I currently have this very very slow query:
SELECT generators.id AS generator_id, COUNT(*) AS cnt
FROM generator_rows
JOIN generators ON generators.id = generator_rows.generator_id
WHERE
generators.id IN (SELECT "generators"."id" FROM "generators" WHERE "generators"."client_id" = 5212 AND ("generators"."state" IN ('enabled'))) AND
(
generators.single_use = 'f' OR generators.single_use IS NULL OR
generator_rows.id NOT IN (SELECT run_generator_rows.generator_row_id FROM run_generator_rows)
)
GROUP BY generators.id;
An I'm trying to refactor it/improve it with this query:
SELECT g.id AS generator_id, COUNT(*) AS cnt
from generator_rows gr
join generators g on g.id = gr.generator_id
join lateral(select case when exists(select * from run_generator_rows rgr where rgr.generator_row_id = gr.id) then 0 else 1 end as noRows) has on true
where g.client_id = 5212 and "g"."state" IN ('enabled') AND
(g.single_use = 'f' OR g.single_use IS NULL OR has.norows = 1)
group by g.id
For reason it doesn't quite work as expected(It returns 0 rows). I think I'm pretty close to the end result but can't get it to work.
I'm running on PostgreSQL 9.6.1.
This appears to be the query, formatted so I can read it:
SELECT gr.generators_id, COUNT(*) AS cnt
FROM generators g JOIN
generator_rows gr
ON g.id = gr.generator_id
WHERE gr.generators_id IN (SELECT g.id
FROM generators g
WHERE g.client_id = 5212 AND
g.state = 'enabled'
) AND
(g.single_use = 'f' OR
g.single_use IS NULL OR
gr.id NOT IN (SELECT rgr.generator_row_id FROM run_generator_rows rgr)
)
GROUP BY gr.generators_id;
I would be inclined to do most of this work in the FROM clause:
SELECT gr.generators_id, COUNT(*) AS cnt
FROM generators g JOIN
generator_rows gr
ON g.id = gr.generator_id JOIN
generators gg
on g.id = gg.id AND
gg.client_id = 5212 AND gg.state = 'enabled' LEFT JOIN
run_generator_rows rgr
ON g.id = rgr.generator_row_id
WHERE g.single_use = 'f' OR
g.single_use IS NULL OR
rgr.generator_row_id IS NULL
GROUP BY gr.generators_id;
This does make two assumptions that I think are reasonable:
generators.id is unique
run_generator_rows.generator_row_id is unique
(It is easy to avoid these assumptions, but the duplicate elimination is more work.)
Then, some indexes could help:
generators(client_id, state, id)
run_generator_rows(id)
generator_rows(generators_id)
Generally avoid inner selects as in
WHERE ... IN (SELECT ...)
as they are usually slow.
As it was already shown for your problem it's a good idea to think of SQL as of set- theory.
You do NOT join tables on their sole identity:
In fact you take (SQL does take) the set (- that is: all rows) of the first table and "multiply" it with the set of the second table - thus ending up with n times m rows.
Then the ON- clause is used to (often strongly) reduce the result by simply selecting each one of those many combinations by evaluating this portion to either true (take) or false (drop). This way you can chose any arbitrary logic to select those combinations in favor.
Things get trickier with LEFT JOIN and RIGHT JOIN, but one can easily think of them as to take one side for granted:
output the combinations of that row IF the logic yields true (once at least) - exactly like JOIN does
output exactly ONE row, with 'the other side' (right side on LEFT JOIN and vice versa) consisting of ALL NULL for every column.
Count(*) is great either, but if things getting complicated don't stick to it: Use Sub- Selects for the keys only, and once all the hard word is done join the Fun- Stuff to it. Like in
SELECT SUM(VALID), ID
FROM SELECT
(
(1 IF X 0 ELSE) AS VALID, ID
FROM ...
)
GROUP BY ID) AS sub
JOIN ... AS details ON sub.id = details.id
Difference is: The inner query is executed only once. The outer query does usually have no indices left to work with and will be slow, but if the inner select here doesn't make the data explode this is usually many times faster than SELECT ... WHERE ... IN (SELECT..) constructs.
