10.6.1 The events_statements_current Table

The events_statements_current table contains current statement events. The table stores one row per thread showing the current status of the thread's most recent monitored statement event, so there is no system variable for configuring the table size.

Of the tables that contain statement event rows, events_statements_current is the most fundamental. Other tables that contain statement event rows are logically derived from the current events. For example, the events_statements_history and events_statements_history_long tables are collections of the most recent statement events that have ended, up to a maximum number of rows per thread and globally across all threads, respectively.

For more information about the relationship between the three events_statements_xxx event tables, see Performance Schema Tables for Current and Historical Events.

For information about configuring whether to collect statement events, see Section 10.6, “Performance Schema Statement Event Tables”.

The events_statements_current table has these columns:

• THREAD_ID, EVENT_ID

  The thread associated with the event and the thread current event number when the event starts. The THREAD_ID and EVENT_ID values taken together uniquely identify the row. No two rows have the same pair of values.

• END_EVENT_ID

  This column is set to NULL when the event starts and updated to the thread current event number when the event ends.

• EVENT_NAME

  The name of the instrument from which the event was collected. This is a NAME value from the setup_instruments table. Instrument names may have multiple parts and form a hierarchy, as discussed in Chapter 7, Performance Schema Instrument Naming Conventions.

  For SQL statements, the EVENT_NAME value initially is statement/com/Query until the statement is parsed, then changes to a more appropriate value, as described in Section 10.6, “Performance Schema Statement Event Tables”.

• SOURCE

  The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs. This enables you to check the source to determine exactly what code is involved.

• TIMER_START, TIMER_END, TIMER_WAIT

  Timing information for the event. The unit for these values is picoseconds (trillionths of a second). The TIMER_START and TIMER_END values indicate when event timing started and ended. TIMER_WAIT is the event elapsed time (duration).

  If an event has not finished, TIMER_END is the current timer value and TIMER_WAIT is the time elapsed so far (TIMER_END − TIMER_START).

  If an event is produced from an instrument that has TIMED = NO, timing information is not collected, and TIMER_START, TIMER_END, and TIMER_WAIT are all NULL.

  For discussion of picoseconds as the unit for event times and factors that affect time values, see Section 5.1, “Performance Schema Event Timing”.

• LOCK_TIME

  The time spent waiting for table locks. This value is computed in microseconds but normalized to picoseconds for easier comparison with other Performance Schema timers.

• SQL_TEXT

  The text of the SQL statement. For a command not associated with an SQL statement, the value is NULL.

  The maximum space available for statement display is 1024 bytes by default. To change this value, set the performance_schema_max_sql_text_length system variable at server startup.

• DIGEST

  The statement digest MD5 value as a string of 32 hexadecimal characters, or NULL if the statements_digest consumer is no. For more information about statement digesting, see Performance Schema Statement Digests.

• DIGEST_TEXT

  The normalized statement digest text, or NULL if the statements_digest consumer is no. For more information about statement digesting, see Performance Schema Statement Digests.

  The performance_schema_max_digest_length system variable determines the maximum number of bytes available per session for digest value storage. However, the display length of statement digests may be longer than the available buffer size due to encoding of statement elements such as keywords and literal values in digest buffer. Consequently, values selected from the DIGEST_TEXT column of statement event tables may appear to exceed the performance_schema_max_digest_length value.

• CURRENT_SCHEMA

  The default database for the statement, NULL if there is none.

• OBJECT_SCHEMA, OBJECT_NAME, OBJECT_TYPE

  For nested statements (stored programs), these columns contain information about the parent statement. Otherwise they are NULL.

• OBJECT_INSTANCE_BEGIN

  This column identifies the statement. The value is the address of an object in memory.

• MYSQL_ERRNO

  The statement error number, from the statement diagnostics area.

• RETURNED_SQLSTATE

  The statement SQLSTATE value, from the statement diagnostics area.

• MESSAGE_TEXT

  The statement error message, from the statement diagnostics area.

• ERRORS

  Whether an error occurred for the statement. The value is 0 if the SQLSTATE value begins with 00 (completion) or 01 (warning). The value is 1 is the SQLSTATE value is anything else.

• WARNINGS

  The number of warnings, from the statement diagnostics area.

• ROWS_AFFECTED

  The number of rows affected by the statement. For a description of the meaning of “affected,” see mysql_affected_rows().

• ROWS_SENT

  The number of rows returned by the statement.

• ROWS_EXAMINED

  The number of rows examined by the server layer (not counting any processing internal to storage engines).

• CREATED_TMP_DISK_TABLES

  Like the Created_tmp_disk_tables status variable, but specific to the statement.

• CREATED_TMP_TABLES

  Like the Created_tmp_tables status variable, but specific to the statement.

• SELECT_FULL_JOIN

  Like the Select_full_join status variable, but specific to the statement.

• SELECT_FULL_RANGE_JOIN

  Like the Select_full_range_join status variable, but specific to the statement.

• SELECT_RANGE

  Like the Select_range status variable, but specific to the statement.

• SELECT_RANGE_CHECK

  Like the Select_range_check status variable, but specific to the statement.

• SELECT_SCAN

  Like the Select_scan status variable, but specific to the statement.

• SORT_MERGE_PASSES

  Like the Sort_merge_passes status variable, but specific to the statement.

• SORT_RANGE

  Like the Sort_range status variable, but specific to the statement.

• SORT_ROWS

  Like the Sort_rows status variable, but specific to the statement.

• SORT_SCAN

  Like the Sort_scan status variable, but specific to the statement.

• NO_INDEX_USED

  1 if the statement performed a table scan without using an index, 0 otherwise.

• NO_GOOD_INDEX_USED

  1 if the server found no good index to use for the statement, 0 otherwise. For additional information, see the description of the Extra column from EXPLAIN output for the Range checked for each record value in EXPLAIN Output Format.

• NESTING_EVENT_ID, NESTING_EVENT_TYPE, NESTING_EVENT_LEVEL

  These three columns are used with other columns to provide information as follows for top-level (unnested) statements and nested statements (executed within a stored program).

  For top level statements:

  OBJECT_TYPE = NULL
  OBJECT_SCHEMA = NULL
  OBJECT_NAME = NULL
  NESTING_EVENT_ID = NULL
  NESTING_EVENT_TYPE = NULL
  NESTING_LEVEL = 0

  For nested statements:

  OBJECT_TYPE = the parent statement object type
  OBJECT_SCHEMA = the parent statement object schema
  OBJECT_NAME = the parent statement object name
  NESTING_EVENT_ID = the parent statement EVENT_ID
  NESTING_EVENT_TYPE = 'STATEMENT'
  NESTING_LEVEL = the parent statement NESTING_LEVEL plus one

TRUNCATE TABLE is permitted for the events_statements_current table. It removes the rows.