MDEV-31892 Server crash upon moving InnoDB table with

			fulltext index between databases

Problem:
========
- When renaming/moving an InnoDB table with fulltext indexes
between databases, the server would crash because
InnoDB attempted to open auxiliary tables using
the old database name instead of the new one.

When creating auxiliary index, InnoDB does create temporary
sort fulltext index using old table reference which creates
the auxiliary table name with the prefix of old database name.

FTS Document ID size optimization in row_merge_create_fts_sort_index()
using dict_table_get_n_rows() to decide between 4-byte
and 8-byte Doc IDs for memory optimization. But
dict_table_get_n_rows() returns estimated statistics that
may be stale or inaccurate, potentially leading to wrong
size decisions and data corruption if 4-byte
Doc IDs are chosen when 8-byte are actually needed.

Solution:
=========
fts_rename_aux_tables(): Iterate through all table indexes
and ensure all fulltext indexes are properly renamed

row_merge_create_fts_sort_index() : Use new_table instead
of old_table when creating temporary FTS sort indexes.

row_merge_build_indexes(): Refactored the logic to do
memory optimization to determine the doc id size for
temporary fts sort index.

 - When adding FTS index for the first time
  (DICT_TF2_FTS_ADD_DOC_ID), always use 8-byte Doc IDs

 - For existing FTS tables or user-supplied Doc ID columns,
   use fts_get_max_doc_id() approach to check actual maximum Doc ID

Author: Thirunarayanan

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

@@ -332,3 +332,13 @@ ALTER TABLE t ADD FULLTEXT INDEX ft1(f1);
 ALTER TABLE t ADD FULLTEXT INDEX ft2(f2);
 INSERT INTO t (f1,f2,f3) VALUES ('bar','baz','qux');
 DROP TABLE t;
+#
+#  MDEV-31892 Server crash upon moving InnoDB table
+#	with fulltext index between databases
+#
+CREATE DATABASE db;
+CREATE TABLE db.t (pk INT PRIMARY KEY, c CHAR(120), FULLTEXT KEY(c)) ENGINE=InnoDB;
+INSERT INTO db.t VALUES (1,'foo'),(2,'bar');
+ALTER TABLE db.t FORCE, RENAME to test.t;
+DROP DATABASE db;
+DROP TABLE IF EXISTS test.t;

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

@@ -441,3 +441,15 @@ ALTER TABLE t ADD FULLTEXT INDEX ft1(f1);
 ALTER TABLE t ADD FULLTEXT INDEX ft2(f2);
 INSERT INTO t (f1,f2,f3) VALUES ('bar','baz','qux');
 DROP TABLE t;
+
+--echo #
+--echo #  MDEV-31892 Server crash upon moving InnoDB table
+--echo #	with fulltext index between databases
+--echo #
+CREATE DATABASE db;
+CREATE TABLE db.t (pk INT PRIMARY KEY, c CHAR(120), FULLTEXT KEY(c)) ENGINE=InnoDB;
+INSERT INTO db.t VALUES (1,'foo'),(2,'bar');
+ALTER TABLE db.t FORCE, RENAME to test.t;
+# Cleanup
+DROP DATABASE db;
+DROP TABLE IF EXISTS test.t;

storage/innobase/fts/fts0fts.cc

@@ -1485,17 +1485,15 @@ fts_rename_aux_tables(
 		}
 	}
 
-	fts_t*	fts = table->fts;
-
-	/* Rename index specific auxiliary tables */
-	for (i = 0; fts->indexes != 0 && i < ib_vector_size(fts->indexes);
-	     ++i) {
-		dict_index_t*	index;
+	for (dict_index_t *index = dict_table_get_first_index(table);
+	     index; index = dict_table_get_next_index(index)) {
+		if (!(index->type & DICT_FTS)) {
+			continue;
+		}
 
-		index = static_cast<dict_index_t*>(
-			ib_vector_getp(fts->indexes, i));
+		FTS_INIT_INDEX_TABLE(&fts_table, nullptr,
+				     FTS_INDEX_TABLE, index);
 