Related
I am new to sql and have created the below sql to fetch the required results.However the query seems to take ages in running and is quite slow. It will be great if any help in optimization is provided.
Below is the sql query i am using:
SELECT
Date_trunc('week',a.pair_date) as pair_week,
a.used_code,
a.used_name,
b.line,
b.channel,
count(
case when b.sku = c.sku then used_code else null end
)
from
a
left join b on a.ma_number = b.ma_number
and (a.imei = b.set_id or a.imei = b.repair_imei
)
left join c on a.used_code = c.code
group by 1,2,3,4,5
I would rewrite the query as:
select Date_trunc('week',a.pair_date) as pair_week,
a.used_code, a.used_name, b.line, b.channel,
count(*) filter (where b.sku = c.sku)
from a left join
b
on a.ma_number = b.ma_number and
a.imei in ( b.set_id, b.repair_imei ) left join
c
on a.used_code = c.code
group by 1,2,3,4,5;
For this query, you want indexes on b(ma_number, set_id, repair_imei) and c(code, sku). However, this doesn't leave much scope for optimization.
There might be some other possibilities, depending on the tables. For instance, or/in in the on clause is usually a bad sign -- but it is unclear what your intention really is.
I am attempting to include a new table with values that need to be checked and included in a stored procedure. Statement 1 is the existing table that needs to be checked against, while statement 2 is the new table to check against.
I currently have 2 EXISTS conditions that function independently and produce the results I am expecting. By this I mean if I comment out Statement 1, statement 2 works and vice versa. When I put them together the query doesn't complete, there is no error but it times out which is unexpected because each statement only takes a few seconds.
I understand there is likely a better way to do this but before I do, I would like to know why I cannot seem to do multiple exists statements like this? Are there not meant to be multiple EXISTS conditions in the WHERE clause?
SELECT *
FROM table1 S
WHERE
--Statement 1
EXISTS
(
SELECT 1
FROM table2 P WITH (NOLOCK)
INNER JOIN table3 SA ON SA.ID = P.ID
WHERE P.DATE = #Date AND P.OTHER_ID = S.ID
AND
(
SA.FILTER = ''
OR
(
SA.FILTER = 'bar'
AND
LOWER(S.OTHER) = 'foo'
)
)
)
OR
(
--Statement 2
EXISTS
(
SELECT 1
FROM table4 P WITH (NOLOCK)
INNER JOIN table5 SA ON SA.ID = P.ID
WHERE P.DATE = #Date
AND P.OTHER_ID = S.ID
AND LOWER(S.OTHER) = 'foo'
)
)
EDIT: I have included the query details. Table 1-5 represent different tables, there are no repeated tables.
Too long to comment.
Your query as written seems correct. The timeout will only be able to be troubleshot from the execution plan, but here are a few things that could be happening or that you could benefit from.
Parameter sniffing on #Date. Try hard-coding this value and see if you still get the same slowness
No covering index on P.OTHER_ID or P.DATE or P.ID or SA.ID which would cause a table scan for these predicates
Indexes for the above columns which aren't optimal (including too many columns, etc)
Your query being serial when it may benefit from parallelism.
Using the LOWER function on a database which doesn't have a case sensitive collation (most don't, though this function doesn't slow things down that much)
You have a bad query plan in cache. Try adding OPTION (RECOMPILE) at the bottom so you get a new query plan. This is also done when comparing the speed of two queries to ensure they aren't using cached plans, or one isn't when another is which would skew the results.
Since your query is timing out, try including the estimated execution plan and post it for us at past the plan
I found putting 2 EXISTS in the WHERE condition made the whole process take significantly longer. What I found fixed it was using UNION and keeping the EXISTS in separate queries. The final result looked like the following:
SELECT *
FROM table1 S
WHERE
--Statement 1
EXISTS
(
SELECT 1
FROM table2 P WITH (NOLOCK)
INNER JOIN table3 SA ON SA.ID = P.ID
WHERE P.DATE = #Date AND P.OTHER_ID = S.ID
AND
(
SA.FILTER = ''
OR
(
SA.FILTER = 'bar'
AND
LOWER(S.OTHER) = 'foo'
)
)
)
UNION
--Statement 2
SELECT *
FROM table1 S
WHERE
EXISTS
(
SELECT 1
FROM table4 P WITH (NOLOCK)
INNER JOIN table5 SA ON SA.ID = P.ID
WHERE P.DATE = #Date
AND P.OTHER_ID = S.ID
AND LOWER(S.OTHER) = 'foo'
)
I am building a complex select statement, and when one of my values (pcf_auto_key) is null it will not disipaly any values for that header entry.
