From ac1320aae8977e62e73839ae6a1e3bfb94bc7f3e Mon Sep 17 00:00:00 2001
From: Jon Luo <20971593+jzluo@users.noreply.github.com>
Date: Wed, 22 Feb 2023 13:34:05 -0500
Subject: [PATCH] fix sqlite internal tables breaking table_info (#1224)

With the current method used to get the SQL table info, sqlite internal
schema tables are being included and are not being handled correctly by
sqlalchemy because the columns have no types. This is easy to see with
the Chinook database:
```python
db = SQLDatabase.from_uri("sqlite:///Chinook.db")
print(db.table_info)
```
```python
...
sqlalchemy.exc.CompileError: (in table 'sqlite_sequence', column 'name'): Can't generate DDL for NullType(); did you forget to specify a type on this Column?
```

SQLAlchemy 2.0 [ignores these by
default](https://github.com/sqlalchemy/sqlalchemy/blob/63d90b0f44016b15bed6c4108d90a71c15f05a09/lib/sqlalchemy/dialects/sqlite/base.py#L856-L880):

https://github.com/sqlalchemy/sqlalchemy/blob/63d90b0f44016b15bed6c4108d90a71c15f05a09/lib/sqlalchemy/dialects/sqlite/base.py#L2096-L2123
---
 langchain/sql_database.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/langchain/sql_database.py b/langchain/sql_database.py
index 2abca30c..3cb96dea 100644
--- a/langchain/sql_database.py
+++ b/langchain/sql_database.py
@@ -94,6 +94,7 @@ class SQLDatabase:
             tbl
             for tbl in self._metadata.sorted_tables
             if tbl.name in set(all_table_names)
+            and not (self.dialect == "sqlite" and tbl.name.startswith("sqlite_"))
         ]
 
         tables = []