-		FTS_INIT_INDEX_TABLE(&fts_table, NULL, FTS_INDEX_TABLE, index);
 
 		for (ulint j = 0; j < FTS_NUM_AUX_INDEX; ++j) {
 			fts_table.suffix = fts_get_suffix(j);

storage/innobase/include/row0ftsort.h

@@ -187,8 +187,8 @@ row_merge_create_fts_sort_index(
 				is created */
 	dict_table_t*	table,	/*!< in,out: table that FTS index
 				is being created on */
-	ibool*		opt_doc_id_size);
-				/*!< out: whether to use 4 bytes
+	bool		opt_doc_id_size);
+				/*!< in: whether to use 4 bytes
 				instead of 8 bytes integer to
 				store Doc ID during sort */
 

storage/innobase/row/row0ftsort.cc

@@ -70,8 +70,8 @@ row_merge_create_fts_sort_index(
 				is created */
 	dict_table_t*	table,	/*!< in,out: table that FTS index
 				is being created on */
-	ibool*		opt_doc_id_size)
-				/*!< out: whether to use 4 bytes
+	bool		opt_doc_id_size)
+				/*!< in: whether to use 4 bytes
 				instead of 8 bytes integer to
 				store Doc ID during sort */
 {
@@ -115,29 +115,8 @@ row_merge_create_fts_sort_index(
 	field->col = static_cast<dict_col_t*>(
 		mem_heap_zalloc(new_index->heap, sizeof(dict_col_t)));
 	field->col->mtype = DATA_INT;
-	*opt_doc_id_size = FALSE;
-
-	/* Check whether we can use 4 bytes instead of 8 bytes integer
-	field to hold the Doc ID, thus reduce the overall sort size */
-	if (DICT_TF2_FLAG_IS_SET(table, DICT_TF2_FTS_ADD_DOC_ID)) {
-		/* If Doc ID column is being added by this create
-		index, then just check the number of rows in the table */
-		if (dict_table_get_n_rows(table) < MAX_DOC_ID_OPT_VAL) {
-			*opt_doc_id_size = TRUE;
-		}
-	} else {
-		doc_id_t	max_doc_id;
-
-		/* If the Doc ID column is supplied by user, then
-		check the maximum Doc ID in the table */
-		max_doc_id = fts_get_max_doc_id((dict_table_t*) table);
-
-		if (max_doc_id && max_doc_id < MAX_DOC_ID_OPT_VAL) {
-			*opt_doc_id_size = TRUE;
-		}
-	}
 
-	if (*opt_doc_id_size) {
+	if (opt_doc_id_size) {
 		field->col->len = sizeof(ib_uint32_t);
 		field->fixed_len = sizeof(ib_uint32_t);
 	} else {

storage/innobase/row/row0merge.cc

@@ -4476,14 +4476,32 @@ row_merge_build_indexes(
 		* static_cast<double>(n_indexes);
 	for (i = 0; i < n_indexes; i++) {
 		if (indexes[i]->type & DICT_FTS) {
-			ibool	opt_doc_id_size = FALSE;
+			bool	opt_doc_id_size = false;
 
 			/* To build FTS index, we would need to extract
 			doc's word, Doc ID, and word's position, so
 			we need to build a "fts sort index" indexing
 			on above three 'fields' */
+
+			/* Check whether we can use 4 bytes instead of 8 bytes
+			integer field to hold the Doc ID, thus reduce
+			the overall sort size. If the fulltext index is being
+			added for the first time then we should use 8 bytes Doc ID
+			size because table->stat_n_rows is an estimation and
+			not reliable to determine the Doc ID size. */
+			if (old_table->fts || !DICT_TF2_FLAG_IS_SET(
+					new_table, DICT_TF2_FTS_ADD_DOC_ID)) {
+				/* If the Doc ID column is supplied by user
+				or rebuilding the existing FTS table, then
+				check the maximum Doc ID in the old table */
+				doc_id_t max_doc_id =
+				  fts_get_max_doc_id((dict_table_t*) old_table);
+				opt_doc_id_size =
+				  (max_doc_id < MAX_DOC_ID_OPT_VAL);
+			}
+
 			fts_sort_idx = row_merge_create_fts_sort_index(
-				indexes[i], old_table, &opt_doc_id_size);
+				indexes[i], new_table, opt_doc_id_size);
 
 			row_merge_dup_t*	dup
 				= static_cast<row_merge_dup_t*>(