MDEV-12676 MySQL#78423 InnoDB FTS duplicate key error

fts_get_next_doc_id(): Assign the first and subsequent FTS_DOC_ID
in the same way: by post-incrementing the cached value.
If there is a user-specified FTS_DOC_ID, do not touch the internal
sequence.

mysql-test/suite/innodb_fts/r/concurrent_insert.result

+CREATE TABLE t1(a VARCHAR(5),FULLTEXT KEY(a)) ENGINE=InnoDB;
+SET DEBUG_SYNC = 'get_next_FTS_DOC_ID SIGNAL prepared WAIT_FOR race';
+REPLACE INTO t1(a) values('aaa');
+SET DEBUG_SYNC = 'now WAIT_FOR prepared';
+REPLACE INTO t1(a) VALUES('aaa');
+SET DEBUG_SYNC = 'now SIGNAL race';
+SET DEBUG_SYNC = 'RESET';
+DROP TABLE t1;

mysql-test/suite/innodb_fts/t/concurrent_insert.test

+--source include/have_innodb.inc
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+
+CREATE TABLE t1(a VARCHAR(5),FULLTEXT KEY(a)) ENGINE=InnoDB;
+SET DEBUG_SYNC = 'get_next_FTS_DOC_ID SIGNAL prepared WAIT_FOR race';
+--send
+REPLACE INTO t1(a) values('aaa');
+
+connect(dml, localhost, root, ,);
+SET DEBUG_SYNC = 'now WAIT_FOR prepared';
+REPLACE INTO t1(a) VALUES('aaa');
+SET DEBUG_SYNC = 'now SIGNAL race';
+disconnect dml;
+
+connection default;
+reap;
+SET DEBUG_SYNC = 'RESET';
+
+DROP TABLE t1;

storage/innobase/fts/fts0fts.cc

@@ -2644,22 +2644,23 @@ fts_get_next_doc_id(
 	will consult the CONFIG table and user table to re-establish
 	the initial value of the Doc ID */
 
-	if (cache->first_doc_id != 0 || !fts_init_doc_id(table)) {
-		if (!DICT_TF2_FLAG_IS_SET(table, DICT_TF2_FTS_HAS_DOC_ID)) {
-			*doc_id = FTS_NULL_DOC_ID;
-			return(DB_SUCCESS);
+	if (!DICT_TF2_FLAG_IS_SET(table, DICT_TF2_FTS_HAS_DOC_ID)) {
+		if (cache->first_doc_id == FTS_NULL_DOC_ID) {
+			fts_init_doc_id(table);
 		}
+		*doc_id = FTS_NULL_DOC_ID;
+		return(DB_SUCCESS);
+	}
 
-		/* Otherwise, simply increment the value in cache */
-		mutex_enter(&cache->doc_id_lock);
-		*doc_id = ++cache->next_doc_id;
-		mutex_exit(&cache->doc_id_lock);
-	} else {
-		mutex_enter(&cache->doc_id_lock);
-		*doc_id = cache->next_doc_id;
-		mutex_exit(&cache->doc_id_lock);
+	if (cache->first_doc_id == FTS_NULL_DOC_ID) {
+		fts_init_doc_id(table);
 	}
 
+	DEBUG_SYNC_C("get_next_FTS_DOC_ID");
+	mutex_enter(&cache->doc_id_lock);
+	*doc_id = cache->next_doc_id++;
+	mutex_exit(&cache->doc_id_lock);
+
 	return(DB_SUCCESS);
 }
 

storage/xtradb/fts/fts0fts.cc

@@ -2644,22 +2644,23 @@ fts_get_next_doc_id(
 	will consult the CONFIG table and user table to re-establish
 	the initial value of the Doc ID */
 
-	if (cache->first_doc_id != 0 || !fts_init_doc_id(table)) {
-		if (!DICT_TF2_FLAG_IS_SET(table, DICT_TF2_FTS_HAS_DOC_ID)) {
-			*doc_id = FTS_NULL_DOC_ID;
-			return(DB_SUCCESS);
+	if (!DICT_TF2_FLAG_IS_SET(table, DICT_TF2_FTS_HAS_DOC_ID)) {
+		if (cache->first_doc_id == FTS_NULL_DOC_ID) {
+			fts_init_doc_id(table);
 		}
+		*doc_id = FTS_NULL_DOC_ID;
+		return(DB_SUCCESS);
+	}
 
-		/* Otherwise, simply increment the value in cache */
-		mutex_enter(&cache->doc_id_lock);
-		*doc_id = ++cache->next_doc_id;
-		mutex_exit(&cache->doc_id_lock);
-	} else {
-		mutex_enter(&cache->doc_id_lock);
-		*doc_id = cache->next_doc_id;
-		mutex_exit(&cache->doc_id_lock);
+	if (cache->first_doc_id == FTS_NULL_DOC_ID) {
+		fts_init_doc_id(table);
 	}
 
+	DEBUG_SYNC_C("get_next_FTS_DOC_ID");
+	mutex_enter(&cache->doc_id_lock);
+	*doc_id = cache->next_doc_id++;
+	mutex_exit(&cache->doc_id_lock);
+
 	return(DB_SUCCESS);
 }