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Why my mview is not refreshing after commit?

JackKFeb 7 2022 — edited Feb 7 2022

Hi All.
I have tables:

create table OS_OUTAGES (
 out_id       NUMBER(22) generated by default on null as identity (nocache),
 out_number     VARCHAR2(40) not null,
 out_status     VARCHAR2(10) not null,
 out_dscr      VARCHAR2(4000),
 out_is_proposition VARCHAR2(1),
 out_usr_id     INTEGER not null,
 out_oki_code    VARCHAR2(20) not null,
 out_bup_code    NUMBER(12) not null,
 out_oup_id     NUMBER(20),
 out_gel_mrid    VARCHAR2(70) not null,
 out_vl_mrid    VARCHAR2(70),
 out_oty_code    VARCHAR2(20) not null,
 out_ouv_id     NUMBER(22) not null,
 out_swl_id     NUMBER(4),
 out_locked_by   NUMBER(22),
 out_locked_until  DATE,
 out_out_id     NUMBER(22),
 out_sch_id     NUMBER(22),
 out_ois_id     NUMBER(22),
 out_number__sort  as ("OMSW"."OS_UTIL"."OBJNUMBER2SORT"("OUT_NUMBER")),
 out_root_out_id  NUMBER(22),
 out_usid      VARCHAR2(55) invisible
);

alter table OS_OUTAGES add constraint OUT_PK primary key (OUT_ID);

alter table OS_OUTAGES
 add constraint OUT_OUV_FK foreign key (OUT_OUV_ID)
 references OS_OUTAGE_VERSIONS (OUV_ID) on delete set null
 deferrable initially deferred;

---

create table OS_OUTAGE_VERSIONS (
 ouv_id           NUMBER(22) generated by default on null as identity (nocache),
 ouv_change_time       DATE default sysdate not null,
 ouv_start          TIMESTAMP(0) WITH TIME ZONE not null,
 ouv_end           TIMESTAMP(0) WITH TIME ZONE not null,
 ouv_readiness        NUMBER,
 ouv_cycle          VARCHAR2(2) not null,
 ouv_break_possibility    CHAR(1),
 ouv_night_work       CHAR(1),
 ouv_saturday_work      CHAR(1),
 ouv_sunday_work       CHAR(1),
 ouv_out_id         NUMBER(22) not null,
 ouv_usr_id         INTEGER not null,
 ouv_status         VARCHAR2(10),
 ouv_version         VARCHAR2(43) not null,
 ouv_ouv_id         NUMBER(22),
 ouv_readiness_u       VARCHAR2(1),
 ouv_required_time      NUMBER,
 ouv_required_time_u     VARCHAR2(1),
 ouv_required_time__sort   as ("OUV_REQUIRED_TIME"*DECODE("OUV_REQUIRED_TIME_U",'d',1440,'h',60,'m',1)),
 ouv_prefered_start     TIMESTAMP(0) WITH TIME ZONE,
 ouv_prefered_end      TIMESTAMP(0) WITH TIME ZONE,
 ouv_cost          NUMBER,
 ouv_refusing_cost      NUMBER,
 ouv_readiness__sort     as ("OUV_READINESS"*DECODE("OUV_READINESS_U",'d',1440,'h',60,'m',1)),
 ouv_crr_id         NUMBER(4),
 ouv_rb2_09_valid      CHAR(1) default 'n' not null,
 ouv_in_cartesian      CHAR(1) default 'y' not null,
 ouv_weekend_work      CHAR(1),
 ouv_holiday_work      CHAR(1),
 ouv_priority        NUMBER(1) default 1,
 ouv_night_readiness     NUMBER(3),
 ouv_night_readiness_u    CHAR(1),
 ouv_busbar_work_possibility CHAR(1),
 ouv_schedule_required    CHAR(1),
 ouv_programme_required   CHAR(1),
 ouv_temp_ver        NUMBER(3),
 ouv_length         as ("OMSW"."OS_OUTAGE"."OUV_LENGTH_CALC"("OUV_START","OUV_END"))
);

alter table OS_OUTAGE_VERSIONS add constraint OUV_PK primary key (OUV_ID);

alter table OS_OUTAGE_VERSIONS
 add constraint OUV_OUT_FK foreign key (OUV_OUT_ID)
 references OS_OUTAGES (OUT_ID) on delete cascade;

---

create table OS_OUTAGE_PACKAGES (
 opa_id      NUMBER(22) generated by default on null as identity (nocache),
 opa_usr_id    NUMBER(22) not null,
 opa_opv_id    NUMBER(22),
 opa_locked_by  NUMBER(22),
 opa_locked_until DATE,
 opa_status    VARCHAR2(5) not null,
 opa_opa_id    NUMBER(22),
 opa_number    VARCHAR2(40),
 opa_sch_id    NUMBER(22),
 opa_pis_id    NUMBER(22),
 opa_bup_code   NUMBER(12) not null,
 opa_number__sort as ("OMSW"."OS_UTIL"."OBJNUMBER2SORT"("OPA_NUMBER")),
 opa_root_opa_id NUMBER(22),
 opa_type     CHAR(1) default 'P' not null,
 opa_category   CHAR(1)
);

alter table OS_OUTAGE_PACKAGES add constraint OPA_PK primary key (OPA_ID);

alter table OS_OUTAGE_PACKAGES
 add constraint OPA_OPV_FK foreign key (OPA_OPV_ID)
 references OS_OUTAGE_PACKAGE_VERSIONS (OPV_ID)
 deferrable initially deferred;

