GaussDB(DWS)性能调优：Sort+Groupagg聚集引起的性能瓶颈案例-526互联

本文分享自华为云社区《GaussDB(DWS)性能调优：Sort+Groupagg聚集引起的性能瓶颈案例》，作者： O泡果奶~ 。

本文针对SQL语句长时间执行不出来，且verbose执行计划中出现Sort+GroupAgg聚集方式的案例进行分析。

1、【问题描述】

语句执行时间过长，2300s+也无法得出结果。从verbose执行计划可以看出存在sort聚合。

2、【原始语句】

SELECT /*+ set global(agg_redistribute_enhancement on) set global (best_agg_plan 3)*/

dm_ebg_glb_kpi_sum_w_v."na_level_name",

dm_ebg_glb_kpi_sum_w_v."na_level",

dm_ebg_glb_kpi_sum_w_v."sales_lv3_prod_list_code",

dm_ebg_glb_kpi_sum_w_v."sales_lv1_prod_list_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv2_prod_list_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv1_prod_list_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv0_prod_list_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv0_prod_list_code",

dm_ebg_glb_kpi_sum_w_v."sales_lv1_prod_list_code",

dm_ebg_glb_kpi_sum_w_v."sales_lv3_prod_list_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv2_prod_list_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv3_prod_list_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv0_prod_list_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv2_prod_list_code",

