I have 6,00,000 records and i want to fetch 10 records from them as i want to display only 10 records in the grid my stored procedure is working properly when i m fetching records between 1-10000 E.G (500-510) after that the execution time is increased when the row number is increased E.G if i fetch record b/w 1,00,000-1,00,010 it takes more time to execute
can any one please help me i have used ROW_NUMBER() to get the number row number and used between to retrieve data.
please give a optimized way to get records
The stored procedure creats a sql query as given below
I have 6,00,000 records and i want to fetch 10 records from them as i want to display only 10 records in the grid my stored procedure is working properly when i m fetching records between 1-10000 E.G (500-510) after that the execution time is increased when the row number is increased E.G if i fetch record b/w 1,00,000-1,00,010 it takes more time to execute
can any one please help me i have used ROW_NUMBER() to get the number row number and used between to retrieve data.
please give a optimized way to get records
The stored procedure create a sql query as given below
SELECT FuelClaimId from
( SELECT fc.FuelClaimId,ROW_NUMBER() OVER ( order by fc.FuelClaimId ) AS RowNum
from FuelClaims fc
INNER JOIN Vehicles v on fc.VehicleId =v.VehicleId
INNER JOIN Drivers d on d.DriverId =v.OfficialID
INNER JOIN Departments de on de.DepartmentId =d.DepartmentId
INNER JOIN Provinces p on de.ProvinceId =p.ProvinceId
INNER JOIN FuelRates f on f.FuelRateId =fc.FuelRateId
INNER JOIN FuelClaimStatuses fs on fs.FuelClaimStatusId= fc.statusid
INNER JOIN LogsheetMonths l on l.LogsheetMonthId =f.LogsheetMonthId
Where fc.IsDeleted = 0) AS MyDerivedTable WHERE MyDerivedTable.RowNum BETWEEN
600000 And 600010
Try this instead:
SELECT TOP 10 fc.FuelClaimId
FROM FuelClaims fc
INNER JOIN Vehicles v ON fc.VehicleId = v.VehicleId
INNER JOIN Drivers d ON d.DriverId = v.OfficialID
INNER JOIN Departments de ON de.DepartmentId = d.DepartmentId
INNER JOIN Provinces p ON de.ProvinceId = p.ProvinceId
INNER JOIN FuelRates f ON f.FuelRateId = fc.FuelRateId
INNER JOIN FuelClaimStatuses fs ON fs.FuelClaimStatusId = fc.statusid
INNER JOIN LogsheetMonths l ON l.LogsheetMonthId = f.LogsheetMonthId
WHERE fc.IsDeleted = 0 AND fc.FuelClaimId BETWEEN 600001 AND 600010
ORDER BY fc.FuelClaimId
Also BETWEEN is inclusive so BETWEEN 10 and 20 actually returns 10,11,12,13,14,15,16,17,18,19 and 20 so 11 rows not 10. As identity values usually start at 1 you really want BETWEEN 11 AND 20 (hence 600001 in the above)
The above query should fix your issue where your performance degrades as you query the larger range of items.
While it won't always return 10 records the fix for that is:
WHERE fc.IsDeleted = 0 AND fc.FuelClaimId > #LastMaxFuelClaimId
Where #LastMaxFuelClaimId is the previous MAX FuelClaimId you had returned from the previous query execution.
Edit: The reason why it keeps getting slower is because it has to read more and more of the table to read the next chunk, it doesn't skip reading the first 600,000 records it reads them all and then only returns the next 10 hence each time you query it reads all the previous records all over again, the above does not suffer from the same problem.
You should post an execution plan but a probable cause of performance problems would be inadequate or lack of indexing.
Make sure you have
an index on all your foreign key relations
a covering index on the fields you retrieve and select from
Covering Index
CREATE INDEX IX_FUELCLAIMS_FUELCLAIMID_ISDELETED
ON dbo.FuelClaims (FuelClaimId, VehicleID, IsDeleted)
Related
If I run the below query I m going to update an Oracle table by 7K rows. I want to do that by 300 of records per time.
INSERT INTO REQUEST
SELECT REQUEST_SEQ.NEXTVAL, REQUEST_ID, 'TEST', REF_ASK_ID, SYSDATE
FROM CITIES
INNER JOIN REFERENCE ON CITY_ID = REF_ID
WHERE REF_ASK_NM= 'DOWN'
AND CITY_WAY IN ('1', '33')
300 rows at a time? Why? To make it slower?
