* perf: eliminate 2 redundant full chat deserialization on every message send (#162)
Problem:
Every message send triggered get_chat_by_id_and_user_id which loads the
entire Chat row — including the potentially massive JSON blob containing
the full conversation history — even when the caller only needed a
simple yes/no ownership check or a single column value.
Two call sites in the message-send hot path were doing this:
1. main.py ownership verification: loaded the entire chat object including
all message history JSON, then checked `if chat is None`. The JSON blob
was immediately discarded — only the existence of the row mattered.
2. middleware.py folder check: loaded the entire chat object including all
message history JSON, then read only `chat.folder_id` — a plain column
on the chat table that requires zero JSON parsing.
Fix:
- Added `chat_exists_by_id_and_user_id()`: uses SQL EXISTS subquery which
returns a boolean without loading any row data. The database can satisfy
this from the primary key index alone.
- Added `get_chat_folder_id()`: queries only the `folder_id` column via
`db.query(Chat.folder_id)`, which tells SQLAlchemy to SELECT only that
single column instead of the entire row.
Both new methods preserve the same error handling semantics (return
False/None on exception) and user_id filtering (ownership check) as
the original get_chat_by_id_and_user_id.
Impact:
- Best case (typical): eliminates deserializing 2 full chat JSON blobs per
message send. For long conversations (hundreds of messages with tool
calls, images, file attachments), this blob can be multiple megabytes.
- Worst case: no regression — the new queries are strictly cheaper than
the old ones (less data transferred, less Python object construction,
no Pydantic model_validate overhead).
- The 3 remaining full chat loads in process_chat_payload (load_messages_from_db,
add_file_context, chat_image_generation_handler) are left untouched as
they genuinely need the full history and require separate analysis.
* Address maintainer feedback: rename method and inline call (#166)
- Rename chat_exists_by_id_and_user_id -> is_chat_owner
- Remove intermediate chat_owned variable; call is_chat_owner directly in if condition
Classic298
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