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Fix usage of "tableoid" in GENERATED expressions.

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We consider this supported (though I've got my doubts that it's a
good idea, because tableoid is not immutable).  However, several
code paths failed to fill the field in soon enough, causing such
a GENERATED expression to see zero or the wrong value.  This
occurred when ALTER TABLE adds a new GENERATED column to a table
with existing rows, and during regular INSERT or UPDATE on a
foreign table with GENERATED columns.

Noted during investigation of a report from Vitaly Ustinov.
Back-patch to v12 where GENERATED came in.

Discussion: https://postgr.es/m/CAM_DEiWR2DPT6U4xb-Ehigozzd3n3G37ZB1+867zbsEVtYoJww@mail.gmail.com
This commit is contained in:
Tom Lane 2021-05-21 15:02:07 -04:00
parent d18ee6f92d
commit 77e3204ecb
4 changed files with 38 additions and 17 deletions
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13
src/backend/commands/tablecmds.c
View File

@ -5373,6 +5373,14 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
foreach(lc, dropped_attrs)
newslot->tts_isnull[lfirst_int(lc)] = true;
/*
* Constraints and GENERATED expressions might reference the
* tableoid column, so fill tts_tableOid with the desired
* value. (We must do this each time, because it gets
* overwritten with newrel's OID during storing.)
*/
newslot->tts_tableOid = RelationGetRelid(oldrel);
/*
* Process supplied expressions to replace selected columns.
*
@ -5416,11 +5424,6 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
&newslot->tts_isnull[ex->attnum - 1]);
}
/*
* Constraints might reference the tableoid column, so
* initialize t_tableOid before evaluating them.
*/
newslot->tts_tableOid = RelationGetRelid(oldrel);
insertslot = newslot;
}
else

24
src/backend/executor/nodeModifyTable.c
View File

@ -437,6 +437,12 @@ ExecInsert(ModifyTableState *mtstate,
}
else if (resultRelInfo->ri_FdwRoutine)
{
/*
* GENERATED expressions might reference the tableoid column, so
* (re-)initialize tts_tableOid before evaluating them.
*/
slot->tts_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
/*
* Compute stored generated columns
*/
@ -458,7 +464,7 @@ ExecInsert(ModifyTableState *mtstate,
/*
* AFTER ROW Triggers or RETURNING expressions might reference the
* tableoid column, so (re-)initialize tts_tableOid before evaluating
* them.
* them. (This covers the case where the FDW replaced the slot.)
*/
slot->tts_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
}
@ -467,8 +473,8 @@ ExecInsert(ModifyTableState *mtstate,
WCOKind wco_kind;
/*
* Constraints might reference the tableoid column, so (re-)initialize
* tts_tableOid before evaluating them.
* Constraints and GENERATED expressions might reference the tableoid
* column, so (re-)initialize tts_tableOid before evaluating them.
*/
slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
@ -1172,6 +1178,12 @@ ExecUpdate(ModifyTableState *mtstate,
}
else if (resultRelInfo->ri_FdwRoutine)
{
/*
* GENERATED expressions might reference the tableoid column, so
* (re-)initialize tts_tableOid before evaluating them.
*/
slot->tts_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
/*
* Compute stored generated columns
*/
@ -1193,7 +1205,7 @@ ExecUpdate(ModifyTableState *mtstate,
/*
* AFTER ROW Triggers or RETURNING expressions might reference the
* tableoid column, so (re-)initialize tts_tableOid before evaluating
* them.
* them. (This covers the case where the FDW replaced the slot.)
*/
slot->tts_tableOid = RelationGetRelid(resultRelationDesc);
}
@ -1204,8 +1216,8 @@ ExecUpdate(ModifyTableState *mtstate,
bool update_indexes;
/*
* Constraints might reference the tableoid column, so (re-)initialize
* tts_tableOid before evaluating them.
* Constraints and GENERATED expressions might reference the tableoid
* column, so (re-)initialize tts_tableOid before evaluating them.
*/
slot->tts_tableOid = RelationGetRelid(resultRelationDesc);

13
src/test/regress/expected/generated.out
View File

@ -64,6 +64,7 @@ ERROR: both identity and generation expression specified for column "b" of tabl
LINE 1: ...t PRIMARY KEY, b int GENERATED ALWAYS AS identity GENERATED ...
^
-- reference to system column not allowed in generated column
-- (except tableoid, which we test below)
CREATE TABLE gtest_err_6a (a int PRIMARY KEY, b bool GENERATED ALWAYS AS (xmin <> 37) STORED);
ERROR: cannot use system column "xmin" in column generation expression
LINE 1: ...a (a int PRIMARY KEY, b bool GENERATED ALWAYS AS (xmin <> 37...
@ -414,14 +415,16 @@ DROP TYPE double_int;
-- using tableoid is allowed
CREATE TABLE gtest_tableoid (
a int PRIMARY KEY,
b bool GENERATED ALWAYS AS (tableoid <> 0) STORED
b bool GENERATED ALWAYS AS (tableoid = 'gtest_tableoid'::regclass) STORED
);
INSERT INTO gtest_tableoid VALUES (1), (2);
ALTER TABLE gtest_tableoid ADD COLUMN
c regclass GENERATED ALWAYS AS (tableoid) STORED;
SELECT * FROM gtest_tableoid;
a | b
---+---
1 | t
2 | t
a | b | c
---+---+----------------
1 | t | gtest_tableoid
2 | t | gtest_tableoid
(2 rows)
-- drop column behavior

5
src/test/regress/sql/generated.sql
View File

@ -29,6 +29,7 @@ CREATE TABLE gtest_err_5a (a int PRIMARY KEY, b int DEFAULT 5 GENERATED ALWAYS A
CREATE TABLE gtest_err_5b (a int PRIMARY KEY, b int GENERATED ALWAYS AS identity GENERATED ALWAYS AS (a * 2) STORED);
-- reference to system column not allowed in generated column
-- (except tableoid, which we test below)
CREATE TABLE gtest_err_6a (a int PRIMARY KEY, b bool GENERATED ALWAYS AS (xmin <> 37) STORED);
-- various prohibited constructs
@ -201,9 +202,11 @@ DROP TYPE double_int;
-- using tableoid is allowed
CREATE TABLE gtest_tableoid (
a int PRIMARY KEY,
b bool GENERATED ALWAYS AS (tableoid <> 0) STORED
b bool GENERATED ALWAYS AS (tableoid = 'gtest_tableoid'::regclass) STORED
);
INSERT INTO gtest_tableoid VALUES (1), (2);
ALTER TABLE gtest_tableoid ADD COLUMN
c regclass GENERATED ALWAYS AS (tableoid) STORED;
SELECT * FROM gtest_tableoid;
-- drop column behavior