Enforce the limit on the maximum number of fields

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

+SET @old_instant=
+(SELECT variable_value FROM information_schema.global_status
+WHERE variable_name = 'innodb_instant_alter_column');
+CREATE TABLE t(a INT PRIMARY KEY, b253 INT, c253 INT, d253 INT, e253 INT)
+ENGINE=InnoDB;
+INSERT INTO t VALUES(1,2,3,4,5);
+SELECT * FROM t;
+b0	d0	a	c0	e0
+NULL	NULL	1	NULL	NULL
+ALTER TABLE t DROP b0, DROP c0, DROP d0, DROP e0,
+ADD COLUMN b INT, ALGORITHM=INSTANT;
+ERROR 0A000: ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=INPLACE
+ALTER TABLE t CHANGE COLUMN b0 b INT AFTER a, ALGORITHM=INSTANT;
+ALTER TABLE t DROP e0, DROP c0, DROP d0, ALGORITHM=INSTANT;
+SELECT * FROM t;
+a	b
+1	NULL
+ALTER TABLE t DROP COLUMN b, ALGORITHM=INSTANT;
+ALTER TABLE t ADD COLUMN b INT, ALGORITHM=INSTANT;
+ERROR 0A000: ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=INPLACE
+SELECT variable_value-@old_instant instants
+FROM information_schema.global_status
+WHERE variable_name = 'innodb_instant_alter_column';
+instants
+256
+ALTER TABLE t ADD COLUMN b INT;
+SELECT variable_value-@old_instant instants
+FROM information_schema.global_status
+WHERE variable_name = 'innodb_instant_alter_column';
+instants
+256
+SELECT * FROM t;
+a	b
+1	NULL
+DROP TABLE t;

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

+--source include/have_innodb.inc
+
+SET @old_instant=
+(SELECT variable_value FROM information_schema.global_status
+WHERE variable_name = 'innodb_instant_alter_column');
+
+CREATE TABLE t(a INT PRIMARY KEY, b INT, c INT, d INT, e INT)
+ENGINE=InnoDB;
+INSERT INTO t VALUES(1,2,3,4,5);
+--disable_query_log
+let $n=253;
+while ($n) {
+dec $n;
+ALTER TABLE t DROP b, DROP c, DROP d, DROP e,
+ADD COLUMN b INT FIRST, ADD COLUMN c INT, ADD COLUMN d INT AFTER b,
+ADD COLUMN e INT AFTER c, ALGORITHM=INSTANT;
+}
+--enable_query_log
+SELECT * FROM t;
+--error ER_ALTER_OPERATION_NOT_SUPPORTED
+ALTER TABLE t DROP b, DROP c, DROP d, DROP e,
+ADD COLUMN b INT, ALGORITHM=INSTANT;
+ALTER TABLE t CHANGE COLUMN b beta INT AFTER a, ALGORITHM=INSTANT;
+ALTER TABLE t DROP e, DROP c, DROP d, ALGORITHM=INSTANT;
+SELECT * FROM t;
+ALTER TABLE t DROP COLUMN beta, ALGORITHM=INSTANT;
+--error ER_ALTER_OPERATION_NOT_SUPPORTED
+ALTER TABLE t ADD COLUMN b INT NOT NULL, ALGORITHM=INSTANT;
+
+SELECT variable_value-@old_instant instants
+FROM information_schema.global_status
+WHERE variable_name = 'innodb_instant_alter_column';
+
+ALTER TABLE t ADD COLUMN b INT NOT NULL;
+
+SELECT variable_value-@old_instant instants
+FROM information_schema.global_status
+WHERE variable_name = 'innodb_instant_alter_column';
+
+SELECT * FROM t;
+
+DROP TABLE t;

storage/innobase/handler/ha_innodb.cc

@@ -9462,12 +9462,14 @@ ha_innobase::change_active_index(
 		}
 #endif
 	} else {
-		dtuple_set_n_fields(m_prebuilt->search_tuple,
-				    m_prebuilt->index->n_fields);
+		ulint n_fields = dict_index_get_n_unique_in_tree(
+			m_prebuilt->index);
+
+		dtuple_set_n_fields(m_prebuilt->search_tuple, n_fields);
 
 		dict_index_copy_types(
 			m_prebuilt->search_tuple, m_prebuilt->index,
-			m_prebuilt->index->n_fields);
+			n_fields);
 
