# 操作指导
- cursor_sharing = exact，仅启用相同语句计划复用功能。
  1. 建表及设置参数。
     ```
     gaussdb=# CREATE TABLE cursor_sharing_exact_tbl(col1 int, col2 int);
     CREATE TABLE
     gaussdb=# INSERT INTO cursor_sharing_exact_tbl VALUES(1, 1);
     INSERT 0 1
     gaussdb=# SET cursor_sharing = exact;
     SET
     ```
     
  
  2. 执行查询。
     ```
     gaussdb=# SELECT * FROM cursor_sharing_exact_tbl WHERE col1 = 1;
      col1 | col2
     ------+------
         1 |    1
     (1 row)
     ```
     
  
  3. 查询视图dbe_perf.gs_plancache_stat展示了该语句的缓存信息。
     ```
     gaussdb=# SELECT parameterized_sql, parameter_types, is_parameterized FROM dbe_perf.gs_plancache_stat WHERE parameterized_sql LIKE '%from cursor_sharing_exact_tbl%';
                                                                           parameterized_sql                                                                      | parameter_types | is
     _parameterized
     -------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------+---
     ---------------
      select * from cursor_sharing_exact_tbl where col1 = 1;                                                                                                      | {}              | f
      select parameterized_sql, parameter_types, is_parameterized from dbe_perf.gs_plancache_stat where parameterized_sql like '%from cursor_sharing_exact_tbl%'; | {}              | f
     (2 rows)
     ```
     
  
  4. 若环境开启了GPC，查询GPC视图DBE_PERF.GLOBAL_PLANCACHE_STATUS，字段parameterized_info被标记为exact表示该语句通过相同语句计划复用特性执行。若环境未开启GPC，请开启enable_global_plancache后重启数据库，并重新执行[1]\~[3]。
     ```
     gaussdb=# SHOW enable_global_plancache;
      enable_global_plancache
     -------------------------
      on
     (1 row)
      
     gaussdb=# SELECT query, parameterized_info FROM DBE_PERF.GLOBAL_PLANCACHE_STATUS WHERE query LIKE '%from cursor_sharing_exact_tbl%';
                                                                                 query                                                                            | parameterized_info
     -------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------
      select query, parameterized_info from DBE_PERF.GLOBAL_PLANCACHE_STATUS where query like '%from cursor_sharing_exact_tbl%';                                  | exact
      select parameterized_sql, parameter_types, is_parameterized from dbe_perf.gs_plancache_stat where parameterized_sql like '%from cursor_sharing_exact_tbl%'; | exact
      select * from cursor_sharing_exact_tbl where col1 = 1;                                                                                                      | exact
     (3 rows)
     ```
     
  
  5. 删表恢复环境。
     ```
     gaussdb=# DROP TABLE cursor_sharing_exact_tbl CASCADE;
     DROP TABLE
     ```
     
   
- cursor_sharing = force，同时启用自动参数化以及相同语句计划复用功能。
  1. 建表及设置参数。
     ```
     gaussdb=# CREATE TABLE cursor_sharing_force_tbl(col1 int, col2 int);
     CREATE TABLE
     gaussdb=# INSERT INTO cursor_sharing_force_tbl VALUES(1, 1);
     INSERT 0 1
     gaussdb=# SET cursor_sharing = force;
     SET
     ```
     
  
  2. EXPLAIN查看计划。
     1. normal模式下，被参数化的计划会显示\[Parameterized\]的tag；
        ```
        gaussdb=# SET explain_perf_mode = 'normal';
        SET
        gaussdb=# EXPLAIN (costs off) SELECT * FROM cursor_sharing_force_tbl WHERE col1 = 1;
                              QUERY PLAN
        ------------------------------------------------------
         [Parameterized]
         Seq Scan on cursor_sharing_force_tbl
           Filter: (col1 = 1), (Expression Flatten Optimized)
        (3 rows)
        ```
        
     
     2. pretty模式下，则会在Query Others中显示Parameterize: Yes，并给出参数化后的模板SQL，表示该计划是经过参数化的计划。
        ```
        gaussdb=# SET explain_perf_mode = 'pretty';
        SET
        gaussdb=# EXPLAIN (costs off) SELECT * FROM cursor_sharing_force_tbl WHERE col1 = 1;
         id |                operation
        ----+------------------------------------------
          1 | ->  Seq Scan on cursor_sharing_force_tbl
        (1 row)
               Predicate Information (identified by plan id)
        ------------------------------------------------------------
           1 --Seq Scan on cursor_sharing_force_tbl
                 Filter: (col1 = 1), (Expression Flatten Optimized)
        (2 rows)
                                          ====== Query Others =====
        ----------------------------------------------------------------------------------------------
         Parameterize: Yes, parameterized sql: select * from cursor_sharing_force_tbl where col1 = ?;
        (1 row)
        ```
        
      
  
  3. 执行语句。
     ```
     gaussdb=# SELECT * FROM cursor_sharing_force_tbl WHERE col1 = 1;
      col1 | col2
     ------+------
         1 |    1
     (1 row)
     ```
     
  
  4. 查询视图dbe_perf.gs_plancache_stat展示了该语句的缓存信息，如parameterized_sql字段展示了对该SQL语句参数化后的结果。
     ```
     gaussdb=# SELECT parameterized_sql, parameter_types, is_parameterized FROM dbe_perf.gs_plancache_stat WHERE parameterized_sql LIKE '%from cursor_sharing_force_tbl%';
                        parameterized_sql                    | parameter_types | is_parameterized
     --------------------------------------------------------+-----------------+------------------
      select * from cursor_sharing_force_tbl where col1 = ?; | {integer}       | t
     (1 row)
     ```
     
  
  5. 查询dbe_perf.statement视图，query字段展示参数化后的语句信息，$表示被参数化的常量。（需要保证当前unique sql记录条数少于最大可记录条数instr_unique_sql_count）。
     ```
     gaussdb=# SELECT query FROM dbe_perf.statement WHERE query LIKE '%from cursor_sharing_force_tbl%';
                               query
     ---------------------------------------------------------
      select * from cursor_sharing_force_tbl where col1 = $1;
     (1 row)
     ```
     
  
  6. 删表恢复环境。
     ```
     gaussdb=# DROP TABLE cursor_sharing_force_tbl CASCADE;
     DROP TABLE
     ```