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Commit4514322

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Disallow changing an inherited column's type if not all parents changed.
If a table inherits from multiple unrelated parents, we must disallowchanging the type of a column inherited from multiple such parents, elseit would be out of step with the other parents. However, it's possiblefor the column to ultimately be inherited from just one common ancestor,in which case a change starting from that ancestor should still beallowed. (I would not be excited about preserving that option, wereit not that we have regression test cases exercising it already ...)It's slightly annoying that this patch looks different from the logicwith the same end goal in renameatt(), and more annoying that itrequires an extra syscache lookup to make the test. However, therecursion logic is quite different in the two functions, and aback-patched bug fix is no place to be trying to unify them.Per report from Manuel Rigger. Back-patch to 9.5. The bug exists in9.4 too (and doubtless much further back); but the way the recursionis done in 9.4 is a good bit different, so that substantial refactoringwould be needed to fix it in 9.4. I'm disinclined to do that, or riskintroducing new bugs, for a bug that has escaped notice for this long.Discussion:https://postgr.es/m/CA+u7OA4qogDv9rz1HAb-ADxttXYPqQdUdPY_yd4kCzywNxRQXA@mail.gmail.com
1 parent6088696 commit4514322

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-6
lines changed

3 files changed

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lines changed

‎src/backend/commands/tablecmds.c

Lines changed: 39 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -8768,7 +8768,11 @@ ATPrepAlterColumnType(List **wqueue,
87688768
errmsg("cannot alter system column \"%s\"",
87698769
colName)));
87708770

8771-
/* Don't alter inherited columns */
8771+
/*
8772+
* Don't alter inherited columns. At outer level, there had better not be
8773+
* any inherited definition; when recursing, we assume this was checked at
8774+
* the parent level (see below).
8775+
*/
87728776
if (attTup->attinhcount>0&& !recursing)
87738777
ereport(ERROR,
87748778
(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
@@ -8892,20 +8896,26 @@ ATPrepAlterColumnType(List **wqueue,
88928896
if (recurse)
88938897
{
88948898
Oidrelid=RelationGetRelid(rel);
8895-
ListCell*child;
8896-
List*children;
8899+
List*child_oids,
8900+
*child_numparents;
8901+
ListCell*lo,
8902+
*li;
88978903

8898-
children=find_all_inheritors(relid,lockmode,NULL);
8904+
child_oids=find_all_inheritors(relid,lockmode,
8905+
&child_numparents);
88998906

89008907
/*
89018908
* find_all_inheritors does the recursive search of the inheritance
89028909
* hierarchy, so all we have to do is process all of the relids in the
89038910
* list that it returns.
89048911
*/
8905-
foreach(child,children)
8912+
forboth(lo,child_oids,li,child_numparents)
89068913
{
8907-
Oidchildrelid=lfirst_oid(child);
8914+
Oidchildrelid=lfirst_oid(lo);
8915+
intnumparents=lfirst_int(li);
89088916
Relationchildrel;
8917+
HeapTuplechildtuple;
8918+
Form_pg_attributechildattTup;
89098919

89108920
if (childrelid==relid)
89118921
continue;
@@ -8914,6 +8924,29 @@ ATPrepAlterColumnType(List **wqueue,
89148924
childrel=relation_open(childrelid,NoLock);
89158925
CheckTableNotInUse(childrel,"ALTER TABLE");
89168926

8927+
/*
8928+
* Verify that the child doesn't have any inherited definitions of
8929+
* this column that came from outside this inheritance hierarchy.
8930+
* (renameatt makes a similar test, though in a different way
8931+
* because of its different recursion mechanism.)
8932+
*/
8933+
childtuple=SearchSysCacheAttName(RelationGetRelid(childrel),
8934+
colName);
8935+
if (!HeapTupleIsValid(childtuple))
8936+
ereport(ERROR,
8937+
(errcode(ERRCODE_UNDEFINED_COLUMN),
8938+
errmsg("column \"%s\" of relation \"%s\" does not exist",
8939+
colName,RelationGetRelationName(childrel))));
8940+
childattTup= (Form_pg_attribute)GETSTRUCT(childtuple);
8941+
8942+
if (childattTup->attinhcount>numparents)
8943+
ereport(ERROR,
8944+
(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
8945+
errmsg("cannot alter inherited column \"%s\" of relation \"%s\"",
8946+
colName,RelationGetRelationName(childrel))));
8947+
8948+
ReleaseSysCache(childtuple);
8949+
89178950
/*
89188951
* Remap the attribute numbers. If no USING expression was
89198952
* specified, there is no need for this step.

‎src/test/regress/expected/inherit.out

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -701,6 +701,16 @@ select * from d;
701701
32 | one | two | three
702702
(1 row)
703703

704+
-- The above verified that we can change the type of a multiply-inherited
705+
-- column; but we should reject that if any definition was inherited from
706+
-- an unrelated parent.
707+
create temp table parent1(f1 int, f2 int);
708+
create temp table parent2(f1 int, f3 bigint);
709+
create temp table childtab(f4 int) inherits(parent1, parent2);
710+
NOTICE: merging multiple inherited definitions of column "f1"
711+
alter table parent1 alter column f1 type bigint; -- fail, conflict w/parent2
712+
ERROR: cannot alter inherited column "f1" of relation "childtab"
713+
alter table parent1 alter column f2 type bigint; -- ok
704714
-- check that oid column is handled properly during alter table inherit
705715
create table oid_parent (a int) with oids;
706716
create table oid_child () inherits (oid_parent);

‎src/test/regress/sql/inherit.sql

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -191,6 +191,15 @@ insert into d values('test','one','two','three');
191191
altertable a alter column aa typeinteger using bit_length(aa);
192192
select*from d;
193193

194+
-- The above verified that we can change the type of a multiply-inherited
195+
-- column; but we should reject that if any definition was inherited from
196+
-- an unrelated parent.
197+
create temp table parent1(f1int, f2int);
198+
create temp table parent2(f1int, f3bigint);
199+
create temp table childtab(f4int) inherits(parent1, parent2);
200+
altertable parent1 alter column f1 typebigint;-- fail, conflict w/parent2
201+
altertable parent1 alter column f2 typebigint;-- ok
202+
194203
-- check that oid column is handled properly during alter table inherit
195204
createtableoid_parent (aint) with oids;
196205

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