perf(oracle): speed up existence check

ibis/backends/oracle/__init__.py

@@ -24,7 +24,7 @@
 from ibis import util
 from ibis.backends import CanListDatabase, CanListSchema
 from ibis.backends.sql import SQLBackend
-from ibis.backends.sql.compilers.base import STAR, C
+from ibis.backends.sql.compilers.base import NULL, STAR, C
 
 if TYPE_CHECKING:
     from urllib.parse import ParseResult
@@ -495,6 +495,21 @@ def drop_table(
 
         super().drop_table(name, database=(catalog, db), force=force)
 
+    def _in_memory_table_exists(self, name: str) -> bool:
+        sql = (
+            sg.select(NULL)
+            .from_(sg.to_identifier("USER_OBJECTS", quoted=self.compiler.quoted))
+            .where(
+                C.OBJECT_TYPE.eq(sge.convert("TABLE")),
+                C.OBJECT_NAME.eq(sge.convert(name)),
+            )
+            .limit(sge.convert(1))
+            .sql(self.dialect)
+        )
+        with self.begin() as cur:
+            results = cur.execute(sql).fetchall()
+        return bool(results)
+
     def _register_in_memory_table(self, op: ops.InMemoryTable) -> None:
         schema = op.schema