小编Mar*_*ary的帖子

尽管所有索引都已到位，但我的查询执行速度非常慢：

SELECT * FROM "entry"
    INNER JOIN "entrytag" ON ("entry"."id" = "entrytag"."entry_id")
    WHERE "entrytag"."tag_id" = 323456
    ORDER BY "entry"."date"
    DESC LIMIT 10'

解释显示太多循环，为什么？如何解决这个问题？

Limit  (cost=1241.85..1241.87 rows=10 width=666) (actual time=23576.449..23576.454 rows=10 loops=1)
  ->  Sort  (cost=1241.85..1242.10 rows=99 width=666) (actual time=23576.446..23576.447 rows=10 loops=1)
        Sort Key: entry.date DESC
        Sort Method: top-N heapsort  Memory: 31kB
        ->  Nested Loop  (cost=0.87..1239.71 rows=99 width=666) (actual time=0.168..22494.187 rows=989105 loops=1)
              ->  Index Scan using entrytag_tag_id_row_idx on entrytag  (cost=0.44..402.17 rows=99 width=4)
                  (actual time=0.093..535.664 **rows=989105** loops=1)
                    Index Cond: (tag_id = 323456)
              -> …