Statistics

MySQL Native Driver contains support for gathering statistics on the communication between the client and the server. The statistics gathered are of two main types:

  • Client statistics
  • Connection statistics

When using the mysqli extension, these statistics can be obtained through two API calls:

Note: Statistics are aggregated among all extensions that use the MySQL Native Driver. For example, if the mysqli extension and the PDO MySQL driver are both set-up to use MySQLnd, then function calls from mysqli and method calls from PDO will affect 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.

Retrieving statistics

Client statistics can be retrieved by calling the mysqli_get_client_stats() function.

Connection statistics can be retrieved by calling the mysqli_get_connection_stats() function.

Both functions return an associative array, where the name of a statistic is the key for the corresponding statistical data.

MySQL Native Driver Statistics

Most statistics are associated to a connection, but some are associated to the process in which case this will be mentioned.

The following statistics are produced by the MySQL Native Driver:

Network Related Statistics
bytes_sent
Number of bytes sent from PHP to the MySQL server.
bytes_received
Number of bytes received from the MySQL server.
packets_sent
Number of packets sent by the MySQL Client Server protocol.
packets_received
Number of packets received from the MySQL Client Server protocol.
protocol_overhead_in
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
protocol_overhead_out
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_received * 4
bytes_received_ok_packet
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.

Note: The total size in bytes includes the size of the header packet (4 bytes, see protocol overhead).

packets_received_ok
Number of MySQL Client Server protocol OK packets received.
bytes_received_eof_packet
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.

Note: The total size in bytes includes the size of the header packet (4 bytes, see protocol overhead).

packets_received_eof
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.
bytes_received_rset_header_packet
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).

Note: The total size in bytes includes the size of the header packet (4 bytes, see protocol overhead).

packets_received_rset_header
Number of MySQL Client Server protocol result set header packets.
bytes_received_rset_field_meta_packet
Total size in bytes of MySQL Client Server protocol result set metadata (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.

Note: The total size in bytes includes the size of the header packet (4 bytes, see protocol overhead).

packets_received_rset_field_meta
Number of MySQL Client Server protocol result set metadata (field information) packets.
bytes_received_rset_row_packet
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. One can compute 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.

Note: The total size in bytes includes the size of the header packet (4 bytes, see protocol overhead).

packets_received_rset_row
Number of MySQL Client Server protocol result set row data packets.
bytes_received_prepare_response_packet
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.

Note: The total size in bytes includes the size of the header packet (4 bytes, see protocol overhead).

packets_received_prepare_response
Number of MySQL Client Server protocol OK for Prepared Statement Initialization packets (prepared statement init packets).
bytes_received_change_user_packet
Total size in bytes of MySQL Client Server protocol COM_CHANGE_USER packets. The packet may also transport an error or EOF.

Note: The total size in bytes includes the size of the header packet (4 bytes, see protocol overhead).

packets_received_change_user
Number of MySQL Client Server protocol COM_CHANGE_USER packets.
packets_sent_command
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.
bytes_received_real_data_normal
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.

However, 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();

bytes_received_real_data_ps
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 have 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.
Result Set Related Statistics
result_set_queries
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.

Note: This statistic can be used as an indirect measure for the number of queries PHP has sent to MySQL. This could help identifying a client that causes a high database load.

non_result_set_queries
Number of queries that did not generate a result set. Examples of queries that do not generate a result set: INSERT, UPDATE, LOAD DATA. The statistic will not be incremented if there is an error reading the result set header packet from the line.

Note: This statistic can be used as an indirect measure for the number of queries PHP has sent to MySQL. This could help identifying a client that causes a high database load.

no_index_used
Number of queries that have generated a result set but did not use an index. (See also the mysqld start option --log-queries-not-using-indexes).

Note: Those queries can be reported via an exception by calling mysqli_report(MYSQLI_REPORT_INDEX);. It is possible to have them be reported via a warning instead by calling mysqli_report(MYSQLI_REPORT_INDEX ^ MYSQLI_REPORT_STRICT);.

bad_index_used
Number of queries that have generated a result set and did not use a good index. (See also the mysqld start option --log-slow-queries).

Note: Those queries can be reported via an exception by calling mysqli_report(MYSQLI_REPORT_INDEX);. It is possible to have them be reported via a warning instead by calling mysqli_report(MYSQLI_REPORT_INDEX ^ MYSQLI_REPORT_STRICT);.

slow_queries
SQL statements that took more than long_query_time seconds to execute and required at least min_examined_row_limit rows to be examined.
Caution

Not reported through mysqli_report().

buffered_sets
Number of buffered result sets returned by normal (i.e. not via a prepared statement) queries.

Examples of API calls that will buffer result sets on the client: mysqli_query(), mysqli_store_result(), mysqli_stmt_get_result()

unbuffered_sets
Number of unbuffered result sets returned by normal (i.e. not via a prepared statement) queries.

Examples of API calls that will not buffer result sets on the client: mysqli_use_result()

ps_buffered_sets
Number of buffered result sets returned by prepared statements.

