From 1c22862929ec5da65156f18bc037307cf843e8f7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kriszti=C3=A1n=20Sz=C5=B1cs?= <szucs.krisztian@gmail.com>
Date: Tue, 12 Dec 2023 14:46:51 +0100
Subject: [PATCH] e

---
 ibis/expr/tests/test_newrels.py | 15 +++++++++++++++
 ibis/expr/types/joins.py        |  2 +-
 ibis/expr/types/relations.py    | 20 ++++++++++++++------
 3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/ibis/expr/tests/test_newrels.py b/ibis/expr/tests/test_newrels.py
index 2f427796bdfb5..7b32e71fa5276 100644
--- a/ibis/expr/tests/test_newrels.py
+++ b/ibis/expr/tests/test_newrels.py
@@ -968,3 +968,18 @@ def test_self_join_view():
         values={"x": t.x, "y": t.y, "z": t.z, "z_right": t_view.z},
     )
     assert expr.op() == expected
+
+
+def test_self_join_with_view_projection():
+    t1 = ibis.memtable({"x": [1, 2], "y": [2, 1], "z": ["a", "b"]})
+    t2 = t1.view()
+    expr = t1.inner_join(t2, ["x"])[[t1]]
+
+    expected = ops.JoinChain(
+        first=t1,
+        rest=[
+            ops.JoinLink("inner", t2, [t1.x == t2.x]),
+        ],
+        values={"x": t1.x, "y": t1.y, "z": t1.z},
+    )
+    assert expr.op() == expected
diff --git a/ibis/expr/types/joins.py b/ibis/expr/types/joins.py
index 53171ac3eb216..30b7e8471577b 100644
--- a/ibis/expr/types/joins.py
+++ b/ibis/expr/types/joins.py
@@ -140,7 +140,7 @@ def select(self, *args, **kwargs):
         # so far, we need to replace them the fields from one of the join links
         tables = list(self._relations())
         extra = {ops.Field(self, k): v for k, v in self.op().fields.items()}
-        values = dereference_values(tables, values, extra=extra)
+        values = dereference_values(tables, values, extra=extra, include_top=True)
 
         return self.finish(values)
 
diff --git a/ibis/expr/types/relations.py b/ibis/expr/types/relations.py
index 5827fd9efebb2..5dccb9b639286 100644
--- a/ibis/expr/types/relations.py
+++ b/ibis/expr/types/relations.py
@@ -152,24 +152,27 @@ def unwrap_aliases(values: Iterator[ir.Value]) -> Mapping[str, ir.Value]:
     return result
 
 
-def dereference_mapping(parents, extra=None):
+def dereference_mapping(parents, extra=None, include_top=False):
     """Generate substitution mapping."""
     mapping = extra.copy() if extra is not None else {}
     for parent in util.promote_list(parents):
+        if include_top:
+            for k in parent.schema:
+                mapping[ops.Field(parent, k)] = ops.Field(parent, k)
         for k, v in parent.fields.items():
             if isinstance(v, ops.Field):
-                while isinstance(v, ops.Field):
+                while isinstance(v, ops.Field) and v not in mapping:
                     mapping[v] = ops.Field(parent, k)
                     v = v.rel.fields.get(v.name)
-            elif v.relations:
+            elif v.relations and v not in mapping:
                 # do not dereference literal expressions
                 mapping[v] = ops.Field(parent, k)
     return mapping
 
 
-def dereference_values(parents, values, extra=None):
+def dereference_values(parents, values, extra=None, include_top=False):
     """Trace and replace fields from earlier relations in the hierarchy."""
-    mapping = dereference_mapping(parents, extra=extra)
+    mapping = dereference_mapping(parents, extra=extra, include_top=include_top)
     return {k: v.replace(mapping, filter=ops.Value) for k, v in values.items()}
 
 
@@ -2960,8 +2963,13 @@ def join(
         """
         from ibis.expr.types.joins import JoinExpr
 
+        # the first participant of the join shouldn't be a self reference
+        left = left.op()
+        if isinstance(left, ops.SelfReference):
+            left = left.parent
+
         # construct an empty join chain and wrap it with a JoinExpr
-        values = {k: ops.Field(left, k) for k in left.schema().names}
+        values = {k: ops.Field(left, k) for k in left.schema}
         node = ops.JoinChain(left, rest=(), values=values)
         # add the first join link to the join chain and return the result
         if how == "left_semi":