MySQL Bugs: #70113: Memory leak in SQLPrepare with queries that use parameters

Bug #70113	Memory leak in SQLPrepare with queries that use parameters
Submitted:	21 Aug 2013 21:15	Modified:	11 Sep 2013 16:06
Reporter:	Denis Parnovsky	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / ODBC	Severity:	S1 (Critical)
Version:	5.2.5	OS:	Microsoft Windows
Assigned to:	Bogdan Degtyariov	CPU Architecture:	Any

Description:
ODBC Connector 5.2.2 and 5.2.5 is leaking on SQLBindParamater. 
Several kilobytes per operation.
3.51.11 is not leaking with the same test program.

If the parameter value is inserted into the query text instead of Bind then the memory is stable.

Memory consumption is visible in Task Manager, the program quickly grows from 1200K to 140000k.

Looks like #31115 is back.

How to repeat:

#include <iostream>

#include <windows.h>

#include <sqltypes.h>

#include <sql.h>

#include <sqlext.h>

 

using namespace std;

 

void show_error(unsigned int handletype, const SQLHANDLE& handle){

    SQLCHAR sqlstate[1024];

    SQLCHAR message[1024];

    if(SQL_SUCCESS == SQLGetDiagRec(handletype, handle, 1, sqlstate, NULL, message, 1024, NULL))

        cout<<"Message: "<<message<<"\nSQLSTATE: "<<sqlstate<<endl;

}

 

int main(){

      SQLHANDLE sqlenvhandle;   

    SQLHANDLE sqlconnectionhandle;

    SQLHANDLE sqlstatementhandle;

    SQLRETURN retcode;

 

    if(SQL_SUCCESS!=SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &sqlenvhandle))

        goto FINISHED;

 

    if(SQL_SUCCESS!=SQLSetEnvAttr(sqlenvhandle,SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0))

        goto FINISHED;

   

    if(SQL_SUCCESS!=SQLAllocHandle(SQL_HANDLE_DBC, sqlenvhandle, &sqlconnectionhandle))

        goto FINISHED;

 

    SQLCHAR retconstring[1024];

    switch(SQLDriverConnect (sqlconnectionhandle,

                NULL,

                (SQLCHAR*)"DSN=l106;SERVER=localhost;UID=root;PWD=root;",

                SQL_NTS,

                retconstring,

                1024,

                NULL,

                SQL_DRIVER_NOPROMPT)){

        case SQL_SUCCESS_WITH_INFO:

            show_error(SQL_HANDLE_DBC, sqlconnectionhandle);

            break;

        case SQL_INVALID_HANDLE:

        case SQL_ERROR:

            show_error(SQL_HANDLE_DBC, sqlconnectionhandle);

            goto FINISHED;

        default:

            break;

    }

 

    for(int i = 0; i < 100000; i++)

    {

      if(SQL_SUCCESS!=SQLAllocHandle(SQL_HANDLE_STMT, sqlconnectionhandle, &sqlstatementhandle))

          goto FINISHED;

 

      SWORD val = 100;

      SQLINTEGER iJunk = SQL_NTS;

 

      char* query = "select exists(select NULL from acdgroup where GROUPID = ?)";

 

      if(SQL_SUCCESS!=SQLPrepare(sqlstatementhandle, (SQLCHAR*)query, strlen(query)))

          goto FINISHED;

 

        if(SQL_SUCCESS!=SQLBindParameter(sqlstatementhandle,1,SQL_PARAM_INPUT,SQL_C_SSHORT,SQL_SMALLINT,2,0,&val,sizeof(val),&iJunk))

          goto FINISHED;

 

      if(SQL_SUCCESS!=SQLExecute(sqlstatementhandle)){

          show_error(SQL_HANDLE_STMT, sqlstatementhandle);

          goto FINISHED;

      }

      else{

          short result = -1;

          while(SQLFetch(sqlstatementhandle)==SQL_SUCCESS){

              SQLGetData(sqlstatementhandle, 1, SQL_C_SHORT, &result, 0, NULL);

              cout<<result<<endl;

          }

      }

      SQLCloseCursor(sqlstatementhandle);

      SQLFreeHandle(SQL_HANDLE_STMT, sqlstatementhandle);

    }

 

FINISHED:

    show_error(SQL_HANDLE_DBC, sqlconnectionhandle);

    SQLDisconnect(sqlconnectionhandle);

    SQLFreeHandle(SQL_HANDLE_DBC, sqlconnectionhandle);

    SQLFreeHandle(SQL_HANDLE_ENV, sqlenvhandle);

   

}

Hi Denis,

Thank you for your interest in MySQL software and for reporting the problem in it.
A special big thanks for providing the working C++ test case, which demonstrated the memory leak as described. We really appreciate your efforts to make the verification task easier for us.

The bug is verified.
This looks like a serious high-priority issue. I will keep you informed about the bug fixing progress.

The actual memory leak occurs in SQLPrepare() because the result of mysql_stmt_result_metadata() is not freed.

Leak #2 was discovered in ssps_close() function, which did not always call free_result_bind() to free the bind result.

When do you expect to have a released fix for this?

Andrew,

Oracle company policy does not allow us to disclose the dates of software product releases before they are officially announced. Sorry if it creates inconveniences.

Patch

Attachment: bug70113.diff (application/octet-stream, text), 3.91 KiB.

When will the msi get rebuilt?

Bogdan, if I remove SQLPrepare and change SQLExecute to SQLExecDirect then the situation remains the same, memory usage grows at the rate of 300Kb per second.

Do I need to create another issue since you changed this one to be specific about SQLPrepare?

Andrew, as I said before - you have to wait for the official announcement of the next version.

Denis,

The patch addressed both memory leaks in SQLPrepare and in SQLExecDirect.
We run valgrind memory checks and no more leaks were reported.

If you cant tell me when the fix will be released can you tell me in what version the bug was introduced so I can roll back. This is creating chaos in a new mission critical application.

Andrew,

No need to rollback to the previous version to stop the memory leak.
It only happens when the Server Side Prepared Statements are used (SSPS).
SSPS are used for any query by default.

SSPS can be disabled by adding "NO_SSPS=1" to the connection string or ticking the checkbox [Details->Misc->Prepare Statements on Client] in the Data Source setup GUI.

Sorry for inconvenience caused by the bug.

Thanks will give it a try

The following changelog entry has been added for Connector/ODBC 5.2.6:

Memory leaks occurred in SQLPrepare() and SQLExecDirect() when SQLBindParamater was used on the SQL statements. This fix frees previous results of mysql_stmt_result_metadata() in order to prevent the memory leaks.