Anyway:
rownum will make sure to take 300 rows
not exists will make sure not to copy what you already have copied (if where condition catches them all).
I don't know which columns belong to which tables as you didn't use table aliases (and yes, you should have)
if there are duplicates for columns being used in where, you might still get duplicates as there's no guarantee that that "set" of rows will be inserted as a whole
In other words: do it all at once.
INSERT INTO offices
SELECT office_seq.NEXTVAL, office_id, office_ref
FROM city INNER JOIN reference ON office_id = ref_id
WHERE ROWNUM <= 300
AND NOT EXISTS
(SELECT NULL
FROM offices b
WHERE b.office_id = city.office_id -- or maybe reference.office_id
AND b.office_ref = city.office_ref); -- or maybe reference.office_ref
I'm trying to speed up the following
create table tab2 parallel 24 nologging compress for query high as
select /*+ parallel(24) index(a ix_1) index(b ix_2)*/
a.usr
,a.dtnum
,a.company
,count(distinct b.usr) as num
,count(distinct case when b.checked_1 = 1 then b.usr end) as num_che_1
,count(distinct case when b.checked_2 = 1 then b.usr end) as num_che_2
from tab a
join tab b on a.company = b.company
and b.dtnum between a.dtnum-1 and a.dtnum-0.0000000001
group by a.usr, a.dtnum, a.company;
by using indexes
create index ix_1 on tab(usr, dtnum, company);
create index ix_2 on tab(usr, company, dtnum, checked_1, checked_2);
but the execution plan tells me that it's going to be an index full scan for both indexes, and the calculations are very long (1 day is not enough).
About the data. Table tab has over 3 mln records. None of the single columns are unique. The unique values here are pairs of (usr, dtnum), where dtnum is a date with time written as a number in the format yyyy,mmddhh24miss. Columns checked_1, checked_2 have values from set (null, 0, 1, 2). Company holds an id for a company.
Each pair can only have one value checked_1, checked_2 and company as it is unique. Each user can be in multple pairs with different dtnum.
Edit
#Roberto Hernandez: I've attached the picture with the execution plan. As for parallel 24, in our company we are told to create tables with options 'parallel [num] nologging compress for query high'. I'm using 24 but I'm no expert in this field.
#Sayan Malakshinov: http://sqlfiddle.com/#!4/40b6b/2 Here I've simplified by giving data with checked_1 = checked_2, but in real life this may not be true.
#scaisEdge:
For
create index my_id1 on tab (company, dtnum);
create index my_id2 on tab (company, dtnum, usr);
I get
For table tab Your join condition is based on columns
company, datun
so you index should be primarly based on these columns
create index my_id1 on tab (company, datum);
The indexes you are using are useless because don't contain in left most position columsn use ij join /where condition
Eventually you can add user right most potition for avoid the needs of table access and let the db engine retrive alla the inf inside the index values
create index my_id1 on tab (company, datum, user, checked_1, checked_2);
Indexes (bitmap or otherwise) are not that useful for this execution. If you look at the execution plan, the optimizer thinks the group-by is going to reduce the output to 1 row. This results in serialization (PX SELECTOR) So I would question the quality of your statistics. What you may need is to create a column group on the three group-by columns, to improve the cardinality estimate of the group by.
My Query is
SELECT unnest(array [repgroupname,repgroupname||'-'
||masteritemname,repgroupname||'-' ||masteritemname||'-'||itemname]) AS grp
,unnest(array [repgroupname,masteritemname,itemname]) AS disp
,groupname1
,groupname2
,groupname3
,sum(qty) AS qty
,sum(freeqty) AS freeqty
,sum(altqty) AS altqty
,sum(discount) AS discount
,sum(amount) AS amount
,sum(stockvalue) AS stockvalue
,sum(itemprofit) AS itemprofit
FROM (
SELECT repgroupname
,masteritemname
,itemname
,groupname1
,groupname2
,groupname3
,units
,unit1
,unit2
,altunits
,altunit1
,altunit2
,sum(s2.totalqty) AS qty
,sum(s2.totalfreeqty) AS freeqty
,sum(s2.totalaltqty) AS altqty
,sum(s2.totaltradis + s2.totaladnldis) AS discount
,sum(amount) AS amount
,sum(itemstockvalue) AS stockvalue
,sum(itemprofit1) AS itemprofit
FROM sales1 s1
INNER JOIN sales2 s2 ON s1.txno = s2.txno
INNER JOIN items i ON i.itemno = s2.itemno
GROUP BY repgroupname
,masteritemname
,itemname
,groupname1
,groupname2
,groupname3
,units
,unit1
,unit2
,altunits
,altunit1
,altunit2
ORDER BY itemname
) AS tt
GROUP BY grp
,disp
,groupname1
,groupname2
,groupname3
Here
Sales1 table have 144513 Records
Sales2 Table have 438915 Records
items Table have 78512 Records
This Query take 6 seconds to produce result.
