Zabbix

/*

** Copyright (C) 2001-2025 Zabbix SIA

**

** This program is free software: you can redistribute it and/or modify it under the terms of

** the GNU Affero General Public License as published by the Free Software Foundation, version 3.

**

** This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;

** without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

** See the GNU Affero General Public License for more details.

**

** You should have received a copy of the GNU Affero General Public License along with this program.

** If not, see <https://www.gnu.org/licenses/>.

**/

​

#include "zbxdbhigh.h"

​

#include "zbxnum.h"

​

/******************************************************************************

 *                                                                            *

 * Purpose: lock maintenances in database                                     *

 *                                                                            *

 * Parameters: maintenanceids - [IN/OUT] a vector of unique maintenance ids   *

 *                                 IN - the maintenances to lock              *

 *                                 OUT - the locked maintenance ids (sorted)  *

 *                                                                            *

 * Return value: SUCCEED - at least one maintenance was locked                *

 *               FAIL    - no maintenances were locked (all target            *

 *                         maintenances were removed by user and              *

 *                         configuration cache was not yet updated)           *

 *                                                                            *

 * Comments: This function locks maintenances in database to avoid foreign    *

 *           key errors when a maintenance is removed in the middle of        *

 *           processing.                                                      *

 *           The output vector might contain less values than input vector if *

 *           a maintenance was removed before lock attempt.                   *

 *                                                                            *

 ******************************************************************************/

int zbx_db_lock_maintenanceids(zbx_vector_uint64_t *maintenanceids)

{

    char        *sql = NULL;

    size_t      sql_alloc = 0, sql_offset = 0;

    zbx_uint64_t    maintenanceid;

    int     i;

    zbx_db_result_t result;

    zbx_db_row_t    row;

​

    zbx_vector_uint64_sort(maintenanceids, ZBX_DEFAULT_UINT64_COMPARE_FUNC);

​

    zbx_strcpy_alloc(&sql, &sql_alloc, &sql_offset, "select maintenanceid from maintenances where");

    zbx_db_add_condition_alloc(&sql, &sql_alloc, &sql_offset, "maintenanceid", maintenanceids->values,

            maintenanceids->values_num);

#if defined(HAVE_MYSQL)

    zbx_strcpy_alloc(&sql, &sql_alloc, &sql_offset, " order by maintenanceid lock in share mode");

#elif defined(HAVE_ORACLE)

    /* Row level shared locks are not supported in Oracle. Table lock in share mode leads to deadlock on */

    /* event_suppress insertion due to locking that occurs in order to satisfy foreign key constraint.   */

    zbx_strcpy_alloc(&sql, &sql_alloc, &sql_offset, " order by maintenanceid" ZBX_FOR_UPDATE);

#else

    /* For PostgreSQL table level locks are used because row level shared locks have reader preference which */

    /* could lead to theoretical situation when server blocks out frontend from maintenances updates.        */

    zbx_db_execute("lock table maintenances in share mode");

    zbx_strcpy_alloc(&sql, &sql_alloc, &sql_offset, " order by maintenanceid");