Postgres 解释计划 High number of Buffers Shared read，对于非常慢的行数

问题描述

Postgres 版本： 12

查询： 解释（分析为真、详细为真、成本为真、缓冲区为真、时间为真） SELECT MIN("id"),MAX("id") FROM "public"."hotel_slot_inventory" WHERE ( "updated_at" >= '2021-03-02 13:30:03' AND "updated_at"

查询计划：

 Result  (cost=512.17..512.18 rows=1 width=8) (actual time=65556.920..65556.926 rows=1 loops=1)
   Output: $0,$1
   Buffers: shared hit=370 read=454012 written=8
   I/O Timings: read=62266.717 write=0.194
   InitPlan 1 (returns $0)
     ->  Limit  (cost=0.57..256.09 rows=1 width=4) (actual time=65251.998..65252.001 rows=1 loops=1)
           Output: hotel_slot_inventory.id
           Buffers: shared hit=1 read=453546 written=8
           I/O Timings: read=61967.042 write=0.194
           ->  Index Only Scan using hotel_slot_inventory_id_updated_at_idx on public.hotel_slot_inventory  (cost=0.57..3291347.07 rows=12881 width=4) (actual time=65251.996..65251.997 rows=1 loops=1)
                 Output: hotel_slot_inventory.id
                 Index Cond: ((hotel_slot_inventory.id IS NOT NULL) AND (hotel_slot_inventory.updated_at >= '2021-03-02 13:30:03'::timestamp without time zone) AND (hotel_slot_inventory.updated_at < '2021-03-03 06:15:19.127884'::timestamp without time zone))
                 Heap Fetches: 1
                 Buffers: shared hit=1 read=453546 written=8
                 I/O Timings: read=61967.042 write=0.194
   InitPlan 2 (returns $1)
     ->  Limit  (cost=0.57..256.09 rows=1 width=4) (actual time=304.902..304.903 rows=1 loops=1)
           Output: hotel_slot_inventory_1.id
           Buffers: shared hit=369 read=466
           I/O Timings: read=299.674
           ->  Index Only Scan Backward using hotel_slot_inventory_id_updated_at_idx on public.hotel_slot_inventory hotel_slot_inventory_1  (cost=0.57..3291347.07 rows=12881 width=4) (actual time=304.899..304.899 rows=1 loops=1)
                 Output: hotel_slot_inventory_1.id
                 Index Cond: ((hotel_slot_inventory_1.id IS NOT NULL) AND (hotel_slot_inventory_1.updated_at >= '2021-03-02 13:30:03'::timestamp without time zone) AND (hotel_slot_inventory_1.updated_at < '2021-03-03 06:15:19.127884'::timestamp without time zone))
                 Heap Fetches: 3892
                 Buffers: shared hit=369 read=466
                 I/O Timings: read=299.674
 Planning Time: 0.229 ms
 Execution Time: 65556.982 ms
(28 rows)

在 InitPlan1 中，为了获取 12881，它必须读取 453546 个缓冲区..这意味着有许多缓冲区不包含数据。真空也没有帮助。请在这里帮忙。我该如何解决这个问题？

编辑索引膨胀详细信息：

真实大小：3751411712 = 3.49 GB

额外大小：470237184 = 448 MB

额外比率：12.53

填充因子：90

膨胀大小：107053056 = 102 MB

膨胀比率：2.85

解决方法

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