select c.company_name, h.prj_number, h.description, s.status_code, h.header_notes, h.cm_udf_001, h.cm_udf_002, h.cm_udf_008, l.classification_code
from project_header h, companies c, project_status s, project_classification l
where exists
(select company_name from companies where h.cmp_auto_key = c.cmp_auto_key)
and exists
(select status_code from project_status s where s.pjs_auto_key = h.pjs_auto_key)
and exists
(select classification_code from project_classification where h.pcf_auto_key = l.pcf_auto_key)
and pjm_auto_key = 11
--and pjt_auto_key = 10
and c.cmp_auto_key = h.cmp_auto_key
and h.pjs_auto_key = s.pjs_auto_key
and l.pcf_auto_key = h.pcf_auto_key
and s.status_type = 'O'
How does my select statement look? Is this an appropriate way of pulling info from other tables?
This is an oracle database, and I am using SQL Developer.
Assuming you want to show all the data that you can find but display the classification as blank when there is no match in that table, you can use a left outer join; which is much clearer with explicit join syntax:
select c.company_name, h.prj_number, h.description, s.status_code, h.header_notes,
h.cm_udf_001, h.cm_udf_002, h.cm_udf_008, l.classification_code
from project_header h
join companies c on c.cmp_auto_key = h.cmp_auto_key
join project_status s on s.pjs_auto_key = h.pjs_auto_key
left join project_classification l on l.pcf_auto_key = h.pcf_auto_key
where pjm_auto_key = 11
and s.status_type = 'O'
I've taken out the exists conditions as they just seem to be replicating the join conditions.
If you might not have matching data in any of the other tables you can make the other inner joins into outer joins in the same way, but be aware that if you outer join to project_status you will need to move the statatus_type check into the join condition as well, or Oracle will convert that back into an inner join.
Read more about the different kinds of joins.
I am using IN keyword in the query in the middle of a section. Since I am using nested query and want to replace In with Exists due to performance issues that my seniors have told me might arise.
Am I missing some column, what you are looking for in this query. This query contain some aliases for readibility.
How can I remove it.
SELECT TX.PK_MAP_ID AS MAP_ID
, MG.PK_GUEST_ID AS Guest_Id
, MG.FIRST_NAME
, H.PK_CATEGORY_ID AS Preference_Id
, H.DESCRIPTION AS Preference_Name
, H.FK_CATEGORY_ID AS Parent_Id
, H.IMMEDIATE_PARENT AS Parent_Name
, H.Department_ID
, H.Department_Name
, H.ID_PATH, H.DESC_PATH
FROM
dbo.M_GUEST AS MG
LEFT OUTER JOIN
dbo.TX_MAP_GUEST_PREFERENCE AS TX
ON
(MG.PK_GUEST_ID = TX.FK_GUEST_ID)
LEFT OUTER JOIN
dbo.GetHierarchy_Table AS H
ON
(TX.FK_CATEGORY_ID = H.PK_CATEGORY_ID)
WHERE
(MG.IS_ACTIVE = 1)
AND
(TX.IS_ACTIVE = 1)
AND
(H.Department_ID IN -----How to remove this IN operator with EXISTS or Count()
(
SELECT C.PK_CATEGORY_ID AS DepartmentId
FROM
dbo.TX_MAP_DEPARTMENT_OPERATOR AS D
INNER JOIN
dbo.M_OPERATOR AS M
ON
(D.FK_OPERATOR_ID = M.PK_OPERATOR_ID)
AND
(D.IS_ACTIVE = M.IS_ACTIVE)
INNER JOIN
dbo.L_USER_ROLE AS R
ON
(M.FK_ROLE_ID = R.PK_ROLE_ID)
AND
(M.IS_ACTIVE = R.IS_ACTIVE)
INNER JOIN
dbo.L_CATEGORY_TYPE AS C
ON
(D.FK_DEPARTMENT_ID = C.PK_CATEGORY_ID)
AND
(D.IS_ACTIVE = C.IS_ACTIVE)
WHERE
(D.IS_ACTIVE = 1)
AND
(M.IS_ACTIVE = 1)
AND
(R.IS_ACTIVE = 1)
AND
(C.IS_ACTIVE = 1)
)--END INNER QUERY
)--END Condition
What new problems might I get if I replace IN with EXISTS or COUNT ?
