Thread: BUG #18502: Upsert on view returns 42P10 error when condition is an expression

The following bug has been logged on the website:

Bug reference:      18502
Logged by:          Michael Wang
Email address:      michael.wanghai.a@outlook.com
PostgreSQL version: 12.5
Operating system:   Official docker Image run in MacOS 14.3
Description:

I have a table, index and view like following:
```
CREATE TABLE my_table
(
    id   uuid primary key,
    data jsonb not null
);
CREATE UNIQUE INDEX ON my_table ((data ->> 'key'));
CREATE VIEW my_view AS SELECT * FROM my_table;
```
The upsert on view returns 42P10 error when I execute the following SQL
```
INSERT INTO my_view (id, data)
VALUES ('990cc75c-2e60-4c0d-8bec-9ac976dc03bc'::uuid,
        '{
          "key": "value"
        }'::jsonb)
ON CONFLICT ((data ->> 'key'))
    DO NOTHING;
```
I tested cast expression and fails as well
```
CREATE UNIQUE INDEX ON my_table ((id::text));
INSERT INTO my_view (id, data)
VALUES ('990cc75c-2e60-4c0d-8bec-9ac976dc03bc'::uuid,
        '{
          "key": "value"
        }'::jsonb)
ON CONFLICT ((id::text))
    DO NOTHING;
```
I also tested `DO UPDATE...`, the same error is returned.
I also tested with the latest official docker image witch is PG 16, same
error returns.

PG Bug reporting form <noreply@postgresql.org> writes:
> I have a table, index and view like following:
> ```
> CREATE TABLE my_table
> (
>     id   uuid primary key,
>     data jsonb not null
> );
> CREATE UNIQUE INDEX ON my_table ((data ->> 'key'));
> CREATE VIEW my_view AS SELECT * FROM my_table;
> ```
> The upsert on view returns 42P10 error when I execute the following SQL
> ```
> INSERT INTO my_view (id, data)
> VALUES ('990cc75c-2e60-4c0d-8bec-9ac976dc03bc'::uuid,
>         '{
>           "key": "value"
>         }'::jsonb)
> ON CONFLICT ((data ->> 'key'))
>     DO NOTHING;
> ```

For the archives' sake: the error being complained of is

ERROR:  there is no unique or exclusion constraint matching the ON CONFLICT specification

Thanks for the report.  The fault lies with infer_arbiter_indexes(),
which assumes that it can match the output of
RelationGetIndexExpressions or RelationGetIndexPredicate
directly to the query without adjusting varnos.  That works
most of the time, because the INSERT target typically has
varno 1, matching the way these trees are stored in the catalogs.
But not so much when we've flattened an updatable view;
so the match fails even when it should succeed.

The attached seems to be enough to fix it.

            regards, tom lane

diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index a51fc34e6e..775955363e 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -695,6 +695,7 @@ infer_arbiter_indexes(PlannerInfo *root)
     OnConflictExpr *onconflict = root->parse->onConflict;

     /* Iteration state */
+    Index        varno;
     RangeTblEntry *rte;
     Relation    relation;
     Oid            indexOidFromConstraint = InvalidOid;
@@ -723,7 +724,8 @@ infer_arbiter_indexes(PlannerInfo *root)
      * the rewriter or when expand_inherited_rtentry() added it to the query's
      * rangetable.
      */
-    rte = rt_fetch(root->parse->resultRelation, root->parse->rtable);
+    varno = root->parse->resultRelation;
+    rte = rt_fetch(varno, root->parse->rtable);

     relation = table_open(rte->relid, NoLock);

@@ -857,6 +859,9 @@ infer_arbiter_indexes(PlannerInfo *root)

         /* Expression attributes (if any) must match */
         idxExprs = RelationGetIndexExpressions(idxRel);
+        if (idxExprs && varno != 1)
+            ChangeVarNodes((Node *) idxExprs, 1, varno, 0);
+
         foreach(el, onconflict->arbiterElems)
         {
             InferenceElem *elem = (InferenceElem *) lfirst(el);
@@ -908,6 +913,8 @@ infer_arbiter_indexes(PlannerInfo *root)
          * CONFLICT's WHERE clause.
          */
         predExprs = RelationGetIndexPredicate(idxRel);
+        if (predExprs && varno != 1)
+            ChangeVarNodes((Node *) predExprs, 1, varno, 0);

         if (!predicate_implied_by(predExprs, (List *) onconflict->arbiterWhere, false))
             goto next;
diff --git a/src/test/regress/expected/insert_conflict.out b/src/test/regress/expected/insert_conflict.out
index 701217ddbc..5cb9cde030 100644
--- a/src/test/regress/expected/insert_conflict.out
+++ b/src/test/regress/expected/insert_conflict.out
@@ -2,6 +2,8 @@
 -- insert...on conflict do unique index inference
 --
 create table insertconflicttest(key int4, fruit text);
+-- These things should work through a view, as well
+create view insertconflictview as select * from insertconflicttest;
 --
 -- Test unique index inference with operator class specifications and
 -- named collations
@@ -43,6 +45,15 @@ explain (costs off) insert into insertconflicttest values(0, 'Crowberry') on con
    ->  Result
 (4 rows)

