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Commitd90d59e

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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 parent7c48734 commitd90d59e

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3 files changed

+67
-10
lines changed

3 files changed

+67
-10
lines changed

‎src/backend/commands/tablecmds.c

Lines changed: 48 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -6475,6 +6475,7 @@ find_composite_type_dependencies(Oid typeOid, Relation origRelation,
64756475
{
64766476
Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
64776477
Relationrel;
6478+
TupleDesctupleDesc;
64786479
Form_pg_attribute att;
64796480

64806481
/* Check for directly dependent types */
@@ -6491,18 +6492,57 @@ find_composite_type_dependencies(Oid typeOid, Relation origRelation,
64916492
continue;
64926493
}
64936494

6494-
/* Else, ignore dependees that aren't user columns of relations */
6495-
/* (we assume system columns are never of interesting types) */
6496-
if (pg_depend->classid != RelationRelationId ||
6497-
pg_depend->objsubid <= 0)
6495+
/* Else, ignore dependees that aren't relations */
6496+
if (pg_depend->classid != RelationRelationId)
64986497
continue;
64996498

65006499
rel = relation_open(pg_depend->objid, AccessShareLock);
6501-
att =TupleDescAttr(rel->rd_att, pg_depend->objsubid - 1);
6500+
tupleDesc =RelationGetDescr(rel);
65026501

6503-
if (rel->rd_rel->relkind == RELKIND_RELATION ||
6504-
rel->rd_rel->relkind == RELKIND_MATVIEW ||
6505-
rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
6502+
/*
6503+
* If objsubid identifies a specific column, refer to that in error
6504+
* messages. Otherwise, search to see if there's a user column of the
6505+
* type. (We assume system columns are never of interesting types.)
6506+
* The search is needed because an index containing an expression
6507+
* column of the target type will just be recorded as a whole-relation
6508+
* dependency. If we do not find a column of the type, the dependency
6509+
* must indicate that the type is transiently referenced in an index
6510+
* expression but not stored on disk, which we assume is OK, just as
6511+
* we do for references in views. (It could also be that the target
6512+
* type is embedded in some container type that is stored in an index
6513+
* column, but the previous recursion should catch such cases.)
6514+
*/
6515+
if (pg_depend->objsubid > 0 && pg_depend->objsubid <= tupleDesc->natts)
6516+
att = TupleDescAttr(tupleDesc, pg_depend->objsubid - 1);
6517+
else
6518+
{
6519+
att = NULL;
6520+
for (int attno = 1; attno <= tupleDesc->natts; attno++)
6521+
{
6522+
att = TupleDescAttr(tupleDesc, attno - 1);
6523+
if (att->atttypid == typeOid && !att->attisdropped)
6524+
break;
6525+
att = NULL;
6526+
}
6527+
if (att == NULL)
6528+
{
6529+
/* No such column, so assume OK */
6530+
relation_close(rel, AccessShareLock);
6531+
continue;
6532+
}
6533+
}
6534+
6535+
/*
6536+
* We definitely should reject if the relation has storage. If it's
6537+
* partitioned, then perhaps we don't have to reject: if there are
6538+
* partitions then we'll fail when we find one, else there is no
6539+
* stored data to worry about. However, it's possible that the type
6540+
* change would affect conclusions about whether the type is sortable
6541+
* or hashable and thus (if it's a partitioning column) break the
6542+
* partitioning rule. For now, reject for partitioned rels too.
6543+
*/
6544+
if (RELKIND_HAS_STORAGE(rel->rd_rel->relkind) ||
6545+
RELKIND_HAS_PARTITIONS(rel->rd_rel->relkind))
65066546
{
65076547
if (origTypeName)
65086548
ereport(ERROR,

‎src/test/regress/expected/alter_table.out

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3093,6 +3093,13 @@ CREATE TYPE test_type1 AS (a int, b text);
30933093
CREATE TABLE test_tbl1 (x int, y test_type1);
30943094
ALTER TYPE test_type1 ALTER ATTRIBUTE b TYPE varchar; -- fails
30953095
ERROR: cannot alter type "test_type1" because column "test_tbl1.y" uses it
3096+
DROP TABLE test_tbl1;
3097+
CREATE TABLE test_tbl1 (x int, y text);
3098+
CREATE INDEX test_tbl1_idx ON test_tbl1((row(x,y)::test_type1));
3099+
ALTER TYPE test_type1 ALTER ATTRIBUTE b TYPE varchar; -- fails
3100+
ERROR: cannot alter type "test_type1" because column "test_tbl1_idx.row" uses it
3101+
DROP TABLE test_tbl1;
3102+
DROP TYPE test_type1;
30963103
CREATE TYPE test_type2 AS (a int, b text);
30973104
CREATE TABLE test_tbl2 OF test_type2;
30983105
CREATE TABLE test_tbl2_subclass () INHERITS (test_tbl2);
@@ -3204,7 +3211,8 @@ Typed table of type: test_type2
32043211
c | text | | |
32053212
Inherits: test_tbl2
32063213

3207-
DROP TABLE test_tbl2_subclass;
3214+
DROP TABLE test_tbl2_subclass, test_tbl2;
3215+
DROP TYPE test_type2;
32083216
CREATE TYPE test_typex AS (a int, b text);
32093217
CREATE TABLE test_tblx (x int, y test_typex check ((y).a > 0));
32103218
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
@@ -1980,6 +1980,14 @@ CREATE TYPE test_type1 AS (a int, b text);
19801980
CREATETABLEtest_tbl1 (xint, y test_type1);
19811981
ALTERTYPE test_type1 ALTER ATTRIBUTE b TYPEvarchar;-- fails
19821982

1983+
DROPTABLE test_tbl1;
1984+
CREATETABLEtest_tbl1 (xint, ytext);
1985+
CREATEINDEXtest_tbl1_idxON test_tbl1((row(x,y)::test_type1));
1986+
ALTERTYPE test_type1 ALTER ATTRIBUTE b TYPEvarchar;-- fails
1987+
1988+
DROPTABLE test_tbl1;
1989+
DROPTYPE test_type1;
1990+
19831991
CREATETYPEtest_type2AS (aint, btext);
19841992
CREATETABLEtest_tbl2 OF test_type2;
19851993
CREATETABLEtest_tbl2_subclass () INHERITS (test_tbl2);
@@ -2007,7 +2015,8 @@ ALTER TYPE test_type2 RENAME ATTRIBUTE a TO aa CASCADE;
20072015
\d test_tbl2
20082016
\d test_tbl2_subclass
20092017

2010-
DROPTABLE test_tbl2_subclass;
2018+
DROPTABLE test_tbl2_subclass, test_tbl2;
2019+
DROPTYPE test_type2;
20112020

20122021
CREATETYPEtest_typexAS (aint, btext);
20132022
CREATETABLEtest_tblx (xint, y test_typexcheck ((y).a>0));

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