What could be the cause of "java.lang.IllegalStateException: get field slot from row 0 col 0 failed"

I have an SQL query running on an 'sqlite' database that is throwing this exception: "java.lang.IllegalStateException: get field slot from row 0 col 0 failed" when I call:

db.rawQuery( "SELECT data FROM session_data WHERE session_id = ?", new String[] { String.format("%d", session_id) } );
if (!cursor.moveToFirst()) return;
bytes[] bytes = cursor.getBlob(0);

The column exists, and if I log in using adb shell sqlite3 /path/to/database.db I can successfully execute the same query.

The resulting cursor shows that there is 1 row selected with 1 co开发者_开发知识库lumn whose name is "data". The size of the blob is about 1.5 MB - could that be it? I have verified that cursor.GetColumnIndex("data") returns 0, so the column exists.

This is running on Android 2.1 SDK. Any ideas?

The problem was that the blob was too big. It appears that cursor.getBlob(0) fails if the blob size is over a megabyte. Reading the blob in segments solved my issue:

// get length of blob data
Cursor cursor = db.rawQuery( "SELECT LENGTH(data) AS len FROM table WHERE id = ?", etc);
if (cursor == null || !cursor.moveToFirst()) throw new Exception("failed");
int size = cursor.getInt(cursor.getColumnIndexOrThrow("len"));
cursor.close();

// read a segment of the blob data
cursor = db.rawQuery( "SELECT SUBSTR(data,0,500000) AS partial FROM table WHERE id = ?", etc);
if (cursor == null || !cursor.moveToFirst()) throw new Exception("failed");
byte[] partial = cursor.getBlob(cursor.getColumnIndexOrThrow("partial"));
cursor.close();

// copy partial bytes, repeat until the whole length has been read...

I assume that you are holding a reference to the cursor from the rawQuery. Before you get any value from the cursor you need to call cursor.moveToFirst() because the cursor is initially positioned at -1. The correct way would be:

Cursor cursor = db.rawQuery( "SELECT data FROM session_data WHERE session_id = ?", new String[] { String.format("%d", session_id) } );
if(cursor!= null && cursor.moveToFirst()){ // checking if the cursor has any rows
   bytes[] bytes = cursor.getBlob(0);
}

and also make sure that your column in the database is blob type