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Here is my much-promised patch to let people add UNIQUE constraints after

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table creation time.  Big deal you say - but this patch is the basis of the
next thing which is adding PRIMARY KEYs after table creation time.  (Which
is currently impossible without twiddling catalogs)

Rundown
-------

* I have made the makeObjectName function of analyze.c non-static, and
exported it in analyze.h

* I have included analyze.h and defrem.h into command.c, to support
makingObjectNames and creating indices

* I removed the 'case CONSTR_PRIMARY' clause so that it properly fails and
says you can't add primary keys, rather than just doing nothing and
reporting nothing!!!

* I have modified the docs.

Algorithm
---------

* If name specified is null, search for a new valid constraint name.  I'm
not sure if I should "lock" my generated name somehow tho - should I open
the relation before doing this step?

* Open relation in access exclusive mode

* Check that the constraint does not already exist

* Define the new index

* Warn if they're doubling up on an existing index

Christopher Kings-Lynne
This commit is contained in:
Bruce Momjian 2001-09-07 21:57:53 +00:00
parent 68e190cfa4
commit bd9b32803b
4 changed files with 172 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
doc/src/sgml/ref/alter_table.sgml
View File

@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.26 2001/09/03 12:57:49 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.27 2001/09/07 21:57:53 momjian Exp $
Postgres documentation
-->
@ -211,9 +211,9 @@ ALTER TABLE <replaceable class="PARAMETER">table</replaceable>
</para>
<para>
In the current implementation, only FOREIGN KEY and CHECK constraints can
be added to a table. To create a unique constraint, create
a unique index (see <xref linkend="SQL-CREATEINDEX"
In the current implementation, only UNIQUE, FOREIGN KEY and CHECK constraints can
be added to a table. To create a primary constraint, create
a unique, not null index (see <xref linkend="SQL-CREATEINDEX"
endterm="SQL-CREATEINDEX-title">).
</para>
@ -297,6 +297,13 @@ ALTER TABLE distributors DROP CONSTRAINT zipchk
ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses(address) MATCH FULL
</programlisting>
</para>
<para>
To add a (multi-column) unique constraint to a table:
<programlisting>
ALTER TABLE distributors ADD CONSTRAINT dist_id_zipcode_key UNIQUE (dist_id, zipcode)
</programlisting>
</para>
</refsect1>
<refsect1 id="R1-SQL-ALTERTABLE-3">

