時系列のギャップを検出して削除します

クエリを1つだけ作成します：

DELETE FROM mytable 
WHERE company in (
  SELECT Company 
  FROM (
    SELECT Company, 
      COUNT(CASE WHEN value IS NULL THEN 1 END) 
         OVER (PARTITION BY company ORDER BY id 
               ROWS BETWEEN CURRENT ROW AND 2 FOLLOWING) As cnt,
      COUNT(CASE WHEN value IS NULL THEN 1 END) 
         OVER (PARTITION BY company)
      / 
      COUNT(*) 
         OVER (PARTITION BY company) As p50
  ) alias
  WHERE cnt >= 3 OR p50 > 0.5
)

（会社+値）列の複合インデックスは、このクエリの最大速度を得るのに役立ちます。

編集

上記のクエリが機能しない
少し修正しました。デモは次のとおりです： http://sqlfiddle.com/#!15/c9bfe/7
2つの変更がありました：
-会社別のパーティション日付別の注文 ORDER BY IDの代わりに
-数値への明示的なキャスト（整数が0に切り捨てられているため）：
OVER（PARTITION BY company） ::numeric

  SELECT company, cnt, p50
  FROM (
    SELECT company, 
      COUNT(CASE WHEN value IS NULL THEN 1 END) 
         OVER (PARTITION BY company ORDER BY date 
               ROWS BETWEEN CURRENT ROW AND 2 FOLLOWING) As cnt,
      SUM(CASE WHEN value IS NULL THEN 1 ELSE 0 END) 
         OVER (PARTITION BY company)::numeric
      / 
      COUNT(*) 
         OVER (PARTITION BY company) As p50
    FROM mytable
  ) alias
--  WHERE cnt >= 3 OR p50 > 0.5 

これで、削除クエリが機能するはずです：

DELETE FROM mytable 
WHERE company in (
      SELECT company
      FROM (
        SELECT company, 
          COUNT(CASE WHEN value IS NULL THEN 1 END) 
             OVER (PARTITION BY company ORDER BY date 
                   ROWS BETWEEN CURRENT ROW AND 2 FOLLOWING) As cnt,
          SUM(CASE WHEN value IS NULL THEN 1 ELSE 0 END) 
             OVER (PARTITION BY company)::numeric
          / 
          COUNT(*) 
             OVER (PARTITION BY company) As p50
        FROM mytable
      ) alias
    WHERE cnt >= 3 OR p50 > 0.5
)