feat(clickhouse): table unnest

ibis/backends/clickhouse/compiler.py

@@ -640,3 +640,58 @@ def visit_RandomUUID(self, op, **kwargs):
     @staticmethod
     def _generate_groups(groups):
         return groups
+
+    def visit_TableUnnest(
+        self, op, *, parent, column, offset: str | None, keep_empty: bool
+    ):
+        quoted = self.quoted
+
+        # tmpname = sg.to_identifier(util.gen_name("table_unnest"), quoted=quoted)
+        column_alias = sg.to_identifier(
+            util.gen_name("table_unnest_column"), quoted=quoted
+        )
+
+        expression = column
+
+        replace = sge.Column(
+            this=sge.Star(replace=[column_alias.as_(op.column.name)]),
+            table=column.args["table"],
+        )
+
+        if offset is not None:
+            offset = sg.to_identifier(offset, quoted=quoted)
+            expression = self.f.arrayZip(
+                expression, self.f.range(self.f.len(expression))
+            )
+            replace = sge.Column(
+                this=sge.Star(
+                    replace=[
+                        sge.Dot(this=column_alias, expression=sge.Var(this="1")).as_(
+                            op.column.name, quoted=quoted
+                        )
+                    ]
+                ),
+                table=column.args["table"],
+            )
+            expr = sg.select(
+                replace,
+                sge.Dot(this=column_alias, expression=sge.Var(this="2")).as_(offset),
+            )
+        else:
+            replace = sge.Column(
+                this=sge.Star(
+                    replace=[column_alias.as_(op.column.name, quoted=quoted)]
+                ),
+                table=column.args["table"],
+            )
+            expr = sg.select(replace)
+
+        # unnest = sge.Unnest(expressions=[expression], alias=alias)
+        res = expr.from_(parent).join(
+            sge.Join(
+                this=expression.as_(column_alias),
+                kind="ARRAY",
+                side=None if not keep_empty else "LEFT",
+            )
+        )
+        return res