From 5dc811d32c40db7b527aea05c8f419c71444088a Mon Sep 17 00:00:00 2001
From: Joey Yang <friedcosey@meta.com>
Date: Mon, 10 Nov 2025 23:08:35 -0800
Subject: [PATCH] Look up and forward raw_ids from tracker to TBE from
 embedding module (#3527)

Summary:

We look up the identities corresponding to slot index from `raw_id_tracker` and forward it to TBE. The identities are stored in `raw_id_tracker` during `mc_module` lookup. `raw_ids` are retrieved per-table from `raw_id_tracker` with the api `get_indexed_lookup()`, we concatenat them to maintain 1-to-1 alignment with `features.values()`.

Reviewed By: chouxi

Differential Revision: D86242001
---
 .../distributed/batched_embedding_kernel.py   | 73 ++++++++++++++++++-
 1 file changed, 71 insertions(+), 2 deletions(-)

diff --git a/torchrec/distributed/batched_embedding_kernel.py b/torchrec/distributed/batched_embedding_kernel.py
index ddef4be14..b8f3bf17b 100644
--- a/torchrec/distributed/batched_embedding_kernel.py
+++ b/torchrec/distributed/batched_embedding_kernel.py
@@ -2605,7 +2605,71 @@ def init_parameters(self) -> None:
                     weight_init_max,
                 )
 
-    def forward(self, features: KeyedJaggedTensor) -> torch.Tensor:
+    def _get_hash_zch_identities(
+        self, features: KeyedJaggedTensor
+    ) -> Optional[torch.Tensor]:
+        if self._raw_id_tracker_wrapper is None or not isinstance(
+            self.emb_module, SplitTableBatchedEmbeddingBagsCodegen
+        ):
+            return None
+
+        raw_id_tracker_wrapper = self._raw_id_tracker_wrapper
+        assert (
+            raw_id_tracker_wrapper is not None
+        ), "self._raw_id_tracker_wrapper should not be None"
+        assert hasattr(
+            self.emb_module, "res_params"
+        ), "res_params should exist when raw_id_tracker is enabled"
+        res_params: RESParams = self.emb_module.res_params  # pyre-ignore[9]
+        table_names = res_params.table_names
+
+        # TODO: get_indexed_lookups() may return multiple IndexedLookup objects
+        # across multiple training iterations. Current logic appends raw_ids from
+        # all batches sequentially. This may cause misalignment with
+        # features.values() which only contains the current batch.
+        raw_ids_dict = raw_id_tracker_wrapper.get_indexed_lookups(
+            table_names, self.emb_module.uuid
+        )
+
+        # Build hash_zch_identities by concatenating raw IDs from tracked tables.
+        # Output maintains 1-to-1 alignment with features.values().
+        # Iterate through table_names explicitly (not raw_ids_dict.values()) to
+        # ensure correct ordering, since there is no guarantee on dict ordering.
+        #
+        # E.g. If features.values() = [f1_val1, f1_val2, f2_val1, f2_val2, ...]
+        #      where table1 has [feature1, feature2] and table2 has [feature3, feature4]
+        #      then hash_zch_identities = [f1_id1, f1_id2, f2_id1, f2_id2, ...]
+        #
+        # TODO: Handle tables without identity tracking. Currently, only tables with
+        # raw_ids are included. If some tables lack identity while others have them,
+        # padding with -1 may be needed to maintain alignment.
+        all_raw_ids = []
+        for table_name in table_names:
+            if table_name in raw_ids_dict:
+                raw_ids_list = raw_ids_dict[table_name]
+                for raw_ids in raw_ids_list:
+                    all_raw_ids.append(raw_ids)
+
+        if not all_raw_ids:
+            return None
+
+        hash_zch_identities = torch.cat(all_raw_ids)
+        assert hash_zch_identities.size(0) == features.values().numel(), (
+            f"hash_zch_identities row count ({hash_zch_identities.size(0)}) must match "
+            f"features.values() length ({features.values().numel()}) to maintain 1-to-1 alignment"
+        )
+
+        return hash_zch_identities
+
+    def forward(
+        self,
+        features: KeyedJaggedTensor,
+    ) -> torch.Tensor:
+        forward_args: Dict[str, Any] = {}
+        hash_zch_identities = self._get_hash_zch_identities(features)
+        if hash_zch_identities is not None:
+            forward_args["hash_zch_identities"] = hash_zch_identities
+
         weights = features.weights_or_none()
         if weights is not None and not torch.is_floating_point(weights):
             weights = None
@@ -2617,17 +2681,22 @@ def forward(self, features: KeyedJaggedTensor) -> torch.Tensor:
                 SSDTableBatchedEmbeddingBags,
             ),
         ):
+            forward_args["batch_size_per_feature_per_rank"] = (
+                features.stride_per_key_per_rank()
+            )
+
+        if len(forward_args) == 0:
             return self.emb_module(
                 indices=features.values().long(),
                 offsets=features.offsets().long(),
                 per_sample_weights=weights,
-                batch_size_per_feature_per_rank=features.stride_per_key_per_rank(),
             )
         else:
             return self.emb_module(
                 indices=features.values().long(),
                 offsets=features.offsets().long(),
                 per_sample_weights=weights,
+                **forward_args,
             )
 
     # pyre-fixme[14]: `state_dict` overrides method defined in `Module` inconsistently.