result set is only
buffered on the client, but not fetched, such as in the following
example:
$mysqli = new mysqli();
$res = $mysqli->query("SELECT 'abc'");
$res->close();
This statistic is available as of PHP version 5.3.4.
|
| bytes_received_real_data_ps |
Connection |
Number of bytes of the payload fetched by the PHP client from
mysqlnd using the prepared statement protocol. |
This is the size of the actual data contained in result sets that
originate from prepared statements and which has been fetched by
the PHP client. The value will not be increased if the result set
is not subsequently read by the PHP client. Note that although a
full result set may have been pulled from MySQL by
mysqlnd, this statistic only counts actual data
pulled from mysqlnd by the PHP client. See also
bytes_received_real_data_normal. This statistic
is available as of PHP version 5.3.4. |
Result Set
Returned mysqlnd statistics: Result Set
| Statistic |
Scope |
Description |
Notes |
| result_set_queries |
Connection |
Number of queries that have generated a result set. Examples of queries
that generate a result set: SELECT,
SHOW. The statistic will not be incremented if
there is an error reading the result set header packet from the
line. |
You may use it as an indirect measure for the number of queries PHP has
sent to MySQL, for example, to identify a client that causes a
high database load. |
| non_result_set_queries |
Connection |
Number of queries that did not generate a result set. Examples of
queries that do not generate a result set:
INSERT, UPDATE,
LOAD DATA, SHOW. The
statistic will not be incremented if there is an error reading the
result set header packet from the line. |
You may use it as an indirect measure for the number of queries PHP has
sent to MySQL, for example, to identify a client that causes a
high database load. |
| no_index_used |
Connection |
Number of queries that have generated a result set but did not use an
index (see also mysqld start option
–log-queries-not-using-indexes). If you want these queries to be
reported you can use mysqli_report(MYSQLI_REPORT_INDEX) to make
ext/mysqli throw an exception. If you prefer a warning instead of
an exception use mysqli_report(MYSQLI_REPORT_INDEX ^
MYSQLI_REPORT_STRICT). |
|
| bad_index_used |
Connection |
Number of queries that have generated a result set and did not use a
good index (see also mysqld start option –log-slow-queries). |
If you want these queries to be reported you can use
mysqli_report(MYSQLI_REPORT_INDEX) to make ext/mysqli throw an
exception. If you prefer a warning instead of an exception use
mysqli_report(MYSQLI_REPORT_INDEX ^ MYSQLI_REPORT_STRICT) |
| slow_queries |
Connection |
SQL statements that took more than long_query_time
seconds to execute and required at least
min_examined_row_limit rows to be examined. |
Not reported through mysqli_report |
| buffered_sets |
Connection |
Number of buffered result sets returned by "normal"
queries. "Normal" means "not prepared
statement" in the following notes. |
Examples of API calls that will buffer result sets on the client:
mysql_query,
mysqli_query,
mysqli_store_result,
mysqli_stmt_get_result. Buffering result sets
on the client ensures that server resources are freed as soon as
possible and it makes result set scrolling easier. The downside is
the additional memory consumption on the client for buffering
data. Note that mysqlnd (unlike the MySQL Client Library) respects
the PHP memory limit because it uses PHP internal memory
management functions to allocate memory. This is also the reason
why memory_get_usage reports a higher memory
consumption when using mysqlnd instead of the MySQL Client
Library. memory_get_usage does not measure
the memory consumption of the MySQL Client Library at all because
the MySQL Client Library does not use PHP internal memory
management functions monitored by the function! |
| unbuffered_sets |
Connection |
Number of unbuffered result sets returned by normal (non prepared
statement) queries. |
Examples of API calls that will not buffer result sets on the client:
mysqli_use_result |
| ps_buffered_sets |
Connection |
Number of buffered result sets returned by prepared statements. By
default prepared statements are unbuffered. |
Examples of API calls that will not buffer result sets on the client:
mysqli_stmt_store_result |
| ps_unbuffered_sets |
Connection |
Number of unbuffered result sets returned by prepared statements. |
By default prepared statements are unbuffered. |
| flushed_normal_sets |
Connection |
Number of result sets from normal (non prepared statement) queries with
unread data which have been flushed silently for you. Flushing