---

create table OS_OUTAGE_PACKAGE_VERSIONS (
 opv_id     NUMBER(22) generated by default on null as identity (nocache),
 opv_change_time DATE default sysdate not null,
 opv_opa_id   NUMBER(22) not null,
 opv_opv_id   NUMBER(22),
 opv_crr_id   NUMBER(4),
 opv_usr_id   NUMBER(22) not null,
 opv_version   VARCHAR2(43) not null,
 opv_management VARCHAR2(4),
 opv_pp_demand  CHAR(1),
 opv_h_demand  CHAR(1),
 opv_bw_demand  CHAR(1),
 opv_pca_code  VARCHAR2(10),
 opv_out_id   NUMBER(22),
 opv_temp_ver  NUMBER(3),
 opv_dscr    VARCHAR2(1500)
);

alter table OS_OUTAGE_PACKAGE_VERSIONS add constraint OPV_PK primary key (OPV_ID);

alter table OS_OUTAGE_PACKAGE_VERSIONS
 add constraint OPV_OPA_FK foreign key (OPV_OPA_ID)
 references OS_OUTAGE_PACKAGES (OPA_ID) on delete cascade;

alter table OS_OUTAGE_PACKAGE_VERSIONS
 add constraint OPV_OUT_FK foreign key (OPV_OUT_ID)
 references OS_OUTAGES (OUT_ID);

---

create table OS_OUTS_IN_PACKAGE (
 oip_id   NUMBER(22) generated by default on null as identity (nocache),
 oip_opv_id NUMBER(22) not null,
 oip_ouv_id NUMBER(22) not null,
 oip_status CHAR(1),
 oip_created DATE default sysdate
);

alter table OS_OUTS_IN_PACKAGE
 add constraint OIP_OPV_FK foreign key (OIP_OPV_ID)
 references OS_OUTAGE_PACKAGE_VERSIONS (OPV_ID) on delete cascade;

alter table OS_OUTS_IN_PACKAGE
 add constraint OIP_OUV_FK foreign key (OIP_OUV_ID)
 references OS_OUTAGE_VERSIONS (OUV_ID) on delete cascade;

There are of course some indexes created on FK columns.
I create materialized view log created:

create materialized view log on OS_OUTAGES
 with primary key, -- uncomment if table has PK
    rowid,
    sequence( -- all but PK columns
out_number
,out_status
,out_dscr
,out_is_proposition
,out_usr_id
,out_oki_code
,out_bup_code
,out_gel_mrid
,out_vl_mrid
,out_oty_code
,out_ouv_id
,out_swl_id
,out_locked_by
,out_locked_until
,out_out_id
,out_sch_id
,out_ois_id
--out_number__sort
,out_root_out_id
--out_usid
) including new values;

create materialized view log on OS_OUTAGE_VERSIONS
 with primary key, -- uncomment if table has PK
    rowid,
    sequence( -- all but PK columns
--ouv_id
ouv_change_time
,ouv_start
,ouv_end
,ouv_readiness
,ouv_cycle
,ouv_break_possibility
,ouv_night_work
,ouv_saturday_work
,ouv_sunday_work
,ouv_out_id
,ouv_usr_id
,ouv_status
,ouv_version
,ouv_ouv_id
,ouv_readiness_u
,ouv_required_time
,ouv_required_time_u
--ouv_required_time__sort
,ouv_prefered_start
,ouv_prefered_end
,ouv_cost
,ouv_refusing_cost
--ouv_readiness__sort
,ouv_crr_id
,ouv_rb2_09_valid
,ouv_in_cartesian
,ouv_weekend_work
,ouv_holiday_work
,ouv_priority
,ouv_night_readiness
,ouv_night_readiness_u
,ouv_busbar_work_possibility
,ouv_schedule_required
,ouv_programme_required
,ouv_temp_ver
--ouv_length
) including new values;

create materialized view log on OS_OUTAGE_PACKAGES
 with primary key, -- uncomment if table has PK
    rowid,
    sequence( -- all but PK columns
--opa_id
opa_usr_id
,opa_opv_id
,opa_locked_by
,opa_locked_until
,opa_status
,opa_opa_id
,opa_number
,opa_sch_id
,opa_pis_id
,opa_bup_code
--,opa_number__sort
,opa_root_opa_id
,opa_type
,opa_category
) including new values;

create materialized view log on OS_OUTAGE_PACKAGE_VERSIONS
 with primary key, -- uncomment if table has PK
    rowid,
    sequence( -- all but PK columns
--opv_id
opv_change_time
,opv_opa_id
,opv_opv_id
,opv_crr_id
,opv_usr_id
,opv_version
,opv_management
,opv_pp_demand
,opv_h_demand
,opv_bw_demand
,opv_pca_code
,opv_out_id
,opv_temp_ver
,opv_dscr
) including new values;

create materialized view log on OS_OUTS_IN_PACKAGE
 with --primary key, -- uncomment if table has PK
    rowid,
    sequence( -- all but PK columns
 oip_id
,oip_opv_id
,oip_ouv_id
,oip_status
,oip_created
) including new values;

