sqlite3.Connection.blobopen() can fail with OverflowError on large rowids

[TheCatPlusPlus]

Bug report

blobopen internally uses int to hold the requested rowid ([1], [2]), but SQLite rowids are actually 64-bit integers:

int sqlite3_blob_open(
  sqlite3*,
  const char *zDb,
  const char *zTable,
  const char *zColumn,
  sqlite3_int64 iRow, // <-- the rowid parameter
  int flags,
  sqlite3_blob **ppBlob
);

This makes an attempt to open a blob with large rowid raise an OverflowError when Python is compiled with 32-bit int, which is the case on Windows even when compiling as 64-bit application.

This might seem like an edge case, but any INTEGER PRIMARY KEY in a rowid table aliases rowid, which means any application that uses non-autoincrement primary keys (e.g. timestamps, checksums) is likely to hit this very trivially -- I know I did on basically the first insert. You don't need to have more than 2**32 rows or anything like that for this to happen.

100% reproducible with:

import sqlite3

con = sqlite3.connect(':memory:')
rowid = 2**32

con.execute("create table t(t blob)")
con.execute("insert into t(rowid, t) values (?, zeroblob(1))", (rowid,))
con.blobopen('t', 't', rowid)

Expected: nothing (i.e. successful call)
Instead:

Traceback (most recent call last):
  File "E:\Temp\blob.py", line 10, in <module>
    con.blobopen('t', 't', rowid)
OverflowError: Python int too large to convert to C int

Your environment

• CPython versions tested on: 3.11.0 (main, Oct 24 2022, 18:26:48) [MSC v.1933 64 bit (AMD64)], 3.12.0a3+ (heads/main-dirty:cb60b6131b, Dec 20 2022, 14:37:41) [MSC v.1934 64 bit (AMD64)]
• Operating system and architecture: Windows x64

Linked PRs

• gh-100370: fix OverflowError in sqlite3.Connection.blobopen for 32-bit builds #103902
• [3.11] gh-100370: fix OverflowError in sqlite3.Connection.blobopen for 32-bit builds (#103902) #104285

[erlend-aasland]

Sorry for the late reply. I'm preparing a PR for this; I'll put it up tomorrow.