happens only with unbuffered result sets. |
Unbuffered result sets must be fetched completely before a new query can
be run on the connection otherwise MySQL will throw an error. If
the application does not fetch all rows from an unbuffered result
set, mysqlnd does implicitly fetch the result set to clear the
line. See also rows_skipped_normal,
rows_skipped_ps. Some possible causes for an
implicit flush:
-
Faulty client application
-
Client stopped reading after it found what it was looking for
but has made MySQL calculate more records than needed
-
Client application has stopped unexpectedly
|
| flushed_ps_sets |
Connection |
Number of result sets from prepared statements with unread data which
have been flushed silently for you. Flushing happens only with
unbuffered result sets. |
Unbuffered result sets must be fetched completely before a new query can
be run on the connection otherwise MySQL will throw an error. If
the application does not fetch all rows from an unbuffered result
set, mysqlnd does implicitly fetch the result set to clear the
line. See also rows_skipped_normal,
rows_skipped_ps. Some possible causes for an
implicit flush:
-
Faulty client application
-
Client stopped reading after it found what it was looking for
but has made MySQL calculate more records than needed
-
Client application has stopped unexpectedly
|
| 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
created by a "normal" query or a prepared statement. |
|
| rows_fetched_from_client_ps_cursor |
Connection |
Total number of rows fetch by the client from a cursor created by a
prepared statement. |
|
| rows_skipped_normal,
rows_skipped_ps |
Connection |
Reserved for future use (currently not supported) |
|
| copy_on_write_saved,
copy_on_write_performed |
Process |
With mysqlnd, variables returned by the extensions point into mysqlnd
internal network result buffers. If you do not change the
variables, fetched data will be kept only once in memory. If you
change the variables, mysqlnd has to perform a copy-on-write to
protect the internal network result buffers from being changed.
With the MySQL Client Library you always hold fetched data twice
in memory. Once in the internal MySQL Client Library buffers and
once in the variables returned by the extensions. In theory
mysqlnd can save up to 40% memory. However, note that the memory
saving cannot be measured using
memory_get_usage. |
|
| explicit_free_result,
implicit_free_result |
Connection, Process (only during prepared statement cleanup) |
Total number of freed result sets. |
The free is always considered explicit but for result sets created by an
init command, for example,
mysqli_options(MYSQLI_INIT_COMMAND , ...) |
| proto_text_fetched_null,
proto_text_fetched_bit,
proto_text_fetched_tinyint
proto_text_fetched_short,
proto_text_fetched_int24,
proto_text_fetched_int
proto_text_fetched_bigint,
proto_text_fetched_decimal,
proto_text_fetched_float
proto_text_fetched_double,
proto_text_fetched_date,
proto_text_fetched_year
proto_text_fetched_time,
proto_text_fetched_datetime,
proto_text_fetched_timestamp
proto_text_fetched_string,
proto_text_fetched_blob,
proto_text_fetched_enum
proto_text_fetched_set,
proto_text_fetched_geometry,
proto_text_fetched_other |
Connection |
Total number of columns of a certain type fetched from a normal query
(MySQL text protocol). |
Mapping from C API / MySQL meta data type to statistics name:
-
MYSQL_TYPE_NULL - proto_text_fetched_null
-
MYSQL_TYPE_BIT - proto_text_fetched_bit
-
MYSQL_TYPE_TINY - proto_text_fetched_tinyint
-
MYSQL_TYPE_SHORT - proto_text_fetched_short
-
MYSQL_TYPE_INT24 - proto_text_fetched_int24
-
MYSQL_TYPE_LONG - proto_text_fetched_int
-
MYSQL_TYPE_LONGLONG -
proto_text_fetched_bigint
-
MYSQL_TYPE_DECIMAL,
MYSQL_TYPE_NEWDECIMAL -
proto_text_fetched_decimal
-
MYSQL_TYPE_FLOAT - proto_text_fetched_float
-
MYSQL_TYPE_DOUBLE -
proto_text_fetched_double
-
MYSQL_TYPE_DATE,
MYSQL_TYPE_NEWDATE - proto_text_fetched_date
-
MYSQL_TYPE_YEAR - proto_text_fetched_year
-
MYSQL_TYPE_TIME - proto_text_fetched_time
-
MYSQL_TYPE_DATETIME -
proto_text_fetched_datetime
-
MYSQL_TYPE_TIMESTAMP -
proto_text_fetched_timestamp
-
MYSQL_TYPE_STRING,
MYSQL_TYPE_VARSTRING,
MYSQL_TYPE_VARCHAR -
proto_text_fetched_string
-
MYSQL_TYPE_TINY_BLOB,
MYSQL_TYPE_MEDIUM_BLOB,
MYSQL_TYPE_LONG_BLOB,
MYSQL_TYPE_BLOB - proto_text_fetched_blob
-
MYSQL_TYPE_ENUM - proto_text_fetched_enum
-
MYSQL_TYPE_SET - proto_text_fetched_set
-
MYSQL_TYPE_GEOMETRY -
proto_text_fetched_geometry
-
Any MYSQL_TYPE_* not listed before (there
should be none) - proto_text_fetched_other
Note that the MYSQL_*-type constants may not be associated with
the very same SQL column types in every version of MySQL.
