branch-4.0: [fix](variable) fix unset global variable in non-master FE #58285 (#58381)

Cherry-picked from #58285

Co-authored-by: Mingyu Chen (Rayner) <[email protected]>

Author: github-actions[bot]

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/commands/UnsetVariableCommand.java

@@ -33,6 +33,7 @@
 import org.apache.doris.qe.ConnectContext;
 import org.apache.doris.qe.StmtExecutor;
 import org.apache.doris.qe.VariableMgr;
+import org.apache.doris.qe.VariableMgr.VarContext;
 
 import org.apache.commons.lang3.StringUtils;
 import org.apache.logging.log4j.LogManager;
@@ -125,7 +126,12 @@ public void afterForwardToMaster(ConnectContext context) throws Exception {
             }
             SetVar var = new SetVar(SetType.SESSION, getVariable(),
                     new StringLiteral(defaultValue), SetVar.SetVarType.SET_SESSION_VAR);
-            VariableMgr.setVar(context.getSessionVariable(), var);
+            VarContext varCtx = VariableMgr.getVarContext(var.getVariable());
+            // only unset for session variable.
+            // If this is a global variable, no need to do this because it has been synced from editlog already.
+            if (varCtx != null && (varCtx.getFlag() & VariableMgr.SESSION) != 0) {
+                VariableMgr.setVar(context.getSessionVariable(), var);
+            }
         }
     }
 

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

@@ -319,7 +319,7 @@ public static void setVarForNonMasterFE(SessionVariable sessionVariable, SetVar
     }
 
     @Nullable
-    private static VarContext getVarContext(String name) {
+    public static VarContext getVarContext(String name) {
         String varName = name;
         boolean hasExpPrefix = false;
         if (varName.startsWith(VariableAnnotation.EXPERIMENTAL.getPrefix())) {
@@ -893,7 +893,7 @@ public static List<List<String>> dumpChangedVars(SessionVariable sessionVar) {
         boolean affectQueryResult() default false;
     }
 
-    private static class VarContext {
+    public static class VarContext {
         private Field field;
         private Object obj;
         private int flag;