#2115 add flag to pointed out whether the variable has word 'session' above

src/main/java/com/alibaba/druid/sql/ast/expr/SQLVariantRefExpr.java

@@ -28,6 +28,8 @@ public class SQLVariantRefExpr extends SQLExprImpl {
 
     private boolean global = false;
 
+    private boolean hasSessionBefore = false;
+
     private int     index  = -1;
 
     public SQLVariantRefExpr(String name){
@@ -39,6 +41,12 @@ public class SQLVariantRefExpr extends SQLExprImpl {
         this.global = global;
     }
 
+    public SQLVariantRefExpr(String name, boolean global,boolean hasSessionBefore){
+        this.name = name;
+        this.global = global;
+        this.hasSessionBefore = hasSessionBefore;
+    }
+
     public SQLVariantRefExpr(){
 
     }
@@ -63,6 +71,15 @@ public class SQLVariantRefExpr extends SQLExprImpl {
         buf.append(this.name);
     }
 
+
+    public boolean isHasSessionBefore() {
+        return hasSessionBefore;
+    }
+
+    public void setHasSessionBefore(boolean hasSessionBefore) {
+        this.hasSessionBefore = hasSessionBefore;
+    }
+
     @Override
     protected void accept0(SQLASTVisitor visitor) {
         visitor.visit(this);

src/main/java/com/alibaba/druid/sql/dialect/mysql/ast/statement/MySqlSetTransactionStatement.java

@@ -29,6 +29,17 @@ public class MySqlSetTransactionStatement extends MySqlStatementImpl {
 
     private String  accessModel;
 
+    private Boolean hasSessionBefore;
+
+
+    public Boolean getHasSessionBefore() {
+        return hasSessionBefore;
+    }
+
+    public void setHasSessionBefore(Boolean hasSessionBefore) {
+        this.hasSessionBefore = hasSessionBefore;
+    }
+
     public void accept0(MySqlASTVisitor visitor) {
         visitor.visit(this);
         visitor.endVisit(this);

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlExprParser.java

@@ -596,7 +596,7 @@ public class MySqlExprParser extends SQLExprParser {
             } else if (identHash == FnvHash.Constants.SESSION) {
                 ident = lexer.stringVal();
                 lexer.nextToken();
-                var = new SQLVariantRefExpr(ident, false);
+                var = new SQLVariantRefExpr(ident, false, true);
             } else {
                 var = new SQLVariantRefExpr(ident);
             }

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlStatementParser.java

@@ -2609,17 +2609,20 @@ public class MySqlStatementParser extends SQLStatementParser {
         }
 
         Boolean global = null;
+        Boolean sessionBefore = null;
         if (lexer.identifierEquals(GLOBAL)) {
             global = Boolean.TRUE;
             lexer.nextToken();
         } else if (lexer.identifierEquals(SESSION)) {
             global = Boolean.FALSE;
+            sessionBefore = Boolean.TRUE;
             lexer.nextToken();
         }
 
         if (lexer.identifierEquals("TRANSACTION")) {
             MySqlSetTransactionStatement stmt = new MySqlSetTransactionStatement();
             stmt.setGlobal(global);
+            stmt.setHasSessionBefore(sessionBefore);
 
             lexer.nextToken();
             if (lexer.identifierEquals("ISOLATION")) {
@@ -2724,6 +2727,11 @@ public class MySqlStatementParser extends SQLStatementParser {
                 varRef.setGlobal(true);
             }
 
+            if(sessionBefore != null && sessionBefore.booleanValue()){
+                SQLVariantRefExpr varRef = (SQLVariantRefExpr) stmt.getItems().get(0).getTarget();
+                varRef.setHasSessionBefore(true);
+            }
+
             if (lexer.token() == Token.HINT) {
                 stmt.setHints(this.exprParser.parseHints());
             }

src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlOutputVisitor.java

@@ -655,6 +655,8 @@ public class MySqlOutputVisitor extends SQLASTOutputVisitor implements MySqlASTV
 
         if (x.isGlobal()) {
             print0("@@global.");
+        }else if(x.isHasSessionBefore()){
+            print0("@@session.");
         }
 
         String varName = x.getName();