[Variable] Add a new global variable "performance_schema" to support Mysql JDBC 8.0.16 or later.#4537# (#4542)

docs/en/administrator-guide/variables.md

@@ -330,6 +330,10 @@ Note that the comment must start with /*+ and can only follow the SELECT.
 * `version`
 
     Used for compatibility with MySQL clients. No practical effect.
+
+* `performance_schema`
+
+    Used for compatibility with MySQL JDBC 8.0.16 or later version. No practical effect.    
     
 * `version_comment`
 

docs/zh-CN/administrator-guide/variables.md

@@ -329,6 +329,10 @@ SELECT /*+ SET_VAR(query_timeout = 1) */ sleep(3);
 * `version`
 
     用于兼容 MySQL 客户端。无实际作用。
+
+* `performance_schema`
+
+    用于兼容 8.0.16及以上版本的MySQL JDBC。无实际作用。     
     
 * `version_comment`
 

fe/fe-core/src/main/java/org/apache/doris/qe/GlobalVariable.java

@@ -40,6 +40,7 @@ public final class GlobalVariable {
     public static final String SYSTEM_TIME_ZONE = "system_time_zone";
     public static final String QUERY_CACHE_SIZE = "query_cache_size";
     public static final String DEFAULT_ROWSET_TYPE = "default_rowset_type";
+    public static final String PERFORMANCE_SCHEMA = "performance_schema";
 
     @VariableMgr.VarAttr(name = VERSION_COMMENT, flag = VariableMgr.READ_ONLY)
     public static String versionComment = "Doris version " + Version.DORIS_BUILD_VERSION;
@@ -74,6 +75,10 @@ public final class GlobalVariable {
     @VariableMgr.VarAttr(name = DEFAULT_ROWSET_TYPE, flag = VariableMgr.GLOBAL)
     public volatile static String defaultRowsetType = "alpha";
 
+    // add performance schema to support MYSQL JDBC 8.0.16 or later versions.
+    @VariableMgr.VarAttr(name = PERFORMANCE_SCHEMA, flag = VariableMgr.READ_ONLY)
+    public static String performanceSchema = "OFF";
+
     // Don't allow create instance.
     private GlobalVariable() {