MDEV-27582 Fulltext DDL decrements the FTS_DOC_ID value

- InnoDB FTS DDL decrements the FTS_DOC_ID when there is a
deleted marked record involved. FTS_DOC_ID must never be
reused. The purpose of FTS_DOC_ID is to be a unique row
identifier that will be changed whenever a fulltext indexed
column is updated.

mysql-test/suite/innodb_fts/r/innodb-fts-ddl.result

@@ -289,3 +289,32 @@ ENGINE=InnoDB;
 ALTER TABLE t1 ADD c SERIAL;
 DROP TABLE t1;
 # End of 10.3 tests
+#
+#  MDEV-27582 Fulltext DDL decrements the FTS_DOC_ID value
+#
+CREATE TABLE t1 (
+f1 INT NOT NULL PRIMARY KEY,
+f2 VARCHAR(64), FULLTEXT ft(f2)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1,'foo'),(2,'bar');
+connect con1,localhost,root,,,;
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+connection default;
+DELETE FROM t1 WHERE f1 = 2;
+ALTER TABLE t1 DROP INDEX ft;
+ALTER TABLE t1 ADD FULLTEXT INDEX ft (f2);
+INSERT INTO t1 VALUES (3, 'innodb fts search');
+SET GLOBAL innodb_optimize_fulltext_only=ON;
+OPTIMIZE TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	optimize	status	OK
+SET GLOBAL innodb_ft_aux_table = 'test/t1';
+SELECT max(DOC_ID) FROM INFORMATION_SCHEMA.INNODB_FT_INDEX_TABLE;
+max(DOC_ID)
+3
+SELECT * FROM t1 WHERE MATCH(f2) AGAINST("+innodb +search" IN BOOLEAN MODE);
+f1	f2
+3	innodb fts search
+DROP TABLE t1;
+disconnect con1;
+SET GLOBAL innodb_optimize_fulltext_only=OFF;
+SET GLOBAL innodb_ft_aux_table = default;

mysql-test/suite/innodb_fts/t/innodb-fts-ddl.opt

 --enable-plugin-innodb-sys-tables
+--innodb_ft_index_table

mysql-test/suite/innodb_fts/t/innodb-fts-ddl.test

@@ -357,3 +357,28 @@ ALTER TABLE t1 ADD c SERIAL;
 DROP TABLE t1;
 
 --echo # End of 10.3 tests
+
+--echo #
+--echo #  MDEV-27582 Fulltext DDL decrements the FTS_DOC_ID value
+--echo #
+CREATE TABLE t1 (
+	f1 INT NOT NULL PRIMARY KEY,
+        f2 VARCHAR(64), FULLTEXT ft(f2)) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1,'foo'),(2,'bar');
+connect(con1,localhost,root,,,);
+START TRANSACTION WITH CONSISTENT SNAPSHOT;
+
+connection default;
+DELETE FROM t1 WHERE f1 = 2;
+ALTER TABLE t1 DROP INDEX ft;
+ALTER TABLE t1 ADD FULLTEXT INDEX ft (f2);
+INSERT INTO t1 VALUES (3, 'innodb fts search');
+SET GLOBAL innodb_optimize_fulltext_only=ON;
+OPTIMIZE TABLE t1;
+SET GLOBAL innodb_ft_aux_table = 'test/t1';
+SELECT max(DOC_ID) FROM INFORMATION_SCHEMA.INNODB_FT_INDEX_TABLE;
+SELECT * FROM t1 WHERE MATCH(f2) AGAINST("+innodb +search" IN BOOLEAN MODE);
+DROP TABLE t1;
+disconnect con1;
+SET GLOBAL innodb_optimize_fulltext_only=OFF;
+SET GLOBAL innodb_ft_aux_table = default;

storage/innobase/fts/fts0fts.cc

@@ -243,18 +243,6 @@ fts_add_doc_by_id(
 /*==============*/
 	fts_trx_table_t*ftt,		/*!< in: FTS trx table */
 	doc_id_t	doc_id);	/*!< in: doc id */
-/******************************************************************//**
-Update the last document id. This function could create a new
-transaction to update the last document id.
-@return DB_SUCCESS if OK */
-static
-dberr_t
-fts_update_sync_doc_id(
-/*===================*/
-	const dict_table_t*	table,		/*!< in: table */
-	doc_id_t		doc_id,		/*!< in: last document id */
-	trx_t*			trx)		/*!< in: update trx, or NULL */
-	MY_ATTRIBUTE((nonnull(1)));
 
