The binary protocol. This is accessed through the MySQL C API and maps onto underlying server commands as shown in the following table.

The text protocol. This is accessed using SQL statements and maps onto underlying server commands as shown in the following table.

Statement preparation

ACOM_STMT_PREPAREorSQLCOM_PREPARE在服务器命令创建一份事先准备好的声明中. If the statement is successfully instrumented, a new row is added to theprepared_statements_instancestable. If the statement cannot be instrumented,Performance_schema_prepared_statements_loststatus variable is incremented.

Prepared statement execution

Execution of aCOM_STMT_EXECUTEorSQLCOM_PREPAREcommand for an instrumented prepared statement instance updates the correspondingprepared_statements_instancestable row.

Prepared statement deallocation

Execution of aCOM_STMT_CLOSEorSQLCOM_DEALLOCATE_PREPAREcommand for an instrumented prepared statement instance removes the correspondingprepared_statements_instancestable row. To avoid resource leaks, removal occurs even if the prepared statement instruments described previously are disabled.

OBJECT_INSTANCE_BEGIN

The address in memory of the instrumented prepared statement.

STATEMENT_ID

The internal statement ID assigned by the server. The text and binary protocols both use statement IDs.

STATEMENT_NAME

For the binary protocol, this column isNULL. For the text protocol, this column is the external statement name assigned by the user. For example, for the following SQL statement, the name of the prepared statement isstmt:

PREPARE stmt FROM 'SELECT 1';

SQL_TEXT

The prepared statement text, with?placeholder markers.

OWNER_THREAD_ID,OWNER_EVENT_ID

These columns indicate the event that created the prepared statement.

OWNER_OBJECT_TYPE,OWNER_OBJECT_SCHEMA,OWNER_OBJECT_NAME

For a prepared statement created by a client session, these columns areNULL. For a prepared statement created by a stored program, these columns point to the stored program. A typical user error is forgetting to deallocate prepared statements. These columns can be used to find stored programs that leak prepared statements:

SELECT OWNER_OBJECT_TYPE, OWNER_OBJECT_SCHEMA, OWNER_OBJECT_NAME, STATEMENT_NAME, SQL_TEXT FROM performance_schema.prepared_statements_instances WHERE OWNER_OBJECT_TYPE IS NOT NULL;

TIMER_PREPARE

The time spent executing the statement preparation itself.

COUNT_REPREPARE

The number of times the statement was reprepared internally (seeSection 8.10.3, “Caching of Prepared Statements and Stored Programs”). Timing statistics for repreparation are not available because it is counted as part of statement execution, not as a separate operation.

COUNT_EXECUTE,SUM_TIMER_EXECUTE,MIN_TIMER_EXECUTE,AVG_TIMER_EXECUTE,MAX_TIMER_EXECUTE

Aggregated statistics for executions of the prepared statement.

SUM_xxx

The remainingSUM_xxxcolumns are the same as for the statement summary tables (seeSection 27.12.20.3, “Statement Summary Tables”).

Primary key on (OBJECT_INSTANCE_BEGIN)

Index on (STATEMENT_ID)

Index on (STATEMENT_NAME)

Index on (OWNER_THREAD_ID,OWNER_EVENT_ID)

Index on (OWNER_OBJECT_TYPE,OWNER_OBJECT_SCHEMA,OWNER_OBJECT_NAME)