在 DB2 Database Partitioning Feature 环境中选择分区键
2010-09-09 00:00:00 来源:WEB开发网示例 2
这个示例展示了通配符在 ESTIMATE_EXISTING_DATA_SKEW 例程中的使用。 清单 3 报告了具有模式 TPCD 且表名以 “PART” 开头的所有表的现有数据倾斜。由于这些表相对比较大,这个例子构建于 1% 的数据以减少性能的损失。
清单 3. 测量多个表的现有数据倾斜
$ db2 "set serveroutput on"
$ db2 "CALL estimate_existing_data_skew('TPCD', 'PART%', 1)"
CALL estimate_existing_data_skew('TPCD', 'PART%', 1)
Return Status = 0
DATA SKEW ESTIMATION REPORT FOR TABLE: TPCD.PART%
This report is based on the existing partitioning key
Accuracy is based on 1% sample of data
------------------------------------------------------------------------
TPCD.PART
Estimated total number of records in the table: : 399,799,400
Estimated average number of records per partition : 49,974,900
Row count at partition 1 : 50,051,800 (Skew: 0.15%)
Row count at partition 2 : 49,951,200 (Skew: -0.04%)
Row count at partition 3 : 49,862,500 (Skew: -0.22%)
Row count at partition 4 : 49,986,500 (Skew: -0.02%)
Row count at partition 5 : 50,096,400 (Skew: 0.24%)
Row count at partition 6 : 49,993,900 (Skew: -0.03%)
Row count at partition 7 : 49,955,900 (Skew: -0.03%)
Row count at partition 8 : 49,901,200 (Skew: -0.14%)
Number of partitions: 8 (1, 2, 3, 4, 5, 6, 7, 8)
------------------------------------------------------------------------
TPCD.PARTSUPP
Estimated total number of records in the table: : 1,600,374,100
Estimated average number of records per partition : 200,046,700
Row count at partition 1 : 200,298,100 (Skew: 0.12%)
Row count at partition 2 : 200,154,900 (Skew: 0.05%)
Row count at partition 3 : 200,006,700 (Skew: 0.01%)
Row count at partition 4 : 199,831,600 (Skew: -0.10%)
Row count at partition 5 : 199,962,200 (Skew: -0.04%)
Row count at partition 6 : 200,083,900 (Skew: 0.01%)
Row count at partition 7 : 199,910,300 (Skew: -0.06%)
Row count at partition 8 : 200,126,400 (Skew: 0.03%)
Number of partitions: 8 (1, 2, 3, 4, 5, 6, 7, 8)
------------------------------------------------------------------------
TPCD.SUPPLIER
Estimated total number of records in the table: : 20,000,000
Estimated average number of records per partition : 2,500,000
Row count at partition 1 : 2,498,411 (Skew: -0.06%)
Row count at partition 2 : 2,498,837 (Skew: -0.04%)
Row count at partition 3 : 2,500,996 (Skew: 0.03%)
Row count at partition 4 : 2,500,170 (Skew: 0.00%)
Row count at partition 5 : 2,501,254 (Skew: 0.05%)
Row count at partition 6 : 2,499,654 (Skew: -0.01%)
Row count at partition 7 : 2,501,429 (Skew: 0.05%)
Row count at partition 8 : 2,499,249 (Skew: -0.03%)
Number of partitions: 8 (1, 2, 3, 4, 5, 6, 7, 8)
------------------------------------------------------------------------
Total execution time: 51 seconds
Tags:DB Database Partitioning
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