Re: Select last date check all rows

[Rick James]

Unfortunately EXPLAIN gives misleading info for number of rows when a LIMIT is involved.

Yes, it should have used the index and come back 'instantly' after fetching only 1 row.

Please provide SHOW CREATE TABLE y -- There might be some subtle reason for the problem (engine, datatype, prefixed index, etc)

Another way to measure the 'effort' taken is via:
FLUSH STATUS;
SELECT ...;
SHOW SESSION STATUS LIKE "Handler%";

Working correctly, that will show tiny numbers; sounds like it is showing 150K or more.