代码干货 | 行存、列存_堆表、AO表性能对比-阿里云HDB for PostgreSQL最佳实践

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标签

PostgreSQL , GIS , PostGIS , Greenplum , 空间检索 , GiST , B-Tree , geohash

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背景

《Greenplum 行存、列存，堆表、AO表的原理和选择》

以上文档详细的介绍了行存、列存，堆表、AO表的原理以及选择的依据。

《一个简单算法可以帮助物联网,金融 用户 节约98%的数据存储成本 (PostgreSQL,Greenplum帮你做到)》

以上文档介绍了提升基于列存的全局数据压缩比的方法。

《解密上帝之手 - 阿里云HDB for PostgreSQL数据库metascan特性(存储级、块级、batch级过滤与数据编排)》

以上文档介绍了局部编排，以及阿里云HDB for PostgreSQL数据库的metascan特性，（在不需要索引的情况下，如何提升任意列的选择性）。

压缩实际上是计算(CPU)换空间(磁盘)的做法，该不该做，我们还是先看看压缩比、性能损耗吧。

堆表

postgres=# create table t_heap(id int, c1 text, c2 int);  
CREATE TABLE  
  
postgres=# insert into t_heap select id, repeat(md5(random()::text), 128), random()*10000 from generate_series(1,10000000) t(id);  
INSERT 0 10000000  
Time: 120526.098 ms  

某个维度count查询。

postgres=# explain analyze select c2,count(*) from t_heap group by c2;  
                                                                          QUERY PLAN                                                                             
---------------------------------------------------------------------------------------------------------------------------------------------------------------  
 Gather Motion 48:1  (slice2; segments: 48)  (cost=1578949.03..1579074.98 rows=10076 width=12)  
   Rows out:  10001 rows at destination with 1354 ms to end, start offset by 519 ms.  
   ->  HashAggregate  (cost=1578949.03..1579074.98 rows=210 width=12)  
         Group By: t_heap.c2  
         Rows out:  Avg 208.4 rows x 48 workers.  Max 223 rows (seg17) with 0.001 ms to first row, 692 ms to end, start offset by 581 ms.  
         ->  Redistribute Motion 48:48  (slice1; segments: 48)  (cost=1578596.37..1578797.89 rows=210 width=12)  
               Hash Key: t_heap.c2  
               Rows out:  Avg 10001.0 rows x 48 workers at destination.  Max 10704 rows (seg17) with 596 ms to end, start offset by 581 ms.  
               ->  HashAggregate  (cost=1578596.37..1578596.37 rows=210 width=12)  
                     Group By: t_heap.c2  
                     Rows out:  Avg 10001.0 rows x 48 workers.  Max 10001 rows (seg0) with 0.006 ms to first row, 131 ms to end, start offset by 566 ms.  
                     ->  Seq Scan on t_heap  (cost=0.00..1528595.58 rows=208337 width=4)  
                           Rows out:  Avg 208333.3 rows x 48 workers.  Max 208401 rows (seg18) with 26 ms to first row, 901 ms to end, start offset by 573 ms.  
 Slice statistics:  
   (slice0)    Executor memory: 359K bytes.  
   (slice1)    Executor memory: 724K bytes avg x 48 workers, 724K bytes max (seg0).  
   (slice2)    Executor memory: 388K bytes avg x 48 workers, 388K bytes max (seg0).  
 Statement statistics:  
   Memory used: 128000K bytes  
 Settings:  optimizer=off  
 Optimizer status: legacy query optimizer  
 Total runtime: 1874.143 ms  
(22 rows)  
  
Time: 1879.480 ms  

无索引，某个单值查询

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