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Commit10bad8c

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Repair bogus handling of multi-assignment Params in upper plan levels.
Our support for multiple-set-clauses in UPDATE assumes that the Paramsreferencing a MULTIEXPR_SUBLINK SubPlan will appear before that SubPlanin the targetlist of the plan node that calculates the updated row.(Yeah, it's a hack...) In some PG branches it's possible that a Resultnode gets inserted between the primary calculation of the update tlistand the ModifyTable node. setrefs.c did the wrong thing in this caseand left the upper-level Params as Params, causing a crash at runtime.What it should do is replace them with "outer" Vars referencing the childplan node's output. That's a result of careless ordering of operationsin fix_upper_expr_mutator, so we can fix it just by reordering the code.Fix fix_join_expr_mutator similarly for consistency, even though joinnodes could never appear in such a context. (In general, it seemslikely to be a bit cheaper to use Vars than Params in such situationsanyway, so this patch might offer a tiny performance improvement.)The hazard extends back to 9.5 where the MULTIEXPR_SUBLINK stuffwas introduced, so back-patch that far. However, this may be a livebug only in 9.6.x and 10.x, as the other branches don't seem to wantto calculate the final tlist below the Result node. (That plan shapechange between branches might be a mini-bug in itself, but I'm notreally interested in digging into the reasons for that right now.Still, add a regression test memorializing what we expect there,so we'll notice if it changes again.)Per bug report from Eduards Bezverhijs.Discussion:https://postgr.es/m/b6cd572a-3e44-8785-75e9-c512a5a17a73@tieto.com
1 parentd2267b6 commit10bad8c

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3 files changed

+54
-11
lines changed

3 files changed

+54
-11
lines changed

‎src/backend/optimizer/plan/setrefs.c

Lines changed: 13 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -2210,8 +2210,6 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
22102210
/* If not supplied by input plans, evaluate the contained expr */
22112211
returnfix_join_expr_mutator((Node*)phv->phexpr,context);
22122212
}
2213-
if (IsA(node,Param))
2214-
returnfix_param_node(context->root, (Param*)node);
22152213
/* Try matching more complex expressions too, if tlists have any */
22162214
if (context->outer_itlist&&context->outer_itlist->has_non_vars)
22172215
{
@@ -2229,6 +2227,9 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
22292227
if (newvar)
22302228
return (Node*)newvar;
22312229
}
2230+
/* Special cases (apply only AFTER failing to match to lower tlist) */
2231+
if (IsA(node,Param))
2232+
returnfix_param_node(context->root, (Param*)node);
22322233
fix_expr_common(context->root,node);
22332234
returnexpression_tree_mutator(node,
22342235
fix_join_expr_mutator,
@@ -2316,6 +2317,16 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
23162317
/* If not supplied by input plan, evaluate the contained expr */
23172318
returnfix_upper_expr_mutator((Node*)phv->phexpr,context);
23182319
}
2320+
/* Try matching more complex expressions too, if tlist has any */
2321+
if (context->subplan_itlist->has_non_vars)
2322+
{
2323+
newvar=search_indexed_tlist_for_non_var(node,
2324+
context->subplan_itlist,
2325+
context->newvarno);
2326+
if (newvar)
2327+
return (Node*)newvar;
2328+
}
2329+
/* Special cases (apply only AFTER failing to match to lower tlist) */
23192330
if (IsA(node,Param))
23202331
returnfix_param_node(context->root, (Param*)node);
23212332
if (IsA(node,Aggref))
@@ -2340,15 +2351,6 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
23402351
}
23412352
/* If no match, just fall through to process it normally */
23422353
}
2343-
/* Try matching more complex expressions too, if tlist has any */
2344-
if (context->subplan_itlist->has_non_vars)
2345-
{
2346-
newvar=search_indexed_tlist_for_non_var(node,
2347-
context->subplan_itlist,
2348-
context->newvarno);
2349-
if (newvar)
2350-
return (Node*)newvar;
2351-
}
23522354
fix_expr_common(context->root,node);
23532355
returnexpression_tree_mutator(node,
23542356
fix_upper_expr_mutator,

‎src/test/regress/expected/update.out

Lines changed: 31 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -169,6 +169,37 @@ SELECT a, b, char_length(c) FROM update_test;
169169
42 | 12 | 10000
170170
(4 rows)
171171

172+
-- Check multi-assignment with a Result node to handle a one-time filter.
173+
EXPLAIN (VERBOSE, COSTS OFF)
174+
UPDATE update_test t
175+
SET (a, b) = (SELECT b, a FROM update_test s WHERE s.a = t.a)
176+
WHERE CURRENT_USER = SESSION_USER;
177+
QUERY PLAN
178+
------------------------------------------------------------------------
179+
Update on public.update_test t
180+
-> Result
181+
Output: ($1), ($2), t.c, ((SubPlan 1 (returns $1,$2))), t.ctid
182+
One-Time Filter: ("current_user"() = "session_user"())
183+
-> Seq Scan on public.update_test t
184+
Output: $1, $2, t.c, (SubPlan 1 (returns $1,$2)), t.ctid
185+
SubPlan 1 (returns $1,$2)
186+
-> Seq Scan on public.update_test s
187+
Output: s.b, s.a
188+
Filter: (s.a = t.a)
189+
(10 rows)
190+
191+
UPDATE update_test t
192+
SET (a, b) = (SELECT b, a FROM update_test s WHERE s.a = t.a)
193+
WHERE CURRENT_USER = SESSION_USER;
194+
SELECT a, b, char_length(c) FROM update_test;
195+
a | b | char_length
196+
-----+----+-------------
197+
101 | 21 |
198+
| |
199+
12 | 41 | 10000
200+
12 | 42 | 10000
201+
(4 rows)
202+
172203
-- Test ON CONFLICT DO UPDATE
173204
INSERT INTO upsert_test VALUES(1, 'Boo');
174205
-- uncorrelated sub-select:

‎src/test/regress/sql/update.sql

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -88,6 +88,16 @@ UPDATE update_test AS t SET b = update_test.b + 10 WHERE t.a = 10;
8888
UPDATE update_testSET c= repeat('x',10000)WHERE c='car';
8989
SELECT a, b, char_length(c)FROM update_test;
9090

91+
-- Check multi-assignment with a Result node to handle a one-time filter.
92+
EXPLAIN (VERBOSE, COSTS OFF)
93+
UPDATE update_test t
94+
SET (a, b)= (SELECT b, aFROM update_test sWHEREs.a=t.a)
95+
WHERECURRENT_USER=SESSION_USER;
96+
UPDATE update_test t
97+
SET (a, b)= (SELECT b, aFROM update_test sWHEREs.a=t.a)
98+
WHERECURRENT_USER=SESSION_USER;
99+
SELECT a, b, char_length(c)FROM update_test;
100+
91101
-- Test ON CONFLICT DO UPDATE
92102
INSERT INTO upsert_testVALUES(1,'Boo');
93103
-- uncorrelated sub-select:

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