Line data    Source code

       1              : /*-------------------------------------------------------------------------
       2              :  *
       3              :  * discard.c
       4              :  *    The implementation of the DISCARD command
       5              :  *
       6              :  * Copyright (c) 1996-2026, PostgreSQL Global Development Group
       7              :  *
       8              :  *
       9              :  * IDENTIFICATION
      10              :  *    src/backend/commands/discard.c
      11              :  *
      12              :  *-------------------------------------------------------------------------
      13              :  */
      14              : #include "postgres.h"
      15              : 
      16              : #include "access/xact.h"
      17              : #include "catalog/namespace.h"
      18              : #include "commands/async.h"
      19              : #include "commands/discard.h"
      20              : #include "commands/prepare.h"
      21              : #include "commands/sequence.h"
      22              : #include "storage/lock.h"
      23              : #include "utils/guc.h"
      24              : #include "utils/portal.h"
      25              : 
      26              : static void DiscardAll(bool isTopLevel);
      27              : 
      28              : /*
      29              :  * DISCARD { ALL | SEQUENCES | TEMP | PLANS }
      30              :  */
      31              : void
      32           24 : DiscardCommand(DiscardStmt *stmt, bool isTopLevel)
      33              : {
      34           24 :     switch (stmt->target)
      35              :     {
      36            4 :         case DISCARD_ALL:
      37            4 :             DiscardAll(isTopLevel);
      38            4 :             break;
      39              : 
      40            3 :         case DISCARD_PLANS:
      41            3 :             ResetPlanCache();
      42            3 :             break;
      43              : 
      44            8 :         case DISCARD_SEQUENCES:
      45            8 :             ResetSequenceCaches();
      46            8 :             break;
      47              : 
      48            9 :         case DISCARD_TEMP:
      49            9 :             ResetTempTableNamespace();
      50            9 :             break;
      51              : 
      52            0 :         default:
      53            0 :             elog(ERROR, "unrecognized DISCARD target: %d", stmt->target);
      54              :     }
      55           24 : }
      56              : 
      57              : static void
      58            4 : DiscardAll(bool isTopLevel)
      59              : {
      60              :     /*
      61              :      * Disallow DISCARD ALL in a transaction block. This is arguably
      62              :      * inconsistent (we don't make a similar check in the command sequence
      63              :      * that DISCARD ALL is equivalent to), but the idea is to catch mistakes:
      64              :      * DISCARD ALL inside a transaction block would leave the transaction
      65              :      * still uncommitted.
      66              :      */
      67            4 :     PreventInTransactionBlock(isTopLevel, "DISCARD ALL");
      68              : 
      69              :     /* Closing portals might run user-defined code, so do that first. */
      70            4 :     PortalHashTableDeleteAll();
      71            4 :     SetPGVariable("session_authorization", NIL, false);
      72            4 :     ResetAllOptions();
      73            4 :     DropAllPreparedStatements();
      74            4 :     Async_UnlistenAll();
      75            4 :     LockReleaseAll(USER_LOCKMETHOD, true);
      76            4 :     ResetPlanCache();
      77            4 :     ResetTempTableNamespace();
      78            4 :     ResetSequenceCaches();
      79            4 : }