you have to update statistics on all tables with full scan after a version upgrade, or restore of a database from a lower version to a higher;

the statistics are treated differently and the new optimizer needs them to be updated.

a quick script like this can help:

DECLARE @Exec VARCHAR(MAX)

SELECT @Exec = ''

SELECT @Exec = 'UPDATE STATISTICS '

+ QUOTENAME(schema_name(schema_id))

+ '.'

+ quotename(name)

+ ' WITH FULLSCAN ; '

+ CHAR(13) + CHAR(10)

+ @Exec

FROM sys.tables ORDER BY name DESC

PRINT LEN(@Exec)

PRINT @Exec

EXEC(@Exec)