Basically, as I understand your question, you are asking how can I replace this:
where H.department_id in (select departmentid from...)
with this:
where exists (select...)
or this:
where (select count(*) from ...) > 1
It is fairly straight forward. One method might be this:
WHERE...
AND EXISTS (select c.pk_category_id
from tx_map_department_operator d
inner join m_operator as m
on d.fk_operator_id = m.pk_operator_id
inner join l_user_role l
on m.fk_role_id = r.pk_role_id
inner join l_category_type c
on d.fk_department_id = c.pk_category_id
where h.department_id = c.pk_category_id
and d.is_active = 1
and m.is_active = 1
and r.is_active = 1
and c.is_active = 1
)
I removed the extra joins on is_active because they were redundant. You should test how it runs with your indexes, because that might have been faster. I doubt it though. But it is worth comparing whether it is faster to add the join clause (join on ... and x.is_active=y.is_active) or to check in the where clause (x.is_active=1 and y.is_active=1 and z.is_active=1...)
And I'd recommend you just use exists, instead of count(*), because I know that exists should stop after finding 1 row, whereas count probably continues to execute until done, and then compares to your reference value (count > 1).
As an aside, that is a strange column naming standard you have. Do you really have PK prefixes for the primary keys, and FK prefixes for the foreign keys? I have never seen that.
I have a big SELECT statement which has many nested selects in it. When I run it, it gives me an ORA-22813 error:
Ora-22813:- The Collection value from one of the inner sub queries has exceeded the system limits and hence this error.
I have given below some of the nested selects which return huge data.
---The 1st select returns the most data.
Can I handle and process the huge data returned by the INNER SELECTs into the tables in any alternate way so that there is no error of memory less, sort size less.
get, any other way so that the QUERY successfully processes without error.
/*****************************************BEGIN
LEFT OUTER JOIN
( SELECT *
FROM STUDENT_COURSE stu_c
LEFT OUTER JOIN STUDENT_history ch on stu_c.course_id = ch.ch_course_id
LEFT OUTER JOIN STUDENT_master stu_mca on ch.course_history_id = stu_mca.item_id
) stu_c ON stu_c.HISTORY_ID = toa.ACTIVITY_ID ----->This table is joined earlier
LEFT OUTER JOIN
(SELECT c_e.EV_ID, c_e.EV_NAME, ma.item_id, ma.cata_id
FROM EVENTS c_e LEFT OUTER
JOIN COURSE_master ma on c_e.event_Id = ma.item_id ) c_e ON c_e.EVENT_ID = toa.ACTIVITY_ID
After these selects---we have GROUP_BYs to further sort.
---I have checked that if I put a extra limit qualification
like where rownum <30,<20 in each of these SELECTs it works fine.
