This topic describes the differences between schema changes in Data Management (DMS) and by using the gh-ost tool. Both of them use no triggers.

The lockless change feature of DMS uses a design without a trigger. This can avoid the issues that are caused by the trigger. For more information about a triggerless design and a trigger-based design, see Appendix to DDL-based lockless change.

To ease the description and your understanding, the following symbols are used in the table of this topic:

  • ✔️ indicates that the feature is supported.
  • ❌ indicates that the feature is not supported.
Table 1. Differences between schema changes in DMS and by using the gh-ost tool
Item DDL-based lockless change in DMS gh-ost
Historical data copy Concurrent copy tasks ✔️ (Manual or automatic copy is supported) ✔️ (Manual copy is supported)
Data consistency ✔️
Fault tolerance ✔️ ✔️ (Some SQL statements are supported)
Adaptive query processing ✔️
Incremental data loading Concurrent replay tasks ✔️ (Manual or automatic replay is supported) ✔️ (Manual replay is supported)
Multi-threading replay task ✔️
Data consistency ✔️
Fault tolerance ✔️ ✔️ (Some SQL statements are supported)
Adaptive query processing ✔️
Backup subscription ✔️
Table switching Atomicity of an event ✔️ ✔️
Replicas for a table to be released after a period of time ✔️
Settings of a switching window ✔️ ✔️
Lock protection mechanism ✔️
Features Secondary database changes ✔️
Seamless integration with Data Transmission Service (DTS) ✔️
Settings of policy changes based on DDL algorithm recognition ✔️
RocksDB engine ✔️
TokuDB engine ✔️
InnoDB engine ✔️ ✔️
Virtual column changes ✔️
JSON column changes ✔️ ✔️
Tablespace optimization ✔️
Replicas for a table to be released after a period of time ✔️
Installation and deployment ✔️ (Free of installation) ✔️ (Installation on your on-premises machine)
Visualized O&M ✔️
Visualized execution progress ✔️