Examples of API calls that will buffer result sets on the client: mysqli_stmt_store_result()

ps_unbuffered_sets
Number of unbuffered result sets returned by prepared statements. By default prepared statements are unbuffered, thus most prepared statements will be accounted in this statistic.
flushed_normal_sets
Number of result sets returned by normal (i.e. not via a prepared statement) queries with unread data that have been silently flushed.

Note: 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
Number of result sets from prepared statements with unread data that have been silently flushed.

Note: 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
Number of statements prepared but never executed.
ps_prepared_once_executed
Number of prepared statements executed only once.
rows_fetched_from_server_normal
rows_fetched_from_server_ps
Total number of result set rows fetched from the server. This includes the rows which were not read by the client but had been implicitly fetched due to flushed unbuffered result sets. See also packets_received_rset_row.
rows_buffered_from_client_normal
Total number of buffered rows originating from a normal query. This is the number of rows that have been fetched from MySQL and buffered on client.

Examples of queries that will buffer results:

rows_buffered_from_client_ps
Same as rows_buffered_from_client_normal but for prepared statements.
rows_fetched_from_client_normal_buffered
Total number of rows fetched by the client from a buffered result set created by a normal query.
rows_fetched_from_client_ps_buffered
Total number of rows fetched by the client from a buffered result set created by a prepared statement.
rows_fetched_from_client_normal_unbuffered
Total number of rows fetched by the client from an unbuffered result set created by a normal query.
rows_fetched_from_client_ps_unbuffered
Total number of rows fetched by the client from an unbuffered result set created by a prepared statement.
rows_fetched_from_client_ps_cursor
Total number of rows fetch by the client from a cursor created by a prepared statement.
rows_skipped_normal
rows_skipped_ps
Reserved for future use (currently not supported).
copy_on_write_saved
copy_on_write_performed
This is a process level scope statistic. With mysqlnd, variables returned by the extensions point into mysqlnd internal network result buffers. If the data are not changed, the fetched data is kept only once in memory. However, any modification to the data will require mysqlnd to perform a copy-on-write operation.
explicit_free_result
implicit_free_result
This is a connection and process level scope statistic. Total number of freed result sets.
proto_text_fetched_null
Total number of columns of type MYSQL_TYPE_NULL fetched from a normal query (MySQL text protocol).
proto_binary_fetched_null
Total number of columns of type MYSQL_TYPE_NULL fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_bit
Total number of columns of type MYSQL_TYPE_BIT fetched from a normal query (MySQL text protocol).
proto_binary_fetched_bit
Total number of columns of type MYSQL_TYPE_BIT fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_tinyint
Total number of columns of type MYSQL_TYPE_TINY fetched from a normal query (MySQL text protocol).
proto_binary_fetched_tinyint
Total number of columns of type MYSQL_TYPE_TINY fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_short
Total number of columns of type MYSQL_TYPE_SHORT fetched from a normal query (MySQL text protocol).
proto_binary_fetched_short
Total number of columns of type MYSQL_TYPE_SHORT fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_int24
Total number of columns of type MYSQL_TYPE_INT24 fetched from a normal query (MySQL text protocol).
proto_binary_fetched_int24
Total number of columns of type MYSQL_TYPE_INT24 fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_int
Total number of columns of type MYSQL_TYPE_LONG fetched from a normal query (MySQL text protocol).
proto_binary_fetched_int
Total number of columns of type MYSQL_TYPE_LONG fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_bigint
Total number of columns of type MYSQL_TYPE_LONGLONG fetched from a normal query (MySQL text protocol).
proto_binary_fetched_bigint
Total number of columns of type MYSQL_TYPE_LONGLONG fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_decimal
Total number of columns of type MYSQL_TYPE_DECIMAL, or MYSQL_TYPE_NEWDECIMAL fetched from a normal query (MySQL text protocol).
proto_binary_fetched_decimal
Total number of columns of type MYSQL_TYPE_DECIMAL, or MYSQL_TYPE_NEWDECIMAL fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_float
Total number of columns of type MYSQL_TYPE_FLOAT fetched from a normal query (MySQL text protocol).
proto_binary_fetched_float
Total number of columns of type MYSQL_TYPE_FLOAT fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_double
Total number of columns of type MYSQL_TYPE_DOUBLE fetched from a normal query (MySQL text protocol).
proto_binary_fetched_double
Total number of columns of type MYSQL_TYPE_DOUBLE fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_date
Total number of columns of type MYSQL_TYPE_DATE, or MYSQL_TYPE_NEWDATE fetched from a normal query (MySQL text protocol).
proto_binary_fetched_date
Total number of columns of type MYSQL_TYPE_DATE, or MYSQL_TYPE_NEWDATE fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_year
Total number of columns of type MYSQL_TYPE_YEAR fetched from a normal query (MySQL text protocol).
proto_binary_fetched_year
Total number of columns of type MYSQL_TYPE_YEAR fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_time
Total number of columns of type MYSQL_TYPE_TIME fetched from a normal query (MySQL text protocol).
proto_binary_fetched_time
Total number of columns of type MYSQL_TYPE_TIME fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_datetime
Total number of columns of type MYSQL_TYPE_DATETIME fetched from a normal query (MySQL text protocol).
proto_binary_fetched_datetime
Total number of columns of type MYSQL_TYPE_DATETIME fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_timestamp
Total number of columns of type MYSQL_TYPE_TIMESTAMP fetched from a normal query (MySQL text protocol).
proto_binary_fetched_timestamp
Total number of columns of type MYSQL_TYPE_TIMESTAMP fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_string
Total number of columns of type MYSQL_TYPE_STRING, MYSQL_TYPE_VARSTRING, or MYSQL_TYPE_VARCHAR fetched from a normal query (MySQL text protocol).
proto_binary_fetched_string
Total number of columns of type MYSQL_TYPE_STRING, MYSQL_TYPE_VARSTRING, or MYSQL_TYPE_VARCHAR fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_blob
Total number of columns of type MYSQL_TYPE_TINY_BLOB, MYSQL_TYPE_MEDIUM_BLOB, MYSQL_TYPE_LONG_BLOB, or MYSQL_TYPE_BLOB fetched from a normal query (MySQL text protocol).
proto_binary_fetched_blob
Total number of columns of type MYSQL_TYPE_TINY_BLOB, MYSQL_TYPE_MEDIUM_BLOB, MYSQL_TYPE_LONG_BLOB, or MYSQL_TYPE_BLOB fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_enum
Total number of columns of type MYSQL_TYPE_ENUM fetched from a normal query (MySQL text protocol).
proto_binary_fetched_enum
Total number of columns of type MYSQL_TYPE_ENUM fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_set
Total number of columns of type MYSQL_TYPE_SET fetched from a normal query (MySQL text protocol).
proto_binary_fetched_set
Total number of columns of type MYSQL_TYPE_SET fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_geometry
Total number of columns of type MYSQL_TYPE_GEOMETRY fetched from a normal query (MySQL text protocol).
proto_binary_fetched_geometry
Total number of columns of type MYSQL_TYPE_GEOMETRY fetched from a prepared statement (MySQL binary protocol).
proto_text_fetched_other
Total number of columns of types MYSQL_TYPE_* not listed previously fetched from a normal query (MySQL text protocol).

