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Commit9f1a223

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committed
Make renaming a temp table behave sensibly. We don't need to touch
the underlying table at all, just change the mapping entry ... butthat logic was missing.
1 parent38db5fa commit9f1a223

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3 files changed

+130
-33
lines changed

3 files changed

+130
-33
lines changed

‎src/backend/commands/rename.c‎

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/commands/Attic/rename.c,v 1.45 2000/05/25 21:30:20 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/commands/Attic/rename.c,v 1.46 2000/06/20 06:41:13 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -29,6 +29,7 @@
2929
#include"utils/acl.h"
3030
#include"utils/relcache.h"
3131
#include"utils/syscache.h"
32+
#include"utils/temprel.h"
3233

3334

3435
/*
@@ -199,6 +200,13 @@ renamerel(const char *oldrelname, const char *newrelname)
199200
elog(ERROR,"renamerel: Illegal class name: \"%s\" -- pg_ is reserved for system catalogs",
200201
newrelname);
201202

203+
/*
204+
* Check for renaming a temp table, which only requires altering
205+
* the temp-table mapping, not the physical table.
206+
*/
207+
if (rename_temp_relation(oldrelname,newrelname))
208+
return;/* all done... */
209+
202210
/*
203211
* Instead of using heap_openr(), do it the hard way, so that we
204212
* can rename indexes as well as regular relations.

‎src/backend/utils/cache/temprel.c‎

Lines changed: 109 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -8,22 +8,29 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/utils/cache/Attic/temprel.c,v 1.23 2000/05/30 00:49:54 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/utils/cache/Attic/temprel.c,v 1.24 2000/06/20 06:41:12 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
1515

1616
/*
1717
* This implements temp tables by modifying the relname cache lookups
1818
* of pg_class.
19-
* When a temp table is created, a linked list of temp table tuples is
20-
* stored here. When a relname cache lookup is done, references to user-named
21-
* temp tables are converted to the internal temp table names.
19+
*
20+
* When a temp table is created, normal entries are made for it in pg_class,
21+
* pg_type, etc using a unique "physical" relation name. We also make an
22+
* entry in the temp table list maintained by this module. Subsequently,
23+
* relname lookups are filtered through the temp table list, and attempts
24+
* to look up a temp table name are changed to look up the physical name.
25+
* This allows temp table names to mask a regular table of the same name
26+
* for the duration of the session. The temp table list is also used
27+
* to drop the underlying physical relations at session shutdown.
2228
*/
2329

2430
#include<sys/types.h>
2531

2632
#include"postgres.h"
33+
2734
#include"catalog/heap.h"
2835
#include"catalog/index.h"
2936
#include"utils/catcache.h"
@@ -39,39 +46,47 @@ static List *temp_rels = NIL;
3946

4047
typedefstructTempTable
4148
{
42-
char*user_relname;
43-
char*relname;
44-
Oidrelid;
49+
char*user_relname;/* logical name of temp table */
50+
char*relname;/* underlying unique name */
51+
Oidrelid;/* needed properties of rel */
4552
charrelkind;
46-
TransactionIdxid;
53+
TransactionIdxid;/* xact in which temp tab was created */
4754
}TempTable;
4855

4956

57+
/*
58+
* Create a temp-relation list entry given the logical temp table name
59+
* and the already-created pg_class tuple for the underlying relation.
60+
*
61+
* NB: we assume a check has already been made for a duplicate logical name.
62+
*/
5063
void
5164
create_temp_relation(constchar*relname,HeapTuplepg_class_tuple)
5265
{
66+
Form_pg_classpg_class_form= (Form_pg_class)GETSTRUCT(pg_class_tuple);
5367
MemoryContextoldcxt;
5468
TempTable*temp_rel;
5569

5670
oldcxt=MemoryContextSwitchTo((MemoryContext)CacheCxt);
5771

58-
temp_rel=palloc(sizeof(TempTable));
59-
temp_rel->user_relname=palloc(NAMEDATALEN);
60-
temp_rel->relname=palloc(NAMEDATALEN);
72+
temp_rel=(TempTable*)palloc(sizeof(TempTable));
73+
temp_rel->user_relname=(char*)palloc(NAMEDATALEN);
74+
temp_rel->relname=(char*)palloc(NAMEDATALEN);
6175

