feat(backend): use SQLAlchemy instead od supabase API (#2516)

# Description

Please include a summary of the changes and the related issue. Please
also include relevant motivation and context.

## Checklist before requesting a review

Please delete options that are not relevant.

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented hard-to-understand areas
- [ ] I have ideally added tests that prove my fix is effective or that
my feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged

## Screenshots (if appropriate):

backend/models/settings.py

@@ -3,6 +3,7 @@ from uuid import UUID
 
 from langchain.embeddings.ollama import OllamaEmbeddings
 from langchain_openai import OpenAIEmbeddings
+from sqlalchemy import Engine, create_engine
 from logger import get_logger
 from models.databases.supabase.supabase import SupabaseDB
 from posthog import Posthog
@@ -114,6 +115,7 @@ class BrainSettings(BaseSettings):
     ollama_api_base_url: str = None
     langfuse_public_key: str = None
     langfuse_secret_key: str = None
+    pg_database_url: str = None
 
 
 class ResendSettings(BaseSettings):
@@ -124,7 +126,15 @@ class ResendSettings(BaseSettings):
 # Global variables to store the Supabase client and database instances
 _supabase_client: Optional[Client] = None
 _supabase_db: Optional[SupabaseDB] = None
+_db_engine: Optional[Engine] = None
 
+def get_pg_database_engine():
+    global _db_engine
+    if _db_engine is None:
+        logger.info("Creating Postgres DB engine")
+        settings = BrainSettings()  # pyright: ignore reportPrivateUsage=none
+        _db_engine = create_engine(settings.pg_database_url)
+    return _db_engine
 
 def get_supabase_client() -> Client:
     global _supabase_client

backend/modules/brain/entity/brain_entity.py

@@ -1,3 +1,4 @@
+from datetime import datetime
 from enum import Enum
 from typing import List, Optional
 from uuid import UUID
@@ -26,7 +27,7 @@ class BrainEntity(BaseModel):
     max_tokens: Optional[int] = None
     status: Optional[str] = None
     prompt_id: Optional[UUID] = None
-    last_update: str
+    last_update: datetime
     brain_type: BrainType
     brain_definition: Optional[ApiBrainDefinitionEntity] = None
     connected_brains_ids: Optional[List[UUID]] = None

backend/modules/brain/repository/brains.py

@@ -1,7 +1,9 @@
 from uuid import UUID
 
+from sqlalchemy import text
+
 from logger import get_logger
-from models.settings import get_embeddings, get_supabase_client
+from models.settings import get_embeddings, get_pg_database_engine, get_supabase_client
 from modules.brain.dto.inputs import BrainUpdatableProperties
 from modules.brain.entity.brain_entity import BrainEntity, PublicBrain
 from modules.brain.repository.interfaces.brains_interface import BrainsInterface
@@ -13,6 +15,8 @@ class Brains(BrainsInterface):
     def __init__(self):
         supabase_client = get_supabase_client()
         self.db = supabase_client
+        pg_engine = get_pg_database_engine()
+        self.pg_engine = pg_engine
 
     def create_brain(self, brain):
         embeddings = get_embeddings()
@@ -54,27 +58,32 @@ class Brains(BrainsInterface):
 
     def update_brain_last_update_time(self, brain_id):
         try:
-            self.db.table("brains").update({"last_update": "now()"}).match(
-                {"brain_id": brain_id}
-            ).execute()
+            with self.pg_engine.begin() as connection:
+                query = """
+                UPDATE brains
+                SET last_update = now()
+                WHERE brain_id = '{brain_id}'
+                """
+                connection.execute(text(query.format(brain_id=brain_id)))
         except Exception as e:
             logger.error(e)
 
     def get_brain_details(self, brain_id):
-        response = (
-            self.db.table("brains")
-            .select("*")
-            .filter("brain_id", "eq", str(brain_id))
-            .execute()
-        )
-        if response.data == []:
+        with self.pg_engine.begin() as connection:
+            query = """
+            SELECT * FROM brains
+            WHERE brain_id = '{brain_id}'
+            """
+            response = connection.execute(text(query.format(brain_id=brain_id))).fetchall()
+        if len(response) == 0:
             return None
-        return BrainEntity(**response.data[0])
+        return BrainEntity(**response[0]._mapping)
 
     def delete_brain(self, brain_id: str):
-        results = (
-            self.db.table("brains").delete().match({"brain_id": brain_id}).execute()
-        )
+        with self.pg_engine.begin() as connection:
+            results = connection.execute(
+                text(f"DELETE FROM brains WHERE brain_id = '{brain_id}'")
+            )
 
         return results
 
@@ -100,14 +109,11 @@ class Brains(BrainsInterface):
 
     def get_brain_by_id(self, brain_id: UUID) -> BrainEntity | None:
         # TODO: merge this method with get_brain_details
-        response = (
-            self.db.from_("brains")
-            .select("id:brain_id, name, *")
-            .filter("brain_id", "eq", brain_id)
-            .execute()
-        ).data
+        with self.pg_engine.begin() as connection:
+            response = connection.execute(
+                text(f"SELECT * FROM brains WHERE brain_id = '{brain_id}'")
+            ).fetchall()
 
         if len(response) == 0:
             return None
-
-        return BrainEntity(**response[0])
+        return BrainEntity(**response[0]._mapping)