Note: In theory, this should always be 0.

proto_binary_fetched_other
Total number of columns of type MYSQL_TYPE_* not listed previously fetched from a prepared statement (MySQL binary protocol).

Note: In theory, this should always be 0.

Connection Related Statistics
connect_success
Total number of successful connection attempts.

Note: connect_success holds the sum of successful persistent and non-persistent connection attempts. Therefore, the number of successful non-persistent connection attempts is connect_success - pconnect_success.

pconnect_success
Total number of successful persistent connection attempts.
connect_failure
Total number of failed connection attempts.
reconnect
This is a process level scope statistic.
active_connections
This is a process level scope statistic. Total number of active persistent and non-persistent connections.

Note: The total number of active non-persistent connections is active_connections - active_persistent_connections.

active_persistent_connections
This is a process level scope statistic. Total number of active persistent connections.
explicit_close
Total number of explicitly closed connections.

Example #1 Examples of code snippets that cause an explicit close

  • $link = new mysqli(/* ... */);
$link->close(/* ... */);

  • $link = new mysqli(/* ... */);
$link->connect(/* ... */);
implicit_close
Total number of implicitly closed connections.

Example #2 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 failures indicated by the C API call mysql_real_connect during an attempt to establish a connection.
in_middle_of_command_close
This is a process level scope statistic. 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).
Warning

Unless asynchronous queries are used, this should only happen if the PHP application terminated unexpectedly, and PHP shuts down the connection automatically.

init_command_executed_count
Total number of init command executions. For example: mysqli_options(MYSQLI_INIT_COMMAND , $value). The number of successful executions is init_command_executed_count - init_command_failed_count.
init_command_failed_count
Total number of failed init commands.
COM_* Command Related Statistics
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
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.
Caution

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.

Example #3 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 Statistics
explicit_stmt_close
implicit_stmt_close
This is a process level scope statistic. Total number of closed prepared statements.

Note: A prepared statement is always explicitly closed. The only time it's closed implicitly is when preparing it fails.

mem_emalloc_count
mem_emalloc_ammount
mem_ecalloc_count
mem_ecalloc_ammount
mem_realloc_count
mem_realloc_ammount
mem_efree_count
mem_malloc_count
mem_malloc_ammount
mem_calloc_count
mem_calloc_ammount
mem_ealloc_count
mem_ealloc_ammount
mem_free_count
This is a process level scope statistic. Memory management calls.
command_buffer_too_small
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 bytes for every connection. If a MySQL Client Server protocol command, e.g. 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 bytes for almost every connection, considerations to increase the default size should be made to avoid re-allocations.
connection_reused
The total number of times a persistent connection has been reused.