refactor(polars): handle memtables like every other backend

ibis/backends/polars/__init__.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import weakref
 from collections.abc import Iterable, Mapping
 from functools import lru_cache
 from pathlib import Path
@@ -75,6 +76,16 @@ def table(self, name: str) -> ir.Table:
         schema = sch.infer(self._tables[name])
         return ops.DatabaseTable(name, schema, self).to_expr()
 
+    def _table_exists(self, name: str) -> bool:
+        return name in self._tables
+
+    def _register_in_memory_table(self, op: ops.InMemoryTable) -> None:
+        df = op.data.to_polars(op.schema).lazy()
+        self._add_table(op.name, df)
+
+    def _register_memtable_finalizer(self, op: ops.InMemoryTable) -> None:
+        weakref.finalize(op, self.drop_table, op.name)
+
     @deprecated(
         as_of="9.1",
         instead="use the explicit `read_*` method for the filetype you are trying to read, e.g., read_parquet, read_csv, etc.",
@@ -466,6 +477,7 @@ def _to_dataframe(
         streaming: bool = False,
         **kwargs: Any,
     ) -> pl.DataFrame:
+        self._run_pre_execute_hooks(expr)
         table_expr = expr.as_table()
         lf = self.compile(table_expr, params=params, **kwargs)
         if limit == "default":

ibis/backends/polars/compiler.py

@@ -9,11 +9,14 @@
 from math import isnan
 
 import polars as pl
+import sqlglot as sg
 
 import ibis.common.exceptions as com
 import ibis.expr.datatypes as dt
 import ibis.expr.operations as ops
 from ibis.backends.pandas.rewrites import PandasAsofJoin, PandasJoin, PandasRename
+from ibis.backends.sql.compilers.base import STAR
+from ibis.backends.sql.dialects import Polars
 from ibis.expr.operations.udf import InputType
 from ibis.formats.polars import PolarsType
 from ibis.util import gen_name
@@ -64,8 +67,9 @@ def dummy_table(op, **kw):
 
 
 @translate.register(ops.InMemoryTable)
-def in_memory_table(op, **_):
-    return op.data.to_polars(op.schema).lazy()
+def in_memory_table(op, *, ctx, **_):
+    sql = sg.select(STAR).from_(sg.to_identifier(op.name, quoted=True)).sql(Polars)
+    return ctx.execute(sql, eager=False)
 
 
 def _make_duration(value, dtype):