Obtain required table lock during cross-table updates, redux.

Commits 8319e5cb5 et al missed the fact that ATPostAlterTypeCleanup
contains three calls to ATPostAlterTypeParse, and the other two
also need protection against passing a relid that we don't yet
have lock on.  Add similar logic to those code paths, and add
some test cases demonstrating the need for it.

In v18 and master, the test cases demonstrate that there's a
behavioral discrepancy between stored generated columns and virtual
generated columns: we disallow changing the expression of a stored
column if it's used in any composite-type columns, but not that of
a virtual column.  Since the expression isn't actually relevant to
either sort of composite-type usage, this prohibition seems
unnecessary; but changing it is a matter for separate discussion.
For now we are just documenting the existing behavior.

Reported-by: jian he <jian.universality@gmail.com>
Author: jian he <jian.universality@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: CACJufxGKJtGNRRSXfwMW9SqVOPEMdP17BJ7DsBf=tNsv9pWU9g@mail.gmail.com
Backpatch-through: 13

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 81ab12df60c3102312d7b300ac9a6a3960aa2ea9..fb64730a7e16a4875aa21d562322a1cc1dab3494 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -13926,6 +13926,14 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
                Oid                     relid;
 
                relid = IndexGetRelation(oldId, false);
+
+               /*
+                * As above, make sure we have lock on the index's table if it's not
+                * the same table.
+                */
+               if (relid != tab->relid)
+                       LockRelationOid(relid, AccessExclusiveLock);
+
                ATPostAlterTypeParse(oldId, relid, InvalidOid,
                                                         (char *) lfirst(def_item),
                                                         wqueue, lockmode, tab->rewrite);
@@ -13942,6 +13950,20 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
                Oid                     relid;
 
                relid = StatisticsGetRelation(oldId, false);
+
+               /*
+                * As above, make sure we have lock on the statistics object's table
+                * if it's not the same table.  However, we take
+                * ShareUpdateExclusiveLock here, aligning with the lock level used in
+                * CreateStatistics and RemoveStatisticsById.
+                *
+                * CAUTION: this should be done after all cases that grab
+                * AccessExclusiveLock, else we risk causing deadlock due to needing
+                * to promote our table lock.
+                */
+               if (relid != tab->relid)
+                       LockRelationOid(relid, ShareUpdateExclusiveLock);
+
                ATPostAlterTypeParse(oldId, relid, InvalidOid,
                                                         (char *) lfirst(def_item),
                                                         wqueue, lockmode, tab->rewrite);

diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 9d90d5505a87afaeb89e18f2cdec697d0e7dc0b9..7cebd50a673c27b857da73070f468667e87ef96a 100644 (file)
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -4620,6 +4620,14 @@ create table attbl(a int);
 create table atref(b attbl check ((b).a is not null));
 alter table attbl alter column a type numeric;  -- someday this should work
 ERROR:  cannot alter table "attbl" because column "atref.b" uses its row type
+alter table atref drop constraint atref_b_check;
+create statistics atref_stat on ((b).a is not null) from atref;
+alter table attbl alter column a type numeric;  -- someday this should work
+ERROR:  cannot alter table "attbl" because column "atref.b" uses its row type
+drop statistics atref_stat;
+create index atref_idx on atref (((b).a));
+alter table attbl alter column a type numeric;  -- someday this should work
+ERROR:  cannot alter table "attbl" because column "atref.b" uses its row type
 drop table attbl, atref;
 /* End test case for bug #18970 */
 -- Test that ALTER TABLE rewrite preserves a clustered index

diff --git a/src/test/regress/expected/generated.out b/src/test/regress/expected/generated.out
index a1f67abb688cf7dc320a73d95ba0e20cd296f741..f7c867e054c147ca98f187d52601ede07eb64ac3 100644 (file)
--- a/src/test/regress/expected/generated.out
+++ b/src/test/regress/expected/generated.out
@@ -1190,6 +1190,30 @@ Inherits: gtest30
 
