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Commitcd07163

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Reject attempts to alter composite types used in indexes.
find_composite_type_dependencies() ignored indexes, which is a poordecision because an expression index could have a stored column ofa composite (or other container) type even when the underlying tabledoes not. Teach it to detect such cases and error out. We have towork a bit harder than for other relations because the pg_depend entrywon't identify the specific index column of concern, but it's not muchnew code.This does not address bug #17872's original complaint that droppinga column in such a type might lead to violations of the uniquenessproperty that a unique index is supposed to ensure. That seems ofmuch less concern to me because it won't lead to crashes.Per bug #17872 from Alexander Lakhin. Back-patch to all supportedbranches.Discussion:https://postgr.es/m/17872-d0fbb799dc3fd85d@postgresql.org
1 parentad5fe74 commitcd07163

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3 files changed

+68
-10
lines changed

3 files changed

+68
-10
lines changed

‎src/backend/commands/tablecmds.c

Lines changed: 49 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -5680,6 +5680,7 @@ find_composite_type_dependencies(Oid typeOid, Relation origRelation,
56805680
{
56815681
Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
56825682
Relationrel;
5683+
TupleDesctupleDesc;
56835684
Form_pg_attribute att;
56845685

56855686
/* Check for directly dependent types */
@@ -5696,18 +5697,58 @@ find_composite_type_dependencies(Oid typeOid, Relation origRelation,
56965697
continue;
56975698
}
56985699

5699-
/* Else, ignore dependees that aren't user columns of relations */
5700-
/* (we assume system columns are never of interesting types) */
5701-
if (pg_depend->classid != RelationRelationId ||
5702-
pg_depend->objsubid <= 0)
5700+
/* Else, ignore dependees that aren't relations */
5701+
if (pg_depend->classid != RelationRelationId)
57035702
continue;
57045703

57055704
rel = relation_open(pg_depend->objid, AccessShareLock);
5706-
att =TupleDescAttr(rel->rd_att, pg_depend->objsubid - 1);
5705+
tupleDesc =RelationGetDescr(rel);
57075706

5708-
if (rel->rd_rel->relkind == RELKIND_RELATION ||
5709-
rel->rd_rel->relkind == RELKIND_MATVIEW ||
5710-
rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
5707+
/*
5708+
* If objsubid identifies a specific column, refer to that in error
5709+
* messages. Otherwise, search to see if there's a user column of the
5710+
* type. (We assume system columns are never of interesting types.)
5711+
* The search is needed because an index containing an expression
5712+
* column of the target type will just be recorded as a whole-relation
5713+
* dependency. If we do not find a column of the type, the dependency
5714+
* must indicate that the type is transiently referenced in an index
5715+
* expression but not stored on disk, which we assume is OK, just as
5716+
* we do for references in views. (It could also be that the target
5717+
* type is embedded in some container type that is stored in an index
5718+
* column, but the previous recursion should catch such cases.)
5719+
*/
5720+
if (pg_depend->objsubid > 0 && pg_depend->objsubid <= tupleDesc->natts)
5721+
att = TupleDescAttr(tupleDesc, pg_depend->objsubid - 1);
5722+
else
5723+
{
5724+
att = NULL;
5725+
for (int attno = 1; attno <= tupleDesc->natts; attno++)
5726+
{
5727+
att = TupleDescAttr(tupleDesc, attno - 1);
5728+
if (att->atttypid == typeOid && !att->attisdropped)
5729+
break;
5730+
att = NULL;
5731+
}
5732+
if (att == NULL)
5733+
{
5734+
/* No such column, so assume OK */
5735+
relation_close(rel, AccessShareLock);
5736+
continue;
5737+
}
5738+
}
5739+
5740+
/*
5741+
* We definitely should reject if the relation has storage. If it's
5742+
* partitioned, then perhaps we don't have to reject: if there are
5743+
* partitions then we'll fail when we find one, else there is no
5744+
* stored data to worry about. However, it's possible that the type
5745+
* change would affect conclusions about whether the type is sortable
5746+
* or hashable and thus (if it's a partitioning column) break the
5747+
* partitioning rule. For now, reject for partitioned rels too.
5748+
*/
5749+
if (RELKIND_HAS_STORAGE(rel->rd_rel->relkind) ||
5750+
rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
5751+
rel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
57115752
{
57125753
if (origTypeName)
57135754
ereport(ERROR,

‎src/test/regress/expected/alter_table.out

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3082,6 +3082,13 @@ CREATE TYPE test_type1 AS (a int, b text);
30823082
CREATE TABLE test_tbl1 (x int, y test_type1);
30833083
ALTER TYPE test_type1 ALTER ATTRIBUTE b TYPE varchar; -- fails
30843084
ERROR: cannot alter type "test_type1" because column "test_tbl1.y" uses it
3085+
DROP TABLE test_tbl1;
3086+
CREATE TABLE test_tbl1 (x int, y text);
3087+
CREATE INDEX test_tbl1_idx ON test_tbl1((row(x,y)::test_type1));
3088+
ALTER TYPE test_type1 ALTER ATTRIBUTE b TYPE varchar; -- fails
3089+
ERROR: cannot alter type "test_type1" because column "test_tbl1_idx.row" uses it
3090+
DROP TABLE test_tbl1;
3091+
DROP TYPE test_type1;
30853092
CREATE TYPE test_type2 AS (a int, b text);
30863093
CREATE TABLE test_tbl2 OF test_type2;
30873094
CREATE TABLE test_tbl2_subclass () INHERITS (test_tbl2);
@@ -3193,7 +3200,8 @@ Typed table of type: test_type2
31933200
c | text | | |
31943201
Inherits: test_tbl2
31953202

3196-
DROP TABLE test_tbl2_subclass;
3203+
DROP TABLE test_tbl2_subclass, test_tbl2;
3204+
DROP TYPE test_type2;
31973205
CREATE TYPE test_typex AS (a int, b text);
31983206
CREATE TABLE test_tblx (x int, y test_typex check ((y).a > 0));
31993207
ALTER TYPE test_typex DROP ATTRIBUTE a; -- fails

‎src/test/regress/sql/alter_table.sql

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1971,6 +1971,14 @@ CREATE TYPE test_type1 AS (a int, b text);
19711971
CREATETABLEtest_tbl1 (xint, y test_type1);
19721972
ALTERTYPE test_type1 ALTER ATTRIBUTE b TYPEvarchar;-- fails
19731973

1974+
DROPTABLE test_tbl1;
1975+
CREATETABLEtest_tbl1 (xint, ytext);
1976+
CREATEINDEXtest_tbl1_idxON test_tbl1((row(x,y)::test_type1));
1977+
ALTERTYPE test_type1 ALTER ATTRIBUTE b TYPEvarchar;-- fails
1978+
1979+
DROPTABLE test_tbl1;
1980+
DROPTYPE test_type1;
1981+
19741982
CREATETYPEtest_type2AS (aint, btext);
19751983
CREATETABLEtest_tbl2 OF test_type2;
19761984
CREATETABLEtest_tbl2_subclass () INHERITS (test_tbl2);
@@ -1998,7 +2006,8 @@ ALTER TYPE test_type2 RENAME ATTRIBUTE a TO aa CASCADE;
19982006
\d test_tbl2
19992007
\d test_tbl2_subclass
20002008

2001-
DROPTABLE test_tbl2_subclass;
2009+
DROPTABLE test_tbl2_subclass, test_tbl2;
2010+
DROPTYPE test_type2;
20022011

20032012
CREATETYPEtest_typexAS (aint, btext);
20042013
CREATETABLEtest_tblx (xint, y test_typexcheck ((y).a>0));

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