Information Schema INNODB_SYS_SEMAPHORE_WAITS Table
The Information Schema INNODB_SYS_SEMAPHORE_WAITS table is meant to contain information about current semaphore waits. At present it is not correctly populated. See MDEV-21330.
The PROCESS privilege is required to view the table.
It contains the following columns:
| Column | Description |
|---|---|
| THREAD_ID | Thread id waiting for semaphore |
| OBJECT_NAME | Semaphore name |
| FILE | File name where semaphore was requested |
| LINE | Line number on above file |
| WAIT_TIME | Wait time |
| WAIT_OBJECT | |
| WAIT_TYPE | Object type (mutex, rw-lock) |
| HOLDER_THREAD_ID | Holder thread id |
| HOLDER_FILE | File name where semaphore was acquired |
| HOLDER_LINE | Line number for above |
| CREATED_FILE | Creation file name |
| CREATED_LINE | Line number for above |
| WRITER_THREAD | Last write request thread id |
| RESERVATION_MODE | Reservation mode (shared, exclusive) |
| READERS | Number of readers if only shared mode |
| WAITERS_FLAG | Flags |
| LOCK_WORD | Lock word (for developers) |
| LAST_READER_FILE | Removed |
| LAST_READER_LINE | Removed |
| LAST_WRITER_FILE | Last writer file name |
| LAST_WRITER_LINE | Above line number |
| OS_WAIT_COUNT | Wait count |
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