如何使用pyspark最大限度地减少查询执行时间？
我正在使用Postgres数据库， 并且将spark安装在具有10GB RAM的本地计算机中
在 PgAdmin中执行查询时间-10秒
在 Pyspark-10秒
中查询执行时间下面是我的pyspark代码
from pyspark.sql import DataFrameReader
url = "jdbc:postgresql://168.23.233.4:5432/MyDatabase"
properties = {
"driver": "org.postgresql.Driver",
"user": "postgres",
"password": "123"
}
df = sqlContext.read.jdbc(url=url,table="(select.. very big query limit 10) AS t", properties=properties)
df.show()
查询必须联接超过 13个表，每个表有100万行。
请帮助我使用Spark更快地查询。
我已经根据此博客enter link description here进行了尝试。
在pyspark代码内部运行的“查找以下”查询
select '2019-02-27' as "Attendance_date",e.id as e_id,concat(e.first_name::text, e.last_name::text) as "Employee_name",e.emp_id as "Employee_id",
e.user_id as "User_id",e.customer_id,att.id attendance_id, al.id as Attendance_logs_id,aa1.id as attendance_approval_id,
e.client_emp_id as "Client_employee_id", e.contact_no as "Contact_no",
att.imei as ImeiNumber,e.email_id as "Email_id",
concat(man.first_name::text, man.last_name::text) as "Manager_name", man.id as "Manager_id",
att.Uniform,att.Samsung_Logo,att.Blue_Color_Check,att.Blue_Color_Percentage,
al.Face_Detection_Flag,rl.role_name as "Role_name",b.branch_name as "Branch_name",
b.branch_code as "Branch_code",cty.city_name as "City",sm.state as "State",
gsv1.name as "Geo_Country",gsv2.name as "Geo_State"
,sh.shift_name as "Shift_name",sh.id as shift_id
,((to_timestamp(EXTRACT(EPOCH FROM al.check_in_time::TIME) + ((tz.operator||''||tz.difference)::INTEGER))::TIME AT TIME ZONE 'utc')::TIME)
as "Check_in_time"
,al.check_in_lat as "Check_in_latitude", al.check_in_long as "Check_in_longitude",
(select string_agg(value, ', ') from json_each_text(al.check_in_address::json))as "Check_in_address",
att.check_in_late as "Check_in_late_remarks",al.check_in_distance_variation as "Check_in_distance",al.check_in_selfie as "Check_in_selfie",
case when @aa1.approval_flag = 2 then ch_in.attendance_reason end as "Check_in_rejection_remarks",qc_ch_in.attendance_reason
as "Check_in_qc_review",
case when @att.regularize_flag = 1 or @att.approval_flag = 1 THEN 'Approved'
when @aa2.approval_flag = 1 THEN 'Approved' when @aa2.approval_flag = 2 THEN 'Rejected' when @aa2.approval_flag = 0
THEN 'Pending' else null END as "Check_out_status",
case when att.attendance_type='P' and @att.approval_flag = 1 or att.attendance_type='L' and el.approval_flag=1 or
att.attendance_type='H' and eh.approval_flag=1 or att.attendance_type='M' and em.approval_flag=1 or
att.attendance_type='W' and ew.approval_flag=1 then 'Approved'
when att.attendance_type='P' and @att.approval_flag = 0 or att.attendance_type='L' and el.approval_flag=0 or
att.attendance_type='H' and eh.approval_flag=0 or att.attendance_type='M' and em.approval_flag=0 or
att.attendance_type='W' and ew.approval_flag=0 then 'Waiting for Approval'
when att.attendance_type='P' and el.approval_flag=2 or att.attendance_type='H' and eh.approval_flag=2 or
att.attendance_type='M' and em.approval_flag=2 or att.attendance_type='W' and ew.approval_flag=2 then 'Rejected'
when att.attendance_type='P' and @att.approval_flag is null then '' else 'Waiting for Approval' end as "TL approval status",
case when att.attendance_type='P' then 'Marked'
when att.attendance_type='L' then 'Marked' when att.attendance_type='HL' or att.attendance_type='HP' then 'Marked'
when att.attendance_type='W' or ewo.weekoff_id is not null then 'Marked' when (e.customer_id is null and cehv.id is not null)
or (e.customer_id is not null and ehv.id is not null) then 'Holiday'when el.employee_id is not null then 'Marked'
when eh.employee_id is not null then 'Marked' when ew.employee_id is not null then 'Marked'
when em.employee_id is not null then 'Marked' else 'Not Marked' end "Status",
case when att.attendance_type='P'
then check_in.attendance_reason when att.attendance_type='L' then lt.leave_type_name when el.employee_id is not null
then lt.leave_type_name when att.attendance_type='HL' or att.attendance_type='HP' then 'Half Day'
