MDEV-26052 Assertion prebuilt->trx_id < table->def_trx_id failed

ha_innobase::truncate(): If the operation fails, preserve
also dict_table_t::def_trx_id.

This fixes a regression that had been introduced in
commit 1bd681c8 (MDEV-25506).

mysql-test/suite/innodb/r/truncate_foreign.result

@@ -68,3 +68,21 @@ TRUNCATE TABLE t1;
 ALTER TABLE t1 ADD c INT;
 UNLOCK TABLES;
 DROP TABLE t1;
+#
+# MDEV-26052 Assertion prebuilt->trx_id < table->def_trx_id failed
+#
+call mtr.add_suppression("InnoDB: In ALTER TABLE `test`\\.`t1` has or is");
+CREATE TABLE t1 (pk INT, a INT, PRIMARY KEY (pk), KEY (a)) ENGINE=InnoDB;
+SET FOREIGN_KEY_CHECKS=0;
+ALTER TABLE t1 ADD FOREIGN KEY (a) REFERENCES t1 (a), ALGORITHM=COPY;
+INSERT INTO t1 VALUES (1,1);
+LOCK TABLES t1 WRITE;
+TRUNCATE t1;
+ERROR HY000: Cannot add foreign key constraint for `t1`
+INSERT INTO t1 VALUES (2,2);
+SELECT * FROM t1;
+pk	a
+1	1
+2	2
+DROP TABLE t1;
+# End of 10.6 tests

mysql-test/suite/innodb/t/truncate_foreign.test

@@ -80,3 +80,22 @@ TRUNCATE TABLE t1;
 ALTER TABLE t1 ADD c INT;
 UNLOCK TABLES;
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-26052 Assertion prebuilt->trx_id < table->def_trx_id failed
+--echo #
+
+call mtr.add_suppression("InnoDB: In ALTER TABLE `test`\\.`t1` has or is");
+
+CREATE TABLE t1 (pk INT, a INT, PRIMARY KEY (pk), KEY (a)) ENGINE=InnoDB;
+SET FOREIGN_KEY_CHECKS=0;
+ALTER TABLE t1 ADD FOREIGN KEY (a) REFERENCES t1 (a), ALGORITHM=COPY;
+INSERT INTO t1 VALUES (1,1);
+LOCK TABLES t1 WRITE;
+--error ER_CANNOT_ADD_FOREIGN
+TRUNCATE t1;
+INSERT INTO t1 VALUES (2,2);
+SELECT * FROM t1;
+DROP TABLE t1;
+
+--echo # End of 10.6 tests

storage/innobase/handler/ha_innodb.cc

@@ -13707,6 +13707,7 @@ int ha_innobase::truncate()
 	} else {
 		const auto update_time = ib_table->update_time;
 		const auto stored_lock = m_prebuilt->stored_select_lock_type;
+		const auto def_trx_id = ib_table->def_trx_id;
 		ib_table->release();
 		m_prebuilt->table = nullptr;
 
@@ -13721,6 +13722,7 @@ int ha_innobase::truncate()
 reload:
 			m_prebuilt->table = dict_table_open_on_name(
 				name, false, false, DICT_ERR_IGNORE_NONE);
+			m_prebuilt->table->def_trx_id = def_trx_id;
 		} else {
 			row_prebuilt_t* prebuilt = m_prebuilt;
 			uchar* upd_buf = m_upd_buf;