优化以下 postgreSQL 代码的可能方法是什么？

Question

我写了这个 SQL 查询来从 greenplum datalake 中获取数据。主要 table 有大约 800,000 行，我正在加入其他 table。下面的查询花费了大量的时间来给出结果。查询时间较长的可能原因是什么？如何解决？

select    
          a.pole,
          t.country_name,
          a.service_area,  
          a.park_name,

          t.turbine_platform_name,
          a.turbine_subtype,
          a.pad as "turbine_name",
          t.system_number as "turbine_id",
          a.customer,
          a.service_contract,   

          a.component,
          c.vendor_mfg as "component_manufacturer",

          a.case_number,
          a.description as "case_description",
          a.rmd_diagnosis as "case_rmd_diagnostic_description",
          a.priority as "case_priority",
          a.status as "case_status",
          a.actual_rootcause as "case_actual_rootcause",
          a.site_trends_feedback as "case_site_feedback",
          a.added as "date_case_added",
          a.start as "date_case_started",
          a.last_flagged as "date_case_flagged_by_algorithm_latest",
          a.communicated as "date_case_communicated_to_field",
          a.field_visible_date as "date_case_field_visbile_date",
          a.fixed as "date_anamoly_fixed",
          a.expected_clse as "date_expected_closure",
          a.request_closure_date as "date_case_request_closure",
          a.validation_date as "date_case_closure",
          a.production_related,
          a.estimated_value as "estimated_cost_avoidance",
          a.cms,
          a.anomaly_category,
          a.additional_information as "case_additional_information",
          a.model,
          a.full_model,
          a.sent_to_field as "case_sent_to_field"

      from app_pul.anomaly_stage a
 left join ge_cfg.turbine_detail t on a.scada_number = t.system_number and a.added > '2017-12-31'
 left join tbwgr_v.pmt_wmf_tur_component_master_t c on a.component = c.component_name

Answer 1

验证联接是否使用各自的主键和外键。
尝试执行查询，一个接一个地删除左联接，这样您就会看到问题的焦点。
尝试使用计划执行。

Answer 2

您的查询基本上是：

 select . . .
 from app_pul.anomaly_stage a left join
      ge_cfg.turbine_detail t 
      on a.scada_number = t.system_number and
         a.added > '2017-12-31' left join
         tbwgr_v.pmt_wmf_tur_component_master_t c
         on a.component = c.component_name

首先，忽略a上的条件，因为它是left join中的第一个table，是on子句。因此，我假设您实际上打算对其进行过滤，因此将查询写为：

 select . . .
 from app_pul.anomaly_stage a left join
      ge_cfg.turbine_detail t 
      on a.scada_number = t.system_number left join
      tbwgr_v.pmt_wmf_tur_component_master_t c
      on a.component = c.component_name
 where a.added > '2017-12-31'

这可能有助于提高性能。然后在 Postgres 中，您需要 turbine_detail(system_number) 和 pmt_wmf_tur_component_master_t(component_name) 上的索引。索引对第一个有帮助是值得怀疑的 table，因为您已经在选择大量数据。

我不确定索引在 Greenplum 中是否合适。

优化以下 postgreSQL 代码的可能方法是什么？

What are the possible ways to optimize the below postgreSQL code?

sql

postgresql

query-optimization

greenplum