mirror of https://github.com/postgres/postgres
RESET SESSION, RESET PLANS, and RESET TEMP are now DISCARD ALL, DISCARD PLANS, and DISCARD TEMP, respectively. This is to avoid confusion with the pre-existing RESET variants: the DISCARD commands are not actually similar to RESET. Patch from Marko Kreen, with some minor editorialization.REL8_3_STABLE
Neil Conway
19 years ago
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$PostgreSQL: pgsql/doc/src/sgml/ref/discard.sgml,v 1.1 2007/04/26 16:13:09 neilc Exp $ |
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PostgreSQL documentation |
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--> |
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<refentry id="SQL-DISCARD"> |
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<refmeta> |
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<refentrytitle id="SQL-DISCARD-TITLE">DISCARD</refentrytitle> |
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<refmiscinfo>SQL - Language Statements</refmiscinfo> |
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</refmeta> |
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<refnamediv> |
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<refname>DISCARD</refname> |
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<refpurpose>Discard internal server state</refpurpose> |
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</refnamediv> |
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<indexterm zone="sql-discard"> |
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<primary>DISCARD</primary> |
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</indexterm> |
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<refsynopsisdiv> |
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<synopsis> |
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DISCARD { ALL | PLANS | TEMPORARY | TEMP } |
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</synopsis> |
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</refsynopsisdiv> |
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<refsect1> |
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<title>Description</title> |
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<para> |
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<command>DISCARD</> releases internal resources associated with a |
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database session. These resources are normally released at the end |
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of the session. |
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</para> |
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<para> |
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<command>DISCARD TEMP</> drops all temporary tables created in the |
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current session. <command>DISCARD PLANS</> releases all internally |
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cached query plans. <command>DISCARD ALL</> resets a session to |
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its original state, discarding temporary resources and resetting |
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session-local configuration changes. |
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</para> |
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</refsect1> |
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<refsect1> |
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<title>Parameters</title> |
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<variablelist> |
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<varlistentry> |
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<term><literal>TEMPORARY</literal> or <literal>TEMP</literal></term> |
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<listitem> |
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<para> |
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Drops all temporary tables created in the current session. |
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</para> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term><literal>PLANS</literal></term> |
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<listitem> |
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<para> |
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Releases all cached query plans. |
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</para> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term><literal>ALL</literal></term> |
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<listitem> |
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<para> |
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Releases all temporary resources associated with the current |
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session and resets the session to its initial state. This has |
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the same effect as executing the following sequence of |
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statements: |
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<programlisting> |
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SET SESSION AUTHORIZATION DEFAULT; |
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RESET ALL; |
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DEALLOCATE ALL; |
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CLOSE ALL; |
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UNLISTEN *; |
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DISCARD PLANS; |
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DISCARD TEMP; |
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</programlisting> |
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</para> |
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</listitem> |
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</varlistentry> |
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</variablelist> |
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</refsect1> |
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<refsect1> |
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<title>Notes</title> |
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<para> |
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<command>DISCARD ALL</> cannot be executed inside a transaction block. |
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</para> |
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</refsect1> |
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<refsect1> |
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<title>Compatibility</title> |
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<para> |
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<command>DISCARD</command> is a <productname>PostgreSQL</productname> extension. |
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</para> |
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</refsect1> |
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</refentry> |
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@ -0,0 +1,71 @@ |
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/*-------------------------------------------------------------------------
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* |
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* discard.c |
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* The implementation of the DISCARD command |
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* |
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* Copyright (c) 1996-2007, PostgreSQL Global Development Group |
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* |
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* |
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* IDENTIFICATION |
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* $PostgreSQL: pgsql/src/backend/commands/discard.c,v 1.1 2007/04/26 16:13:10 neilc Exp $ |
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* |
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*------------------------------------------------------------------------- |
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*/ |
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#include "postgres.h" |
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#include "access/xact.h" |
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#include "catalog/namespace.h" |
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#include "commands/async.h" |
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#include "commands/discard.h" |
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#include "commands/prepare.h" |
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#include "commands/variable.h" |
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#include "utils/plancache.h" |
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#include "utils/portal.h" |
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static void DiscardAll(bool isTopLevel); |
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/*
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* DISCARD { ALL | TEMP | PLANS } |
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*/ |
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void |
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DiscardCommand(DiscardStmt *stmt, bool isTopLevel) |
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{ |
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switch (stmt->target) |
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{ |
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case DISCARD_ALL: |
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DiscardAll(isTopLevel); |
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break; |
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case DISCARD_PLANS: |
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ResetPlanCache(); |
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break; |
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case DISCARD_TEMP: |
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ResetTempTableNamespace(); |
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break; |
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default: |
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elog(ERROR, "unrecognized DISCARD target: %d", stmt->target); |
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} |
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} |
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static void |
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DiscardAll(bool isTopLevel) |
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{ |
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/*
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* Disallow DISCARD ALL in a transaction block. This is arguably |
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* inconsistent (we don't make a similar check in the command |
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* sequence that DISCARD ALL is equivalent to), but the idea is |
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* to catch mistakes: DISCARD ALL inside a transaction block |
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* would leave the transaction still uncommitted. |
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*/ |
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PreventTransactionChain(isTopLevel, "DISCARD ALL"); |
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SetPGVariable("session_authorization", NIL, false); |
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ResetAllOptions(); |
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DropAllPreparedStatements(); |
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PortalHashTableDeleteAll(); |
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Async_UnlistenAll(); |
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ResetPlanCache(); |
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ResetTempTableNamespace(); |
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} |
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@ -0,0 +1,20 @@ |
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/*-------------------------------------------------------------------------
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* |
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* discard.h |
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* prototypes for discard.c. |
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* |
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* |
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* Copyright (c) 1996-2007, PostgreSQL Global Development Group |
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* |
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* $PostgreSQL: pgsql/src/include/commands/discard.h,v 1.1 2007/04/26 16:13:13 neilc Exp $ |
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* |
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*------------------------------------------------------------------------- |
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*/ |
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#ifndef DISCARD_H |
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#define DISCARD_H |
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#include "nodes/parsenodes.h" |
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extern void DiscardCommand(DiscardStmt *stmt, bool isTopLevel); |
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#endif /* DISCARD_H */ |
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