PostgreSQL Source Code: src/backend/commands/discard.c Source File

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discard.c
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1/*-------------------------------------------------------------------------
2 *
3 * discard.c
4 * The implementation of the DISCARD command
5 *
6 * Copyright (c) 1996-2025, 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
25static void DiscardAll(bool isTopLevel);
26
27/*
28 * DISCARD { ALL | SEQUENCES | TEMP | PLANS }
29 */
30void
31 DiscardCommand(DiscardStmt *stmt, bool isTopLevel)
32{
33 switch (stmt->target)
34 {
35 case DISCARD_ALL:
36 DiscardAll(isTopLevel);
37 break;
38
39 case DISCARD_PLANS:
40 ResetPlanCache();
41 break;
42
43 case DISCARD_SEQUENCES:
44 ResetSequenceCaches();
45 break;
46
47 case DISCARD_TEMP:
48 ResetTempTableNamespace();
49 break;
50
51 default:
52 elog(ERROR, "unrecognized DISCARD target: %d", stmt->target);
53 }
54}
55
56static void
57 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 PreventInTransactionBlock(isTopLevel, "DISCARD ALL");
67
68 /* Closing portals might run user-defined code, so do that first. */
69 PortalHashTableDeleteAll();
70 SetPGVariable("session_authorization", NIL, false);
71 ResetAllOptions();
72 DropAllPreparedStatements();
73 Async_UnlistenAll();
74 LockReleaseAll(USER_LOCKMETHOD, true);
75 ResetPlanCache();
76 ResetTempTableNamespace();
77 ResetSequenceCaches();
78}
void Async_UnlistenAll(void)
Definition: async.c:770
void DropAllPreparedStatements(void)
Definition: prepare.c:540
void ResetSequenceCaches(void)
Definition: sequence.c:1966
static void DiscardAll(bool isTopLevel)
Definition: discard.c:57
void DiscardCommand(DiscardStmt *stmt, bool isTopLevel)
Definition: discard.c:31
#define ERROR
Definition: elog.h:39
#define elog(elevel,...)
Definition: elog.h:226
void ResetAllOptions(void)
Definition: guc.c:2009
void SetPGVariable(const char *name, List *args, bool is_local)
Definition: guc_funcs.c:315
#define stmt
Definition: indent_codes.h:59
void LockReleaseAll(LOCKMETHODID lockmethodid, bool allLocks)
Definition: lock.c:2307
#define USER_LOCKMETHOD
Definition: lock.h:128
void ResetTempTableNamespace(void)
Definition: namespace.c:4714
@ DISCARD_ALL
Definition: parsenodes.h:4063
@ DISCARD_PLANS
Definition: parsenodes.h:4064
@ DISCARD_SEQUENCES
Definition: parsenodes.h:4065
@ DISCARD_TEMP
Definition: parsenodes.h:4066
#define NIL
Definition: pg_list.h:68
void ResetPlanCache(void)
Definition: plancache.c:2323
void PortalHashTableDeleteAll(void)
Definition: portalmem.c:607
void PreventInTransactionBlock(bool isTopLevel, const char *stmtType)
Definition: xact.c:3660

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