How to Optimize this query?
am using postgresql 9.3
That is a truly horrible query.
You should start by losing the ORDER BY in the sub-select - the ordering is discarded by the outer query.
Beyond that, ask yourself why you need to look to see a summary of every songle row in th DBMS - does this serve any useful purpose (if the query is returning more than 20 rows, then the answer is no).
You might be able to make it go faster by ensuring that the foreign keys in the tables are indexed (indexes are THE most important bit of information to look at whenever you're talking about performance and you've told us nothing about them).
Maintaining the query as a regular snapshot will mitigate the performance impact.
I'm working on a query (Oracle 11g) that does a lot of date manipulation. Using a row generator, I'm examining each date within a range of dates for each record in another table. Through another query, I know that my row generator needs to generate 8500 dates, and this amount will grow by 365 days each year. Also, the table that I'm examining has about 18000 records, and this table is expected to grow by several thousand records a year.
The problem comes when joining the row generator to the other table to get the range of dates for each record. SQLTuning Advisor says that there's an expensive Cartesian product, which makes sense given that the query currently could generate up to 8500 x 18000 records. Here's the query in its stripped down form, without all the date logic etc.:
with n as (
select level n
from dual
connect by level <= 8500
)
select t.id, t.origdate + n origdate
from (
select id, origdate, closeddate
from my_table
) t
join n on origdate + n - 1 <= closeddate -- here's the problem join
order by t.id, t.origdate;
Is there an alternate way to join these two tables without the Cartesian product?
I need to calculate the elapsed time for each of these records, disallowing weekends and federal holidays, so that I can sort on the elapsed time. Also, the pagination for the table is done server-side, so we can't just load into the table and sort client-side.
The maximum age of a record in the system right now is 3656 days, and the average is 560, so it's not quite as bad as 8500 x 18000; but it's still bad.
I've just about resigned myself to adding a field to store the opendays, computing it once and storing the elapsed time, and creating a scheduled task to update all open records every night.
I think that you would get better performance if you rewrite the join condition slightly:
with n as (
select level n
from dual
connect by level <= 8500
)
select t.id, t.origdate + n origdate
from (
select id, origdate, closeddate
from my_table
) t
join n on Closeddate - Origdate + 1 <= n --you could even create a function-based index
order by t.id, t.origdate;
Have the following tables (Oracle 10g):
catalog (
id NUMBER PRIMARY KEY,
name VARCHAR2(255),
owner NUMBER,
root NUMBER REFERENCES catalog(id)
...
)
university (
id NUMBER PRIMARY KEY,
...
)
securitygroup (
id NUMBER PRIMARY KEY
...
)
catalog_securitygroup (
catalog REFERENCES catalog(id),
securitygroup REFERENCES securitygroup(id)
)
catalog_university (
catalog REFERENCES catalog(id),
university REFERENCES university(id)
)
Catalog: 500 000 rows, catalog_university: 500 000, catalog_securitygroup: 1 500 000.
I need to select any 50 rows from catalog with specified root ordered by name for current university and current securitygroup. There is a query:
SELECT ccc.* FROM (
SELECT cc.*, ROWNUM AS n FROM (
SELECT c.id, c.name, c.owner
FROM catalog c, catalog_securitygroup cs, catalog_university cu
WHERE c.root = 100
AND cs.catalog = c.id
AND cs.securitygroup = 200
AND cu.catalog = c.id
AND cu.university = 300
ORDER BY name
) cc
) ccc WHERE ccc.n > 0 AND ccc.n <= 50;
Where 100 - some catalog, 200 - some securitygroup, 300 - some university. This query return 50 rows from ~ 170 000 in 3 minutes.
