mirror of https://github.com/postgres/postgres
temp table entries in pg_class have the names the user would expect.ecpg_big_bison
Tom Lane
24 years ago
parent
5f4745adf4
commit
3114102521
@ -1,335 +0,0 @@ |
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/*-------------------------------------------------------------------------
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* |
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* temprel.c |
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* POSTGRES temporary relation handling |
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* |
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* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group |
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* Portions Copyright (c) 1994, Regents of the University of California |
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* |
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* |
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* IDENTIFICATION |
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* $Header: /cvsroot/pgsql/src/backend/utils/cache/Attic/temprel.c,v 1.36 2002/03/29 19:06:16 tgl Exp $ |
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* |
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*------------------------------------------------------------------------- |
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*/ |
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/*
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* This implements temp tables by modifying the relname cache lookups |
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* of pg_class. |
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* |
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* When a temp table is created, normal entries are made for it in pg_class, |
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* pg_type, etc using a unique "physical" relation name. We also make an |
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* entry in the temp table list maintained by this module. Subsequently, |
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* relname lookups are filtered through the temp table list, and attempts |
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* to look up a temp table name are changed to look up the physical name. |
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* This allows temp table names to mask a regular table of the same name |
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* for the duration of the session. The temp table list is also used |
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* to drop the underlying physical relations at session shutdown. |
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*/ |
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#include "postgres.h" |
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#include <sys/types.h> |
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#include "catalog/heap.h" |
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#include "catalog/index.h" |
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#include "miscadmin.h" |
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#include "utils/temprel.h" |
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/* ----------------
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* global variables |
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* ---------------- |
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*/ |
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static List *temp_rels = NIL; |
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typedef struct TempTable |
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{ |
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NameData user_relname; /* logical name of temp table */ |
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NameData relname; /* underlying unique name */ |
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Oid relid; /* needed properties of rel */ |
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char relkind; |
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/*
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* If this entry was created during this xact, it should be deleted at |
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* xact abort. Conversely, if this entry was deleted during this |
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* xact, it should be removed at xact commit. We leave deleted |
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* entries in the list until commit so that we can roll back if needed |
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* --- but we ignore them for purposes of lookup! |
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*/ |
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bool created_in_cur_xact; |
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bool deleted_in_cur_xact; |
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} TempTable; |
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/*
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* Create a temp-relation list entry given the logical temp table name |
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* and the already-created pg_class tuple for the underlying relation. |
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* |
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* NB: we assume a check has already been made for a duplicate logical name. |
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*/ |
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void |
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create_temp_relation(const char *relname, HeapTuple pg_class_tuple) |
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{ |
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Form_pg_class pg_class_form = (Form_pg_class) GETSTRUCT(pg_class_tuple); |
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MemoryContext oldcxt; |
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TempTable *temp_rel; |
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oldcxt = MemoryContextSwitchTo(CacheMemoryContext); |
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temp_rel = (TempTable *) palloc(sizeof(TempTable)); |
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StrNCpy(NameStr(temp_rel->user_relname), relname, |
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NAMEDATALEN); |
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StrNCpy(NameStr(temp_rel->relname), NameStr(pg_class_form->relname), |
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NAMEDATALEN); |
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temp_rel->relid = pg_class_tuple->t_data->t_oid; |
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temp_rel->relkind = pg_class_form->relkind; |
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temp_rel->created_in_cur_xact = true; |
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temp_rel->deleted_in_cur_xact = false; |
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temp_rels = lcons(temp_rel, temp_rels); |
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MemoryContextSwitchTo(oldcxt); |
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} |
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/*
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* Remove a temp relation map entry (part of DROP TABLE on a temp table). |
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* We don't actually remove the entry, just mark it dead. |
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* |
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* We don't have the relname for indexes, so we just pass the oid. |
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*/ |
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void |
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remove_temp_rel_by_relid(Oid relid) |
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{ |
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List *l; |
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foreach(l, temp_rels) |
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{ |
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TempTable *temp_rel = (TempTable *) lfirst(l); |
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if (temp_rel->relid == relid) |
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temp_rel->deleted_in_cur_xact = true; |
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/*
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* Keep scanning 'cause there could be multiple matches; see |
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* RENAME |
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*/ |
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} |
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} |
