Merge pull request #91 from michalc/feat/better-error-with-short-sqlite-file

feat: raise slightly better error when the object in S3 is too short

Author: michalc

sqlite_s3_query.py

@@ -36,6 +36,7 @@ def sqlite_s3_query_multi(url, get_credentials=lambda now: (
     SQLITE_NOTFOUND = 12
     SQLITE_ROW = 100
     SQLITE_DONE = 101
+    SQLITE_IOERR_SHORT_READ = 522
     SQLITE_TRANSIENT = c_void_p(-1)
     SQLITE_OPEN_READONLY = 0x00000001
     SQLITE_OPEN_NOMUTEX = 0x00008000
@@ -208,7 +209,13 @@ def x_read(p_file, p_out, i_amt, i_ofst):
                 set_pending_exception(exception)
                 return SQLITE_IOERR
 
-            if offset != i_amt:
+            if offset < i_amt:
+                # The SQLite docs strongly suggest to fill unused with zeroes
+                remainder = i_amt - offset
+                memmove(p_out + offset, b'\0' * remainder, remainder)
+                return SQLITE_IOERR_SHORT_READ
+
+            if offset > i_amt:
                 return SQLITE_IOERR
 
             return SQLITE_OK

test.py

@@ -459,7 +459,7 @@ def test_short_db_header(self):
             'wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY',
             None,
         ), get_libsqlite3=get_libsqlite3) as query:
-            with self.assertRaisesRegex(SQLiteError, 'disk I/O error'):
+            with self.assertRaisesRegex(SQLiteError, 'not a database'):
                 query("SELECT * FROM non_table").__enter__()
 
     def test_bad_db_header(self):
@@ -471,7 +471,7 @@ def test_bad_db_header(self):
             'wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY',
             None,
         ), get_libsqlite3=get_libsqlite3) as query:
-            with self.assertRaisesRegex(SQLiteError, 'disk I/O error'):
+            with self.assertRaisesRegex(SQLiteError, 'not a database'):
                 query("SELECT * FROM non_table").__enter__()
 
     def test_bad_db_first_page(self):