dm_ebg_glb_kpi_sum_w_v."period_id",

dm_ebg_glb_kpi_sum_w_v."year",

dm_ebg_glb_kpi_sum_w_v."month",

dm_ebg_glb_kpi_sum_w_v."report_category_cn_name",

dm_ebg_glb_kpi_sum_w_v."report_category_en_name",

dm_ebg_glb_kpi_sum_w_v."currency_code",

dm_ebg_glb_kpi_sum_w_v."exchange_rate_type_cn_name",

dm_ebg_glb_kpi_sum_w_v."exchange_rate_type_en_name",

dm_ebg_glb_kpi_sum_w_v."report_item_code",

dm_ebg_glb_kpi_sum_w_v."report_item_cn_name",

dm_ebg_glb_kpi_sum_w_v."report_item_en_name",

dm_ebg_glb_kpi_sum_w_v."report_item_type",

dm_ebg_glb_kpi_sum_w_v."report_item_flag",

dm_ebg_glb_kpi_sum_w_v."region_code",

dm_ebg_glb_kpi_sum_w_v."region_cn_name",

dm_ebg_glb_kpi_sum_w_v."region_en_name",

dm_ebg_glb_kpi_sum_w_v."oversea_flag",

dm_ebg_glb_kpi_sum_w_v."repoffice_code",

dm_ebg_glb_kpi_sum_w_v."repoffice_cn_name",

dm_ebg_glb_kpi_sum_w_v."repoffice_en_name",

dm_ebg_glb_kpi_sum_w_v."ebg_focus_cn_name",

dm_ebg_glb_kpi_sum_w_v."ebg_focus_en_name",

dm_ebg_glb_kpi_sum_w_v."lv0_prod_rnd_team_code",

dm_ebg_glb_kpi_sum_w_v."lv0_prod_rd_team_cn_name",

dm_ebg_glb_kpi_sum_w_v."lv0_prod_rd_team_en_name",

dm_ebg_glb_kpi_sum_w_v."lv1_prod_rnd_team_code",

dm_ebg_glb_kpi_sum_w_v."lv1_prod_rd_team_cn_name",

dm_ebg_glb_kpi_sum_w_v."lv1_prod_rd_team_en_name",

dm_ebg_glb_kpi_sum_w_v."lv2_prod_rnd_team_code",

dm_ebg_glb_kpi_sum_w_v."lv2_prod_rd_team_cn_name",

dm_ebg_glb_kpi_sum_w_v."lv2_prod_rd_team_en_name",

dm_ebg_glb_kpi_sum_w_v."lv3_prod_rnd_team_code",

dm_ebg_glb_kpi_sum_w_v."lv3_prod_rd_team_cn_name",

dm_ebg_glb_kpi_sum_w_v."lv3_prod_rd_team_en_name",

dm_ebg_glb_kpi_sum_w_v."named_account_flag",

dm_ebg_glb_kpi_sum_w_v."domtc_entps_indu_class_code",

dm_ebg_glb_kpi_sum_w_v."domtc_entps_indu_class_cn_name",

dm_ebg_glb_kpi_sum_w_v."domtc_entps_indu_class_en_name",

dm_ebg_glb_kpi_sum_w_v."industry_class_code",

dm_ebg_glb_kpi_sum_w_v."industry_class_cn_name",

dm_ebg_glb_kpi_sum_w_v."industry_class_en_name",

dm_ebg_glb_kpi_sum_w_v."sub_industry_class_code",

dm_ebg_glb_kpi_sum_w_v."sub_industry_class_cn_name",

dm_ebg_glb_kpi_sum_w_v."sub_industry_class_en_name",

dm_ebg_glb_kpi_sum_w_v."focus_industry_cn_name",

dm_ebg_glb_kpi_sum_w_v."focus_industry_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_mode_code",

dm_ebg_glb_kpi_sum_w_v."sales_mode_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_mode_en_name",

SUM(dm_ebg_glb_kpi_sum_w_v."ptd_amt") as "ptd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."py_ptd_amt") as "py_ptd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."pp_ptd_amt") as "pp_ptd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."qtd_amt") as "qtd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."py_qtd_amt") as "py_qtd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."pp_qtd_amt") as "pp_qtd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."ytd_amt") as "ytd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."py_ytd_amt") as "py_ytd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."py_all_ytd_amt") as "py_all_ytd_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."end_bal_amt") as "end_bal_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."cp_open_bal_amt") as "cp_open_bal_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."pq_end_bal_amt") as "pq_end_bal_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."cy_open_bal_amt") as "cy_open_bal_amt",

SUM(dm_ebg_glb_kpi_sum_w_v."py_end_bal_amt") as "py_end_bal_amt"

FROM fin_dmr_ebgdis.dm_ebg_glb_kpi_sum_w_v

where 1 = 1

and 1 = 1

AND dm_ebg_glb_kpi_sum_w_v."period_id" = 202302

group by dm_ebg_glb_kpi_sum_w_v."na_level_name",

dm_ebg_glb_kpi_sum_w_v."na_level",

dm_ebg_glb_kpi_sum_w_v."sales_lv3_prod_list_code",

dm_ebg_glb_kpi_sum_w_v."sales_lv1_prod_list_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv2_prod_list_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv1_prod_list_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv0_prod_list_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv0_prod_list_code",

dm_ebg_glb_kpi_sum_w_v."sales_lv1_prod_list_code",

dm_ebg_glb_kpi_sum_w_v."sales_lv3_prod_list_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv2_prod_list_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv3_prod_list_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv0_prod_list_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_lv2_prod_list_code",