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/*
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* To implement ALTER TABLE RENAME on a temp table, we shouldn't touch |
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* the underlying physical table at all, just change the map entry! |
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* |
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* This routine is invoked early in ALTER TABLE RENAME to check for |
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* the temp-table case. If oldname matches a temp table name, change |
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* the mapping to the new logical name and return TRUE (or elog if |
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* there is a conflict with another temp table name). If there is |
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* no match, return FALSE indicating that normal rename should proceed. |
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* |
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* We also reject an attempt to rename a normal table to a name in use |
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* as a temp table name. That would fail later on anyway when rename.c |
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* looks for a rename conflict, but we can give a more specific error |
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* message for the problem here. |
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* |
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* It might seem that we need to check for attempts to rename the physical |
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* file underlying a temp table, but that'll be rejected anyway because |
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* pg_tempXXX looks like a system table name. |
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*/ |
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bool |
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rename_temp_relation(const char *oldname, |
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const char *newname) |
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{ |
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List *l; |
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foreach(l, temp_rels) |
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{ |
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TempTable *temp_rel = (TempTable *) lfirst(l); |
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MemoryContext oldcxt; |
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TempTable *new_temp_rel; |
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if (temp_rel->deleted_in_cur_xact) |
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continue; /* ignore it if logically deleted */ |
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if (strcmp(NameStr(temp_rel->user_relname), oldname) != 0) |
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continue; /* ignore non-matching entries */ |
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/* We are renaming a temp table --- is it OK to do so? */ |
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if (is_temp_rel_name(newname)) |
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elog(ERROR, "Cannot rename temp table \"%s\": temp table \"%s\" already exists", |
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oldname, newname); |
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/*
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* Create a new mapping entry and mark the old one deleted in this |
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* xact. One of these entries will be deleted at xact end. |
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* |
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* NOTE: the new mapping entry is inserted into the list just after |
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* the old one. We could alternatively insert it before the old |
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* one, but that'd take more code. It does need to be in one spot |
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* or the other, to ensure that deletion of temp rels happens in |
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* the right order during remove_all_temp_relations(). |
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*/ |
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oldcxt = MemoryContextSwitchTo(CacheMemoryContext); |
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new_temp_rel = (TempTable *) palloc(sizeof(TempTable)); |
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memcpy(new_temp_rel, temp_rel, sizeof(TempTable)); |
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StrNCpy(NameStr(new_temp_rel->user_relname), newname, NAMEDATALEN); |
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new_temp_rel->created_in_cur_xact = true; |
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lnext(l) = lcons(new_temp_rel, lnext(l)); |
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temp_rel->deleted_in_cur_xact = true; |
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MemoryContextSwitchTo(oldcxt); |
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return true; |
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} |
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/* Old name does not match any temp table name, what about new? */ |
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if (is_temp_rel_name(newname)) |
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elog(ERROR, "Cannot rename \"%s\" to \"%s\": a temp table by that name already exists", |
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oldname, newname); |
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return false; |
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} |
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/*
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* Remove underlying relations for all temp rels at backend shutdown. |
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*/ |
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void |
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remove_all_temp_relations(void) |
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{ |
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List *l; |
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/* skip xact start overhead if nothing to do */ |
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if (temp_rels == NIL) |
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return; |
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AbortOutOfAnyTransaction(); |
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StartTransactionCommand(); |
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/*
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* Scan the list and delete all entries not already deleted. We need |
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* not worry about list entries getting deleted from under us, because |
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* remove_temp_rel_by_relid() doesn't remove entries, only mark them |
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* dead. Note that entries will be deleted in reverse order of |
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* creation --- that's critical for cases involving inheritance. |
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*/ |
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foreach(l, temp_rels) |
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{ |
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TempTable *temp_rel = (TempTable *) lfirst(l); |
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if (temp_rel->deleted_in_cur_xact) |
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continue; /* ignore it if deleted already */ |
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if (temp_rel->relkind != RELKIND_INDEX) |
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heap_drop_with_catalog(temp_rel->relid, allowSystemTableMods); |
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else |
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index_drop(temp_rel->relid); |
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/* advance cmd counter to make catalog changes visible */ |
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CommandCounterIncrement(); |
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} |
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CommitTransactionCommand(); |
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} |
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/*
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* Clean up temprel mapping entries during transaction commit or abort. |
