/*-------------------------------------------------------------------------
 *
 * delay_execution.c
 *  Test module to allow delay between parsing and execution of a query.
 *
 * The delay is implemented by taking and immediately releasing a specified
 * advisory lock.  If another process has previously taken that lock, the
 * current process will be blocked until the lock is released; otherwise,
 * there's no effect.  This allows an isolationtester script to reliably
 * test behaviors where some specified action happens in another backend
 * between parsing and execution of any desired query.
 *
 * Copyright (c) 2020-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *   src/test/modules/delay_execution/delay_execution.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <limits.h>

#include "optimizer/planner.h"
#include "utils/fmgrprotos.h"
#include "utils/guc.h"
#include "utils/inval.h"


PG_MODULE_MAGIC;

/* GUC: advisory lock ID to use.  Zero disables the feature. */
static int post_planning_lock_id = 0;

/* Save previous planner hook user to be a good citizen */
static planner_hook_type prev_planner_hook = NULL;


/* planner_hook function to provide the desired delay */
static PlannedStmt *
delay_execution_planner(Query *parse, const char *query_string,
      int cursorOptions, ParamListInfo boundParams)
{
 PlannedStmt *result;

 /* Invoke the planner, possibly via a previous hook user */
 if (prev_planner_hook)
  result = prev_planner_hook(parse, query_string, cursorOptions,
           boundParams);
 else
  result = standard_planner(parse, query_string, cursorOptions,
          boundParams);

 /* If enabled, delay by taking and releasing the specified lock */
 if (post_planning_lock_id != 0)
 {
  DirectFunctionCall1(pg_advisory_lock_int8,
       Int64GetDatum((int64) post_planning_lock_id));
  DirectFunctionCall1(pg_advisory_unlock_int8,
       Int64GetDatum((int64) post_planning_lock_id));

  /*
   * Ensure that we notice any pending invalidations, since the advisory
   * lock functions don't do this.
 */
  AcceptInvalidationMessages();
 }

 return result;
}

/* Module load function */
void
_PG_init(void)
{
 /* Set up the GUC to control which lock is used */
 DefineCustomIntVariable("delay_execution.post_planning_lock_id",
       "Sets the advisory lock ID to be locked/unlocked after planning.",
       "Zero disables the delay.",
       &post_planning_lock_id,
       0,
       0, INT_MAX,
       PGC_USERSET,
       0,
       NULL,
       NULL,
       NULL);

 MarkGUCPrefixReserved("delay_execution");

 /* Install our hook */
 prev_planner_hook = planner_hook;
 planner_hook = delay_execution_planner;
}