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+## PostgreSQL 商用版本EPAS(阿里云ppas) 索引推荐功能使用   
+                              
+### 作者                              
+digoal                              
+
+### 日期                              
+2018-01-13                             
+
+### 标签                              
+PostgreSQL , PPAS , enterprisedb , 索引推荐   
+
+----                              
+                              
+## 背景    
+PostgreSQL商用版本EnterpriseDB，内置了索引推荐功能，原理与这里描述类似。   
+
+[《PostgreSQL SQL自动优化案例 - 极简，自动推荐索引》](../201801/20180111_02.md)     
+
+目前仅支持BTREE索引的（单列或多列）推荐，（有一些限制，暂时不支持继承表的推荐，暂时不支持表达式索引的推荐）。   
+
+## 索引推荐用法   
+1、创建推荐存储表与推荐查阅函数。   
+
+```   
+-- 在需要用到索引推荐的数据库中，安装索引推荐用到的表、函数、视图   
+-- 调用 index_advisor.sql    
+psql -f $PGHOME/share/contrib/index_advisor.sql    
+   
+psql.bin:/opt/edb/as10/share/contrib/index_advisor.sql:22: ERROR:  relation "index_advisor_log" already exists   
+psql.bin:/opt/edb/as10/share/contrib/index_advisor.sql:25: ERROR:  relation "ia_reloid" already exists   
+psql.bin:/opt/edb/as10/share/contrib/index_advisor.sql:28: ERROR:  relation "ia_backend_pid" already exists   
+CREATE FUNCTION   
+CREATE FUNCTION   
+CREATE VIEW   
+```   
+
+2、加载推荐模块   
+
+```   
+-- 在需要用到索引推荐的会话中加载推荐模块   
+load 'index_advisor';   
+```   
+
+或者可以设置为自动加载。   
+
+```   
+vi $PGDATA/postgresql.conf   
+   
+shared_preload_libraries = 'index_advisor'   
+   
+   
+# - Other Defaults -   
+   
+#dynamic_library_path = '$libdir'   
+#local_preload_libraries = ''   
+#session_preload_libraries = ''   
+   
+#oracle_home =''        # path to the Oracle home directory;   
+                                        # only used by OCI Dblink; defaults   
+                                        # to ORACLE_HOME environment variable.   
+```   
+
+3、设置会话参数，选择是否需要推荐。如果需要推荐，则会自动对这个会话接下来的SQL进行索引推荐（如果多次执行，并被推荐的话，SQL都会被记录在表中）。   
+
+```   
+postgres=# set index_advisor.enabled TO on;   
+SET   
+```   
+
+设置后，这个会话的所有QUERY都会被推荐模块进行计算。并将需要推荐的SQL记录下来，包括PID，索引列，索引估算大小，成本估算等。   
+
+```   
+postgres=# select * from pgbench_history where bid=2;   
+ tid  | bid |   aid   | delta |           mtime           | filler    
+------+-----+---------+-------+---------------------------+--------   
+  444 |   2 | 4438685 | -2029 | 12-JAN-18 20:46:43.07816  |    
+   
+postgres=# select pg_backend_pid();   
+ pg_backend_pid    
+----------------   
+          32898   
+(1 row)   
+   
+postgres=# select * from index_advisor_log ;   
+ reloid |     relname      | attrs | benefit | index_size | backend_pid |            timestamp                
+--------+------------------+-------+---------+------------+-------------+----------------------------------   
+  16397 | pgbench_history  | {2}   |  175955 |    1260456 |       32898 | 14-JAN-18 21:32:19.564707 +08:00   
+```   
+
+4、查阅推荐。   
+
+```   
+postgres=# select * from show_index_recommendations(32898);   
+                                                      show_index_recommendations                                                         
+--------------------------------------------------------------------------------------------------------------------------------------   
+ create index idx_pgbench_history_bid on public.pgbench_history(bid);/* size: 1260456 KB, benefit: 175955, gain: 0.139596676718584 */   
+(1 row)   
+   
+或   
+   
+postgres=# select * from show_index_recommendations();   
+                                                      show_index_recommendations                                                         