Full query
SELECT * FROM (SELECT
mcat.CATALOG_ITEM_ID,
mcat.CATALOG_ITEM_NAME ,
mcat.DESCRIPTION,
mcat.CATALOG_ITEM_TYPE,
mcat.DELIVERY_METHOD,
XMLElement("TRAINING_PLAN",XMLAttributes( TP.TPLAN_ID as "id" ),
XMLELEMENT("COMPLETE_QUANTITY", TP.COMPLETE_QUANTITY),
XMLELEMENT("COMPLETE_UNIT", TP.COMPLETE_UNIT),
XMLElement("TOTAL_CREDITS", TP.numberOfCredits ),
XMLELEMENT("IS_CREDIT_BASED", TP.IS_CREDIT_BASED),
XMLELEMENT("IS_FOR_CERT", TP.IS_FOR_CERT),
XMLELEMENT("ACCREDIT_ORG_NAME", TP.ACCRED_ORG_NAME),
XMLELEMENT("ACCREDIT_ORG_ID", TP.accredit_org_id ),
XMLElement("OBJECTIVE_LIST", TP.OBJECTIVE_LIST )
).extract('/').getClobVal() AS PLAN_LIST
FROM
student_master_catalog mcat
INNER JOIN
(SELECT stu_tp.TPLAN_ID,
stu_tp.COMPLETE_QUANTITY,
stu_tp.COMPLETE_UNIT,
stu_tp.TPLAN_XML_DATA.extract('//numberOfCredits/text()').getStringVal() as numberOfCredits,
stu_tp.IS_CREDIT_BASED,
stu_tp.IS_FOR_CERT,
stu_oa.ACCRED_ORG_NAME,
stu_tp.TPLAN_XML_DATA.extract('//accreditingOrg/text()').getStringVal() as accredit_org_id,
objective_list.OBJECTIVE_LIST
FROM
student_training_catalog stu_tp
LEFT OUTER JOIN
stu_accrediting_org stu_oa on stu_tp.TPLAN_XML_DATA.extract('//accreditingOrg/text()').getStringVal() = stu_oa.ACCRED_ORG_ID
INNER JOIN
(SELECT *
FROM
(SELECT
stu_tpo.TPLAN_ID AS OBJECTIVE_TPLAN_ID,
XMLAgg(
XMLElement("OBJECTIVE",
XMLElement("OBJECTIVE_ID",stu_tpo.T_OBJECTIVE_ID ),
XMLElement("OBJECTIVE_NAME",stu_to.T_OBJECTIVE_NAME ),
XMLElement("OBJECTIVE_REQUIRED_CREDITS_OR_ACTIVITIES",stu_tpo.REQUIRED_CREDITS ),
XMLElement("ITEM_ORDER", stu_tpo.ITEM_ORDER ),
XMLElement("ACTIVITY_LIST", activity_list.ACTIVITY_LIST )
)
) as OBJECTIVE_LIST
FROM
stu_TP_OBJECTIVE stu_tpo
INNER JOIN
stu_TRAINING_OBJECTIVE stu_to ON stu_tpo.T_OBJECTIVE_ID = stu_to.T_OBJECTIVE_ID
INNER JOIN
(SELECT *
FROM
(SELECT stu_toa.T_OBJECTIVE_ID AS ACTIVITY_TOBJ_ID, XMLAgg(
XMLElement("ACTIVITY",
XMLElement("ACTIVITY_ID",stu_toa.ACTIVITY_ID ),
XMLElement("CATALOG_ID",COALESCE(stu_c.CATALOG_ID, COALESCE( stu_e.CATALOG_ID, stu_t.CATALOG_ID ) ) ),
XMLElement("CATALOG_ITEM_ID",COALESCE(stu_c.CATALOG_ITEM_ID, COALESCE( stu_e.CATALOG_ITEM_ID, stu_t.CATALOG_ITEM_ID ) ) ),
XMLElement("DELIVERY_METHOD",COALESCE(stu_c.DELIVERY_METHOD, COALESCE( stu_e.DELIVERY_METHOD, stu_t.DELIVERY_METHOD ) ) ),
XMLElement("ACTIVITY_NAME",COALESCE(stu_c.COURSE_NAME, COALESCE( stu_e.EVENT_NAME, stu_t.TEST_NAME ) ) ),
XMLElement("ACTIVITY_TYPE",initcap( stu_toa.ACTIVITY_TYPE ) ),
XMLElement("IS_REQUIRED",stu_toa.IS_REQUIRED ),
XMLElement("IS_PREFERRED",stu_toa.IS_PREFERRED ),
XMLElement("NUMBER_OF_CREDITS",stu_lac.CREDIT_HOURS),
XMLElement("ITEM_ORDER", stu_toa.ITEM_ORDER )
)) as ACTIVITY_LIST
FROM stu_TRAIN_OBJ_ACTIVITY stu_toa
LEFT OUTER JOIN
(
SELECT distinct lac.LEARNING_ACTIVITY_ID, lac.CREDIT_HOURS
FROM student_training_catalog tp
INNER JOIN stu_TP_OBJECTIVE tpo on tp.TPLAN_ID = tpo.TPLAN_ID
INNER JOIN stu_TRAIN_OBJ_ACTIVITY toa on tpo.T_OBJECTIVE_ID = toa.T_OBJECTIVE_ID
INNER JOIN stu_LEARNINGACTIVITY_CREDITS lac on lac.LEARNING_ACTIVITY_ID = toa.ACTIVITY_ID and tp.TPLAN_XML_DATA.extract ('//accreditingOrg/text()').getStringVal() = lac.ACC_ORG_ID
where tp.tplan_id ='*************'
) stu_lac ON stu_lac.LEARNING_ACTIVITY_ID = stu_toa.ACTIVITY_ID ------>This Select returns correct no. of rows
I want to join the below nested SELECTs with stu_toa.ACTIVITY_ID. This would solve my issues.
