From 6073b0ed81ffbe56b49423b8a9f206bdd0eebe09 Mon Sep 17 00:00:00 2001
From: Rafi Shamim <rafi@cockroachlabs.com>
Date: Sat, 25 Feb 2023 00:18:49 -0500
Subject: [PATCH] pg_catalog: handle temp tables in lookup joins

The included test previously would have failed with
an error like `unknown schema "[151]"`. In Postgres, temporary tables
from other sessions are visible in pg_catalog, so we match that
behavior.

Release note (bug fix): Fixed an error that could occur when querying a
pg_catalog table that included information about a temporary table
created in another session.
---
 .../logictest/testdata/logic_test/temp_table  | 24 +++++++++++++++++++
 pkg/sql/pg_catalog.go                         | 23 +++++++++++++++---
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/pkg/sql/logictest/testdata/logic_test/temp_table b/pkg/sql/logictest/testdata/logic_test/temp_table
index 762d099916d8..774a51dc44a6 100644
--- a/pkg/sql/logictest/testdata/logic_test/temp_table
+++ b/pkg/sql/logictest/testdata/logic_test/temp_table
@@ -397,3 +397,27 @@ SELECT * FROM pg_temp.t
 statement ok
 USE defaultdb;
 DROP DATABASE to_drop CASCADE;
+
+subtest end
+
+subtest temp_table_in_other_session
+
+user testuser
+
+statement ok
+USE defaultdb;
+CREATE TEMPORARY TABLE from_other_session(i INT PRIMARY KEY)
+
+user root
+
+statement ok
+USE defaultdb
+
+query TT
+SELECT c.relname, a.attname FROM pg_attribute a
+INNER LOOKUP JOIN pg_class c ON c.oid = a.attrelid
+WHERE c.relname = 'from_other_session'
+----
+from_other_session  i
+
+subtest end
diff --git a/pkg/sql/pg_catalog.go b/pkg/sql/pg_catalog.go
index a91c755c5b5d..96d644d67269 100644
--- a/pkg/sql/pg_catalog.go
+++ b/pkg/sql/pg_catalog.go
@@ -1142,9 +1142,26 @@ func makeAllRelationsVirtualTableWithDescriptorIDIndex(
 					}
 					h := makeOidHasher()
 					scResolver := oneAtATimeSchemaResolver{p: p, ctx: ctx}
-					sc, err := p.Descriptors().ByIDWithLeased(p.txn).WithoutNonPublic().Get().Schema(ctx, table.GetParentSchemaID())
-					if err != nil {
-						return false, err
+					var sc catalog.SchemaDescriptor
+					if table.IsTemporary() {
+						// Temp tables from other sessions should still be visible here.
+						// Ideally, the catalog API would be able to return the temporary
+						// schemas from other sessions, but it cannot right now. See
+						// https://github.com/cockroachdb/cockroach/issues/97822.
+						if err := forEachSchema(ctx, p, db, false /* requiresPrivileges*/, func(schema catalog.SchemaDescriptor) error {
+							if schema.GetID() == table.GetParentSchemaID() {
+								sc = schema
+							}
+							return nil
+						}); err != nil {
+							return false, err
+						}
+					}
+					if sc == nil {
+						sc, err = p.Descriptors().ByIDWithLeased(p.txn).WithoutNonPublic().Get().Schema(ctx, table.GetParentSchemaID())
+						if err != nil {
+							return false, err
+						}
 					}
 					if err := populateFromTable(ctx, p, h, db, sc, table, scResolver,
 						addRow); err != nil {