Fix Text2SQL (#2131)

### What problem does this PR solve?

Fix exeSQL component 
Update DB Assistant template 
Fix canvas Message window size

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

agent/canvas.py

@@ -260,7 +260,7 @@ class Canvas(ABC):
 
     def get_history(self, window_size):
         convs = []
-        for role, obj in self.history[window_size * -2:]:
+        for role, obj in self.history[(window_size + 1) * -1:]:
             convs.append({"role": role, "content": (obj if role == "user" else
                                                     '\n'.join(pd.DataFrame(obj)['content']))})
         return convs

agent/component/exesql.py

@@ -77,7 +77,7 @@ class ExeSQL(ComponentBase, ABC):
         except Exception as e:
             return ExeSQL.be_output("**Error**: \nDatabase Connection Failed! \n" + str(e))
         sql_res = []
-        for single_sql in re.split(r';', ans):
+        for single_sql in re.split(r';', ans.replace(r"\n", " ")):
             if not single_sql:
                 continue
             try:

agent/templates/DB Assistant.json

@@ -63,7 +63,7 @@
                                 }
                             ],
                             "presence_penalty": 0.4,
-                            "prompt": "## You are the Repair SQL Statement Helper, please modify the original SQL statement based on the SQL query error report.\n\n## The contents of the SQL query error report and the original SQL statement are as follows:\n{exesql_input}\n\n## Answer only the modified SQL statement. Please do not give any explanation, just answer the code.",
+                            "prompt": "## You are the Repair SQL Statement Helper, please modify the original SQL statement based on the SQL query error report.\n\n## The contents of the SQL query error report and the original SQL statement are as follows:\n{exesql_input}\n\n## Answer only the modified SQL statement. Each SQL statement ends with semicolon and do not give any explanation, just answer the code.",
                             "temperature": 0.1,
                             "top_p": 0.3
                         }
@@ -102,7 +102,7 @@
                                 }
                             ],
                             "presence_penalty": 0.4,
-                            "prompt": "\n##The user provides a question and you provide SQL. You will only respond with SQL code and not with any explanations.\n\n##You may use the following DDL statements as a reference for what tables might be available. Use responses to past questions also to guide you: {ddl_input}.\n\n##You may use the following documentation as a reference for what tables might be available. Use responses to past questions also to guide you: {db_input}.\n\n##You may use the following SQL statements as a reference for what tables might be available. Use responses to past questions also to guide you: {sql_input}.\n\n##Respond with only SQL code. Do not answer with any explanations -- just the code.",
+                            "prompt": "\n##The user provides a question and you provide SQL. You will only respond with SQL code and not with any explanations.\n\n##You may use the following DDL statements as a reference for what tables might be available. Use responses to past questions also to guide you: {ddl_input}.\n\n##You may use the following documentation as a reference for what tables might be available. Use responses to past questions also to guide you: {db_input}.\n\n##You may use the following SQL statements as a reference for what tables might be available. Use responses to past questions also to guide you: {sql_input}.\n\n##Respond with only SQL code. Each SQL code ends with semicolon and do not give any explanation -- just the code.",
                             "temperature": 0.1,
                             "top_p": 0.3
                         }