159
src/backend/commands/command.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.141 2001/08/21 16:36:01 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.142 2001/09/07 21:57:53 momjian Exp $
*
* NOTES
* The PerformAddAttribute() code, like most of the relation
@ -32,6 +32,7 @@
#include "catalog/pg_type.h"
#include "commands/command.h"
#include "commands/trigger.h"
#include "commands/defrem.h" /* For add constraint unique, primary */
#include "executor/execdefs.h"
#include "executor/executor.h"
#include "miscadmin.h"
@ -42,6 +43,7 @@
#include "parser/parse_expr.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/analyze.h" /* For add constraint unique, primary */
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
@ -1339,11 +1341,160 @@ AlterTableAddConstraint(char *relationName,
break;
}
case CONSTR_PRIMARY:
case CONSTR_UNIQUE:
{
char *iname = constr->name;
bool istemp = is_temp_rel_name(relationName);
Relation rel;
List *indexoidlist;
List *indexoidscan;
Form_pg_attribute *rel_attrs;
int num_keys = 0;
int keys_matched = 0;
bool index_found = false;
bool index_found_unique = false;
bool index_found_primary = false;
break;
}
/* If the constraint name is not specified, generate a name */
if (iname == NULL) {
Oid indoid;
int pass = 0;
char *typename = palloc(NAMEDATALEN);
Ident *key;
/* Assume that the length of the attr list is already > 0 */
/* Get the first attribute so we can use its name */
key = (Ident *)lfirst(constr->keys);
/* Initialise typename to 'key' */
snprintf(typename, NAMEDATALEN, "key");
for (;;)
{
iname = makeObjectName(relationName, key->name, typename);
/* Check for a conflict */
indoid = RelnameFindRelid(iname);
/* If the oid was not found, then we have a safe name */
if ((!istemp && !OidIsValid(indoid)) ||
(istemp && !is_temp_rel_name(iname)))
break;
/* Found a conflict, so try a new name component */
pfree(iname);
snprintf(typename, NAMEDATALEN, "key%d", ++pass);
}
}
/* Need to check for unique key already on field(s) */
rel = heap_openr(relationName, AccessExclusiveLock);
/*
* First we check for limited correctness of the
* constraint
*/
rel_attrs = rel->rd_att->attrs;
/* Retrieve the oids of all indices on the relation */
indexoidlist = RelationGetIndexList(rel);
index_found = false;
index_found_unique = false;
index_found_primary = false;
/* Loop over all indices on the relation */
foreach(indexoidscan, indexoidlist)
{
Oid indexoid = lfirsti(indexoidscan);
HeapTuple indexTuple;
Form_pg_index indexStruct;
List *keyl;
int i;
indexTuple = SearchSysCache(INDEXRELID,
ObjectIdGetDatum(indexoid),
0, 0, 0);
if (!HeapTupleIsValid(indexTuple))
elog(ERROR, "ALTER TABLE/ADD CONSTRAINT: Index \"%u\" not found",
indexoid);
indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);
/*
* Make sure this index has the same number of
* keys as the constraint -- It obviously won't match otherwise.
*/
for (i = 0; i < INDEX_MAX_KEYS && indexStruct->indkey[i] != 0; i++);
num_keys = length(constr->keys);
keys_matched = 0;
if (i == num_keys)
{
/* Loop over each key in the constraint and check that there is a
corresponding key in the index. */
i = 0;
foreach(keyl, constr->keys)
{
Ident *key = lfirst(keyl);
/* Look at key[i] in the index and check that it is over the same column
as key[i] in the constraint. This is to differentiate between (a,b)
and (b,a) */
if (i < INDEX_MAX_KEYS && indexStruct->indkey[i] != 0)
{
int keyno = indexStruct->indkey[i];
if (keyno > 0)
{
char *name = NameStr(rel_attrs[keyno - 1]->attname);
if (strcmp(name, key->name) == 0) keys_matched++;
}
}
else elog(ERROR, "ALTER TABLE/ADD CONSTRAINT: Key \"%u[%u]\" not found", indexoid, i);
i++;
}
if (keys_matched == num_keys) {
index_found = true;
index_found_unique = indexStruct->indisunique;
index_found_primary = indexStruct->indisprimary;
if (index_found_unique || index_found_primary) break;
}
}
ReleaseSysCache(indexTuple);
}
freeList(indexoidlist);
if (index_found_primary)
elog(ERROR, "Unique primary key already defined on relation \"%s\"", relationName);
else if (index_found_unique)
elog(ERROR, "Unique constraint already defined on the specified attributes in relation \"%s\"", relationName);
/* If everything is ok, create the new index (constraint) */
DefineIndex(
relationName,
iname,
"btree",
constr->keys,
true,
false,
NULL,
NIL);
/* Issue notice */
elog(NOTICE, "ALTER TABLE/ADD UNIQUE will create implicit index '%s' for table '%s'",
iname, relationName);
if (index_found)
elog(NOTICE, "Unique constraint supercedes existing index on relation \"%s\". Drop the existing index to remove redundancy.", relationName);
pfree(iname);
/* Finally, close relation */
heap_close(rel, NoLock);
break;
}
default:
elog(ERROR, "ALTER TABLE / ADD CONSTRAINT is not implemented for that constraint type.");
}

4
src/backend/parser/analyze.c
View File

@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.197 2001/08/24 20:03:45 petere Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.198 2001/09/07 21:57:53 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -562,7 +562,7 @@ transformInsertStmt(ParseState *pstate, InsertStmt *stmt)
* from the truncated characters. Currently it seems best to keep it simple,
* so that the generated names are easily predictable by a person.
*/
static char *
char *
makeObjectName(char *name1, char *name2, char *typename)
{
char *name;

5
src/include/parser/analyze.h
View File

@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: analyze.h,v 1.14 2001/01/24 19:43:26 momjian Exp $
* $Id: analyze.h,v 1.15 2001/09/07 21:57:53 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -19,4 +19,7 @@ extern List *parse_analyze(Node *parseTree, ParseState *parentParseState);
extern void CheckSelectForUpdate(Query *qry);
/* This was exported to allow ADD CONSTRAINT to make use of it */
extern char *makeObjectName(char *name1, char *name2, char *typename);
#endif /* ANALYZE_H */