Greenplum:分区前思考几个问题

Deciding on a Table Partitioning Strategy 分区前思考几个问题Not all tables are good candidates for partitioning. If the answer is yes to all or most of the following questions, then table partitioning is a viable database design strategy for improving query performance. If the answer is no to most of the following questions, then table partitioning is not the right solution for that table:• Is the table large enough?表足够大？超过一千万条记录？Large fact tables are good candidates for table partitioning. If you have millions or billions of records in a table, you will see performance benefits from logically breaking that data up into smaller chunks. For smaller tables with only a few thousand rows or less, the administrative overhead of maintaining the partitions will outweigh any performance benefits you might see.• Are you experiencing unsatisfactory performance?查询性能满意否？As with any performance tuning initiative, a table should be partitioned only if queries against that table are producing slower response times than desired. • Do your query predicates have identifiable access patterns? 查询where条件有规律可循？Examine the WHERE clauses of your query workload and look for table columns that are consistently used to access data. For example, if most of your queries tend to look up records by date, then a monthly or weekly date-partitioning design might be beneficial. Or if you tend to access records by region, consider a list-partitioning design to divide the table by region.• Does your data warehouse maintain a window of historical data? 数据时间窗口定长？例如只保留12个月?Another consideration for partition design is your organization’s business requirements for maintaining historical data. For example, your data warehouse may only require you to keep the past twelve months worth of data. If the data is partitioned by month, you can easily drop the oldest monthly partition from the warehouse, and load current data into the most recent monthly partition.• Can the data be divided into somewhat equal parts based on some defining criteria? 每个分区差不多大？You should choose partitioning criteria that will divide your data as evenly as possible. If the partitions contain a relatively equal number of records, query performance improves based on the number of partitions created. For example, by dividing a large table into 10 partitions, a query will execute 10 times faster than it would against the unpartitioned table (provided that the partitions are designed to support the query’s criteria).