62-
/* save user-supplied name */
63-
strcpy(temp_rel->user_relname,relname);
64-
StrNCpy(temp_rel->relname,NameStr(((Form_pg_class)
65-
GETSTRUCT(pg_class_tuple))->relname),NAMEDATALEN);
76+
StrNCpy(temp_rel->user_relname,relname,NAMEDATALEN);
77+
StrNCpy(temp_rel->relname,NameStr(pg_class_form->relname),NAMEDATALEN);
6678
temp_rel->relid=pg_class_tuple->t_data->t_oid;
67-
temp_rel->relkind=((Form_pg_class)GETSTRUCT(pg_class_tuple))->relkind;
79+
temp_rel->relkind=pg_class_form->relkind;
6880
temp_rel->xid=GetCurrentTransactionId();
6981

7082
temp_rels=lcons(temp_rel,temp_rels);
7183

7284
MemoryContextSwitchTo(oldcxt);
7385
}
7486

87+
/*
88+
* Remove underlying relations for all temp rels at backend shutdown.
89+
*/
7590
void
7691
remove_all_temp_relations(void)
7792
{
@@ -87,7 +102,7 @@ remove_all_temp_relations(void)
87102
l=temp_rels;
88103
while (l!=NIL)
89104
{
90-
TempTable*temp_rel=lfirst(l);
105+
TempTable*temp_rel=(TempTable*)lfirst(l);
91106

92107
next=lnext(l);/* do this first, l is deallocated */
93108

@@ -108,11 +123,14 @@ remove_all_temp_relations(void)
108123
CommitTransactionCommand();
109124
}
110125

111-
/* we don't have the relname for indexes, so we just pass the oid */
126+
/*
127+
* Remove a temp relation map entry (part of DROP TABLE on a temp table)
128+
*
129+
* we don't have the relname for indexes, so we just pass the oid
130+
*/
112131
void
113132
remove_temp_relation(Oidrelid)
114133
{
115-
116134
MemoryContextoldcxt;
117135
List*l,
118136
*prev;
@@ -123,7 +141,7 @@ remove_temp_relation(Oid relid)
123141
l=temp_rels;
124142
while (l!=NIL)
125143
{
126-
TempTable*temp_rel=lfirst(l);
144+
TempTable*temp_rel=(TempTable*)lfirst(l);
127145

128146
if (temp_rel->relid==relid)
129147
{
@@ -154,7 +172,12 @@ remove_temp_relation(Oid relid)
154172
MemoryContextSwitchTo(oldcxt);
155173
}
156174

157-
/* remove entries from aborted transactions */
175+
/*
176+
* Remove freshly-created map entries during transaction abort.
177+
*
178+
* The underlying physical rel will be removed by normal abort processing.
179+
* We just have to delete the map entry.
180+
*/
158181
void
159182
invalidate_temp_relations(void)
160183
{
@@ -168,7 +191,7 @@ invalidate_temp_relations(void)
168191
l=temp_rels;
169192
while (l!=NIL)
170193
{
171-
TempTable*temp_rel=lfirst(l);
194+
TempTable*temp_rel=(TempTable*)lfirst(l);
172195

173196
if (temp_rel->xid==GetCurrentTransactionId())
174197
{
@@ -194,35 +217,96 @@ invalidate_temp_relations(void)
194217
prev=l;
195218
l=lnext(l);
196219
}
197-
198220
}
199221