+explain (costs off) insert into insertconflictview values(0, 'Crowberry') on conflict (lower(fruit), key,
lower(fruit),key) do nothing; 
+                   QUERY PLAN
+-------------------------------------------------
+ Insert on insertconflicttest
+   Conflict Resolution: NOTHING
+   Conflict Arbiter Indexes: both_index_expr_key
+   ->  Result
+(4 rows)
+
 explain (costs off) insert into insertconflicttest values(0, 'Crowberry') on conflict (key, fruit) do update set fruit
=excluded.fruit 
   where exists (select 1 from insertconflicttest ii where ii.key = excluded.key);
                                   QUERY PLAN
@@ -380,6 +391,7 @@ create unique index partial_key_index on insertconflicttest(key) where fruit lik
 -- Succeeds
 insert into insertconflicttest values (23, 'Blackberry') on conflict (key) where fruit like '%berry' do update set
fruit= excluded.fruit; 
 insert into insertconflicttest as t values (23, 'Blackberry') on conflict (key) where fruit like '%berry' and t.fruit
='inconsequential' do nothing; 
+insert into insertconflictview as t values (23, 'Blackberry') on conflict (key) where fruit like '%berry' and t.fruit
='inconsequential' do nothing; 
 -- fails
 insert into insertconflicttest values (23, 'Blackberry') on conflict (key) do update set fruit = excluded.fruit;
 ERROR:  there is no unique or exclusion constraint matching the ON CONFLICT specification
@@ -445,6 +457,7 @@ explain (costs off) insert into insertconflicttest as i values (23, 'Avocado') o

 drop index plain;
 -- Cleanup
+drop view insertconflictview;
 drop table insertconflicttest;
 --
 -- Verify that EXCLUDED does not allow system column references. These
diff --git a/src/test/regress/sql/insert_conflict.sql b/src/test/regress/sql/insert_conflict.sql
index 653f9baf98..549c46452e 100644
--- a/src/test/regress/sql/insert_conflict.sql
+++ b/src/test/regress/sql/insert_conflict.sql
@@ -3,6 +3,9 @@
 --
 create table insertconflicttest(key int4, fruit text);

+-- These things should work through a view, as well
+create view insertconflictview as select * from insertconflicttest;
+
 --
 -- Test unique index inference with operator class specifications and
 -- named collations
@@ -20,6 +23,7 @@ explain (costs off) insert into insertconflicttest values(0, 'Crowberry') on con
 explain (costs off) insert into insertconflicttest values(0, 'Crowberry') on conflict (key, fruit) do nothing;
 explain (costs off) insert into insertconflicttest values(0, 'Crowberry') on conflict (fruit, key, fruit, key) do
nothing;
 explain (costs off) insert into insertconflicttest values(0, 'Crowberry') on conflict (lower(fruit), key,
lower(fruit),key) do nothing; 
+explain (costs off) insert into insertconflictview values(0, 'Crowberry') on conflict (lower(fruit), key,
lower(fruit),key) do nothing; 
 explain (costs off) insert into insertconflicttest values(0, 'Crowberry') on conflict (key, fruit) do update set fruit
=excluded.fruit 
   where exists (select 1 from insertconflicttest ii where ii.key = excluded.key);
 -- Neither collation nor operator class specifications are required --
@@ -218,6 +222,7 @@ create unique index partial_key_index on insertconflicttest(key) where fruit lik
 -- Succeeds
 insert into insertconflicttest values (23, 'Blackberry') on conflict (key) where fruit like '%berry' do update set
fruit= excluded.fruit; 
 insert into insertconflicttest as t values (23, 'Blackberry') on conflict (key) where fruit like '%berry' and t.fruit
='inconsequential' do nothing; 
+insert into insertconflictview as t values (23, 'Blackberry') on conflict (key) where fruit like '%berry' and t.fruit
='inconsequential' do nothing; 

 -- fails
 insert into insertconflicttest values (23, 'Blackberry') on conflict (key) do update set fruit = excluded.fruit;
@@ -250,6 +255,7 @@ explain (costs off) insert into insertconflicttest as i values (23, 'Avocado') o
 drop index plain;

 -- Cleanup
+drop view insertconflictview;
 drop table insertconflicttest;