Cleanup: Remove fts_t::bg_threads_mutex, fts_t::bg_threads

The unused fts_t::bg_threads was added in
mysql/mysql-server@4b1049625c00dbfcd9d7a11ad12a84695ab747e3.

Any usage of fts_t::bg_threads_mutex was removed in
mysql/mysql-server@33c2404b397e1077daaf0ef0ff9edba445430f5f.

storage/innobase/fts/fts0fts.cc

@@ -5359,7 +5359,6 @@ fts_t::fts_t(
 	mem_heap_t*		heap)
 	:
 	added_synced(0), dict_locked(0),
-	bg_threads(0),
 	add_wq(NULL),
 	cache(NULL),
 	doc_col(ULINT_UNDEFINED), in_queue(false),
@@ -5367,8 +5366,6 @@ fts_t::fts_t(
 {
 	ut_a(table->fts == NULL);
 
-	mutex_create(LATCH_ID_FTS_BG_THREADS, &bg_threads_mutex);
-
 	ib_alloc_t*	heap_alloc = ib_heap_allocator_create(fts_heap);
 
 	indexes = ib_vector_create(heap_alloc, sizeof(dict_index_t*), 4);
@@ -5379,8 +5376,6 @@ fts_t::fts_t(
 /** fts_t destructor. */
 fts_t::~fts_t()
 {
-	mutex_free(&bg_threads_mutex);
-
 	ut_ad(add_wq == NULL);
 
 	if (cache != NULL) {

storage/innobase/handler/ha_innodb.cc

@@ -586,7 +586,6 @@ static PSI_mutex_info all_innodb_mutexes[] = {
 	PSI_KEY(file_format_max_mutex),
 	PSI_KEY(fil_system_mutex),
 	PSI_KEY(flush_list_mutex),
-	PSI_KEY(fts_bg_threads_mutex),
 	PSI_KEY(fts_delete_mutex),
 	PSI_KEY(fts_doc_id_mutex),
 	PSI_KEY(log_flush_order_mutex),

storage/innobase/include/fts0fts.h

@@ -317,19 +317,11 @@ class fts_t {
 	/** fts_t destructor. */
 	~fts_t();
 
-	/** Mutex protecting bg_threads* and fts_add_wq. */
-	ib_mutex_t	bg_threads_mutex;
-
-	/** Whether the ADDED table record sync-ed after
-	crash recovery; protected by bg_threads_mutex */
+	/** Whether the ADDED table record sync-ed after crash recovery */
 	unsigned	added_synced:1;
-	/** Whether the table holds dict_sys->mutex;
-	protected by bg_threads_mutex */
+	/** Whether the table holds dict_sys->mutex */
 	unsigned	dict_locked:1;
 
-	/** Number of background threads accessing this table. */
-	ulint		bg_threads;
-
 	/** Work queue for scheduling jobs for the FTS 'Add' thread, or NULL
 	if the thread has not yet been created. Each work item is a
 	fts_trx_doc_ids_t*. */

storage/innobase/include/sync0sync.h

@@ -60,7 +60,6 @@ extern mysql_pfs_key_t	dict_sys_mutex_key;
 extern mysql_pfs_key_t	file_format_max_mutex_key;
 extern mysql_pfs_key_t	fil_system_mutex_key;
 extern mysql_pfs_key_t	flush_list_mutex_key;
-extern mysql_pfs_key_t	fts_bg_threads_mutex_key;
 extern mysql_pfs_key_t	fts_delete_mutex_key;
 extern mysql_pfs_key_t	fts_doc_id_mutex_key;
 extern mysql_pfs_key_t	fts_pll_tokenize_mutex_key;

storage/innobase/include/sync0types.h

@@ -219,7 +219,6 @@ enum latch_level_t {
 
 	SYNC_FTS_TOKENIZE,
 	SYNC_FTS_OPTIMIZE,
-	SYNC_FTS_BG_THREADS,
 	SYNC_FTS_CACHE_INIT,
 	SYNC_RECV,
 	SYNC_LOG_FLUSH_ORDER,
@@ -305,7 +304,6 @@ enum latch_id_t {
 	LATCH_ID_FILE_FORMAT_MAX,
 	LATCH_ID_FIL_SYSTEM,
 	LATCH_ID_FLUSH_LIST,
-	LATCH_ID_FTS_BG_THREADS,
 	LATCH_ID_FTS_DELETE,
 	LATCH_ID_FTS_DOC_ID,
 	LATCH_ID_FTS_PLL_TOKENIZE,

storage/innobase/sync/sync0debug.cc

@@ -464,7 +464,6 @@ LatchDebug::LatchDebug()
 	LEVEL_MAP_INSERT(SYNC_WORK_QUEUE);
 	LEVEL_MAP_INSERT(SYNC_FTS_TOKENIZE);
 	LEVEL_MAP_INSERT(SYNC_FTS_OPTIMIZE);
-	LEVEL_MAP_INSERT(SYNC_FTS_BG_THREADS);
 	LEVEL_MAP_INSERT(SYNC_FTS_CACHE_INIT);
 	LEVEL_MAP_INSERT(SYNC_RECV);
 	LEVEL_MAP_INSERT(SYNC_LOG_FLUSH_ORDER);
@@ -743,7 +742,6 @@ LatchDebug::check_order(
 
 	case SYNC_MONITOR_MUTEX:
 	case SYNC_RECV:
-	case SYNC_FTS_BG_THREADS:
 	case SYNC_WORK_QUEUE:
 	case SYNC_FTS_TOKENIZE:
 	case SYNC_FTS_OPTIMIZE:
@@ -1315,9 +1313,6 @@ sync_latch_meta_init()
 
 	LATCH_ADD_MUTEX(FLUSH_LIST, SYNC_BUF_FLUSH_LIST, flush_list_mutex_key);
 
-	LATCH_ADD_MUTEX(FTS_BG_THREADS, SYNC_FTS_BG_THREADS,
-			fts_bg_threads_mutex_key);
-
 	LATCH_ADD_MUTEX(FTS_DELETE, SYNC_FTS_OPTIMIZE, fts_delete_mutex_key);
 
 	LATCH_ADD_MUTEX(FTS_DOC_ID, SYNC_FTS_OPTIMIZE, fts_doc_id_mutex_key);

storage/innobase/sync/sync0sync.cc

@@ -46,7 +46,6 @@ mysql_pfs_key_t	dict_sys_mutex_key;
 mysql_pfs_key_t	file_format_max_mutex_key;
 mysql_pfs_key_t	fil_system_mutex_key;
 mysql_pfs_key_t	flush_list_mutex_key;
-mysql_pfs_key_t	fts_bg_threads_mutex_key;
 mysql_pfs_key_t	fts_delete_mutex_key;
 mysql_pfs_key_t	fts_doc_id_mutex_key;
 mysql_pfs_key_t	fts_pll_tokenize_mutex_key;