200222
MemoryContextSwitchTo(oldcxt);
201223
}
202224

225+
/*
226+
* To implement ALTER TABLE RENAME on a temp table, we shouldn't touch
227+
* the underlying physical table at all, just change the map entry!
228+
*
229+
* This routine is invoked early in ALTER TABLE RENAME to check for
230+
* the temp-table case. If oldname matches a temp table name, change
231+
* the map entry to the new logical name and return TRUE (or elog if
232+
* there is a conflict with another temp table name). If there is
233+
* no match, return FALSE indicating that normal rename should proceed.
234+
*
235+
* We also reject an attempt to rename a normal table to a name in use
236+
* as a temp table name. That would fail later on anyway when rename.c
237+
* looks for a rename conflict, but we can give a more specific error
238+
* message for the problem here.
239+
*
240+
* It might seem that we need to check for attempts to rename the physical
241+
* file underlying a temp table, but that'll be rejected anyway because
242+
* pg_tempXXX looks like a system table name.
243+
*
244+
* A nitpicker might complain that the rename should be undone if the
245+
* current xact is later aborted, but I'm not going to fix that now.
246+
* This whole mapping mechanism ought to be replaced with something
247+
* schema-based, anyhow.
248+
*/
249+
bool
250+
rename_temp_relation(constchar*oldname,
251+
constchar*newname)
252+
{
253+
List*l;
254+
255+
foreach(l,temp_rels)
256+
{
257+
TempTable*temp_rel= (TempTable*)lfirst(l);
258+
259+
if (strcmp(temp_rel->user_relname,oldname)==0)
260+
{
261+
if (get_temp_rel_by_username(newname)!=NULL)
262+
elog(ERROR,"Cannot rename temp table \"%s\": temp table \"%s\" already exists",
263+
oldname,newname);
264+
/* user_relname was palloc'd NAMEDATALEN, so safe to re-use it */
265+
StrNCpy(temp_rel->user_relname,newname,NAMEDATALEN);
266+
return true;
267+
}
268+
}
269+
270+
/* Old name does not match any temp table name, what about new? */
271+
if (get_temp_rel_by_username(newname)!=NULL)
272+
elog(ERROR,"Cannot rename \"%s\" to \"%s\": a temp table by that name already exists",
273+
oldname,newname);
274+
275+
return false;
276+
}
277+
278+
279+
/*
280+
* Map user name to physical name --- returns NULL if no entry.
281+
*
282+
* This is the normal way to test whether a name is a temp table name.
283+
*/
203284
char*
204285
get_temp_rel_by_username(constchar*user_relname)
205286
{
206287
List*l;
207288

208289
foreach(l,temp_rels)
209290
{
210-
TempTable*temp_rel=lfirst(l);
291+
TempTable*temp_rel=(TempTable*)lfirst(l);
211292

212293
if (strcmp(temp_rel->user_relname,user_relname)==0)
213294
returntemp_rel->relname;
214295
}
215296
returnNULL;
216297
}
217298

299+
/*
300+
* Map physical name to user name --- returns pstrdup'd input if no match.
301+
*/
218302
char*
219303
get_temp_rel_by_physicalname(constchar*relname)
220304
{
221305
List*l;
222306

223307
foreach(l,temp_rels)
224308
{
225-
TempTable*temp_rel=lfirst(l);
309+
TempTable*temp_rel=(TempTable*)lfirst(l);
226310

227311
if (strcmp(temp_rel->relname,relname)==0)
228312
returntemp_rel->user_relname;

‎src/include/utils/temprel.h‎

Lines changed: 12 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $Id: temprel.h,v 1.9 2000/04/12 17:16:55 momjian Exp $
10+
* $Id: temprel.h,v 1.10 2000/06/20 06:41:11 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -16,11 +16,16 @@
1616

1717
#include"access/htup.h"
1818

19-
voidcreate_temp_relation(constchar*relname,HeapTuplepg_class_tuple);
20-
voidremove_all_temp_relations(void);
21-
voidinvalidate_temp_relations(void);
22-
voidremove_temp_relation(Oidrelid);
23-
char*get_temp_rel_by_username(constchar*user_relname);
24-
char*get_temp_rel_by_physicalname(constchar*relname);
19+
externvoidcreate_temp_relation(constchar*relname,
20+
HeapTuplepg_class_tuple);
21+
externvoidremove_temp_relation(Oidrelid);
22+
externboolrename_temp_relation(constchar*oldname,
23+
constchar*newname);
24+
25+
externvoidremove_all_temp_relations(void);
26+
externvoidinvalidate_temp_relations(void);
27+
28+
externchar*get_temp_rel_by_username(constchar*user_relname);
29+
externchar*get_temp_rel_by_physicalname(constchar*relname);
2530

2631
#endif/* TEMPREL_H */

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