+--------------------------------------------------------------------------------------------------------------------------------------   
+ create index idx_pgbench_history_bid on public.pgbench_history(bid);/* size: 1260456 KB, benefit: 175955, gain: 0.139596676718584 */   
+(1 row)   
+```   
+
+5、查看虚拟索引执行计划(HYPOTHETICAL PLAN 表示包含虚拟索引时的执行计划)。   
+
+```   
+postgres=# explain select * from pgbench_history where bid=2;   
+                                             QUERY PLAN                                                 
+-----------------------------------------------------------------------------------------------------   
+ Gather  (cost=1000.00..455329.29 rows=470413 width=116)   
+   Workers Planned: 6   
+   ->  Parallel Seq Scan on pgbench_history  (cost=0.00..407287.99 rows=78402 width=116)   
+         Filter: (bid = 2)   
+ Result  (cost=0.00..0.00 rows=0 width=0)   
+   One-Time Filter: '===[ HYPOTHETICAL PLAN ]==='::text   
+   ->  Bitmap Heap Scan on pgbench_history  (cost=5339.17..279373.83 rows=470413 width=116)   
+         Recheck Cond: (bid = 2)   
+         ->  Bitmap Index Scan on "<hypothetical-index>:8"  (cost=0.00..5221.56 rows=470413 width=0)   
+               Index Cond: (bid = 2)   
+(10 rows)   
+```   
+
+6、关闭推荐。   
+
+```   
+postgres=# set index_advisor.enabled TO off;   
+SET   
+```   
+
+关闭推荐后，不会使用虚拟索引，也不会再计算是否需要推荐索引。   
+
+```   
+postgres=# explain select * from pgbench_history where bid=2;   
+                                       QUERY PLAN                                           
+-----------------------------------------------------------------------------------------   
+ Gather  (cost=1000.00..455329.29 rows=470413 width=116)   
+   Workers Planned: 6   
+   ->  Parallel Seq Scan on pgbench_history  (cost=0.00..407287.99 rows=78402 width=116)   
+         Filter: (bid = 2)   
+(4 rows)   
+```   
+
+7、解读推荐索引信息。   
+
+```   
+postgres=# select * from show_index_recommendations();   
+                                                      show_index_recommendations                                                         
+--------------------------------------------------------------------------------------------------------------------------------------   
+ create index idx_pgbench_history_bid on public.pgbench_history(bid);/* size: 1260456 KB, benefit: 175955, gain: 0.139596676718584 */   
+(1 row)   
+```   
+
+size，这个索引占用的空间，对应index_advisor_log.index_size。   
+
+benefit，这个推荐索引涉及的index_advisor_log.benefit，即加上索引后，相比没有索引时的explain成本估算COST差异。   
+
+gain，index_advisor_log -> sum(benefit)/greatest(size(s))，即多次推荐的统计，获得了多少提升空间，越大，表示提升效果越好。   
+
+### 如何让普通用户支持推荐   
+1、允许普通用户加载推荐模块   
+
+需要将$PGHOME/lib/index_advisor.so拷贝到$PGHOME/lib/plugins/index_advisor.so。普通用户才能LOAD。   
+
+2、允许普通用户增删改查推荐存储表   
+
+- Grant SELECT and INSERT privileges on the index_advisor_log table to allow a user to invoke Index Advisor.   
+
+- Grant DELETE privileges on the index_advisor_log table to allow the specified user to delete the table contents.   
+
+- Grant SELECT privilege on the index_recommendations view.   
+
+### 推荐的配置   
+1、在template1模板库中安装   
+
+```   
+psql template1 -f $PGHOME/share/contrib/index_advisor.sql    
+```   
+
+2、配置postgresql.conf，默认加载模块   
+
+```   
+vi $PGDATA/postgresql.conf   
+   
+shared_preload_libraries = 'index_advisor'   
+```   
+
+3、配置postgresql.conf，index_advisor.enabled=off，默认关闭计算   
+
+```   
+vi $PGDATA/postgresql.conf   
+   
+index_advisor.enabled=off   
+```   
+
+4、当用户需要用到推荐模块时，只要打开index_advisor.enabled参数即可。   
+
+```   
+psql   
+psql.bin (10.1.5)   
+Type "help" for help.   
