rs is in the form "rs12364789", max. length of the string is 12; always "rs" before a number
- with 480,000,000 rows everything is OK
- with 490,000,000 rows nothing will be found.
EXPLAIN says: "Impossible WHERE noticed after reading const tables"
The row can still be found with IGNORE INDEX (PRIMARY)
If I build another table with only a non unique index on `rs` , EXPLAIN says it's using the index but the query won't find anything..
A server version from 3 or 4 Months ago worked OK.
Hope it helps