MySQL performance optimization (OR to UNION)

01-Original.sql

# tbla idx1 b,e,f
SELECT a.*
FROM tblA a
INNER JOIN tblB b ON a.id = b.aId
WHERE a.b IN (1,2,3)
AND (a.c IN (3,4,5) OR a.d IS NOT NULL)
AND a.e = 0
AND a.f = 0
ORDER BY a.g ASC

02-Improved.sql

# tbla idx2 b,c,e,f
# tbla idx3 b,d,e,f
SELECT a.*
FROM tblA a
INNER JOIN tblB b ON a.id = b.aId
WHERE a.id IN (
  SELECT id
  FROM (
    SELECT id
    FROM tblA a2
    WHERE a2.b IN (1,2,3)
      AND a2.c IN (3,4,5)
      AND a2.e = 0
      AND a2.f = 0
    UNION ALL
    SELECT id
    FROM tblA a3
    WHERE a3.b IN (1,2,3)
      AND a3.d IS NOT NULL
      AND a3.e = 0
      AND a3.f = 0
    UNION ALL
  ) subIds
)
ORDER BY a.g ASC