+   
+postgres=# show index_advisor.enabled ;   
+ index_advisor.enabled    
+-----------------------   
+ off   
+(1 row)   
+   
+postgres=# explain select * from pgbench_history where bid=2;   
+                                       QUERY PLAN                                           
+-----------------------------------------------------------------------------------------   
+ Gather  (cost=1000.00..455329.29 rows=470413 width=116)   
+   Workers Planned: 6   
+   ->  Parallel Seq Scan on pgbench_history  (cost=0.00..407287.99 rows=78402 width=116)   
+         Filter: (bid = 2)   
+(4 rows)   
+   
+postgres=# set index_advisor.enabled =on;   
+SET   
+postgres=# explain select * from pgbench_history where bid=2;   
+                                             QUERY PLAN                                                 
+-----------------------------------------------------------------------------------------------------   
+ Gather  (cost=1000.00..455329.29 rows=470413 width=116)   
+   Workers Planned: 6   
+   ->  Parallel Seq Scan on pgbench_history  (cost=0.00..407287.99 rows=78402 width=116)   
+         Filter: (bid = 2)   
+ Result  (cost=0.00..0.00 rows=0 width=0)   
+   One-Time Filter: '===[ HYPOTHETICAL PLAN ]==='::text   
+   ->  Bitmap Heap Scan on pgbench_history  (cost=5339.17..279373.83 rows=470413 width=116)   
+         Recheck Cond: (bid = 2)   
+         ->  Bitmap Index Scan on "<hypothetical-index>:2"  (cost=0.00..5221.56 rows=470413 width=0)   
+               Index Cond: (bid = 2)   
+(10 rows)   
+   
+postgres=# set index_advisor.enabled =off;   
+SET   
+```   
+
+## 参考      
+[《PostgreSQL SQL自动优化案例 - 极简，自动推荐索引》](../201801/20180111_02.md)     
+
+[阿里云PPAS商用版本(兼容Oracle)](https://www.aliyun.com/product/rds/ppas)       
+
+https://www.enterprisedb.com/docs/en/10.0/EPAS_Guide_v10/EDB_Postgres_Advanced_Server_Guide.1.36.html#pID0E0ZUE0HA     
diff --git a/201801/readme.md b/201801/readme.md
@@ -1,5 +1,6 @@
 ### 文章列表  
 ----  
+##### 20180113_02.md   [《PostgreSQL 商用版本EPAS(阿里云ppas) 索引推荐功能使用》](20180113_02.md)  
 ##### 20180113_01.md   [《PostgreSQL HTAP功能之资源隔离管理 - CPU与刷脏资源组管理 (阿里云EDB PPAS resource queue)》](20180113_01.md)  
 ##### 20180111_02.md   [《PostgreSQL SQL自动优化案例 - 极简，自动推荐索引》](20180111_02.md)  
 ##### 20180111_01.md   [《PostgreSQL SQL filter (SQL 成本|语义过滤器)》](20180111_01.md)  

diff --git a/README.md b/README.md
@@ -29,6 +29,7 @@ digoal's|PostgreSQL|文章|归类
 
 ### 未归类文档如下  
 ----  
+##### 201801/20180113_02.md   [《PostgreSQL 商用版本EPAS(阿里云ppas) 索引推荐功能使用》](201801/20180113_02.md)  
 ##### 201801/20180113_01.md   [《PostgreSQL HTAP功能之资源隔离管理 - CPU与刷脏资源组管理 (阿里云EDB PPAS resource queue)》](201801/20180113_01.md)  
 ##### 201801/20180111_02.md   [《PostgreSQL SQL自动优化案例 - 极简，自动推荐索引》](201801/20180111_02.md)  
 ##### 201801/20180111_01.md   [《PostgreSQL SQL filter (SQL 成本|语义过滤器)》](201801/20180111_01.md)