perf: skip unused callers JSON decode in ProfileStats

The callers BLOB column was fetched and JSON-decoded for every row
during FunctionRanker initialization, but the resulting data was
never accessed — FunctionRanker.load_function_stats() discards it
as `_callers`. This eliminates O(n) JSON parsing at ranking startup.

Also fixes all pre-existing mypy errors in this file by declaring
pstats.Stats attributes that the type stubs don't expose.

Author: KRRT7

codeflash/tracing/profile_stats.py

@@ -1,25 +1,44 @@
-import json
+from __future__ import annotations
+
 import pstats
 import sqlite3
 from copy import copy
 from pathlib import Path
+from typing import Any, TextIO
 
 from codeflash.cli_cmds.console import logger
 
 
 class ProfileStats(pstats.Stats):
+    # Attributes set by pstats.Stats.init() — stubs don't expose them
+    files: list[str]
+    stream: TextIO
+    top_level: set[tuple[str, int, str]]
+    total_calls: int
+    prim_calls: int
+    total_tt: float
+    max_name_len: int
+    fcn_list: list[tuple[str, int, str]] | None
+    sort_arg_dict: dict[str, tuple[Any, ...]]
+    all_callees: dict[tuple[str, int, str], dict[tuple[str, int, str], tuple[int, int, float, float]]] | None
+    stats: dict[tuple[str, int, str], tuple[int, int, int | float, int | float, dict[Any, Any]]]
+
     def __init__(self, trace_file_path: str, time_unit: str = "ns") -> None:
         assert Path(trace_file_path).is_file(), f"Trace file {trace_file_path} does not exist"
         assert time_unit in {"ns", "us", "ms", "s"}, f"Invalid time unit {time_unit}"
         self.trace_file_path = trace_file_path
         self.time_unit = time_unit
         logger.debug(hasattr(self, "create_stats"))
-        super().__init__(copy(self))
+        super().__init__(copy(self))  # type: ignore[arg-type]  # pstats uses duck-typed create_stats interface
 
     def create_stats(self) -> None:
         self.con = sqlite3.connect(self.trace_file_path)
         cur = self.con.cursor()
-        pdata = cur.execute("SELECT * FROM pstats").fetchall()
+        pdata = cur.execute(
+            "SELECT filename, line_number, function, class_name,"
+            " call_count_nonrecursive, num_callers, total_time_ns, cumulative_time_ns"
+            " FROM pstats"
+        ).fetchall()
         self.con.close()
         time_conversion_factor = {"ns": 1, "us": 1e3, "ms": 1e6, "s": 1e9}[self.time_unit]
         self.stats = {}
@@ -32,31 +51,18 @@ def create_stats(self) -> None:
             num_callers,
             total_time_ns,
             cumulative_time_ns,
-            callers,
         ) in pdata:
-            loaded_callers = json.loads(callers)
-            unmapped_callers = {}
-            for caller in loaded_callers:
-                caller_key = caller["key"]
-                if isinstance(caller_key, list):
-                    caller_key = tuple(caller_key)
-                elif not isinstance(caller_key, tuple):
-                    caller_key = (caller_key,) if not isinstance(caller_key, (list, tuple)) else tuple(caller_key)
-                unmapped_callers[caller_key] = caller["value"]
-
-            # Create function key with class name if present (matching tracer.py format)
             function_name = f"{class_name}.{function}" if class_name else function
 
             self.stats[(filename, line_number, function_name)] = (
                 call_count_nonrecursive,
                 num_callers,
                 total_time_ns / time_conversion_factor if time_conversion_factor != 1 else total_time_ns,
                 cumulative_time_ns / time_conversion_factor if time_conversion_factor != 1 else cumulative_time_ns,
-                unmapped_callers,
+                {},
             )
 
-    def print_stats(self, *amount) -> pstats.Stats:  # noqa: ANN002
-        # Copied from pstats.Stats.print_stats and modified to print the correct time unit
+    def print_stats(self, *amount: str | float) -> ProfileStats:
         for filename in self.files:
             print(filename, file=self.stream)
         if self.files:
@@ -74,8 +80,8 @@ def print_stats(self, *amount) -> pstats.Stats:  # noqa: ANN002
         _width, list_ = self.get_print_list(amount)
         if list_:
             self.print_title()
-            for func in list_:
-                self.print_line(func)
+            for fn in list_:
+                self.print_line(fn)
             print(file=self.stream)
             print(file=self.stream)
         return self