|
| proto_binary_fetched_null,
proto_binary_fetched_bit,
proto_binary_fetched_tinyint
proto_binary_fetched_short,
proto_binary_fetched_int24,
proto_binary_fetched_int,
proto_binary_fetched_bigint,
proto_binary_fetched_decimal,
proto_binary_fetched_float,
proto_binary_fetched_double,
proto_binary_fetched_date,
proto_binary_fetched_year,
proto_binary_fetched_time,
proto_binary_fetched_datetime,
proto_binary_fetched_timestamp,
proto_binary_fetched_string,
proto_binary_fetched_blob,
proto_binary_fetched_enum,
proto_binary_fetched_set,
proto_binary_fetched_geometry,
proto_binary_fetched_other |
Connection |
Total number of columns of a certain type fetched from a prepared
statement (MySQL binary protocol). |
For type mapping see proto_text_* described in the
preceding text. |
Returned mysqlnd statistics: Connection
| Statistic |
Scope |
Description |
Notes |
| connect_success, connect_failure |
Connection |
Total number of successful / failed connection attempt. |
Reused connections and all other kinds of connections are included. |
| reconnect |
Process |
Total number of (real_)connect attempts made on an already opened
connection handle. |
The code sequence $link = new mysqli(...);
$link->real_connect(...) will cause a reconnect. But
$link = new mysqli(...); $link->connect(...)
will not because $link->connect(...) will
explicitly close the existing connection before a new connection
is established. |
| pconnect_success |
Connection |
Total number of successful persistent connection attempts. |
Note that connect_success holds the sum of successful
persistent and non-persistent connection attempts. The number of
successful non-persistent connection attempts is
connect_success -
pconnect_success. |
| active_connections |
Connection |
Total number of active persistent and non-persistent connections. |
|
| active_persistent_connections |
Connection |
Total number of active persistent connections. |
The total number of active non-persistent connections is
active_connections -
active_persistent_connections. |
| explicit_close |
Connection |
Total number of explicitly closed connections (ext/mysqli only). |
Examples of code snippets that cause an explicit close :
$link = new mysqli(...); $link->close(...)
$link = new mysqli(...); $link->connect(...)
|
| implicit_close |
Connection |
Total number of implicitly closed connections (ext/mysqli only). |
Examples of code snippets that cause an implicit close :
-
$link = new mysqli(...);
$link->real_connect(...)
