MySQL limits on huge number return zero rows
Table have 1,000,000 records but It look like Table doesn't have 800000+ records where 

`articles`.`hash` NOT
IN (
'1z8y'
)


But table have 2000+ records where 

`articles`.`hash` NOT
IN (
'1z8y'
)


LIMIT 800000,10 will return 10 records after 800000th records but it looks like you didn't have 800000 records which satisfy your where clause condition.

You can find no. of records which satisfy your where clause using this query

SELECT Count(*) FROM `articles`
WHERE `articles`.`hash` NOT
IN (
'1z8y'
)