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* |
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* During commit, remove entries that were deleted during this transaction; |
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* during abort, remove those created during this transaction. |
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* |
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* We do not need to worry about removing the underlying physical relation; |
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* that's someone else's job. |
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*/ |
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void |
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AtEOXact_temp_relations(bool isCommit) |
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{ |
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List *l, |
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*prev; |
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prev = NIL; |
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l = temp_rels; |
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while (l != NIL) |
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{ |
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TempTable *temp_rel = (TempTable *) lfirst(l); |
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if (isCommit ? temp_rel->deleted_in_cur_xact : |
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temp_rel->created_in_cur_xact) |
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{ |
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/* This entry must be removed */ |
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if (prev != NIL) |
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{ |
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lnext(prev) = lnext(l); |
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pfree(l); |
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l = lnext(prev); |
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} |
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else |
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{ |
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temp_rels = lnext(l); |
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pfree(l); |
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l = temp_rels; |
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} |
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pfree(temp_rel); |
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} |
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else |
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{ |
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/* This entry must be preserved */ |
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temp_rel->created_in_cur_xact = false; |
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temp_rel->deleted_in_cur_xact = false; |
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prev = l; |
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l = lnext(l); |
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} |
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} |
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} |
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/*
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* Map user name to physical name --- returns NULL if no entry. |
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* |
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* This also supports testing whether a name is a temp table name; |
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* see is_temp_rel_name() macro. |
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*/ |
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char * |
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get_temp_rel_by_username(const char *user_relname) |
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{ |
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List *l; |
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foreach(l, temp_rels) |
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{ |
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TempTable *temp_rel = (TempTable *) lfirst(l); |
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if (temp_rel->deleted_in_cur_xact) |
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continue; /* ignore it if logically deleted */ |
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if (strcmp(NameStr(temp_rel->user_relname), user_relname) == 0) |
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return NameStr(temp_rel->relname); |
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} |
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return NULL; |
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} |
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/*
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* Map physical name to user name --- returns pstrdup'd input if no match. |
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*/ |
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char * |
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get_temp_rel_by_physicalname(const char *relname) |
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{ |
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List *l; |
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foreach(l, temp_rels) |
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{ |
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TempTable *temp_rel = (TempTable *) lfirst(l); |
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if (temp_rel->deleted_in_cur_xact) |
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continue; /* ignore it if logically deleted */ |
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if (strcmp(NameStr(temp_rel->relname), relname) == 0) |
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return NameStr(temp_rel->user_relname); |
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} |
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/* needed for bootstrapping temp tables */ |
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return pstrdup(relname); |
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} |
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@ -1,33 +0,0 @@ |
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/*-------------------------------------------------------------------------
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* |
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* temprel.h |
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* Temporary relation functions |
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* |
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* |
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* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group |
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* Portions Copyright (c) 1994, Regents of the University of California |
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* |
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* $Id: temprel.h,v 1.20 2001/11/05 17:46:36 momjian Exp $ |
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* |
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*------------------------------------------------------------------------- |
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*/ |
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#ifndef TEMPREL_H |
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#define TEMPREL_H |
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#include "access/htup.h" |
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extern void create_temp_relation(const char *relname, |
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HeapTuple pg_class_tuple); |
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extern void remove_temp_rel_by_relid(Oid relid); |
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extern bool rename_temp_relation(const char *oldname, |
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const char *newname); |
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extern void remove_all_temp_relations(void); |
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extern void AtEOXact_temp_relations(bool isCommit); |
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extern char *get_temp_rel_by_username(const char *user_relname); |
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extern char *get_temp_rel_by_physicalname(const char *relname); |
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#define is_temp_rel_name(relname) (get_temp_rel_by_username(relname) != NULL) |
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#endif /* TEMPREL_H */ |
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