-
unset($link)
-
Persistent connection: pooled connection has been created with
real_connect and there may be unknown options set - close
implicitly to avoid returning a connection with unknown options
-
Persistent connection: ping/change_user fails and ext/mysqli
closes the connection
-
end of script execution: close connections that have not been
closed by the user
|
| disconnect_close |
Connection |
Connection failures indicated by the C API call
mysql_real_connect during an attempt to
establish a connection. |
It is called disconnect_close because the connection
handle passed to the C API call will be closed. |
| in_middle_of_command_close |
Process |
A connection has been closed in the middle of a command execution
(outstanding result sets not fetched, after sending a query and
before retrieving an answer, while fetching data, while
transferring data with LOAD DATA). |
Unless you use asynchronous queries this should only happen if your
script stops unexpectedly and PHP shuts down the connections for
you. |
| init_command_executed_count |
Connection |
Total number of init command executions, for example,
mysqli_options(MYSQLI_INIT_COMMAND , ...). |
The number of successful executions is
init_command_executed_count -
init_command_failed_count. |
| init_command_failed_count |
Connection |
Total number of failed init commands. |
|
Returned mysqlnd statistics: COM_* Command
| Statistic |
Scope |
Description |
Notes |
| com_quit, com_init_db,
com_query, com_field_list,
com_create_db, com_drop_db,
com_refresh, com_shutdown,
com_statistics,
com_process_info,
com_connect,
com_process_kill, com_debug,
com_ping, com_time,
com_delayed_insert,
com_change_user,
com_binlog_dump,
com_table_dump,
com_connect_out,
com_register_slave,
com_stmt_prepare,
com_stmt_execute,
com_stmt_send_long_data,
com_stmt_close,
com_stmt_reset,
com_stmt_set_option,
com_stmt_fetch, com_daemon |
Connection |
Total number of attempts to send a certain COM_* command from PHP to
MySQL. |
The statistics are incremented after checking the line and
immediately before sending the corresponding MySQL client server
protocol packet. If mysqlnd fails to send the packet over the
wire the statistics will not be decremented. In case of a failure
mysqlnd emits a PHP warning "Error while sending %s packet.
PID=%d."
Usage examples:
-
Check if PHP sends certain commands to MySQL, for example,
check if a client sends COM_PROCESS_KILL
-
Calculate the average number of prepared statement executions
by comparing COM_EXECUTE with
COM_PREPARE
-
Check if PHP has run any non-prepared SQL statements by
checking if COM_QUERY is zero
-
Identify PHP scripts that run an excessive number of SQL
statements by checking COM_QUERY and
COM_EXECUTE
|
Miscellaneous
Returned mysqlnd statistics: Miscellaneous
| Statistic |
Scope |
Description |
Notes |
| explicit_stmt_close,
implicit_stmt_close |
Process |
Total number of close prepared statements. |
A close is always considered explicit but for a failed prepare. |
| mem_emalloc_count,
mem_emalloc_ammount,
mem_ecalloc_count,
mem_ecalloc_ammount,
mem_erealloc_count,
mem_erealloc_ammount,
mem_efree_count,
mem_malloc_count,
mem_malloc_ammount,
mem_calloc_count,
mem_calloc_ammount,
mem_realloc_count,
mem_realloc_ammount,
mem_free_count |
Process |
Memory management calls. |
Development only. |
| command_buffer_too_small |
Connection |
Number of network command buffer extensions while sending commands from
PHP to MySQL. |
mysqlnd allocates an internal command/network buffer of
mysqlnd.net_cmd_buffer_size
(php.ini) bytes for every connection. If a
MySQL Client Server protocol command, for example,
COM_QUERY (normal query), does not fit into
the buffer, mysqlnd will grow the buffer to what is needed for
sending the command. Whenever the buffer gets extended for one
connection command_buffer_too_small will be
incremented by one.
If mysqlnd has to grow the buffer beyond its initial size of
mysqlnd.net_cmd_buffer_size
(php.ini) bytes for almost every connection,
you should consider to increase the default size to avoid
re-allocations.
The default buffer size is 2048 bytes in PHP 5.3.0. In future
versions the default will be 4kB or larger. The default can
changed either through the php.ini setting
mysqlnd.net_cmd_buffer_size or using
mysqli_options(MYSQLI_OPT_NET_CMD_BUFFER_SIZE, int
size).
It is recommended to set the buffer size to no less than 4096
bytes because mysqlnd also uses it when reading certain
communication packet from MySQL. In PHP 5.3.0, mysqlnd will not
grow the buffer if MySQL sends a packet that is larger than the
current size of the buffer. As a consequence mysqlnd is unable to
decode the packet and the client application will get an error.
There are only two situations when the packet can be larger than
the 2048 bytes default of
mysqlnd.net_cmd_buffer_size in PHP 5.3.0: the
packet transports a very long error message or the packet holds
column meta data from COM_LIST_FIELD
(mysql_list_fields) and the meta data comes
from a string column with a very long default value (>1900
bytes). No bug report on this exists - it should happen rarely.
As of PHP 5.3.2 mysqlnd does not allow setting buffers smaller
than 4096 bytes.
|
| connection_reused |
|
|
|
|