refactor: optimize is_master subquery using EXISTS instead of COUNT

queries/general.py

@@ -1,6 +1,6 @@
 from typing import Union, TypedDict
 
-from sqlalchemy import select, func, and_, cast, String, case, or_
+from sqlalchemy import select, func, and_, cast, String, case, or_, exists
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import joinedload
 
@@ -142,31 +142,20 @@ async def get_stocks_data(
         .subquery()
     )
 
-    is_master_first_subquery = (
-        select(
-            ProductRelation.master_product_id,
-            (func.count(ProductRelation.master_product_id) > 0).label('is_master')
-        )
-        .where(
-            ProductRelation.relation_type == ProductRelationType.MAIN_PRODUCT
-        )
-        .group_by(
-            ProductRelation.master_product_id
-        )
-        .subquery()
-    )
-
     is_master_subquery = (
         select(
-            Product.id.label('product_id'),
-            func.coalesce(is_master_first_subquery.c.is_master, False).label('is_master')
-        )
-        .select_from(
-            Product
-        )
-        .outerjoin(
-            is_master_first_subquery,
-            Product.id == is_master_first_subquery.c.master_product_id
+            Product.id.label("product_id"),
+            # EXISTS возвращает bool, не нужно COUNT > 0 и GROUP BY
+            exists(
+                select(1)
+                .select_from(ProductRelation)
+                .where(
+                    and_(
+                        ProductRelation.master_product_id == Product.id,
+                        ProductRelation.relation_type == ProductRelationType.MAIN_PRODUCT,
+                    )
+                )
+            ).label("is_master"),
         )
         .subquery()
     )
@@ -264,7 +253,7 @@ async def get_stocks_data(
             .label('warehouse_stock'),
             mix_stock_full_subquery.c.mix_stock.label('mix_stock'),
             func.coalesce(in_block_subquery.c.in_block_value, 1).label('in_block_value'),
-            is_master_subquery.c.is_master.label('is_master'),
+            func.coalesce(is_master_subquery.c.is_master, False).label('is_master'),
             func.coalesce(slaves_stock_subquery.c.slaves_stock, 0).label('slaves_stock'),
             MarketplaceProduct.price_recommended.label('price_recommended'),
             MarketplaceProduct.is_archived.label('is_archived'),
@@ -317,7 +306,6 @@ async def get_stocks_data(
     )
 
     result = await session.execute(stmt)
-
     marketplace_products = result.all()
     response: List[StockData] = []
     for (marketplace_product,