Line data    Source code

       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * discard.c
       4             :  *    The implementation of the DISCARD command
       5             :  *
       6             :  * Copyright (c) 1996-2024, 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 "utils/guc.h"
      23             : #include "utils/portal.h"
      24             : 
      25             : static void DiscardAll(bool isTopLevel);
      26             : 
      27             : /*
      28             :  * DISCARD { ALL | SEQUENCES | TEMP | PLANS }
      29             :  */
      30             : void
      31          30 : DiscardCommand(DiscardStmt *stmt, bool isTopLevel)
      32             : {
      33          30 :     switch (stmt->target)
      34             :     {
      35           6 :         case DISCARD_ALL:
      36           6 :             DiscardAll(isTopLevel);
      37           6 :             break;
      38             : 
      39           4 :         case DISCARD_PLANS:
      40           4 :             ResetPlanCache();
      41           4 :             break;
      42             : 
      43          12 :         case DISCARD_SEQUENCES:
      44          12 :             ResetSequenceCaches();
      45          12 :             break;
      46             : 
      47           8 :         case DISCARD_TEMP:
      48           8 :             ResetTempTableNamespace();
      49           8 :             break;
      50             : 
      51           0 :         default:
      52           0 :             elog(ERROR, "unrecognized DISCARD target: %d", stmt->target);
      53             :     }
      54          30 : }
      55             : 
      56             : static void
      57           6 : DiscardAll(bool isTopLevel)
      58             : {
      59             :     /*
      60             :      * Disallow DISCARD ALL in a transaction block. This is arguably
      61             :      * inconsistent (we don't make a similar check in the command sequence
      62             :      * that DISCARD ALL is equivalent to), but the idea is to catch mistakes:
      63             :      * DISCARD ALL inside a transaction block would leave the transaction
      64             :      * still uncommitted.
      65             :      */
      66           6 :     PreventInTransactionBlock(isTopLevel, "DISCARD ALL");
      67             : 
      68             :     /* Closing portals might run user-defined code, so do that first. */
      69           6 :     PortalHashTableDeleteAll();
      70           6 :     SetPGVariable("session_authorization", NIL, false);
      71           6 :     ResetAllOptions();
      72           6 :     DropAllPreparedStatements();
      73           6 :     Async_UnlistenAll();
      74           6 :     LockReleaseAll(USER_LOCKMETHOD, true);
      75           6 :     ResetPlanCache();
      76           6 :     ResetTempTableNamespace();
      77           6 :     ResetSequenceCaches();
      78           6 : }