refactor(formats): turn TypeParser into a TypeMapper implementation for sqlglot

ibis/backends/base/sql/alchemy/__init__.py

@@ -553,7 +553,6 @@ def _handle_failed_column_type_inference(
         self, table: sa.Table, nulltype_cols: Iterable[str]
     ) -> sa.Table:
         """Handle cases where SQLAlchemy cannot infer the column types of `table`."""
-
         self.inspector.reflect_table(table, table.columns)
 
         dialect = self.con.dialect
@@ -565,15 +564,15 @@ def _handle_failed_column_type_inference(
             )
         )
 
-        for colname, type in self._metadata(quoted_name):
+        for colname, dtype in self._metadata(quoted_name):
             if colname in nulltype_cols:
                 # replace null types discovered by sqlalchemy with non null
                 # types
                 table.append_column(
                     sa.Column(
                         colname,
-                        self.compiler.translator_class.get_sqla_type(type),
-                        nullable=type.nullable,
+                        self.compiler.translator_class.get_sqla_type(dtype),
+                        nullable=dtype.nullable,
                         quote=self.compiler.translator_class._quote_column_names,
                     ),
                     replace_existing=True,
@@ -925,7 +924,7 @@ def _get_sqla_table(
         db = "".join(db) or database or current_db
         ident = ".".join(map(self._quote, filter(None, (db, schema))))
 
-        pairs = self._metadata(f"SELECT * FROM {ident}.{self._quote(name)}")
+        pairs = self._metadata(f"SELECT * FROM {ident}.{self._quote(name)} LIMIT 0")
         ibis_schema = ibis.schema(pairs)
 
         with self._use_schema(ident, current_db, current_schema):

ibis/backends/base/sql/alchemy/datatypes.py

@@ -9,6 +9,7 @@
 
 import ibis.expr.datatypes as dt
 from ibis.backends.base.sql.alchemy.geospatial import geospatial_supported
+from ibis.backends.base.sqlglot.datatypes import SqlglotType
 from ibis.common.collections import FrozenDict
 from ibis.formats import TypeMapper
 
@@ -225,6 +226,10 @@ def to_string(cls, dtype: dt.DataType):
             sa.types.to_instance(cls.from_ibis(dtype)).compile(dialect=dialect_class())
         )
 
+    @classmethod
+    def from_string(cls, type_string, nullable=True):
+        return SqlglotType.from_string(type_string, nullable=nullable)
+
     @classmethod
     def from_ibis(cls, dtype: dt.DataType) -> sat.TypeEngine:
         """Convert an Ibis type to a SQLAlchemy type.
@@ -279,7 +284,6 @@ def to_ibis(cls, typ: sat.TypeEngine, nullable: bool = True) -> dt.DataType:
         -------
         Ibis type.
         """
-
         if dtype := _from_sqlalchemy_types.get(type(typ)):
             return dtype(nullable=nullable)
         elif isinstance(typ, sat.Float):