 ALTER TABLE gtest30_1 ALTER COLUMN b DROP EXPRESSION;  -- error
 ERROR:  cannot drop generation expression from inherited column
+-- composite type dependencies
+CREATE TABLE gtest31_1 (a int, b text GENERATED ALWAYS AS ('hello') STORED, c text);
+CREATE TABLE gtest31_2 (x int, y gtest31_1);
+ALTER TABLE gtest31_1 ALTER COLUMN b TYPE varchar;  -- fails
+ERROR:  cannot alter table "gtest31_1" because column "gtest31_2.y" uses its row type
+-- bug #18970: these cases are unsupported, but make sure they fail cleanly
+ALTER TABLE gtest31_2 ADD CONSTRAINT cc CHECK ((y).b IS NOT NULL);
+ALTER TABLE gtest31_1 ALTER COLUMN b SET EXPRESSION AS ('hello1');
+ERROR:  cannot alter table "gtest31_1" because column "gtest31_2.y" uses its row type
+ALTER TABLE gtest31_2 DROP CONSTRAINT cc;
+CREATE STATISTICS gtest31_2_stat ON ((y).b is not null) FROM gtest31_2;
+ALTER TABLE gtest31_1 ALTER COLUMN b SET EXPRESSION AS ('hello2');
+ERROR:  cannot alter table "gtest31_1" because column "gtest31_2.y" uses its row type
+DROP STATISTICS gtest31_2_stat;
+CREATE INDEX gtest31_2_y_idx ON gtest31_2(((y).b));
+ALTER TABLE gtest31_1 ALTER COLUMN b SET EXPRESSION AS ('hello3');
+ERROR:  cannot alter table "gtest31_1" because column "gtest31_2.y" uses its row type
+DROP TABLE gtest31_1, gtest31_2;
+-- Check it for a partitioned table, too
+CREATE TABLE gtest31_1 (a int, b text GENERATED ALWAYS AS ('hello') STORED, c text) PARTITION BY LIST (a);
+CREATE TABLE gtest31_2 (x int, y gtest31_1);
+ALTER TABLE gtest31_1 ALTER COLUMN b TYPE varchar;  -- fails
+ERROR:  cannot alter table "gtest31_1" because column "gtest31_2.y" uses its row type
+DROP TABLE gtest31_1, gtest31_2;
 -- triggers
 CREATE TABLE gtest26 (
     a int PRIMARY KEY,

diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index df08e93b70fe097d952b996d3b4c68a3b44a8b48..16ed0782fa173576e5ad5076b7bd487f9545a0f9 100644 (file)
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -3032,6 +3032,14 @@ drop table attbl, atref;
 create table attbl(a int);
 create table atref(b attbl check ((b).a is not null));
 alter table attbl alter column a type numeric;  -- someday this should work
+alter table atref drop constraint atref_b_check;
+
+create statistics atref_stat on ((b).a is not null) from atref;
+alter table attbl alter column a type numeric;  -- someday this should work
+drop statistics atref_stat;
+
+create index atref_idx on atref (((b).a));
+alter table attbl alter column a type numeric;  -- someday this should work
 drop table attbl, atref;
 
 /* End test case for bug #18970 */

diff --git a/src/test/regress/sql/generated.sql b/src/test/regress/sql/generated.sql
index ba59325da87ee44a971d7720dc3cf27e15bc4392..2816ac4a74ab44450c1ed91ff1187f775262cafb 100644 (file)
--- a/src/test/regress/sql/generated.sql
+++ b/src/test/regress/sql/generated.sql
@@ -550,6 +550,31 @@ ALTER TABLE ONLY gtest30 ALTER COLUMN b DROP EXPRESSION;  -- error
 \d gtest30_1
 ALTER TABLE gtest30_1 ALTER COLUMN b DROP EXPRESSION;  -- error
 
+-- composite type dependencies
+CREATE TABLE gtest31_1 (a int, b text GENERATED ALWAYS AS ('hello') STORED, c text);
+CREATE TABLE gtest31_2 (x int, y gtest31_1);
+ALTER TABLE gtest31_1 ALTER COLUMN b TYPE varchar;  -- fails
+
+-- bug #18970: these cases are unsupported, but make sure they fail cleanly
+ALTER TABLE gtest31_2 ADD CONSTRAINT cc CHECK ((y).b IS NOT NULL);
+ALTER TABLE gtest31_1 ALTER COLUMN b SET EXPRESSION AS ('hello1');
+ALTER TABLE gtest31_2 DROP CONSTRAINT cc;
+
+CREATE STATISTICS gtest31_2_stat ON ((y).b is not null) FROM gtest31_2;
+ALTER TABLE gtest31_1 ALTER COLUMN b SET EXPRESSION AS ('hello2');
+DROP STATISTICS gtest31_2_stat;
+
+CREATE INDEX gtest31_2_y_idx ON gtest31_2(((y).b));
+ALTER TABLE gtest31_1 ALTER COLUMN b SET EXPRESSION AS ('hello3');
+
+DROP TABLE gtest31_1, gtest31_2;
+
+-- Check it for a partitioned table, too
+CREATE TABLE gtest31_1 (a int, b text GENERATED ALWAYS AS ('hello') STORED, c text) PARTITION BY LIST (a);
+CREATE TABLE gtest31_2 (x int, y gtest31_1);
+ALTER TABLE gtest31_1 ALTER COLUMN b TYPE varchar;  -- fails
+DROP TABLE gtest31_1, gtest31_2;
+
 -- triggers
 CREATE TABLE gtest26 (
     a int PRIMARY KEY,