Compatibility update for outer join reorder

pingcap · Aug 23, 2022 · c1d059c · c1d059c
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diff --git a/join-reorder.md b/join-reorder.md
@@ -47,8 +47,9 @@ The above process is the Join Reorder algorithm currently used in TiDB.
 
 ## Limitations of Join Reorder algorithm
 
-The current Join Reorder algorithm has the following limitation:
+The current Join Reorder algorithm has the following limitations:
 
 - Limited by the calculation methods of the result sets, the algorithm cannot ensure it selects the optimum join order.
+- Currently, the Join Reorder algorithm's support for Outer Join is disabled by default. To enable it, set the value of the system variable [`tidb_enable_outer_join_reorder`](/system-variables.md#tidb_enable_outer_join_reorder-new-in-v610) to `ON`.
 
 Currently, the `STRAIGHT_JOIN` syntax is supported in TiDB to force a join order. For more information, refer to [Description of the syntax elements](/sql-statements/sql-statement-select.md#description-of-the-syntax-elements).
diff --git a/system-variables.md b/system-variables.md
@@ -1192,9 +1192,9 @@ Constraint checking is always performed in place for pessimistic transactions (d
 
 - Scope: SESSION | GLOBAL
 - Persists to cluster: Yes
-- Default value: `ON`
-- Since v6.1.0, the [Join Reorder](/join-reorder.md) algorithm of TiDB supports Outer Join. This variable controls the support behavior, and the default value is `ON`.
-- For a cluster upgraded from a version earlier than v6.1.0, the default value is still `TRUE`.
+- Default value: In v6.1.0, the default value is `ON`. After v6.1.0, the default value is `OFF`.
+- Since v6.1.0, the [Join Reorder](/join-reorder.md) algorithm of TiDB supports Outer Join. This variable controls the support behavior. The default value is `OFF`, which means the Join Reorder's support for Outer Join is disabled by default.
+- For a cluster upgraded from a version earlier than v6.1.0, the default value is `OFF`. For a cluster upgraded from v6.1.0, the default value is `ON`.
 
 ### tidb_enable_ordered_result_mode