The strategy selected by the query optimiser to process a query.

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71 views

MySQL optimizer won't use my index

With the following query: SELECT * FROM geoname LEFT JOIN alternatename ON geoname.geonameid = alternatename.geonameid AND alternatename.isPreferredName = 1 AND ...
2
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2answers
60 views

Understanding Execution Plan

I am really having hard time understanding the below execution plan. Query 1: (Simple Select Query) Record count of ##SALES_UNIT_RESULT is 168. In first execution plan it is fine. ;WITH ...
2
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1answer
200 views

High I/O for part of query

I have a large query that I'm trying to tune. I write lots of queries but haven't done a lot of tuning. I've included a screenshot from SQL Sentry Plan Explorer Free (SSPEF): In the above part of ...
2
votes
1answer
564 views

Oracle 11g bug ? not returning the record until I triggered index to invisible and then to visible

We are using Oracle 11g, 11.2.0.3. We know a record exists in a table but a select is not returning it for some odd reason. The execution plans the general query, not forcing any index, shows that ...
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1answer
126 views

intermittent performance issue - query with multiple CTE and trashed execution plan

I'm trying to optimize a SQL query that shows variable performance (less than 2 to more than 15s). Overview This is a ColdFusion website, with a SQL Server 2008 R2 backend The query is part of the ...
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1answer
89 views

Simple select query taking too long

I have been having a hard time with this query, I have a webpage which is supposed to run this query a dozen of times, and with an execution time up to 40 - 50 seconds per query, you can see how this ...
0
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1answer
82 views

Optimizing a DMV query

I have found a query that is a major performance issue in my environment. I looked at the actual execution plan for this query and found out the main problem is the remote scan (98%). Its remote ...
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1answer
105 views

same query different servers,different execution plan and time

I have this query and it runs less than 2 minutes on Test but on Prod it takes 10 minutes. Both are the same version,CPU,RAM,OS the same. I have four tempdb files on Prod but one one Test. I ...
3
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0answers
51 views

Is execution plan cached “better” for stored procedures than for a non-dynamic query?

Reading different explanations about execution plan caching by Microsoft SQL Server, I'm confused about the benefits of using stored procedures instead of non-dynamic queries. By a non-dynamic query ...
3
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0answers
95 views

Bad Plan after a couple of days

I have this query that runs fine for a couple of days (from the application) and then slows down to where it can't even finish. If I rebuild the plan, it flies. There is a signifigant amount of data ...
2
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0answers
62 views

Performance differs on same query against two (almost) identical tables?

I'm running these two queries in SQL Server 2012: SELECT tpua.Field1, CAST(round(twg.Field2 * 2, 0) / 2 As Decimal(8,1)) As Field2, CAST((round((twg.Field3/10.0) * 2, 0) / 2) * 10 As int) As ...
2
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0answers
87 views

Execution plan of query inside pl/pgsql function

Briefly, we have a pl/pgsql function which collects some intermediate data in several temporary tables ("on commit drop") and then returns REFCURSOR which joins those temporary tables with some static ...
2
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0answers
83 views

When will SQL Server automatically use a supporting indexed view?

I have the following expensive query that runs against our data warehouse: SELECT d.DateYear, COUNT_BIG(*) AS WidgetCount FROM Widgets AS w JOIN Dates AS d ON d.DateId = w.DateId WHERE ...
2
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0answers
210 views

Does Oracle ADO.NET varchar parameter size influence query plan reuse?

I am considering to apply a fix which will generate constant parameter sizes for (n)varchar parameters. The application is based on NHibernate with the old OracleClientDriver (using Microsoft Oracle ...
2
votes
0answers
146 views

Multi-Statement Template Plan Guide

A piece of, um, software seems to be issuing ~20k queries of this form every few seconds: DELETE FROM macVendor WHERE companyId=N' 08-00-'; INSERT INTO macVendor (companyId,organization) VALUES (N' ...
2
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0answers
233 views

Postgres - Partitioning old tables, partition query planning, optimisation

I've been trying to optimise our database, but not being a DBA and not having done a whole lot of tuning before I'm struggling a little with "too many options". I've already run pg_tune and bumped a ...
1
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0answers
42 views

Why does the first query scan and the second seek?

Please could somebody explain why the first query below scans on every JOIN to the REFERENCE_VALUES table but the second query seeks on the same JOINs. The first query does have other JOINs but I ...
1
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0answers
28 views

Reasons why plans of sys.dm_exec_cached_plans do not match actual plans?

I re-assess index / query optimization and actually focus on key/bookmark lookpus that could be eliminated. Using a script of Jonathan Kehayas I go through the list of query plans that used those ...
1
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0answers
72 views

Odd Execution Plan

I have a table in SQL Server that is performing very slowly and I have been trying different indexing options to try to speed it up to no avail. I suspect all of the varchar(max) fields may be a ...
1
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0answers
124 views

Different Execution Plans Picked for Similar Queries

Thank you in advance for reading it. This question is kind of long and need a little patience to read. I will provide as much details as I can to void interference factors to solve this problem. ...
0
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0answers
38 views

Large differences between estimated and actual row counts but stats are OK

I'm having a problem with a Function which is taking 10 times longer to run than it used to and high CPU usage. And I'm puzzled by what I'm seeing in the execution plan with some index seek operators ...
0
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0answers
68 views

Eager Spool 100%

I have a query like below, when I execute it, the parallel query always takes very long time to finish, I found there is index spool(Eager Spool) which costs 100% in execution plan... How can I ...
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0answers
68 views

SQL query running slow compared to its earlier execution time

One of our application using an SQL query is reported running slow. Current execution time:- 15 minutes and so Earlier execution time:- 30 seconds. SQL-Sentry Plan for the slow query I've ...
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0answers
84 views

Query plan reads vs statistics io reads

I have a very strange problem. When I run a query with SET STATISTICS IO ON, it shows that I had a total of 183 reads. But when I look at the query plan dmv it shows I did 555,132 reads. I cleared the ...
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0answers
86 views

Index Tuning Question

I have the following query: SELECT T1.ITEMID, T1.ITEMTYPE, T1.PURCHMODEL, T1.HEIGHT, T1.WIDTH, T1.SALESMODEL, T1.COSTGROUPID, T1.REQGROUPID, T1.EPCMANAGER, ...
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0answers
33 views

Analize Query in MySQL Server 5.1

I try use MySQL Workbench 6 to analyze the cost, but they don't show the cost of query. How i get this costs?