branch-4.1: [fix](show variables) Fix changed variable output in show variables #63734

fe/fe-core/src/main/java/org/apache/doris/nereids/parser/LogicalPlanBuilder.java

@@ -6524,28 +6524,28 @@ public AlterTableOp visitDropRollupClause(DorisParser.DropRollupClauseContext ct
     @Override
     public LogicalPlan visitShowVariables(ShowVariablesContext ctx) {
         SetType statementScope = visitStatementScope(ctx.statementScope());
-        if (ctx.wildWhere() != null) {
-            if (ctx.wildWhere().LIKE() != null) {
-                return new ShowVariablesCommand(statementScope,
-                        stripQuotes(ctx.wildWhere().STRING_LITERAL().getText()));
+        LogicalPlan plan;
+        if (ctx.wildWhere() == null) {
+            plan = new ShowVariablesCommand(statementScope, null);
+        } else if (ctx.wildWhere().LIKE() != null) {
+            plan = new ShowVariablesCommand(statementScope,
+                    stripQuotes(ctx.wildWhere().STRING_LITERAL().getText()));
+        } else {
+            StringBuilder sb = new StringBuilder();
+            sb.append("SELECT `VARIABLE_NAME` AS `Variable_name`, `VARIABLE_VALUE` AS `Value` FROM ");
+            sb.append("`").append(InternalCatalog.INTERNAL_CATALOG_NAME).append("`");
+            sb.append(".");
+            sb.append("`").append(InfoSchemaDb.DATABASE_NAME).append("`");
+            sb.append(".");
+            if (statementScope == SetType.GLOBAL) {
+                sb.append("`global_variables` ");
             } else {
-                StringBuilder sb = new StringBuilder();
-                sb.append("SELECT `VARIABLE_NAME` AS `Variable_name`, `VARIABLE_VALUE` AS `Value` FROM ");
-                sb.append("`").append(InternalCatalog.INTERNAL_CATALOG_NAME).append("`");
-                sb.append(".");
-                sb.append("`").append(InfoSchemaDb.DATABASE_NAME).append("`");
-                sb.append(".");
-                if (statementScope == SetType.GLOBAL) {
-                    sb.append("`global_variables` ");
-                } else {
-                    sb.append("`session_variables` ");
-                }
-                sb.append(getOriginSql(ctx.wildWhere()));
-                return new NereidsParser().parseSingle(sb.toString());
+                sb.append("`session_variables` ");
             }
-        } else {
-            return new ShowVariablesCommand(statementScope, null);
+            sb.append(getOriginSql(ctx.wildWhere()));
+            plan = new NereidsParser().parseSingle(sb.toString());
         }
+        return plan;
     }
 
     @Override

fe/fe-core/src/main/java/org/apache/doris/service/FrontendServiceImpl.java

@@ -121,6 +121,7 @@
 import org.apache.doris.qe.NereidsCoordinator;
 import org.apache.doris.qe.QeProcessorImpl;
 import org.apache.doris.qe.QueryState;
+import org.apache.doris.qe.SessionVariable;
 import org.apache.doris.qe.StmtExecutor;
 import org.apache.doris.qe.VariableMgr;
 import org.apache.doris.service.arrowflight.FlightSqlConnectProcessor;
@@ -992,7 +993,19 @@ public TShowVariableResult showVariables(TShowVariableRequest params) throws TEx
         if (ctx == null) {
             return result;
         }
-        vars = VariableMgr.dump(SetType.fromThrift(params.getVarType()), ctx.getSessionVariable(), null);
+        // SHOW VARIABLES can be evaluated through an internal schema query. Planning that
+        // internal query may call setVarOnce() and temporarily change the live session
+        // variable (for example disable_join_reorder). Cloning alone is not enough,
+        // because the clone would keep both the temporary value and its recorded origin.
+        // Revert only the clone so Changed reflects user-visible session settings,
+        // while the real session remains untouched.
+        SessionVariable sessionVariable = VariableMgr.cloneSessionVariable(ctx.getSessionVariable());
+        try {
+            VariableMgr.revertSessionValue(sessionVariable);
+        } catch (DdlException e) {
+            throw new TException(e);
+        }
+        vars = VariableMgr.dump(SetType.fromThrift(params.getVarType()), sessionVariable, null);
         result.setVariables(vars);
         return result;
     }

regression-test/data/nereids_p0/ddl/show_variables/show_variables_command.out

@@ -8,3 +8,11 @@ license	Apache License, Version 2.0
 -- !cmd --
 license	Apache License, Version 2.0
 
+-- !changed --
+enable_profile	true
+
+-- !not_changed --
+
+-- !global --
+license	Apache License, Version 2.0
+

regression-test/suites/nereids_p0/ddl/show_variables/show_variables_command.groovy

@@ -20,7 +20,15 @@ suite("show_variables_command") {
     checkNereidsExecute("""show variables like 'li_ense'""")
     checkNereidsExecute("""show variables where variable_name like 'li_ense'""")
     checkNereidsExecute("""show variables where variable_name = 'license'""")
+    checkNereidsExecute("""show variables where changed = 1""")
+    checkNereidsExecute("""show global variables where variable_name = 'license'""")
     qt_cmd("""show variables like 'li_ense'""")
     qt_cmd("""show variables where variable_name like 'li_ense'""")
     qt_cmd("""show variables where variable_name = 'license'""")
+
+    sql "set enable_profile = true"
+    qt_changed("""show variables where changed = 1 and variable_name = 'enable_profile'""")
+    qt_not_changed("""show variables where changed = 1 and variable_name = 'license'""")
+    qt_global("""show global variables where variable_name = 'license'""")
+    sql "UNSET VARIABLE ALL"
 }