/*-------------------------------------------------------------------------
 *
 * discard.c
 *   The implementation of the DISCARD command
 *
 * Copyright (c) 1996-2025, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *   src/backend/commands/discard.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/xact.h"
#include "catalog/namespace.h"
#include "commands/async.h"
#include "commands/discard.h"
#include "commands/prepare.h"
#include "commands/sequence.h"
#include "utils/guc.h"
#include "utils/portal.h"

static void DiscardAll(bool isTopLevel);

/*
 * DISCARD { ALL | SEQUENCES | TEMP | PLANS }
 */
void
DiscardCommand(DiscardStmt *stmt, bool isTopLevel)
{
 switch (stmt->target)
 {
  case DISCARD_ALL:
   DiscardAll(isTopLevel);
   break;

  case DISCARD_PLANS:
   ResetPlanCache();
   break;

  case DISCARD_SEQUENCES:
   ResetSequenceCaches();
   break;

  case DISCARD_TEMP:
   ResetTempTableNamespace();
   break;

  default:
   elog(ERROR, "unrecognized DISCARD target: %d", stmt->target);
 }
}

static void
DiscardAll(bool isTopLevel)
{
 /*
  * Disallow DISCARD ALL in a transaction block. This is arguably
  * inconsistent (we don't make a similar check in the command sequence
  * that DISCARD ALL is equivalent to), but the idea is to catch mistakes:
  * DISCARD ALL inside a transaction block would leave the transaction
  * still uncommitted.
 */
 PreventInTransactionBlock(isTopLevel, "DISCARD ALL");

 /* Closing portals might run user-defined code, so do that first. */
 PortalHashTableDeleteAll();
 SetPGVariable("session_authorization", NIL, false);
 ResetAllOptions();
 DropAllPreparedStatements();
 Async_UnlistenAll();
 LockReleaseAll(USER_LOCKMETHOD, true);
 ResetPlanCache();
 ResetTempTableNamespace();
 ResetSequenceCaches();
}