fix jdbc memleaks #3098

src/client/src/TSDBJNIConnector.c

@@ -327,13 +327,12 @@ JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getResultSetImp(
   STscObj *pObj = pSql->pTscObj;
 
   if (tscIsUpdateQuery(pSql)) {
-    // taos_free_result(pSql);  // free result here
-    jniDebug("jobj:%p, conn:%p, no resultset, %p", jobj, pObj, (void *)tres);
-    return 0;
+    jniDebug("jobj:%p, conn:%p, update query, no resultset, %p", jobj, pObj, (void *)tres);
   } else {
     jniDebug("jobj:%p, conn:%p, get resultset, %p", jobj, pObj, (void *)tres);
-    return tres;
   }
+
+  return tres;
 }
 
 JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_freeResultSetImp(JNIEnv *env, jobject jobj, jlong con,

src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBJNIConnector.java

@@ -111,6 +111,8 @@ public class TSDBJNIConnector {
      * @throws SQLException
      */
     public long executeQuery(String sql) throws SQLException {
+    	// close previous result set if the user forgets to invoke the 
+    	// free method to close previous result set.
         if (!this.isResultsetClosed) {
             freeResultSet(taosResultSetPointer);
         }
@@ -123,21 +125,20 @@ public class TSDBJNIConnector {
             this.freeResultSet(pSql);
             throw new SQLException(TSDBConstants.WrapErrMsg("Unsupported encoding"));
         }
+        
         int code = this.getErrCode(pSql);
         if (code != 0) {
             affectedRows = -1;
-            String err_msg = this.getErrMsg(pSql);
+            String msg = this.getErrMsg(pSql);
+            
             this.freeResultSet(pSql);
-            throw new SQLException(TSDBConstants.WrapErrMsg(err_msg), "", code);
+            throw new SQLException(TSDBConstants.WrapErrMsg(msg), "", code);
         }
 
-        // Try retrieving result set for the executed SQL using the current connection pointer. If the executed
-        // SQL is a DML/DDL which doesn't return a result set, then taosResultSetPointer should be 0L. Otherwise,
-        // taosResultSetPointer should be a non-zero value.
+        // Try retrieving result set for the executed SQL using the current connection pointer. 
         taosResultSetPointer = this.getResultSetImp(this.taos, pSql);
-        if (taosResultSetPointer != TSDBConstants.JNI_NULL_POINTER) {
-            isResultsetClosed = false;
-        }
+        isResultsetClosed = (taosResultSetPointer == TSDBConstants.JNI_NULL_POINTER);
+        
         return pSql;
     }
 
@@ -178,13 +179,14 @@ public class TSDBJNIConnector {
         int res = TSDBConstants.JNI_SUCCESS;
         if (result != taosResultSetPointer && taosResultSetPointer != TSDBConstants.JNI_NULL_POINTER) {
             throw new RuntimeException("Invalid result set pointer");
-        } else if (taosResultSetPointer != TSDBConstants.JNI_NULL_POINTER) {
+        }
+
+        if (taosResultSetPointer != TSDBConstants.JNI_NULL_POINTER) {
             res = this.freeResultSetImp(this.taos, result);
-            isResultsetClosed = true; // reset resultSetPointer to 0 after freeResultSetImp() return
             taosResultSetPointer = TSDBConstants.JNI_NULL_POINTER;
-        } else {
-            isResultsetClosed = true;
         }
+        
+        isResultsetClosed = true;
         return res;
     }
 

src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBStatement.java

@@ -51,6 +51,8 @@ public class TSDBStatement implements Statement {
         if (isClosed) {
             throw new SQLException("Invalid method call on a closed statement.");
         }
+        
+        // TODO make sure it is not a update query
 		pSql = this.connecter.executeQuery(sql);
 
 		long resultSetPointer = this.connecter.getResultSet();
@@ -71,20 +73,19 @@ public class TSDBStatement implements Statement {
         if (isClosed) {
             throw new SQLException("Invalid method call on a closed statement.");
         }
+        
+        // TODO check if current query is update query
 		pSql = this.connecter.executeQuery(sql);
 		long resultSetPointer = this.connecter.getResultSet();
 
 		if (resultSetPointer == TSDBConstants.JNI_CONNECTION_NULL) {
 			this.connecter.freeResultSet(pSql);
 			throw new SQLException(TSDBConstants.FixErrMsg(TSDBConstants.JNI_CONNECTION_NULL));
-		} else if (resultSetPointer != TSDBConstants.JNI_NULL_POINTER) {
-			this.connecter.freeResultSet();
-			throw new SQLException("The executed SQL is not a DML or a DDL");
-		} else {
-			int num = this.connecter.getAffectedRows(pSql);
-			this.connecter.freeResultSet(pSql);
-			return num;
-		}
+		}	
+
+		int num = this.connecter.getAffectedRows(pSql);
+		this.connecter.freeResultSet(pSql);
+		return num;
 	}
 
 	public String getErrorMsg(long pSql) {