when att.attendance_type='W' or ewo.weekoff_id is not null then 'Week off' when (e.customer_id is null and cehv.id is not null
) or (e.customer_id is not null and ehv.id is not null) then 'Holiday' when eh.employee_id is not null then 'Holiday' when
ew.employee_id is not null then 'Week off' when em.employee_id is not null then 'Marketoff' else 'Absent'
end as "Attendance_reason",
case when att.on_behalf_attendance is not null then concat(man_behalf.first_name::text,
man_behalf.last_name::text) else null end as "Onbehalf_name",att.Check_Out_Qc_Review,att.Check_Out_Distance,
al.Check_Out_Address
from employees e
left join employee_applied_holidays eh on eh.employee_id=e.id and date('2019-02-27') between eh.from_date and eh.to_date
left join employee_applied_weekoffs ew on ew.employee_id=e.id and date('2019-02-27') between ew.from_date and ew.to_date
left join employee_applied_marketoffs em on em.employee_id=e.id and date('2019-02-27') between em.from_date and em.to_date
inner join users u on u.ref_id = e.id and u.customer_id=200
inner join user_role_groups urg on u.id = urg.user_id and urg.active_flag = 1
inner join attendance_setups ass on ass.role_group_id = urg.role_group_id
left join attendances att on att.employee_id = e.id and att.start_date = '2019-02-27' and att.delete_flag = 0
left join employee_leaves el ON el.id=(select id from employee_leaves el2 where el2.employee_id=e.id and
el2.active_flag=1 and date('2019-02-27') between el2.from_date and el2.to_date order by id desc limit 1)
left join leave_types lt ON lt.id=(select leave_type from employee_leaves el where el.employee_id=e.id and
el.active_flag=1 and date('2019-02-27') between el.from_date and el.to_date order by id desc limit 1)
left join attendance_logs al on al.attendance_id = att.id and al.attendance_flag = 1
left join attendance_approvals aa1 on al.id = aa1.attendance_log_id and aa1.action = 1 and aa1.active_flag = 1
left join attendance_approvals aa2 on al.id = aa2.attendance_log_id and aa1.action = 2 and aa2.active_flag = 1
inner join branches b on b.id = e.branch_id left join employees man on man.id = e.manager_id
left join employees man_behalf on man_behalf.id = att.on_behalf_attendance
left join employee_weekoff ewo on e.id = ewo.emp_id and date_part('dow','2019-02-27'::TIMESTAMP)+1 = ewo.weekoff_id and
ewo.active_flag =1 left join employee_holidays_view ehv on e.id = ehv.id and ehv.holiday_date = '2019-02-27'
left join company_employee_holidays_view cehv on e.id = cehv.id and ehv.holiday_date = '2019-02-27'
inner join roles rl on rl.id = e.role_id inner join cities cty on cty.id = b.city_id
inner join states on states.id = b.state_id inner join state_master sm on sm.id = states.state_id
inner join countries on countries.id = b.country_id inner join country_master cm on cm.country_id = countries.country_id
left join shifts sh on sh.id = att.shift_id left join attendance_reasons ch_in on ch_in.id = aa1.reason_id
left join sessions se on sh.id=se.shift_id left join attendance_reasons ch_out on ch_out.id = aa2.reason_id
left join attendance_reasons qc_ch_in on qc_ch_in.id = att.check_in_qc_review
left join attendance_reasons qc_ch_out on qc_ch_out.id = att.check_out_qc_review
left join attendance_reasons check_in on check_in.id = al.reason_id
left join time_zones tz on b.timezone = tz.time_zone inner join geo_outlet_mapping gom
on b.id = gom.outlet_id left join geo_structure_values gsv1 on gsv1.id = gom.level1 left join
geo_structure_values gsv2 on gsv2.id = gom.level2 left join geo_structure_values gsv3 on gsv3.id = gom.level3
where e.customer_id=200
group by concat(e.first_name::text, e.last_name::text) ,e.emp_id ,e.user_id ,e.client_emp_id , e.contact_no , e.email_id,e.profile_picture,(select string_agg(role_group_name, ', ') from role_group where role_group_id = any((select array_agg(role_group_id) from user_role_groups where user_id = u.id and active_flag = 1)::int[])),concat(man.first_name::text, man.last_name::text), rl.role_name,b.branch_name,b.branch_code,cty.city_name,sm.state,cm.country,gsv1.name,gsv2.name,case when @ass.reference_point = 1 THEN b.latitude else e.latitude END,case when @ass.reference_point = 1 THEN b.longitude else e.longitude END,sh.shift_name,sh.start_time, sh.end_time,((to_timestamp(EXTRACT(EPOCH FROM al.check_in_time::TIME) + ((tz.operator||''||tz.difference)::INTEGER))::TIME AT TIME ZONE 'utc')::TIME),case