But next query return this rows in 2 sec:
SELECT ccc.* FROM (
SELECT cc.*, ROWNUM AS n FROM (
SELECT c.id, c.name, c.owner
FROM catalog c
WHERE c.root = 100
ORDER BY name
) cc
) ccc WHERE ccc.n > 0 AND ccc.n <= 50;
I build next indexes: (catalog.id, catalog.name, catalog.owner), (catalog_securitygroup.catalog, catalog_securitygroup.index), (catalog_university.catalog, catalog_university.university).
Plan for first query (using PLSQL Developer):
http://habreffect.ru/66c/f25faa5f8/plan2.jpg
Plan for second query:
http://habreffect.ru/f91/86e780cc7/plan1.jpg
What are the ways to optimize the query I have?
The indexes that can be useful and should be considered deal with
WHERE c.root = 100
AND cs.catalog = c.id
AND cs.securitygroup = 200
AND cu.catalog = c.id
AND cu.university = 300
So the following fields can be interesting for indexes
c: id, root
cs: catalog, securitygroup
cu: catalog, university
So, try creating
(catalog_securitygroup.catalog, catalog_securitygroup.securitygroup)
and
(catalog_university.catalog, catalog_university.university)
EDIT:
I missed the ORDER BY - these fields should also be considered, so
(catalog.name, catalog.id)
might be beneficial (or some other composite index that could be used for sorting and the conditions - possibly (catalog.root, catalog.name, catalog.id))
EDIT2
Although another question is accepted I'll provide some more food for thought.
I have created some test data and run some benchmarks.
The test cases are minimal in terms of record width (in catalog_securitygroup and catalog_university the primary keys are (catalog, securitygroup) and (catalog, university)). Here is the number of records per table:
test=# SELECT (SELECT COUNT(*) FROM catalog), (SELECT COUNT(*) FROM catalog_securitygroup), (SELECT COUNT(*) FROM catalog_university);
?column? | ?column? | ?column?
----------+----------+----------
500000 | 1497501 | 500000
(1 row)
Database is postgres 8.4, default ubuntu install, hardware i5, 4GRAM
First I rewrote the query to
SELECT c.id, c.name, c.owner
FROM catalog c, catalog_securitygroup cs, catalog_university cu
WHERE c.root < 50
AND cs.catalog = c.id
AND cu.catalog = c.id
AND cs.securitygroup < 200
AND cu.university < 200
ORDER BY c.name
LIMIT 50 OFFSET 100
note: the conditions are turned into less then to maintain comparable number of intermediate rows (the above query would return 198,801 rows without the LIMIT clause)
If run as above, without any extra indexes (save for PKs and foreign keys) it runs in 556 ms on a cold database (this is actually indication that I oversimplified the sample data somehow - I would be happier if I had 2-4s here without resorting to less then operators)
This bring me to my point - any straight query that only joins and filters (certain number of tables) and returns only a certain number of the records should run under 1s on any decent database without need to use cursors or to denormalize data (one of these days I'll have to write a post on that).
Furthermore, if a query is returning only 50 rows and does simple equality joins and restrictive equality conditions it should run even much faster.
Now let's see if I add some indexes, the biggest potential in queries like this is usually the sort order, so let me try that:
CREATE INDEX test1 ON catalog (name, id);
This makes execution time on the query - 22ms on a cold database.
And that's the point - if you are trying to get only a page of data, you should only get a page of data and execution times of queries such as this on normalized data with proper indexes should take less then 100ms on decent hardware.
I hope I didn't oversimplify the case to the point of no comparison (as I stated before some simplification is present as I don't know the cardinality of relationships between catalog and the many-to-many tables).
So, the conclusion is
if I were you I would not stop tweaking indexes (and the SQL) until I get the performance of the query to go below 200ms as rule of the thumb.
only if I would find an objective explanation why it can't go below such value I would resort to denormalisation and/or cursors, etc...
First I assume that your University and SecurityGroup tables are rather small. You posted the size of the large tables but it's really the other sizes that are part of the problem
Your problem is from the fact that you can't join the smallest tables first. Your join order should be from small to large. But because your mapping tables don't include a securitygroup-to-university table, you can't join the smallest ones first. So you wind up starting with one or the other, to a big table, to another big table and then with that large intermediate result you have to go to a small table.
If you always have current_univ and current_secgrp and root as inputs you want to use them to filter as soon as possible. The only way to do that is to change your schema some. In fact, you can leave the existing tables in place if you have to but you'll be adding to the space with this suggestion.
