Optimize init_internal_db by running PRAGMA in a single function

Refs #1555

datasette/utils/internal_db.py

@@ -1,4 +1,5 @@
 import textwrap
+from datasette.utils import table_column_details
 
 
 async def init_internal_db(db):
@@ -70,6 +71,8 @@ async def populate_schema_tables(internal_db, db):
         "DELETE FROM tables WHERE database_name = ?", [database_name], block=True
     )
     tables = (await db.execute("select * from sqlite_master WHERE type = 'table'")).rows
+
+    def collect_info(conn):
         tables_to_insert = []
         columns_to_delete = []
         columns_to_insert = []
@@ -84,7 +87,7 @@ async def populate_schema_tables(internal_db, db):
                 (database_name, table_name, table["rootpage"], table["sql"])
             )
             columns_to_delete.append((database_name, table_name))
-        columns = await db.table_column_details(table_name)
+            columns = table_column_details(conn, table_name)
             columns_to_insert.extend(
                 {
                     **{"database_name": database_name, "table_name": table_name},
@@ -93,9 +96,9 @@ async def populate_schema_tables(internal_db, db):
                 for column in columns
             )
             foreign_keys_to_delete.append((database_name, table_name))
-        foreign_keys = (
+            foreign_keys = conn.execute(
-            await db.execute(f"PRAGMA foreign_key_list([{table_name}])")
+                f"PRAGMA foreign_key_list([{table_name}])"
-        ).rows
+            ).fetchall()
             foreign_keys_to_insert.extend(
                 {
                     **{"database_name": database_name, "table_name": table_name},
@@ -104,7 +107,7 @@ async def populate_schema_tables(internal_db, db):
                 for foreign_key in foreign_keys
             )
             indexes_to_delete.append((database_name, table_name))
-        indexes = (await db.execute(f"PRAGMA index_list([{table_name}])")).rows
+            indexes = conn.execute(f"PRAGMA index_list([{table_name}])").fetchall()
             indexes_to_insert.extend(
                 {
                     **{"database_name": database_name, "table_name": table_name},
@@ -112,6 +115,25 @@ async def populate_schema_tables(internal_db, db):
                 }
                 for index in indexes
             )
+        return (
+            tables_to_insert,
+            columns_to_delete,
+            columns_to_insert,
+            foreign_keys_to_delete,
+            foreign_keys_to_insert,
+            indexes_to_delete,
+            indexes_to_insert,
+        )
+
+    (
+        tables_to_insert,
+        columns_to_delete,
+        columns_to_insert,
+        foreign_keys_to_delete,
+        foreign_keys_to_insert,
+        indexes_to_delete,
+        indexes_to_insert,
+    ) = await db.execute_fn(collect_info)
 
     await internal_db.execute_write_many(
         """