Then I create mview:

create materialized view OS_OPV_AGGR_MVW
refresh fast on commit
as
SELECT opa_id, opv_id,
    min(ouv_start) AS min_start,
    max(ouv_end)  AS max_end
   ,count(*)    AS cnt
 FROM OS_OUTAGE_PACKAGES
   ,OS_OUTAGE_PACKAGE_VERSIONS
   ,OS_OUTS_IN_PACKAGE
   ,OS_OUTAGES
   ,OS_OUTAGE_VERSIONS
 WHERE opv_id = opa_opv_id
  AND oip_opv_id = opa_opv_id
  AND out_ouv_id = oip_ouv_id
  AND ouv_id = out_ouv_id
 GROUP BY opa_id, opv_id;

Mview is created correctly. However, when transaction is commited, mview is not being refreshed and rows in mvlogs persist.
I don't know where is the problem.
Could anyone help me?
I am using Oracle 19c.
Best regards,
Jacek
This post has been answered by Jonathan Lewis on Feb 7 2022
Jump to Answer

Comments

Mike Kutz

Query 1b
Use ANSI joins

Select t1.emp_id, t1.emp_name, t2.dept_name
from EMPLOYEES t1
    Left join DEPARTMENTS t2. 
      On t1.dept_id = t2.dept_id
order by t1.emp_name

In Query 2, the scalar sub query is ran for each returning row of EMPLOYEES.

1 person found this helpful
User_H3J7U

To be equivalent, emp.department_id must be fk not null. And depends on function.

1 person found this helpful
Jonathan Lewis

Calling a pl/sql function to return a string that could simply be a column (or concatenation of columns) from a table is introducing an overhead and a possible threat. It's not necessary.
Assuming you have the standard referential integrity between employees and departments (i.e. unique id for departments, foreign key on employees to departments) then your inline scalar subquery could be:

(select dep.dept_name from departments dep where dep.dept_id = emp.dept_id)

It's worth noting that the return from the function would be varchar2(4000) which might affect the output of the final query, or if you're pulling the data across a network might (depending on the client tool) waste a lot of memory if (for example) the client code allocated memory based on the maximum possible return length).
If employees allows for employees not yet assigned to a department (i.e. null dept_id) this would report NULL in the final query, whereas the join would lose the employee unless you changed the join to an outer join.
You are presumably hoping to benefit from scalar subquery caching with the scalar subquery approach - or possibly result caching, or pl/sql function caching. Two things to remember if you depend on such things - how long does the cache persist, what happens if you get a cache collision. The more different departments you have (and millions of employees may mean thousands of departments) the more likely you are to get a hash collision on the cache and end up with randomly variable performance.
In your example the simply join is likely to be a hash join using the departments table as the build table with optimal workarea usage - which means an in-memory hash lookup by each employee, and you can't really get much faster than that.
With an example like this "millions of employees, no filtering" your performance problems are more likely to be related to transporting the volume of data to the client - so setting a large fetch arraysize is likely to be far more important than fiddling with such simple SQL. And while there is a way to write the query so that it can perform a little faster, there are two other aspects of coding to consider: how fragile is the code, and what are the chances that the next person who has to modify the code will not understand the tweaks you've used and do something that makes things worse.

Here's a very old example of the performance instability that can appear with scalar subquery caching - in this case it's a filter subquery, but the principle is the same: https://jonathanlewis.wordpress.com/2006/11/06/filter-subqueries/

Regards
Jonathan Lewis

Nic Pilot

Thank you all for your replies & tips.
So better go for Query 1 or Query 1b.
Is there any difference in term of performance between Query 1 & Query 1b ?

Jonathan Lewis

Bear in mind that if employees.dept_id is allowed to be null then the two queries will return different results. In that case the outer join equivalent using Oracle's traditional syntax would be:

Select t1.emp_id, t1.emp_name, t2.dept_name
from EMPLOYEES t1, DEPARTMENTS t2
where t1.dept_id = t2.dept_id(+)
order by t1.emp_name

(which you could view as "we add an empty row to t2/departments to give employees without a department something to join to")
Generally it is now seen strategically as a good thing to use the "ANSI" syntax rather than traditional Oracle syntax. There are a few oddities (whichevet you choose) that mean in some boundary cases you get different plans as you switch. In this case there would be no performance difference.
Regards
Jonathan Lewis

Nic Pilot

Thank you Jonathan.
Regards

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Post Details

Added on Feb 7 2022
#database
12 comments
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