Optimise CSV data store. (#1334)

pdr_backend/lake/csv_data_store.py

@@ -3,7 +3,7 @@
 # SPDX-License-Identifier: Apache-2.0
 #
 import os
-from typing import Optional, Union
+from typing import Dict, Optional, Union
 
 import polars as pl
 from enforce_typing import enforce_types
@@ -168,15 +168,34 @@ def _get_folder_path(self) -> str:
 
         return folder_path
 
-    def get_file_paths(self, do_sort=True) -> list:
+    def get_file_paths(self, sort_by="alpha", filter_by: Optional[Dict] = None) -> list:
         """
         Returns the file paths for the given table name (key).
         """
         folder_path = self._get_folder_path()
         file_names = os.listdir(folder_path)
 
-        if do_sort:
+        if sort_by == "alpha":
             file_names = sorted(file_names)
+        elif sort_by == "none":
+            pass
+
+        if filter_by:
+            filtered_file_names = []
+
+            for file_name in file_names:
+                from_val = _get_from_value(file_name)
+                to_val = _get_to_value(file_name)
+
+                if to_val is not None and to_val < filter_by["from"]:
+                    continue
+
+                if from_val > filter_by["to"]:
+                    continue
+
+                filtered_file_names.append(file_name)
+
+            file_names = filtered_file_names
 
         return [os.path.join(folder_path, file_name) for file_name in file_names]
 
@@ -187,7 +206,7 @@ def has_data(self) -> bool:
         @returns:
             bool - True if the csv files have data
         """
-        file_paths = self.get_file_paths(do_sort=False)
+        file_paths = self.get_file_paths(sort_by="none")
 
         # check if the csv file has more than 0 bytes
         return any(os.path.getsize(file_path) > 0 for file_path in file_paths)
@@ -252,14 +271,16 @@ def _append_remaining_rows(
 
         return data.slice(remaining_rows, len(data) - remaining_rows)
 
-    def read_all(self, schema: Optional[SchemaDict] = None) -> pl.DataFrame:
+    def read_all(
+        self, schema: Optional[SchemaDict] = None, filters: Optional[Dict] = None
+    ) -> pl.DataFrame:
         """
         Reads all the data from the csv files in the folder
         corresponding to the given table name (key).
         @returns:
             pl.DataFrame - data read from the csv files
         """
-        file_paths = self.get_file_paths()
+        file_paths = self.get_file_paths(filter_by=filters)
 
         if not file_paths:
             return pl.DataFrame([], schema=schema)
@@ -289,7 +310,9 @@ def read(
         @returns:
             pl.DataFrame - data read from the csv file
         """
-        data = self.read_all(schema=schema)
+        data = self.read_all(
+            schema=schema, filters={"from": start_time, "to": end_time}
+        )
         # if the data is empty, return
         if len(data) == 0:
             return data