This below SELECT inside the LEFT OUTER JOIN is the Problem. it returns too much because 3 tables are joined directly without any value qualification.
LEFT OUTER JOIN
( SELECT ch.COURSE_HISTORY_ID, stu_c.COURSE_NAME, mca.catalog_item_id, mca.catalog_id, mca.delivery_method
FROM stu_COURSE stu_c
LEFT OUTER JOIN stu_course_history ch on stu_c.course_id = ch.ch_course_id -
--If I can qualify here with ch.ch_course_id = stu_toa.ACTIVITY_ID (stu_toa.ACTIVITY_ID from the above select with correct no. of rows )
--Here, I get errors because I can't access outside values inside a left outer join
LEFT OUTER JOIN student_master_catalog mca on ch.course_history_id = mca.catalog_item_id
) stu_c ON stu_c.COURSE_HISTORY_ID = stu_toa.ACTIVITY_ID
LEFT OUTER JOIN
(SELECT stu_e.EVENT_ID, stu_e.EVENT_NAME, mca.catalog_item_id, mca.catalog_id, mca.delivery_method FROM stu_EVENTS stu_e LEFT OUTER JOIN student_master_catalog mca on stu_e.event_Id = mca.catalog_item_id ) stu_e ON stu_e.EVENT_ID = stu_toa.ACTIVITY_ID
LEFT OUTER JOIN
(SELECT stu_t.TEST_HISTORY_ID, stu_t.TEST_NAME, mca.catalog_item_id, mca.catalog_id, mca.delivery_method FROM stu_TEST_HISTORY stu_t LEFT OUTER JOIN student_master_catalog mca on stu_t.test_history_id = mca.catalog_item_id) stu_t ON stu_t.test_history_id = stu_toa.ACTIVITY_ID
GROUP BY stu_toa.T_OBJECTIVE_ID) ) activity_list ON activity_list.ACTIVITY_TOBJ_ID = stu_tpo.T_OBJECTIVE_ID
GROUP BY stu_tpo.TPLAN_ID) ) objective_list ON objective_list.OBJECTIVE_TPLAN_ID = stu_tp.TPLAN_ID
)TP ON TP.TPLAN_ID = mcat.CATALOG_ITEM_ID
WHERE
mcat.CATALOG_ITEM_ID = '*****************' and mcat.CATALOG_ORG_ID = '********')
Please post the DDLs, approximate sizes (relative to each other), and the complete query, rather than just an excerpt.
Some quick hits that may or may not solve your problem (for better help, I need better information) --
Are you sure you mean OUTER join? Outer joining students to courses means students who are not taking any courses will still be around. Is that the desired behaviour?
Don't select * if you only want a limited subset of the columns. Enumerate the exact columns you need. The rest might not seem like much on a row-by-row basis, but when you multiply by the total number of rows you have, this sort of thing can mean the difference between in-memory sorts and spilling to disk.
How many rows of data are you looking at? there are times when separate queries with programmatic aggregation can work better. Someone with more knowledge of Oracle query optimization may be able to help, also, tweaking the settings could help here too...
I've had instances where a sproc was being called that aggregated data from more than one source took exponentially longer than two calls in the app, and putting it together in memory.
Post DDL of your tables and exact plan of the query.
Meanwhile, try increasing pga_aggregate_target, sort_area_size and hash_area_size