SQL 联接性能不佳的查询

Question

我在为 Oracle 12c 编写的查询中遇到了非常糟糕的性能。这可能与我对连接的低效使用有关，希望有人能帮助我解决我出错的地方。我的查询目前 需要一分钟才能运行。

我正在尝试 return table 和列名称，其中：

列属于主键
列类型为数字
table 的所有者是 MY_OWNER
主键是单列约束

目前我的查询如下所示

SELECT consCols.table_name, consCols.column_name 
FROM all_cons_columns consCols
INNER JOIN all_constraints cons 
  ON cons.constraint_name = consCols.constraint_name
INNER JOIN all_tab_columns cols 
  ON consCols.table_name = cols.table_name AND consCols.column_name = cols.column_name
WHERE cons.constraint_type = 'P' 
AND cons.owner = 'MY_OWNER'
AND cols.data_type = 'NUMBER'
AND consCols.table_name IN(
  SELECT consCols2.table_name 
  FROM all_cons_columns consCols2
  INNER JOIN all_constraints cons2 
    ON cons2.constraint_name = consCols2.constraint_name
  WHERE cons2.constraint_type = 'P' 
  AND cons2.owner = 'MY_OWNER' 
  GROUP BY consCols2.table_name
  HAVING COUNT(consCols2.table_name) = 1
);

谢谢你能给我的任何帮助。

Answer 1

使用分析函数会加快查询速度吗？

SELECT table_name, column_name
FROM (SELECT consCols.table_name, consCols.column_name, cols.data_type,
             COUNT(*) OVER (PARTITION BY consCols.table_name) as cnt
      FROM all_cons_columns consCols INNER JOIN
           all_constraints cons 
           ON cons.constraint_name = consCols.constraint_name INNER JOIN
           all_tab_columns cols 
           ON consCols.table_name = cols.table_name AND consCols.column_name = cols.column_name
      WHERE cons.constraint_type = 'P' AND
            cons.owner = 'MY_OWNER'
     ) tc               
WHERE data_type = 'NUMBER' AND cnt = 1;

甚至聚合？

  SELECT consCols.table_name, consCols.column_name
  FROM all_cons_columns consCols INNER JOIN
       all_constraints cons 
       ON cons.constraint_name = consCols.constraint_name INNER JOIN
       all_tab_columns cols 
       ON consCols.table_name = cols.table_name AND consCols.column_name = cols.column_name
  WHERE cons.constraint_type = 'P' AND
        cons.owner = 'MY_OWNER'
  GROUP BY consCols.table_name, consCols.column_name
  HAVING COUNT(*) = 1 AND
         MAX(cols.data_type) = 'NUMBER';

这是第三个选项：

  SELECT consCols.table_name, consCols.column_name
  FROM all_cons_columns consCols INNER JOIN
       all_constraints cons 
       ON cons.constraint_name = consCols.constraint_name INNER JOIN
       all_tab_columns cols 
       ON consCols.table_name = cols.table_name AND consCols.column_name = cols.column_name
  WHERE cons.constraint_type = 'P' AND
        cons.owner = 'MY_OWNER' AND
        cols.data_type = 'NUMBER' AND
        NOT EXISTS (SELECT 1
                    FROM all_cons_columns acc
                    WHERE acc.constraint_name = consCols.constraint_name AND
                          acc.table_name = consCols.table_name AND
                          acc.column_name <> consCols.column_name
                   );

这消除了聚合，查找应该相对较快。

SQL 联接性能不佳的查询

SQL query with poor join performance

sql

oracle

join

oracle12c