when current_date='2019-02-27' and sh.end_time<cast(current_time as time without time zone) then null else (case when se.check_out_flag=1 then cast(att.total_hours as interval) when se.check_out_flag=0 then sh.end_time-((to_timestamp(EXTRACT(EPOCH FROM al.check_in_time::TIME) + ((tz.operator||''||tz.difference)::INTEGER))::TIME AT TIME ZONE 'utc')::TIME) end) end,al.check_in_lat, al.check_in_long,(select string_agg(value, ', ') from json_each_text(al.check_in_address::json)),att.check_in_late,al.check_in_distance_variation,al.check_in_selfie,case when @att.regularize_flag = 1 or @att.approval_flag = 1 THEN 'Approved' when @aa1.approval_flag = 1 THEN 'Approved' when @aa1.approval_flag = 2 THEN 'Rejected' when @aa1.approval_flag = 0 THEN 'Pending' else null END,case when @aa1.approval_flag = 2 then ch_in.attendance_reason end,qc_ch_in.attendance_reason,case when @att.regularize_flag = 1 or @att.approval_flag = 1 THEN 'Approved' when @aa2.approval_flag = 1 THEN 'Approved' when @aa2.approval_flag = 2 THEN 'Rejected' when @aa2.approval_flag = 0 THEN 'Pending' else null END,
case when att.attendance_type='P' and @att.approval_flag = 1 or att.attendance_type='L' and el.approval_flag=1 or
att.attendance_type='H' and eh.approval_flag=1 or att.attendance_type='M' and em.approval_flag=1 or
att.attendance_type='W' and ew.approval_flag=1 then 'Approved'
when att.attendance_type='P' and @att.approval_flag = 0 or att.attendance_type='L' and el.approval_flag=0 or
att.attendance_type='H' and eh.approval_flag=0 or att.attendance_type='M' and em.approval_flag=0 or
att.attendance_type='W' and ew.approval_flag=0 then 'Waiting for Approval'
when att.attendance_type='P' and el.approval_flag=2 or att.attendance_type='H' and eh.approval_flag=2 or
att.attendance_type='M' and em.approval_flag=2 or att.attendance_type='W' and ew.approval_flag=2 then 'Rejected'
when att.attendance_type='P' and @att.approval_flag is null then '' else 'Waiting for Approval' end,
case when att.attendance_type='P' then 'Marked' when att.attendance_type='L' then 'Marked'
when att.attendance_type='HL' or att.attendance_type='HP' then 'Marked' when att.attendance_type='W'
or ewo.weekoff_id is not null then 'Marked' when (e.customer_id is null and cehv.id is not null) or (e.customer_id is not null and ehv.id is not null) then 'Holiday' when el.employee_id is not null then 'Marked' when eh.employee_id is not null then 'Marked' when ew.employee_id is not null then 'Marked' when em.employee_id is not null then 'Marked' else 'Not Marked' end,case when att.attendance_type='P' then check_in.attendance_reason when att.attendance_type='L' then lt.leave_type_name when el.employee_id is not null then lt.leave_type_name when att.attendance_type='HL' or att.attendance_type='HP' then 'Half Day' when att.attendance_type='W' or ewo.weekoff_id is not null then 'Week off' when (e.customer_id is null and cehv.id is not null) or (e.customer_id is not null and ehv.id is not null) then 'Holiday' when eh.employee_id is not null then 'Holiday' when ew.employee_id is not null then 'Week off' when em.employee_id is not null then 'Marketoff' else 'Absent' end ,case when att.on_behalf_attendance is not null then concat(man_behalf.first_name::text,man_behalf.last_name::text) else null end
,att.id,e.customer_id,al.id,aa1.id,att.imei,man.id,att.Uniform,att.Samsung_Logo,att.Blue_Color_Check,att.Blue_Color_Percentage,
al.Face_Detection_Flag,att.Check_Out_Qc_Review,att.Check_Out_Distance,sh.id,att.id,e.id;
答案 0 :(得分：-1)
据我所知，在这种情况下，在pyspark和pgAdmin中的查询执行时间显然会花费相同的时间，因为两个查询都是只能在Postgres DB上执行。
这时，您尚未使用spark的分布式计算和存储功能。您刚刚从Postgres DB的SQL输出中创建了RDD。只有在此之后，您使用此RDD进行的操作才会显示出速度差异。
因此，优化只能在Postgres DB方面进行。以下几点将有所帮助：