You've normalized the data very well. That's great for speed of update... not so great for querying. We denormalize to speed querying (that's the whole reason for datawarehouses (ok that and history)). Build a single mapping table with the following columns.
Univ_id, SecGrp_ID, Root, catalog_id. Make it an index organized table of the first 3 columns as pk.
Now when you query that index with all three PK values, you'll finish that index scan with a complete list of allowable catalog Id, now it's just a single join to the cat table to get the cat item details and you're off an running.
The Oracle cost-based optimizer makes use of all the information that it has to decide what the best access paths are for the data and what the least costly methods are for getting that data. So below are some random points related to your question.
The first three tables that you've listed all have primary keys. Do the other tables (catalog_university and catalog_securitygroup) also have primary keys on them?? A primary key defines a column or set of columns that are non-null and unique and are very important in a relational database.
Oracle generally enforces a primary key by generating a unique index on the given columns. The Oracle optimizer is more likely to make use of a unique index if it available as it is more likely to be more selective.
If possible an index that contains unique values should be defined as unique (CREATE UNIQUE INDEX...) and this will provide the optimizer with more information.
The additional indexes that you have provided are no more selective than the existing indexes. For example, the index on (catalog.id, catalog.name, catalog.owner) is unique but is less useful than the existing primary key index on (catalog.id). If a query is written to select on the catalog.name column, it is possible to do and index skip scan but this starts being costly (and most not even be possible in this case).
Since you are trying to select based in the catalog.root column, it might be worth adding an index on that column. This would mean that it could quickly find the relevant rows from the catalog table. The timing for the second query could be a bit misleading. It might be taking 2 seconds to find 50 matching rows from catalog, but these could easily be the first 50 rows from the catalog table..... finding 50 that match all your conditions might take longer, and not just because you need to join to other tables to get them. I would always use create table as select without restricting on rownum when trying to performance tune. With a complex query I would generally care about how long it take to get all the rows back... and a simple select with rownum can be misleading
Everything about Oracle performance tuning is about providing the optimizer enough information and the right tools (indexes, constraints, etc) to do its job properly. For this reason it's important to get optimizer statistics using something like DBMS_STATS.GATHER_TABLE_STATS(). Indexes should have stats gathered automatically in Oracle 10g or later.
Somehow this grew into quite a long answer about the Oracle optimizer. Hopefully some of it answers your question. Here is a summary of what is said above:
Give the optimizer as much information as possible, e.g if index is unique then declare it as such.
Add indexes on your access paths
Find the correct times for queries without limiting by rowwnum. It will always be quicker to find the first 50 M&Ms in a jar than finding the first 50 red M&Ms
Gather optimizer stats
Add unique/primary keys on all tables where they exist.
The use of rownum is wrong and causes all the rows to be processed. It will process all the rows, assigned them all a row number, and then find those between 0 and 50. When you want to look for in the explain plan is COUNT STOPKEY rather than just count
The query below should be an improvement as it will only get the first 50 rows... but there is still the issue of the joins to look at too:
SELECT ccc.* FROM (
SELECT cc.*, ROWNUM AS n FROM (
SELECT c.id, c.name, c.owner
FROM catalog c
WHERE c.root = 100
ORDER BY name
) cc
where rownum <= 50
) ccc WHERE ccc.n > 0 AND ccc.n <= 50;
Also, assuming this for a web page or something similar, maybe there is a better way to handle this than just running the query again to get the data for the next page.
try to declare a cursor. I dont know oracle, but in SqlServer would look like this:
declare #result
table (
id numeric,
name varchar(255)
);
declare __dyn_select_cursor cursor LOCAL SCROLL DYNAMIC for
--Select
select distinct
c.id, c.name
From [catalog] c
inner join university u
on u.catalog = c.id
and u.university = 300
inner join catalog_securitygroup s
on s.catalog = c.id
and s.securitygroup = 200
Where
c.root = 100
Order by name
--Cursor
declare #id numeric;
declare #name varchar(255);
open __dyn_select_cursor;
fetch relative 1 from __dyn_select_cursor into #id,#name declare #maxrowscount int
set #maxrowscount = 50
while (##fetch_status = 0 and #maxrowscount <> 0)
begin
insert into #result values (#id, #name);
set #maxrowscount = #maxrowscount - 1;
fetch next from __dyn_select_cursor into #id, #name;
end
close __dyn_select_cursor;
deallocate __dyn_select_cursor;
--Select temp, final result
select
id,
name
from #result;