dm_ebg_glb_kpi_sum_w_v."period_id",

dm_ebg_glb_kpi_sum_w_v."year",

dm_ebg_glb_kpi_sum_w_v."month",

dm_ebg_glb_kpi_sum_w_v."report_category_cn_name",

dm_ebg_glb_kpi_sum_w_v."report_category_en_name",

dm_ebg_glb_kpi_sum_w_v."currency_code",

dm_ebg_glb_kpi_sum_w_v."exchange_rate_type_cn_name",

dm_ebg_glb_kpi_sum_w_v."exchange_rate_type_en_name",

dm_ebg_glb_kpi_sum_w_v."report_item_code",

dm_ebg_glb_kpi_sum_w_v."report_item_cn_name",

dm_ebg_glb_kpi_sum_w_v."report_item_en_name",

dm_ebg_glb_kpi_sum_w_v."report_item_type",

dm_ebg_glb_kpi_sum_w_v."report_item_flag",

dm_ebg_glb_kpi_sum_w_v."region_code",

dm_ebg_glb_kpi_sum_w_v."region_cn_name",

dm_ebg_glb_kpi_sum_w_v."region_en_name",

dm_ebg_glb_kpi_sum_w_v."oversea_flag",

dm_ebg_glb_kpi_sum_w_v."repoffice_code",

dm_ebg_glb_kpi_sum_w_v."repoffice_cn_name",

dm_ebg_glb_kpi_sum_w_v."repoffice_en_name",

dm_ebg_glb_kpi_sum_w_v."ebg_focus_cn_name",

dm_ebg_glb_kpi_sum_w_v."ebg_focus_en_name",

dm_ebg_glb_kpi_sum_w_v."lv0_prod_rnd_team_code",

dm_ebg_glb_kpi_sum_w_v."lv0_prod_rd_team_cn_name",

dm_ebg_glb_kpi_sum_w_v."lv0_prod_rd_team_en_name",

dm_ebg_glb_kpi_sum_w_v."lv1_prod_rnd_team_code",

dm_ebg_glb_kpi_sum_w_v."lv1_prod_rd_team_cn_name",

dm_ebg_glb_kpi_sum_w_v."lv1_prod_rd_team_en_name",

dm_ebg_glb_kpi_sum_w_v."lv2_prod_rnd_team_code",

dm_ebg_glb_kpi_sum_w_v."lv2_prod_rd_team_cn_name",

dm_ebg_glb_kpi_sum_w_v."lv2_prod_rd_team_en_name",

dm_ebg_glb_kpi_sum_w_v."lv3_prod_rnd_team_code",

dm_ebg_glb_kpi_sum_w_v."lv3_prod_rd_team_cn_name",

dm_ebg_glb_kpi_sum_w_v."lv3_prod_rd_team_en_name",

dm_ebg_glb_kpi_sum_w_v."named_account_flag",

dm_ebg_glb_kpi_sum_w_v."domtc_entps_indu_class_code",

dm_ebg_glb_kpi_sum_w_v."domtc_entps_indu_class_cn_name",

dm_ebg_glb_kpi_sum_w_v."domtc_entps_indu_class_en_name",

dm_ebg_glb_kpi_sum_w_v."industry_class_code",

dm_ebg_glb_kpi_sum_w_v."industry_class_cn_name",

dm_ebg_glb_kpi_sum_w_v."industry_class_en_name",

dm_ebg_glb_kpi_sum_w_v."sub_industry_class_code",

dm_ebg_glb_kpi_sum_w_v."sub_industry_class_cn_name",

dm_ebg_glb_kpi_sum_w_v."sub_industry_class_en_name",

dm_ebg_glb_kpi_sum_w_v."focus_industry_cn_name",

dm_ebg_glb_kpi_sum_w_v."focus_industry_en_name",

dm_ebg_glb_kpi_sum_w_v."sales_mode_code",

dm_ebg_glb_kpi_sum_w_v."sales_mode_cn_name",

dm_ebg_glb_kpi_sum_w_v."sales_mode_en_name" limit 200

3、【性能分析】

由于语句长时间无法执行完毕，通过其verbose执行计划中的E-rows可以看出，由于较小且去重后行数变化不大，优化器采用了Sort+GroupAgg的聚集方式。

通常情况下，Sort+GroupAgg性能并不如Hashagg，此时，可以通过利用

set enable_sort = off;

或是

+set [gloabal] (enable_sort off)

来避免使用Sort+GroupAgg聚集方式。

补充：Sort+GroupAgg与Hashagg对比

	Hashagg	Sort+GroupAgg
执行方式	每行元组根据聚集列散列建立hash表，进行去重比较	所有元组排序后进行聚集去重操作
限制	所有聚集列支持hash散列	所有聚集列支持排序
优势	通过哈希散列比较可以快速定位到重复元组	输出结果保持有序，有利于后续有序操作
劣势	受初始散列桶个数影响较大	如果初始集较大，Sort性能较差
适合使用的情况	去重后行数较少的场景	相比Hashagg，当去重后行数和输入行数差不多，且输入行数较少时适用