 		/* If it's FTS query and FTS_DOC_ID exists FTS_DOC_ID field is
 		always added to read_set. */

storage/innobase/handler/handler0alter.cc

@@ -883,14 +883,47 @@ check_v_col_in_order(
 }
 
 /** Determine if an instant operation is possible for altering columns.
+@param[in]	ib_table	InnoDB table definition
 @param[in]	ha_alter_info	the ALTER TABLE operation
 @param[in]	table		table definition before ALTER TABLE */
 static
 bool
 instant_alter_column_possible(
+	const dict_table_t&		ib_table,
 	const Alter_inplace_info*	ha_alter_info,
 	const TABLE*			table)
 {
+	if (!ib_table.supports_instant()) {
+		return false;
+	}
+#if 1 // MDEV-17459: adjust fts_fetch_doc_from_rec() and friends; remove this
+	if (ib_table.fts) {
+		return false;
+	}
+#endif
+	const dict_index_t* index = ib_table.indexes.start;
+	if (ha_alter_info->handler_flags & ALTER_ADD_STORED_BASE_COLUMN) {
+		List_iterator_fast<Create_field> cf_it(
+			ha_alter_info->alter_info->create_list);
+		uint n_add = 0;
+		while (const Create_field* cf = cf_it++) {
+			n_add += !cf->field;
+		}
+		if (index->n_fields >= REC_MAX_N_USER_FIELDS + DATA_N_SYS_COLS
+		    - n_add) {
+			return false;
+		}
+	}
+#if 1 // MDEV-17468: fix bugs with indexed virtual columns & remove this
+	ut_ad(index->is_primary());
+	ut_ad(!index->has_virtual());
+	while ((index = index->indexes.next) != NULL) {
+		if (index->has_virtual()) {
+			ut_ad(ib_table.n_v_cols);
+			return false;
+		}
+	}
+#endif
 	// Making table system-versioned instantly is not implemented yet.
 	if (ha_alter_info->handler_flags & ALTER_ADD_SYSTEM_VERSIONING) {
 		return false;
@@ -1059,21 +1092,6 @@ innobase_fts_check_doc_id_col(
 	return(false);
 }
 
-#if 1 // MDEV-17468: fix bugs with indexed virtual columns & remove this
-static bool has_virtual_index(const dict_table_t& table)
-{
-	const dict_index_t* index = table.indexes.start;
-	ut_ad(!index->has_virtual());
-	while ((index = index->indexes.next) != NULL) {
-		if (index->has_virtual()) {
-			ut_ad(table.n_v_cols);
-			return true;
-		}
-	}
-	return false;
-}
-#endif
-
 /** Check if InnoDB supports a particular alter table in-place
 @param altered_table TABLE object for new version of table.
 @param ha_alter_info Structure describing changes to be done
@@ -1253,18 +1271,8 @@ ha_innobase::check_if_supported_inplace_alter(
 		DBUG_RETURN(HA_ALTER_INPLACE_NOT_SUPPORTED);
 	}
 
-	const bool supports_instant = m_prebuilt->table->supports_instant()
-		&& instant_alter_column_possible(ha_alter_info, table)
-#if 1 // MDEV-17468: fix bugs with indexed virtual columns & remove this
-		&& !has_virtual_index(*m_prebuilt->table)
-#endif
-#if 1 // MDEV-17459: adjust fts_fetch_doc_from_rec() and friends; remove this
-		&& !m_prebuilt->table->fts
-		&& !innobase_fulltext_exist(altered_table)
-		&& !innobase_fulltext_exist(table)
-#endif
-		;
-
+	const bool supports_instant = instant_alter_column_possible(
+		*m_prebuilt->table, ha_alter_info, table);
 	bool	add_drop_v_cols = false;
 
 	/* If there is add or drop virtual columns, we will support operations
@@ -5716,15 +5724,10 @@ prepare_inplace_alter_table_dict(
 			    == !!new_clustered);
 	}
 
-	if (ctx->need_rebuild() && user_table->supports_instant()
-	    && instant_alter_column_possible(ha_alter_info, old_table)
-#if 1 // MDEV-17468: fix bugs with indexed virtual columns & remove this
-	    && !has_virtual_index(*user_table)
-#endif
+	if (ctx->need_rebuild() && instant_alter_column_possible(
+		    *user_table, ha_alter_info, old_table)
 #if 1 // MDEV-17459: adjust fts_fetch_doc_from_rec() and friends; remove this
-	    && !user_table->fts
-	    && !innobase_fulltext_exist(altered_table)
-	    && !innobase_fulltext_exist(old_table)
+		&& !innobase_fulltext_exist(altered_table)
 #endif
 	    ) {
 		for (uint a = 0; a < ctx->num_to_add_index; a++) {