 /** Tokenize a document.
 @param[in,out]	doc	document to tokenize
@@ -2552,27 +2540,6 @@ fts_get_max_cache_size(
 }
 #endif
 
-/*********************************************************************//**
-Update the next and last Doc ID in the CONFIG table to be the input
-"doc_id" value (+ 1). We would do so after each FTS index build or
-table truncate */
-void
-fts_update_next_doc_id(
-/*===================*/
-	trx_t*			trx,		/*!< in/out: transaction */
-	const dict_table_t*	table,		/*!< in: table */
-	doc_id_t		doc_id)		/*!< in: DOC ID to set */
-{
-	table->fts->cache->synced_doc_id = doc_id;
-	table->fts->cache->next_doc_id = doc_id + 1;
-
-	table->fts->cache->first_doc_id = table->fts->cache->next_doc_id;
-
-	fts_update_sync_doc_id(
-		table, table->fts->cache->synced_doc_id, trx);
-
-}
-
 /*********************************************************************//**
 Get the next available document id.
 @return DB_SUCCESS if OK */
@@ -2731,17 +2698,17 @@ fts_cmp_set_sync_doc_id(
 	return(error);
 }
 
-/*********************************************************************//**
-Update the last document id. This function could create a new
+/** Update the last document id. This function could create a new
 transaction to update the last document id.
-@return DB_SUCCESS if OK */
-static
+@param  table   table to be updated
+@param  doc_id  last document id
+@param  trx     update trx or null
+@retval DB_SUCCESS if OK */
 dberr_t
 fts_update_sync_doc_id(
-/*===================*/
-	const dict_table_t*	table,		/*!< in: table */
-	doc_id_t		doc_id,		/*!< in: last document id */
-	trx_t*			trx)		/*!< in: update trx, or NULL */
+	const dict_table_t*	table,
+	doc_id_t		doc_id,
+	trx_t*			trx)
 {
 	byte		id[FTS_MAX_ID_LEN];
 	pars_info_t*	info;

storage/innobase/include/fts0fts.h

@@ -402,17 +402,6 @@ fts_get_next_doc_id(
 /*================*/
 	const dict_table_t*	table,	/*!< in: table */
 	doc_id_t*		doc_id);/*!< out: new document id */
-/*********************************************************************//**
-Update the next and last Doc ID in the CONFIG table to be the input
-"doc_id" value (+ 1). We would do so after each FTS index build or
-table truncate */
-void
-fts_update_next_doc_id(
-/*===================*/
-	trx_t*			trx,		/*!< in/out: transaction */
-	const dict_table_t*	table,		/*!< in: table */
-	doc_id_t		doc_id)		/*!< in: DOC ID to set */
-	MY_ATTRIBUTE((nonnull(2)));
 
 /******************************************************************//**
 Create a new fts_doc_ids_t.
@@ -976,4 +965,16 @@ bool fts_check_aux_table(const char *name,
                          table_id_t *table_id,
                          index_id_t *index_id);
 
+/** Update the last document id. This function could create a new
+transaction to update the last document id.
+@param	table	table to be updated
+@param	doc_id	last document id
+@param	trx	update trx or null
+@retval DB_SUCCESS if OK */
+dberr_t
+fts_update_sync_doc_id(const dict_table_t *table,
+		       doc_id_t  doc_id,
+		       trx_t *trx)
+MY_ATTRIBUTE((nonnull(1)));
+
 #endif /*!< fts0fts.h */

storage/innobase/row/row0merge.cc

@@ -2862,7 +2862,21 @@ row_merge_read_clustered_index(
 		err = fts_sync_table(const_cast<dict_table_t*>(new_table));
 
 		if (err == DB_SUCCESS) {
-			fts_update_next_doc_id(NULL, new_table, max_doc_id);
+			new_table->fts->cache->synced_doc_id = max_doc_id;
+
+		        /* Update the max value as next FTS_DOC_ID */
+			if (max_doc_id >= new_table->fts->cache->next_doc_id) {
+				new_table->fts->cache->next_doc_id =
+					max_doc_id + 1;
+			}
+
+			new_table->fts->cache->first_doc_id =
+				new_table->fts->cache->next_doc_id;
+
+			err= fts_update_sync_doc_id(
+				new_table,
+				new_table->fts->cache->synced_doc_id,
+				NULL);
 		}
 	}